U.S. patent application number 11/612935 was filed with the patent office on 2007-05-31 for vertical services integration enabled content distribution mechanism.
This patent application is currently assigned to VERIZON COMMUNICATIONS INC.. Invention is credited to Robert T. Baum, Eric A. Voit.
Application Number | 20070124488 11/612935 |
Document ID | / |
Family ID | 27092434 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070124488 |
Kind Code |
A1 |
Baum; Robert T. ; et
al. |
May 31, 2007 |
Vertical Services Integration Enabled Content Distribution
Mechanism
Abstract
The invention relates to an enhanced ADSL Data Network (ADN)
with vertical services capabilities. In general, vertical services
capabilities are data services offered directly from a central
office to an end user, without compromising the integrity of the
user's guaranteed bit rate to the Internet through the ADN. One
such vertical service is content downloadable at a high data rate
from a content server located in or proximate to a central office
that serves the end user. The content of the local server is
updated and upgraded periodically and systematically from a central
content server that distributes content to a number of remote
central offices. The content is distributed between the central
content server and the respective local content servers using
available bandwidth, that is to say bandwidth on at least certain
network links that is unused by subscriber traffic.
Inventors: |
Baum; Robert T.;
(Gaithersburg, MD) ; Voit; Eric A.; (Bethesda,
MD) |
Correspondence
Address: |
VERIZON;PATENT MANAGEMENT GROUP
1515 N. COURTHOUSE ROAD
SUITE 500
ARLINGTON
VA
22201-2909
US
|
Assignee: |
VERIZON COMMUNICATIONS INC.
140 West Street
New York
NY
10007
|
Family ID: |
27092434 |
Appl. No.: |
11/612935 |
Filed: |
December 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09835649 |
Apr 17, 2001 |
7170905 |
|
|
11612935 |
Dec 19, 2006 |
|
|
|
09635695 |
Aug 10, 2000 |
6904054 |
|
|
09835649 |
Apr 17, 2001 |
|
|
|
Current U.S.
Class: |
709/230 |
Current CPC
Class: |
H04L 2012/5672 20130101;
H04L 2012/561 20130101; H04L 2012/5632 20130101; H04L 2012/5658
20130101; H04Q 11/0478 20130101; H04L 2012/5667 20130101; H04L
47/2408 20130101 |
Class at
Publication: |
709/230 |
International
Class: |
G06F 15/16 20060101
G06F015/16 |
Claims
1. A method of replicating content data stored on a first server to
at least one second server, comprising the steps: determining
unused bandwidth on a common link of an access data network,
carrying subscriber traffic and over which the first server and the
at least one second server communicate; and transmitting content
data stored on the first server to the at least one second server
substantially on the determined unused bandwidth.
2. The method of claim 1, wherein said at least one second server
comprises a server located in a vertical services domain proximate
to at least one end user terminal.
3. The method of claim 2, wherein the vertical services domain is
located in a central office that provides Digital Subscriber Line
(DSL) service to the at least one end user terminal.
4. The method of claim 2, wherein: the first server is a local
content server; and said at least one second server comprises a
central content server.
5. The method of claim 4, wherein: the local content server is
located in a central office that provides Digital Subscriber Line
(DSL) service to the at least one end user terminal; and the
central content server is located in a hub site.
6. The method of claim 1, comprising the further steps of: storing
the content data transmitted to the at least one second server on
the at least one second server; and transmitting the content data
stored on the at least one second server to at least one end user
terminal proximate to the at least one second server.
7. The method of claim 6, wherein the step of transmitting the
content data stored on the at least one second server to the at
least one end user terminal comprises the steps of: transmitting
the content data stored on the at least one second server to a data
switch proximate to the at least one second server; integrating the
content data transmitted from the at least one second server with
other data destined to the at least one end user terminal received
at the data switch via the common link; and distributing the
integrated data from the data switch to a link to equipment of the
at least one end user terminal via a multiplexer.
8. The method of claim 7, wherein the multiplexer is a Digital
Subscriber Line Access Multiplexer (DSLAM).
9. The method of claim 6, wherein the step of transmitting the
content data stored on the at least one second server to the at
least one end user terminal proximate to the at least one second
server comprises the steps of: provisioning a logical communication
circuit extending from the at least one end user terminal through
the network to a communication access node coupled to a first
network domain, at least a portion of the logical communication
circuit extending through the common link, wherein the provisioning
comprises defining the logical communication circuit in terms of a
layer-2 protocol defining switched connectivity through the
network; at the data switch, examining communicated information in
transmissions from the customer premises, for a protocol
encapsulated within said layer-2 protocol, to distinguish
transmission types; forwarding each detected transmission of a
first transmission type from the data switch to the communication
access node over the logical communication circuit defined in terms
of the layer-2 protocol; and forwarding each detected transmission
of a second type, different from the first transmission type, to a
second network domain logically separate from the first network
domain, wherein the at least one second server is coupled to the
second network domain to receive at least one transmission of a
second type for control of the step of transmitting the content
data stored on the at least one second server to at least one end
user terminal proximate to the at least one second server.
10. A method as in claim 9, further comprising the steps of:
receiving first downstream transmissions intended for the at least
one end user terminal at the data switch, over the logical
communication circuit from the first network domain; receiving
second downstream transmissions intended for the at least one end
user terminal from the second network domain at the data switch,
content data from the at least one second server; and inserting the
second downstream transmissions into the logical communication
circuit, to combine the first and second downstream transmissions
for communication over the logical communication circuit from the
data switch to the at least one end user terminal.
11. A method as in claim 10, wherein the logical communication
circuit comprises an asynchronous transfer mode (ATM) permanent
virtual circuit (PVC).
12. The method of claim 1, wherein a part of the bandwidth of the
common link is reserved for transmitting the content data stored on
the first server to the at least one second server, to prevent the
loss of a session between the first server and the at least one
second server.
13. The method of claim 1, wherein the steps of determining unused
bandwidth and transmitting content data utilize priority and
queuing in at least one node of the access data network, to
implement a minimum bandwidth and provide additional bandwidth as
available on the common link, for the transmitting of the content
data over the common link.
14. The method of claim 1, wherein the steps of determining unused
bandwidth and transmitting content data implement a congestion
mechanism to prevent data loss and utilize unused bandwidth.
15. The method of claim 14, wherein the congestion mechanism
comprises Transmission Control Protocol (TCP).
16. The method of claim 1, wherein the transmitting step utilizes
an unspecified bit rate service through the common link.
17. The method of claim 1, wherein the common link of the network
also carries logical circuits for wide area data communications of
a plurality end user terminals.
18. A software product for replicating content data stored on a
first server to at least one second server, said software product
comprising: at least one machine readable medium; and programming
code, carried by the at least one machine readable medium, for
execution by at least one computer, wherein the programming code
comprises: a congestion mechanism for determining unused bandwidth
on a portion of a common link of an access data network, carrying
subscriber traffic and over which the first server and the at least
one second server communicate; and a first transmitting mechanism
for causing transmission of content data stored on the first server
to the at least one second server substantially on the determined
unused bandwidth.
19. The software product of claim 18, wherein the congestion
mechanism comprises Transmission Control Protocol (TCP).
20. The software product as in claim 19, wherein the first
transmitting mechanism is for causing the transmission of content
data using an unspecified bit rate service.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of application
Ser. No. 09/635,695, entitled SUPPORT FOR QUALITY OF SERVICE AND
VERTICAL SERVICES IN DIGITAL SUBSCRIBER LINE DOMAIN, filed Aug. 10,
2000.
FIELD OF THE INVENTION
[0002] Certain concepts involved in the present invention relate to
techniques for implementing data communication services, for
example in a local access network utilizing digital subscriber line
technology, to support quality of service (QoS) and local
introduction of vertical services. Other concepts involved in the
present invention relate to distribution of content from a hub site
to a server located at a central office through such a network.
BACKGROUND
[0003] Modern society continues to create exponentially increasing
demands for digital information and the communication of such
information between data devices. Local area networks use a
network, cable or other media to link stations on the network for
exchange of information in the form of packets of digital data.
These networks have proven quite successful in providing data
communications in commercial applications. However, the common
local area network architectures require installation of
specialized wiring and use of specific wiring topologies. For
example, the most popular network protocols, such as Ethernet,
require special rules for the wiring, for example with regard to
quality of wire, range of transmission and termination.
Furthermore, to extend communications to a wider domain still
requires connection of at least one node of the local area network
out to a wider area network, such as the network of an Internet
Service Provider (ISP). High speed links enabling such wide area
access from a LAN domain, for example using T1 lines, are quite
expensive and justified only for hi-end commercial users.
[0004] A number of technologies are being developed and are in
early stages of deployment, for providing substantially higher
rates of data communication, for example ranging form 640 kb/s to
7.1 Mb/s. For example, cable television companies are now beginning
to offer `cable modem` services, which allow customers to
communicate data over available bandwidth on the coaxial cable of a
cable television network. After considering several other options,
a number of the local telephone carriers are working on
enhancements to their existing copper-wire loop networks, based on
various xDSL technologies.
[0005] The term xDSL here is used as a generic term for a group of
higher-rate digital subscriber line communication schemes capable
of utilizing twisted pair wiring from an office or other terminal
node of a telephone network to the subscriber premises. Examples
under various stages of development include ADSL (Asymmetrical
Digital Subscriber Line), HDSL (High data rate Digital Subscriber
Line) and VDSL (Very high data rate Digital Subscriber Line).
[0006] The current design goals of DSL data networks for Internet
access do not support high-end vertical services, that is to say
services demanding IP-based applications that require assurance of
some level of quality of service (QoS). For example,
packet-switched Voice over IP (VoIP) requires low latency, low
jitter (i.e., a relatively constant bit rate), and non-correlated
packet loss. Streaming video has similar requirements, and in
addition, requires high bandwidth. DSL data networks designed to
support high speed Internet and Intranet access have been optimized
to support traffic that is bursty and is not sensitive to latency
or jitter. For example, current implementations supporting ATM cell
traffic employ the Unspecified Bit Rate (UBR) class of service,
which does not provide any bandwidth or delay guarantees.
Consequently, transport of video materials through such DSL data
networks inflicts video delays, loss of audio/video
synchronization, and image fragmentation.
[0007] Furthermore, lengthy bandwidth intensive sessions for video
or other broadband applications may degrade the throughput to all
other subscribers served through a shared node, such as a gateway
router or a concentrated link. For two-way video, upstream will
have even worse quality and throughput problems, due to the best
effort nature of the DSL data network implemented for Internet
access and because the upstream bandwidth is significantly less
than that of the downstream channel.
[0008] To appreciate the situation and problems, it may be helpful
here to consider an ADSL data implementation of a local access
network, as a representative example, in somewhat more detail. FIG.
8 is a block diagram of a typical ADSL data network of the type
currently in-use by a number of incumbent and competitive local
exchange carriers to provide high-speed access to Internet Service
Providers (ISPs) and thus to the Internet. FIG. 9 provides an
alternative functional illustration of the elements of such a
network. Of particular note, FIG. 9 shows the various protocol
stacks in association with the appropriate network elements.
[0009] As shown in FIG. 8, a central office (CO) 100 provides plain
old telephone service (POTS) and digital subscriber line data
service for a number of customers. For purposes of discussion,
assume that the equipment at each of the various customer premises
200 connects directly to the CO 100 via twisted pair type copper
wiring 300. In an actual implementation, many customers may connect
through such wiring to a remote terminal linked to the CO via
optical fiber.
[0010] At each customer premises 200 in our example, the copper
loop 300 carrying both the POTS and ADSL signals connects through a
Network Interface Device (NID) 201 placed at the side of the home.
A two pair loop is installed from the NID to the location where the
ADSL unit 203, typically an ATU-R modem, is located in the home.
One pair connects all of the signals on the line 300 from the NID
201 to the ADSL modem 203. Within the ATU-R type modem 203, a
passive splitter/combiner type filter segregates the POTS signal
and the data signals. The POTS signal is transmitted over the
second twisted pair back to the NID 201. The POTS line is then
connected to the in-home wiring extensions at the NID 201, for
distribution to one or more standard telephone devices 205 in the
home.
[0011] Within the ATU-R type ADSL modem 203, the downstream coded
ADSL signal is demodulated and decoded to an appropriate data
interface protocol for connection to the PC 215. The PC 215 or
other data device (FIG. 9) also sends data to the ADSL modem 203.
The modem 203 modulates the upstream data and transmits appropriate
signals over the line 300.sub.1 or 300.sub.2 to the corresponding
modem 113.sub.1 or 113.sub.2 in the CO 100 (FIG. 8). The ATU-R
interface may support bridging, such that multiple users can share
the ADSL modem 203, for two-way data communication through the CO
100.
[0012] The lines 300 for the customer premises 200 connect through
the main distribution frame (MDF) 101 to a Digital Subscriber Line
Access Multiplexer (DSLAM) 111. The DSLAM includes a bank of ADSL
terminal units of the type intended for central office
applications, identified as ATU-Cs 113. The DSLAM also includes a
multiplexer/demultiplexer (MUX) 115.
[0013] Within the DSLAM 111, each customer line 300 connects to an
assigned ADSL terminal unit 113 in the central office (ATU-C). In
the example illustrated, the first customer's line 300.sub.1
connects through the MDF 101 to a first ATU-C 113.sub.1 in the CO
100. The second customer's line 3002 connects through the MDF 101
to a second ATU-C 113.sub.2 in the CO 100. The ATU-C type ADSL
units 113 include appropriate frequency dependent
combiner/splitters, for segregating out the voice telephone
traffic. Thus each ADSL unit 113 provides a connection for
telephone traffic from the associated line 300 to the POTS switch
103.
[0014] The ADSL units 113 in the CO (ATU-Cs) essentially act as
modulator/demodulators (modems) for sending and receiving data over
the subscriber telephone lines 300. On the network side, each of
the ATU-Cs 113 connects to the MUX 115. The MUX 115 multiplexes and
demultiplexes the upstream and downstream data for the ADSL modems
113 and provides a connection to a high-speed link 119. Through
subtending, the MUX 115 may also provide a data concentration for
the communications over the link 119.
[0015] In a typical implementation, the concentrated data
communications utilize a DS-3 link 119. However, because of
increasing traffic demands, it is becoming necessary to upgrade the
link 119 to SONET optical fiber, such as OC-3 or in some cases even
OC-12. The link 119 provides two-way data communication between the
central office 100 and a data hub 121. In practice, this is a
relatively long or wide area link using expensive interoffice
facilities.
[0016] On the upstream side, the high-speed interoffice link 119
terminates on an ATM switch 123 for the ADSL data network (ADN).
Although only one link 119 appears in the drawing, the asynchronous
transfer mode (ATM) switch 123 will typically service a number of
DSLAMs 111 in various end offices via similar DS or OC links. The
ATM switch 123, in turn, provides a high-speed connection to a
gateway router 125 coupled to an ATM cell relay network 129.
Typically, the ATM switch 123 will aggregate traffic from a number
of such links 119 onto an OC-3 or higher rate SONET link to the
router 125. The router 125 and the cell relay network 129 enable
transport of ATM cells for the subscribers to and from equipment of
one or more Internet Service Providers (ISPs), shown by way of
example as a concentrator 131 coupled to the public packet switched
network commonly known as the Internet 132.
[0017] The illustrated local access type ADN network provides ATM
cell transport from a customer premises 200 to the ISP concentrator
131. The ATM cells serve as the layer-2 routing or switching
protocol for the lowest level definition of connectivity between
two points of the network. Higher level protocols ride within the
ATM cells.
[0018] The ATU-Rs 203 and the customer premises data equipment 215
connect via an Ethernet coupler. The customers' equipment
communicates across the ADSL data network utilizing Ethernet, and
the wide area communication involves transport of Internet protocol
information typically in TCP/IP frames within Ethernet frames. The
Ethernet frames carrying the TCP/IP frames are adapted into ATM
cells. Attention is directed to the protocol stacks illustrated in
the lower half of FIG. 9.
[0019] To efficiently provide cell relay, each customer is assigned
an ATM virtual circuit that extends from the ATU-R 203 in the
respective customer premises 200 to the gateway router 125.
Although it was originally envisioned that ATM would support
switched logical channels or virtual circuits, to date, such
logical switching has proven impractical to implement and
administer. Consequently, current practical ATM networks actually
utilize permanent virtual circuits, not switched virtual circuits.
For a given subscriber, the carrier therefore provisions an ATM
permanent virtual circuit from the ATU-R 203 to the gateway router
125. The carrier programs one or more nodes along the path of that
logical circuit, particularly the DSLAM 111, to regulate traffic on
the virtual circuit to the upstream and downstream rates
corresponding to the grade of service to which the particular
customer subscribers. All data traffic for the subscriber goes over
the entire length of the permanent virtual circuit, and most if not
all nodes along that path limit that traffic to the rates of the
subscription as defined in the provisioning data.
[0020] The virtual circuit may be thought of as a solid pipe. All
traffic passes through the entire length of the pipe-like virtual
circuit, regardless of how many switches or other nodes the circuit
passes through. The layer-2 protocol defining the circuit carries
all of the higher level traffic end-to-end. Higher layer protocols
are visible only at the ends of the pipe. Hence, any traffic flow
processing intended to utilize the higher layers must occur at some
point past one end or the other end of the virtual circuit.
[0021] The gateway router 125 also terminates permanent virtual
circuits through the cell relay network 129 going to/from the ISP
concentrators 131. The gateway router 125 aggregates traffic
between a number of subscribers and each respective ISP. The ISP
equipment 131 typically implements a variation of a point-to-point
protocol (PPP) specifically adapted to ride over Ethernet, referred
to as "PPP over Ethernet" (PPPoE). The virtual circuits to the
ISPs, however, do not have sufficient capacity to simultaneously
carry all subscriber traffic at the maximum rates of the customers'
subscriptions. The MUX 115, the ATM switch 123, and the gateway
router 125 concentrate and regulate the subscriber traffic going to
and from the ISPs, typically on some type of "best efforts"
basis.
[0022] In a typical Internet access service offering, the most
expensive service tier provides 7.1 Mbps for downstream
communication and 680 kbps for upstream communication. The next
grade of service provides 1.6 Mbps for downstream communication and
90 kbps for upstream communication, whereas the lowest tier of
service provides 640 kbps for downstream communication and 90 kbps
for upstream communication. The maximum grade of service offered to
an individual subscriber depends on the rates for which the
subscriber's line can qualify, although the subscriber may opt for
a lower rate service since the higher-rate service is more
expensive.
[0023] The approach outlined above relative to FIGS. 8 and 9 works
well for Internet access if the traffic relates to web access, file
transfers and the like, which do not require guaranteed quality of
service. Various segments of the Internet industry, however, are
rapidly developing new multimedia services and applications that
already are pushing the capabilities of such a network. For
example, increasingly, Internet traffic includes a number of types
of communication that require a guaranteed quality of service.
Voice telephone communication over IP is extremely sensitive to
latency and jitter. The permanent virtual circuits provide an
unspecified bit rate (UBR) service and do not guarantee any minimal
amount of delay or jitter. Also, because the rates are set by
subscription, the service tends to be relatively inflexible. Some
services, such as multicasting of broadband information from the
Internet into the local access ADN for a large number of concurrent
users, can quickly overload one or more nodes or critical links of
the network, for example the link 119 between the DSLAM 111 and the
ATM switch 123 at the hub 121.
[0024] Most industry experts propose to increase the services
available via the public Internet. However, because the higher
layer protocols are visible only on the Internet side of the
virtual circuit "pipe," these services all must be implemented out
past the end of the virtual circuit, at least behind the gateway
router 129 and most likely in the public network, where it is
possible to view and route based on higher level protocols,
particularly Internet protocol (IP). Such a migration strategy to
implement new services creates severe problems. For example, in the
network of FIG. 8, if a customer at premises 200.sub.1 desired to
order a video on demand, the customer would communicate via the
assigned permanent virtual circuit and the ISP to a server on the
Internet 132. The server would send the video stream back through
the Internet 132, the ISP equipment 131, the cell relay network 129
and the virtual circuit from the router 125 to the ATU-R 203 for
handoff to a PC or the like at 215. If the rate of the requested
video exceeds the customer's subscription rate, the customer could
not view the video in real time during the download. Even if the
rate of the requested video is below the customer's subscription
rate, loading in the Internet or the local access network may
impose delays and/or jitter in communication of some segments of
the requested video. Assuming that the hub 121 and the links 119
implement a subscriber concentration, ordering of videos or similar
broadband files from the Internet 132 quickly consumes the shared
resources through the hub 121 and the links 119, reducing the rates
of service provided to other customers seeking concurrent Internet
access.
[0025] It might be possible to increase the capacity of the links
119 and/or the hubs 121; however, this tends to increase the
carrier's recurring costs and often makes the overall service(s) of
the ADN network economically impractical.
[0026] It has also been suggested to provide customers guaranteed
quality of services for some portion of their communications, by
segregating the traffic carried between the customer premises and
the hub 121. This would require assigning a plurality of ATM
permanent virtual circuits to each subscriber, one for each
different guaranteed level of quality of service and one for all
other Internet traffic for the subscriber. Administration and
provisioning of one virtual circuit per subscriber is already
complicated, and the number of virtual circuits through any given
ATM node is limited by current equipment designs. Expanding the
number of permanent virtual circuits per subscriber to support
multiple QoS tiers of service therefore would be quite expensive,
and the management thereof would become a nightmare. To support an
increased number of virtual circuits, many having guaranteed QoS
requiring some substantial minimum rate at all times, would also
require that the operator substantially upgrade the network to
increase the end-to-end capacity all the way to the wide area
network 132.
[0027] Furthermore, to actually receive the desired QoS requires
that all elements involved in the communication must guarantee the
desired level or quality of service. For communications across the
public Internet 132, this means that various nodes and links on the
public Internet must be available and capable of providing a
guarantee of the desired QoS. In point of fact, few nodes on the
public Internet actually support any type of QoS. Hence, even if
the ADN supported a desired QoS, most subscribers would not benefit
from that service because their communications over the public
Internet would have no QoS guarantee, and would suffer from the
usual problems of latency and jitter.
[0028] Consequently, current deployments of ADSL-based data
networks, such as shown in FIGS. 8 and 9 generate many customer
complaints. From the customer perspective, the service does not
deliver the data rates that the customer pays for on a consistent
basis. The customer typically blames such problems on network
equipment failure. In fact, most of the problems already are due to
virtual circuit congestion problems, of the kinds outlined above.
Essentially, the ADN network is crippled by the unpredictable
nature of the service levels that the customers perceive due to
congestion on the ADN and on the public Internet.
[0029] Also, with this approach, because all of the major service
elements are implemented in servers accessible to the Internet, all
of the services are subject to severe security risks. Each service
provider's server is accessible to virtually any computer coupled
for communication via the Internet. This openness is a desirable
feature of the public Internet. However, a consequence is that any
such server is accessible to and thus subject to attack from any
hacker having Internet communications capabilities. Popular
services, particularly those generating substantial revenues,
become prime targets for attack.
[0030] Another area of problems is that the ADN does not offer the
carrier any technique for offering its own differentiated service
applications. To compete with other service providers, the carrier
operating the ADSL-based data network needs to introduce its own
multimedia services, for example, its own video services to compete
with video services of cable television companies (that offer
competing Internet access services). As noted above, however,
introduction of a new service, such as true video on demand or
broadcast video requires communications via the public Internet
132. This is true even if the carrier operating the network of
FIGS. 8 and 9 wanted to initiate its own video service(s).
[0031] Hence, there is an ongoing need to improve the architecture
and operation of a digital subscriber line data communication
network, particularly to facilitate finer gradation of services
within the local network. The need, first, is for such a local
network to support introduction of services on a `vertical` basis
within the local access network separate and apart from the common
forms of Internet traffic, both for commercial differentiation and
for increased security.
[0032] As one type of vertical service, there is a further need for
services implemented within the local access network for
distribution of content to the customers, e.g. local video or music
or multimedia, on-demand. Such vertical service insertion of
locally stored content creates certain related needs. For example,
this insertion would give rise to a further need, which is to
transfer content from a central content server, within some hub
site, to local content servers within the respective central
offices. Further, this distribution of content must utilize some
mechanism so that it will not compromise the quality of service for
broader network traffic between the hub site and the respective
central offices.
[0033] In a related need, the local network needs to support a
number of different levels of quality of service (QoS). There also
exists a need for upstream traffic to be shaped by customer
equipment located at or near the interface between a customer's
network and the ADN according to traffic destinations.
SUMMARY OF THE INVENTION
[0034] A general objective of the invention is to implement an
enhanced digital communication network for subscriber lines that
supports vertical introduction of new communication and/or
multimedia services.
[0035] A further objective is to support multiple levels or grades
of quality of service within the access network.
[0036] Another objective of the invention relates to improvement of
the cost effectiveness of the data network, for example, by
reducing the demand for high-capacity interoffice links while
increasing the bandwidth available at the network edge for at least
some types of services.
[0037] A related objective is to provide a technique for
introduction of new high-end services near the network edge, such
as content distribution, from a domain that is more secure and
therefore less subject to hacker attacks.
[0038] A further objective of the invention is to distribute
content between a central content server within a hub site and
local content servers in the vertical services domains of the
respective central offices. The distribution of content is
accomplished utilizing bandwidth between the hub site and the
respective vertical services domains that are unused by subscriber
traffic.
[0039] The invention relates to methods and network architectures
facilitating distribution of content between servers, in an access
data network. Over a common network link, the distribution uses
otherwise available capacity. Broader classes of traffic have a
higher priority for accessing the bandwidth and are not impacted by
the transport of content data over the common link. The distributed
content then is available for delivery, for example on an
"on-demand" basis to end-use customers.
[0040] The preferred embodiments of the ADN architecture alleviate
many of the other noted problems by providing an intermediate node,
typically an enhanced switch, to segregate upstream traffic based
on analysis of the type of communication. This analysis utilizes
protocol information contained in each communication, for a
protocol higher than the switching protocol, that is to say higher
than a protocol used to define the customer's logical circuit. One
type of traffic remains on the virtual circuit, whereas other
traffic is handed off to a vertical services domain. The node also
provides a point to aggregate traffic from the vertical services
domain with other traffic on the subscriber's logical circuit, for
transport to the customer premises equipment.
[0041] The switch at the intermediate node essentially subdivides
the upstream traffic and aggregates downstream traffic, associated
with each subscriber line. One branch goes to a gateway router and
hence to one or more ISP(s) at the rate corresponding to the
Internet access subscription. It may be helpful to consider this as
long distance or wide area traffic for the subscriber. The other
branch is for local traffic, to and from the locally connected
vertical services domain. The remote content delivery servers are
coupled to various vertical services domains, typically in
different end offices. The interconnection to the vertical services
domain supports QoS and introduction of vertical services not
easily provided from the public Internet, such as video on demand,
multicasting, and voice over IP. The vertical services domain is
relatively secure since it is not accessible from the public
Internet.
[0042] The vertical services domain also represents a communication
network. The vertical services domain, however, preferably takes
the form of a data network optimized for local transport of
vertically injected services, that is to say local data traffic. In
view of its local nature, it is easier and more cost effective to
provide high bandwidth services, such as content distribution to
customers, from the local domain. The vertical services network,
for example, could take the form of a giga-bit Ethernet type local
area network. Also, it is easier to adapt the vertical services
network to support service level agreements with customers with
regard to quality of service. In many cases, it actually is
sufficient to support QoS on the one hop through the ATM switch,
itself.
[0043] An aspect of the invention relates to the distribution of
content from a central content server within a hub site to local
content servers within the respective vertical services domains of
remote central offices. Content is routinely and periodically
distributed between a plurality of local vertical services domains
and the hub site server. The hub site may include a gateway router,
which is an ATM switch, and the central content server in
communication with the gateway router. Alternatively, the hub site
may include an enhanced hub switch and one or more further local
services domains. In such an implementation the central content
server communicates via the local services domain and the hub
switch.
[0044] Each of the remote central offices may house another switch,
with vertical services insertion capabilities, and local content
servers in communication with the vertical services insertion
switch. The content is distributed, such that the distribution of
content does not interfere with subscriber traffic between the hub
site and the respective switches at the respective central offices.
This is accomplished by utilization of otherwise unused bandwidth
between the hub site and remote central offices during time periods
when subscriber traffic does not utilize the entirety of this
bandwidth. Once the content is distributed and stored on the local
content servers at the remote central offices, the end users served
by each central office can access content at a high speed from the
nearest vertical services domain, without compromising the
bandwidth allocated for Internet traffic or other traffic between
the hub site and the respective remote central office.
[0045] A further aspect of the invention relates to unique software
for implementing the distribution of content. A software product,
in accord with this aspect, includes at least one machine readable
medium and programming code, carried by that medium. Although the
inventive concepts encompass operation from a single, common
server, in a preferred embodiment, the code includes several
cooperating applications which may reside in separate media and run
on two or more servers or other network nodes.
[0046] A computer readable medium, as used herein, may be any
physical element or carrier wave, which can bear instructions or
code for performing a sequence of steps in a machine readable form.
Examples of physical forms of such media include floppy disks,
flexible disks, hard disks, magnetic tape, any other magnetic
medium, a CD-ROM, any other optical medium, a RAM, a ROM, a PROM,
an EPROM, a FLASH-EPROM, any other memory chip or cartridge, as
well as media bearing the software in a scannable format. A carrier
wave type of medium is any type of signal that may carry digital
information representative of the instructions or code for
performing the sequence of steps. Such a carrier wave may be
received via a wireline or fiber-optic network, via a modem, or as
a radio-frequency or infrared signal, or any other type of signal
which a computer or the like may receive and decode.
[0047] To support the QoS requirements, a feature of the preferred
embodiments involves certain queuing and tagging operations within
the switch at the intermediate node. Essentially, the switch will
maintain two or more queues for each permanent virtual circuit. The
switch distinguishes the queues based on importance. As the switch
receives cell transmissions for transport over the virtual circuit,
for example to the customer premises or between servers, the switch
will internally tag each cell as to its importance level and place
the cell in the appropriate queue. The switch may implement any one
of a number of different algorithms to select and transmit cells
from the various queues. For subscriber services, for example, the
particular algorithm is selected to implement QoS in conformance
with the subscriber's service level agreement with the carrier
and/or agreements between the carrier and the vertical services
providers.
[0048] In preferred embodiments, the same QoS mechanisms are
applied to the logical circuit(s) carrying content between the
servers. Using these mechanisms, it is possible to provision such a
circuit with a combination of a small guaranteed rate and an
"as-available" capacity, such as unspecified or available bit rate
service. Alternative embodiments use one or more ATM PVC circuits,
for each logical link between the servers. If one PVC is used, for
example, the ATM circuit may be provisional with UBR+ service, to
have a minimal reserved bandwidth in combination with an
unspecified bit rate (UBR) service.
[0049] Within the one virtual circuit assigned to the individual
subscriber, the invention actually provides multiple tiers of
service, preferably with multiple levels of QoS. Also, at different
sections along the virtual circuit "pipe," the network provides
different levels of rate shaping. All layers and all services are
available at the home, but different services receive different
treatments in the network conforming to the different levels of
QoS. The inventive approach, however, does not require each
subscriber to have multiple virtual circuits.
[0050] Services provided on the vertical services domain appear as
IP data services. Virtually any communication service may utilize
the vertical services network and through it to gain access to the
carrier's local customer base, simply by providing an IP interface
for coupling to the vertical services network. For example, it is a
simple matter to connect any digital source of broadcast audio or
video information, such as a direct satellite broadcast receiver
system similar to those used today in residential applications,
through an IP interface. Such a broadcast source and interface can
provide the full range of received video services, over the
vertical services network. The access data network may distribute
the video programming to a number of access switches within a local
geographic area. The switch provides an optimum point for frame or
cell replication for multicasting services. Hence, in our video
example, the switch replicates and distributes frames for the
broadcast service over the digital subscriber line circuits to
customers desiring to view the programming.
[0051] Additional objects, advantages and novel features of the
invention will be set forth in part in the description which
follows, and in part will become apparent to those skilled in the
art upon examination of the following and the accompanying drawings
or may be learned by practice of the invention. The objects and
advantages of the invention may be realized and attained by means
of the instrumentalities and combinations particularly pointed out
in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0052] The drawing figures depict preferred embodiments of the
present invention by way of example, not by way of limitations. In
the figures, like reference numerals refer to the same or similar
elements.
[0053] FIG. 1 is a functional block diagram of a digital subscriber
line data network supporting enhanced services in accord with the
inventive concepts.
[0054] FIG. 2 is a slightly modified functional block diagram of
network of FIG. 1, illustrating the protocol stacks used in the
various network elements.
[0055] FIG. 3 is a functional block diagram of the network showing
the service level agreements (SLAs) for which the network provides
appropriate QoS.
[0056] FIG. 4A is a logical diagram of the functional elements of
an L3/4 switch, for use in the inventive network of FIGS. 1-3.
[0057] FIG. 4B is a functional block diagram of a digital
subscriber line data network with a central content server
proximate to the hub site and a local content server in the
vertical services domain, proximate to the central office.
[0058] FIG. 4C is a bandwidth utilization graph illustrating
content distribution over bandwidth unused by subscriber traffic,
in accord with the invention.
[0059] FIG. 5 is a block diagram of a modified portion of the
network, useful in explaining migration to other types of physical
transport and switching/routing protocols.
[0060] FIG. 6 is a block diagram of a portion of the network of
FIG. 5, showing the interconnection thereof with the wide area
network and the local vertical services domain.
[0061] FIG. 7 is a block diagram of a modified embodiment of the
network, useful in explaining certain preferred aspects of the
content distribution in accord with the invention.
[0062] FIG. 8 is a block diagram of a prior art asymmetrical
digital subscriber line data network.
[0063] FIG. 9 is a slightly modified functional block diagram of
the prior art network illustrating the protocol stacks used in the
various network elements.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0064] The inventive network architecture introduces QoS into the
ADN, in a manner that enables the delivery of sophisticated and
demanding IP-based services to subscribers. The architecture does
not affect existing Internet tiers of service such that the
promised rates for such access appear the same as offered today.
Also, the new architecture is cost-effective in terms of initial
costs, build-out, and ongoing operations. The architecture utilizes
an access switch or router capable of examining and selectively
forwarding packets based on a relatively higher layers of the
protocol stack, that is to say based on information encapsulated
within the layer-2 information utilized as the lowest level
definition of connectivity through the network. The access switch
enables segregation of upstream traffic by communication type and
downstream aggregation of wide area traffic together with traffic
from a local vertical services domain.
[0065] In the downstream direction, the switch aggregates traffic
for each subscriber. The switch receives the rate-limited traffic
from the packet switched network, on the subscriber's logical
circuit. The switch also receives any downstream traffic intended
for the subscriber, from the vertical services network. The switch
combines this traffic and sends the combined communications
downstream over the subscriber's logical circuit to the customer
premises, at the optimum downstream rate that the subscriber's
facilities can support.
[0066] The upstream segregation and the downstream aggregation
allow insertion of new localized services on a "vertical" basis, at
the intermediate node. The invention encompasses vertical insertion
of a wide range of services from the new vertical domain. One class
of services, of particular interest here, relates to content
distribution from servers in the vertical domain, e.g. on-demand.
To support such services, the network should also allow efficient
distribution of content between a central or "hub" site and the
servers in the local vertical services domains.
[0067] In accord with the invention, content data stored on a
central content server at a hub site is systematically and
periodically replicated and updated to and from local content
servers in the vertical services domains at the respective central
offices. Accordingly, a customer serviced by a central office has
access to the content stored on the local content servers at a
relatively high data rate that does not substantially compromise
the rate to which the customers access a broader network, such as
the Internet. Data replicated from the central content server to
the respective local content servers can be conveniently
communicated over the link between the hub site and central
offices, which also carries the customers' broader network traffic.
The present invention mitigates the problem of network congestion
during replication of data between the central content server and
the respective local content servers, by only transferring such
content data using bandwidth that is not used by the broader
class(es) of network traffic. This aspect of the invention requires
continuous analysis of the bandwidth utilizational of the link
between the hub site and the respective central offices.
[0068] FIG. 1 provides a high-level functional illustration of an
exemplary digital subscriber line network, specifically an ADSL
data network 10, implementing the various concepts of the present
invention. FIG. 2 provides an alternative functional illustration
of the elements of such a network. Of particular note, FIG. 2 shows
the various protocol stacks associated with the appropriate network
elements that utilize those stacks. The end-user may be a single PC
user or a small business or a residential LAN user. The data
equipment of such users typically includes servers and PCs and may
include a variety of other devices, such as fax machines,
televisions, recorders and remote controlled appliances, having
data communication capabilities.
[0069] The customer access link comprises an XDSL twisted pair,
although those skilled in the art will recognize that the invention
is readily adaptable to networks using other types of links to the
subscriber premises. In the illustrated embodiment, the network 10
supports ADSL, which the carrier may offer in grades supporting 640
kbps, 1.6 Mbps or 7.1 Mbps (downstream) rates for Internet access.
The actual communications over the DSL loops, however, run
adaptively at the maximum rates that the line conditions allow.
[0070] The illustrated first embodiment of the ADSL-based local
access data network or "ADN" 10 provides access to two different
network domains for communication services. The two network domains
are logically separate. In most implementations, the first domain
may be considered as a long distance or wide area domain, whereas
the second domain is a local network domain. In the illustrated
example, the ADN 10 provides access to a first domain in the form
of a wide area internetwork, such as the public Internet, corporate
local area networks (LANs), and the like, represented by the
network cloud 11 for the ISPs. The high speeds available through
the local network 10 enable a wide range of communications, for
example, of text data, of video data, for multimedia, for web
browsing, of transfers of files, for database searching, and the
like via the network(s) 11.
[0071] The inventive ADSL-based local access network 10 also offers
access to a wide variety of other IP-based services through a local
data network 13 serving as the vertical services domain (VSD). The
vertical services typically are high-end services requiring certain
QoS levels and often having a certain local characteristic. Many of
these services entail distribution of content, from local storage
servers in the vertical services domain to actual customers.
Examples of the vertical services, including content distribution
services, are discussed in more detail later. The vertical services
network offers an efficient domain from which the carrier can
locally inject high-end services and/or services of other local
providers. Because the vertical services domain is separate from
the public Internet, equipment providing the vertical services is
not subject to attacks directly from the public Internet.
[0072] The invention in this case particularly involves content
distribution between a hub site and the servers in various vertical
services domains. However, to appreciate the operation and
advantages of that aspect of the invention, it may be helpful first
to consider the overall network operation and the details of the
vertical services insertion.
[0073] As shown in FIGS. 1 and 2, a central office (CO) 15
comprises one or more DSLAMs 17 and L3/4 ATM switch 19. Elements of
the CO 15 providing plain old telephone service (POTS) have been
omitted for simplicity of illustration, since they are generally
similar to those shown in FIGS. 8 and 9.
[0074] The switch 19 is designated as an "L3/4" switch here as a
matter of convenience, to illustrate that the switch 19 has the
capability to make selective packet forwarding decisions based on
protocol information at some level that is above the L2 level that
the switch normally utilizes to define or establish logical circuit
connectivity. It will be recognized, however, that some of the
protocols, although higher than the ATM type level 2 protocol used
by the preferred switch are themselves often thought of as level 2
protocols even though they are above or encapsulated in the ATM
type level 2 information. Also, decisions as to the selective
forwarding may be made in response to monitoring of any level of
the protocol stack above the L2 level that the switch normally
utilizes to define or establish logical circuit connectivity, for
example from any level above ATM all the way up to the L7
application layer.
[0075] Returning to the discussion of FIGS. 1 and 2, for purposes
of this discussion, assume that the equipment at the various
customer premises connect directly to the CO 15 via twisted pair
type copper wiring 21. In an actual implementation, many customers
may connect through such wiring to a remote terminal linked to the
CO 15 via optical fiber. Other hardwired, optical or wireless
implementations of the digital subscriber lines are discussed
later. In the illustrated embodiment, each line 21 from a customer
premises connects to an ATU-C within one of the DSLAMs 17.
[0076] On the customer premises side, the digital subscriber line
circuit 21 connects to an ADSL terminal unit (remote) or ATU-R 23.
The ATU-R 23 is a modulator/demodulator (modem) for communicating
over a twisted wire pair type line 21, in accord with the ADSL
protocols. The ATU-R in turn connects to customer premises
equipment, shown by way of example as a PC 25 at each location
(FIGS. 1 and 2). Those skilled in the art will recognize that the
customer premises equipment 25 may include a wide range of other
types of devices having data communications capabilities (see e.g.,
FIG. 3).
[0077] The ADSL user's normal telephone equipment (not shown) also
connects to the line 21, either directly or through a frequency
combiner/splitter, which often is incorporated in the ATU-R. The
normal telephone signals are split off at both ends of the line and
processed in the normal manner.
[0078] For digital data communication purposes, the ATU-C and ATU-R
modem units create at least two logical channels in the frequency
spectrum above that used for the normal telephone traffic. One of
these channels is a medium speed duplex channel; the other is a
high-speed downstream only channel. Such modems may implement
either one of two techniques for dividing the usable bandwidth of
the telephone line to provide these channels. One approach is to
divide the usable bandwidth of a twisted wire pair telephone line
by frequency, that is to say by Frequency Division Multiplexing
(FDM). The other approach uses Echo Cancellation. FDM uses one
frequency band for upstream data and another frequency band for
downstream data. The downstream path is then divided by time
division multiplexing signals into one or more high-speed channels
and one or more low speed channels. The upstream path also may be
time-division multiplexed into corresponding low speed channels.
With echo Cancellation, the upstream band and downstream band
substantially over-lap. The modems separate the upstream and
downstream signals by means of local echo cancellors, in a manner
similar to that used in V.32 and V.34 modems.
[0079] The DSL modems may use a number of different modulation
techniques to physically transport digital data streams. A number
of implementations of the modems have used carrierless amplitude
phase (CAP) modulation. Most current xDSL modems, however, utilize
a discrete multi-tone (DMT) approach.
[0080] Returning to the discussion of the CO 11, the structure and
operation of each DSLAM 17 is essentially the same as those of the
DSLAM 111 in the embodiment of FIG. 8, except that the control
functionality of the DSLAM 17 is somewhat different. The DSLAM 17
controls the ATU-Cs to implement a rate-adaptive ADSL service, to
adapt operations so as to maximize data rates for the
communications over the individual subscriber lines. Essentially,
the ATU-Cs and ATU-Rs signal each other over the lines to
synchronize their modes of operation at parameter settings, which
achieve optimum data throughput. Also, the DSLAM 17 does not need
to monitor or limit the line rates, but instead relies on the
rate-adaptive control algorithm to maximize the rates achieved over
the ADSL circuits or provide rate-shaping for the ATM virtual
circuits. Other network elements limit rates, where necessary.
[0081] The L3/4 ATM switch 19 is co-located with the DSLAMs 17,
within one central office 15. As a result, it is practical to
connect the multiplexer within each of the DSLAMs 17 over a
high-speed data link directly to an appropriate port of the ATM
switch 19. Because these links are short, there is little or no
cost imposed when implementing such links using wideband equipment.
By itself, the co-location of the L3/4 ATM switch 19 with the
DSLAM(s) 17 does not increase bandwidth. Rather, it makes increased
bandwidth at the network edge economically feasible, due to
proximity. Co-location removes the requirement to purchase
expensive wide area transport (the SONET ring) to increase
bandwidth. In particular, the direct OC3/OC12 connections between
the DSLAM 17 and the L3/4 ATM switch 19 do not incur any recurring
tariff expenses.
[0082] The ATM switch 19 connects through a SONET ring 27 to a
gateway router 29 providing ATM transport through a cell relay
network 30 (FIG. 2) to the ISPs shown at network 11 in the
drawings. Most of the ISPs will utilize a concentrator or other
equipment as their point of presence for Internet access (FIG. 2).
In the preferred embodiment, the equipment 31 provides a
point-to-point protocol (PPP) interface designed for transport over
Ethernet (PPPoE). The ATM switch 19 also provides a connection to
the local implementation of the VSD network 13, for example via a
giga-bit Ethernet port to a switch or other local network elements
18.
[0083] The illustrated local access type ADN network 10 provides
ATM cell transport from the customer premises to the ISP network(s)
11. The ATM cells serve as the layer-2 protocol for defining
contiguous switched connectivity. Higher level routing protocols,
such as Ethernet and TCP/IP frames, ride within the ATM cells.
Services of different types utilize different protocols at one or
more layers above the ATM cell layer. In the preferred embodiments,
all communications utilize Ethernet. However, communications to and
from the ISPs use the noted PPPoE type Ethernet protocol. In
contrast, communications to and from the vertical services domain
use one or more of the other Ethertype protocols.
[0084] To efficiently provide cell relay, each customer is assigned
a virtual circuit that extends from the ATU-R 23 in the respective
customer premises to the gateway router 29. This logical circuit is
defined at the layer-2 protocol level. The presently preferred
embodiments implement this logical communication circuit as an ATM
permanent virtual circuit, although the inventive concepts may
apply to other types of logical circuits or channels.
[0085] The gateway router 29 is the communication node of the
access network 10 providing access to the wide area IP packet
networks, of corporations or more often of Internet Service
providers. The gateway router 29 terminates permanent virtual
circuits through the cell relay network 30, from the equipment 31
of each such wide area packet network provider 11. The gateway
router 29 also terminates the permanent virtual circuits from the
subscribers through the data network 10. For communication with a
selected ISP network 11, for example, the gateway router 29 routes
cells from the permanent virtual circuit from the subscriber
through to the permanent virtual circuit of the selected ISP
network 11. In the opposite direction, the gateway router 29 routes
cells from the permanent virtual circuit from the selected ISP
network 11 through to the permanent virtual circuit of the
particular subscriber.
[0086] For the leg of the subscriber's logical circuit, extending
from the L3/4 ATM switch 19 through the gateway router 29, the
carrier programs one or more nodes along the path behind the DSLAMs
17, to regulate traffic on the virtual circuit to the rate
corresponding to the grade of Internet access service to which the
particular customer subscribes. In the preferred embodiment, at
least one such node performing this rate shaping function is the
L3/4 ATM switch 19. All traffic going to and from the ISP
network(s) 11 therefore is still limited to the rates defined in
the service level agreement (SLA) for Internet access that the
carrier has with the particular customer.
[0087] The portion of the virtual circuit extending between the ATM
switch 19 and the ATU-R 23, however, is not rate limited but
instead runs at the maximum rate that the line will support using
the rate-adaptive ADSL modem operation. In most cases, the
rate-adaptive ADSL modem operation will support rates substantially
higher than the subscription rate for Internet access service.
[0088] The L3/4 ATM switch 19 also provides the interconnection to
the subscriber's virtual circuit for insertion of downstream
traffic from the vertical services domain 13 and separation of
upstream traffic from the subscriber's virtual circuit going to the
vertical services domain 13. In the preferred embodiments,
decisions as to whether upstream traffic is destined for the
vertical services domain 13 or should remain on the subscriber's
virtual circuit going through the gateway router 29 and the cell
relay network 30 to the ISPs 11 are based on an analysis of traffic
type. The traffic type analysis relies on protocol information
contained in the communications, which relates to layers of the
protocol stack that are higher than the layer-2 switching protocol,
in this case above the ATM layer.
[0089] As shown in FIG. 2, traffic destined for an ISP 11 utilizes
a variation of a point to point protocol (PPP) intended to run on
top of Ethernet, referred to as PPP over Ethernet or "PPPoE." A
`type` indicator contained within the Ethernet frames identifies
the PPPoE protocol. In contrast, traffic going to and from the
vertical services domain utilizes other `types` of Ethernet
protocol. All traffic to and from the customer premises uses
Ethernet frames carried within ATM cells.
[0090] The switch 19 therefore routes a subscriber's traffic going
to and from an ISP 11, upon detection of the PPPoE indicator in the
level 3 data contained within the Ethernet cells. This traffic will
also utilize public IP addressing. In contrast, the ATM switch 19
routes a subscriber's traffic going to and from the vertical
services domain, upon detection of any other type of Ethernet
protocol at level 3 or above in the protocol stack. The IP
addressing in the vertical services domain 13 utilizes private-IP
addresses, for example, as administered with a DHCP server (not
shown) coupled to the network cloud 33. Although shown separately,
the cloud 33 may be implemented as a portion of the network
providing the physical elements of the vertical services domain.
The portion 33, however, would typically be a logically separate
domain that the carrier controls and restricts for its own network
administration use.
[0091] FIG. 3 depicts the logical division of the subscriber's
traffic, as implemented at the ATM switch 19 in accord with the
invention. As shown, the network 10 provides a logical "pipe" or
circuit 35 extending to the networks 11 of one or more of the ISPs,
for an Internet access application. The ATM switch 19 (FIG. 1)
preferably performs a rate shaping or control function. The leg 35
of the subscriber's traffic extending to the ISP 11 provides
upstream and downstream communication rates conforming to a service
level agreement (SLA) applicable to the subscriber's Internet
access application. As such, the communications over the
subscriber's logical circuit, extending from the switch to the ISP,
provide a first level of QoS. To the subscriber, service over the
leg 35 appears the same as a subscriber selected grade of Internet
access service as provided by older ADN architectures. FIG. 3
illustrates chat rooms, web surfing and e-mail as examples of
services an ISP might offer through the Internet Application SLA
circuit 35 and the attendant portion of the subscriber's assigned
logical circuit through the access network.
[0092] The network 10 also supports communications over one or more
logical application paths 36 to local applications 37 hosted in the
vertical services domain. Assuming that a subscriber with various
equipment 25 also subscribes or otherwise participates in one or
more of the vertical services, the local carrier (e.g. Verizon
Communications in FIG. 3) offers a corresponding number of
additional application SLAs with the customer. Each SLA for a
vertical service may specify QoS parameters for the particular
application, such as rate/bandwidth, latency, jitter, packet loss,
packet sequence, security and/or availability. Examples of such
applications hosted in the carrier's vertical services domain 37
include the illustrated voice over IP service shown as a V/IP
gateway, as well as video services and some caching for high volume
local web services. Communications for such applications utilize
the one or more paths 36. The present invention also supports
segregation and aggregation of traffic for three or more domains,
based on the higher-level traffic type analysis.
[0093] A feature of the switch, in accord with the invention, is
that it prioritizes traffic for each customer to support QoS for
the various services as required by service level agreements (SLAs)
between the customer and the carrier. In this regard, one
implementation of the L3/4 ATM switch 19 performs queuing and
tagging operations in accord with the desired prioritization. The
switch will maintain two or more queues for each subscriber's
permanent virtual circuit. The switch distinguishes the queues
based on importance or priority. As the switch receives cell
transmissions for transport over the virtual circuit to the
customer premises, the switch will internally tag each cell as to
its importance level and place each cell in the appropriate queue
based on the tag.
[0094] The tagging and prioritization may be based on traffic type
or `Type of Service` (ToS). Table 1 illustrates one example of the
possible ToS levels that may be assigned to different
communications. TABLE-US-00001 TABLE 1 Internal Customer BA Mgmt
Traffic Traffic Relative ToS AR Encapsulated Rewritten Priority
Value Queuing TOS TOS Critical 0 WFQ OSPF, SNMP, Management
(Control ICMP, BGP 25%) Future 1 Real Time 2 WFQ Port numbers
Interactive (High identified 40%) IP 3 WFQ ICMP, IGMP, EGP, IGMP,
RADIUS Application (Medium DNS, H.323 signal- Control 30%) ing,
BGP, SIP, Microsoft Media Player Streaming Media Control, RTSP One
Way 4 UDP Streaming (ports 1024+) Media One Way 5 HTTP, HTTPS,
Batch SNMP, Telnet Unknown 6 WFQ Other Other (Low 5%) Non time 7
FTP, TFTP, sensitive SMTP
[0095] The access switch 19 will examine the content of each
communication and determine an appropriate ToS level, for example
in accord with the table above. Based on the ToS level, the switch
will add a tag to the cell(s) as part of its internal processing.
Using the ToS tags, the switch will place each of the cells for a
given subscriber into a corresponding one of a plurality of queues
that the switch maintains for the subscriber's traffic.
[0096] The switch may implement any one of a number of different
queue servicing algorithms to select and transmit cells from the
various queues. For example, the switch 19 may implement one of
several statistical algorithms, equal queuing, weighted queuing,
priority selection from queues, etc. The particular algorithm is
selected to implement QoS in conformance with the subscriber's
service level agreements (SLAs) with the carrier. In most cases,
particularly for service applications from the vertical services
domain, the switch 19 will not normally drop any cells or packets.
In the rare event that the switch 19 becomes congested, any
dropping of cells is based on the priority level assigned to the
frame, i.e., lowest priority first. Also, if the switch ever drops
cells, it drops all cells for an effected lowest priority frame
from the relevant queue.
[0097] The ability to prioritize traffic across the vertically
inserted streams and the wide area (typically Internet) stream
enables the operator to control flows through the ADN 10 so that
the local access facility is not overwhelmed with content which
exceeds its physical (rate adaptive) limitations. For example, the
queuing rules preferably ensure that the `proper` applications
(based on insertion device based rules) obtain access to the
limited rate adaptive bandwidth available on any given subscriber's
line. Also, the insertion point, switch 19, will usually sit behind
the media conversion point (e.g., the DSLAM 17). An OC3 or other
facility between the switch 19 and the DSLAM 17 also could become
congested. Preferably, the switch 19 or other element at the
insertion point queues the traffic in such a manner that no
downstream facility (OC3) limitations (which are independent of the
rate adaptive DSL loop limitations) will result in packets being
dropped.
[0098] The queuing will be done based on customer and network
provider determined rules so that contention for the facilities
facing the subscriber will be addressed via the dropping of the
appropriate packets. That way an inserted video stream doesn't
overwhelm an Internet or Voice stream (due to facility
limitations). Among others, appropriate industry understood methods
for accomplishing this queuing control include Weighted Fair
Queuing (WFQ), Priority (PQ) Queuing, and Weighted Random Early
Discard (WRED).
[0099] Also, the ability of the switch 19 to examine higher level
information provides other advantages in network operations. For
example, the switch can implement sophisticated filters on the
higher level information, e.g., to provide security. As another
example, the switch preferably performs measuring and monitoring to
determine what if any packets are dropped (based on the physical
rate adaptive limitations), and generates appropriate reports to an
external operations system (not shown).
[0100] The introduction of the L3/4 ATM switch 19 in proximity to
the DSLAM(s) 17 also provides benefits in terms of operation of the
gateway router 29. Due to the end-to-end use of the Unspecified Bit
Rate (UBR) PVCs, the gateway router interface to the cell relay
network 30 has been engineered to support a maximum of 2000-4000
PVCs (end users). This is essentially an over-provisioning of
bandwidth that probabilistically avoids service degradation that
could result from simultaneous demand for bandwidth. The ability of
the L3/4 ATM switch 19 to perform QoS and rate shaping essentially
reduces or ever removes this concern, because it significantly
reduces the risk that the gateway router 29 will become a
bottleneck. As a result, the ADN 10 can increase bandwidth
efficiencies for this interface. Further, the capacity through the
gateway router 29 need not be upgraded as often to support demand
for increased bandwidth associated with new bandwidth-intensive
services, since many such services are now introduced through the
vertical services domain 13 and the L3/4 ATM switch 19.
[0101] To fully understand an exemplary implementation of the
various inventive concepts, it may be helpful to consider an
ATM-based embodiment of the L3/4 switch 19. FIG. 4A is a block
diagram of the elements and functions of such a preferred
embodiment of the switch 19.
[0102] The preferred embodiments utilize Ethernet framing. As shown
in the drawing, the switch 19 includes an Ethernet interface 41, an
ATM interface 42 and an associated physical interface 43 facing
toward the subscribers. In an embodiment for use in the network of
FIGS. 1 and 2, the physical interface might take the form of one or
more OC-3 or OC-12 links to the DSLAMs 17. These links carry all
ATM cell traffic going to and from the DSLAMs and hence to and from
the customer equipment served through the particular switch 19.
[0103] The switch 19 also includes an Ethernet interface 44, an ATM
interface 45 and associated physical interface 46 facing toward the
gateway router 29 and hence the ISPs 11. The physical interface 46
might take the form of one or more OC-12 or OC-48 links to the
gateway router 29. These links carry all ATM cell traffic going to
and from the ISPs or other wide area inter-networks 11. For these
communications, the Ethernet interface 44 passes through PPPoE
traffic, as specified by the Ethertype indicator in the cells
transporting the relevant frame segments.
[0104] Facing the vertical services domain, the switch 19 includes
an Ethernet interface 47 and a physical interface 48. These
interfaces conform to the particular network utilized by the
carrier for the vertical services domain, such as giga-bit Ethernet
over wire or optical links.
[0105] The switch fabric 49 performs the physical switching of data
along various paths through the switch 19, in response to
instructions from a programmed routing controller 50. FIG. 4A also
shows the communications flow through the switch, for each
subscriber. The switch 19 also implements a Decision Point 51,
shown for example within the Ethernet interface processing 41 on
the subscriber facing side. At that point, the PPPoE traffic is
separated from all other traffic. From that point, the PPPoE Flow
52 for each subscriber extends as a portion of the subscriber's ATM
virtual circuit, facing the cell relay network and hence the ISPs
11. The PPPoE Flow 52 contains Ethernet frames that are of PPPoE
Ethertype. Facing towards the subscriber premises, the switch 19
implements an Aggregate Flow path 53, in the form of another
portion of the ATM virtual circuit, which contains all
ingress/egress subscriber traffic. The switch implements a Generic
Path 54 extending through the interfaces to the vertical services
network. In the first embodiment, this path 54 carries all traffic
other than PPPoE.
[0106] In this example, the switch 19 implements the Decision Point
51 based on recognition of the Ethertype indicator, which is above
the layer-2 ATM cell routing information. However, the switch may
implement the Decision Point 51 based on still higher-level
protocol information. Also, those skilled in the art will recognize
that the concepts of the present invention are applicable in
networks using different protocol stacks, for example, based on
native IP.
[0107] In a preferred embodiment, the Ethernet and ATM interfaces
41 and 42 and the Ethernet and ATM interfaces 44 and 45 implement
segmentation and reassemble (SAR) functions, essentially providing
two-way conversions between ATM cell format and Ethernet frame
format. Segmentation involves dividing an Ethernet frame into a
number of 48-byte blocks and adding ATM headers to the blocks to
form a corresponding number of ATM cells. Any blocks that do not
include a complete 48-byte payload are padded as necessary.
Reassembly entails receiving and buffering ATM cells until it is
recognized that a complete frame has been received. The ATM headers
of the cells and any padding are stripped, and the payload data is
reassembled into the form of an Ethernet frame.
[0108] In such an embodiment of the switch 19, the decision point
51 determines how to selectively forward the Ethernet frame
information taken from a particular series of upstream ATM cells
based on the Ethernet information taken from the ATM cell payloads,
for example, by examining the frame header and recognizing the
particular Ethertype indicator. Internally, the actual switch
fabric 49 for such an embodiment of the switch 19 would comprise an
Ethernet switch, even though to other elements of the ADN network
10 the switch 19 appears to perform an ATM switching function.
[0109] Those skilled in the art will recognize however, that the
decision and switch fabric may be implemented in other ways. For
example, a series of cells corresponding to an Ethernet frame could
be buffered and the payloads examined just to recognize and
identify the Ethertype indicator, without a complete reassemble of
the Ethernet frame. This later implementation therefore could
utilize an ATM cell-based switch fabric.
[0110] From the discussion above, it should already be apparent
that certain aspects of the invention relate to setting up logical
communication circuits at a relatively low protocol layer
corresponding to switching or routing functions and then
segregating traffic by distinguishing communication type using
higher level protocol information. To insure full understanding on
these points, it may be helpful to consider the protocol layer
definitions, with particular reference to the illustration of the
preferred layers in FIG. 2. The International Standards
Organization (ISO) Open Systems Interconnection (OSI) reference
model specifies a hierarchy of protocol layers and defines the
function of each layer in the network.
[0111] The lowest layer defined by the OSI model is the physical
layer (L1). This layer provides transmission of raw data bits over
the physical communication channel through the particular network.
For example, on the subscriber lines in the preferred embodiment,
the physical layer (L1) uses ADSL. Within the customer premises,
communications use an Ethernet physical layer (L1), such as
10Base-T. Upstream network elements may use DS3 at some points, but
most use SONET, for example OC-3 or OC-12 physical layer transport.
Attention is directed to the lower half of the diagram in FIG. 2,
which depicts the various protocol stacks throughout the network
10.
[0112] The layer defined by the OSI model next to the physical
layer is the data link layer (L2). The data link layer transforms
the physical layer, which interfaces directly with the channel
medium, into a communication link that appears error-free to the
next layer above, known as the network layer (L3). The data link
layer performs such functions as structuring data into packets or
frames, and attaching control information to the packets or frames,
such as checksums for error detection, and packet numbers. In the
network 10, the data link layer (L2) is used to define certain
switching functions through the network. The network layer (L3)
provides capabilities required to control connections between end
systems through the network, e.g., set-up and tear-down of
connections.
[0113] The preferred embodiments utilize ATM cell transport as the
lowest element of the data link layer (L2), for example to define
the connectivity extending from the ATU-Rs 23 through the ADN
network 10 to the ISP or corporate networks 11. Subscriber virtual
circuits are provisioned at the ATM cell layer, that is to say at
the data link layer (L2). Similarly ISP virtual circuits are
provisioned at this ATM data link layer (L2), from the gateway
router 29 through the cell relay network 30 to the ISP access
concentrators 31. The ATM protocol therefore is the layer-2 (L2)
protocol used to define the logical connectivity from the
subscriber premises to the gateway router 29. The ATM protocol also
is the layer-2 (L2) protocol used to define the logical
connectivity from the gateway router 29 to the ISP concentrators
31.
[0114] For purposes of this discussion, higher level protocols are
protocols that ride on or are encapsulated within the particular
layer-2 protocol, that is to say in the payloads of the ATM cells
in the preferred embodiment. Such higher level protocols include
some protocols, which are often considered themselves to be level-2
protocols, where they are transported within ATM cells. The
preferred embodiments use Ethernet, a local area network protocol
above the ATM portion of the L2 layer. Technically, the Ethernet
protocol may be considered as another L2 layer protocol. However,
because it is segmented and encapsulated into the payloads of the
ATM cells, the Ethernet protocol information actually is a higher
level protocol information above the specific level-2 protocol
(ATM) that defines the normal connectivity through the ADN network
10.
[0115] In the OSI model, a transport layer protocol (L4) runs above
the network layer. The transport layer provides control of data
transfer between end systems. Above the transport layer, a session
layer (L5) is responsible for establishing and managing
communication between presentation entities. For example, the
session layer determines which entity communicates at a given time
and establishes any necessary synchronization between the entities.
Above the session layer, a presentation layer (L6) serves to
represent information transferred between applications in a manner
that preserves its meaning (semantics) while resolving differences
in the actual representation (syntax). A protocol (L7) that is
specific to the actual application that utilizes the information
communicated runs at the top of the protocol stack.
[0116] In accord with one inventive concept, the network 10
actually utilizes two or more different types of protocol at levels
above the protocol within the L2 layer that actually defines the
network connectivity. The ADN network 10 may use different
protocols at the higher layers as well. By distinguishing
transmissions based on differences in these higher-level protocol
types, the ATM switch 19 separately forwards different types of
communication traffic for each subscriber. In the preferred
embodiment, communications to and from the ISP or corporate
networks 11 utilize point-to-point protocol (PPP) as the network
layer (L3) protocol and a shim for transport of PPP over Ethernet
(PPPoE). PPPoE, as one Ethertype protocol could also be considered
as a second layer (L2) protocol albeit above the Ethernet layer
itself, which in turn rides on the ATM cells used for routing at
least through the permanent virtual circuit at the L2 layer.
[0117] In the illustrated implementation, however, the use of the
PPPoE or a different protocol actually is an indication of a
difference in type of the higher layer protocols. In the
illustrated example of FIG. 2, the vertical services domain traffic
utilizes Ethernet (802.3 SNAP) above the ATM adaptation layer
(AAL). As noted, the presently preferred L3/4 switch 19 implements
its routing decision based on recognition of the Ethertype
indicator, that is to say to distinguish the PPPoE traffic from all
other types of transmission from the customers' data equipment. In
view of the use of ATM as the data link layer (L2) protocol of the
network defining the lowest layer of network connectivity for
communications services through the ADN network 10, the
discrimination based on Ethernet actually implements a decision
based on an effectively higher protocol layer.
[0118] IP protocol carries the actual higher-level applications
information, for transport to and from the vertical services domain
and for transport to and from the wide area internetwork. As such,
IP and its related transport protocol referred to as the
"Transmission Control Protocol" (TCP) ride on top of (are actually
encapsulated within) the lower level protocol elements discussed
above. Presentation and application layer elements ride on top of
the IP layer. IP communication requires that each user device have
an assigned IP address. IP addresses, however, are a scarce
commodity. Because of the use of IP transport for both wide area
services and vertical domain services, the network 10 actually may
at times assign two different IP addresses to each active data
communication device of an end-user, albeit on a temporary basis.
The wide area communications and the vertical services network may
also be viewed as two separate `broadcast` domains.
[0119] First, the carrier operating the ADSL data network 10 and
the vertical services domain network 13 will maintain a pool of
local addresses for assignment, on an as-needed basis, to end user
equipment 25. To the carrier, the available IP addresses are a
limited resource. Accordingly, the carrier assigns IP addresses on
a dynamic basis, only to those users actually on-line at any given
time. The carrier preferably utilizes private network type IP
addresses and dynamically administers such addresses using dynamic
host configuration protocol (DHCP). DHCP is a protocol for
automatic TCP/IP configuration, which enables dynamic address
allocation and management.
[0120] When a particular device 25 becomes active via the ATU-R 23
and the DSLAM 17, it will activate a basic protocol stack,
including an IP portion enabling communication with a DHCP server.
The device will transmit an address request upstream through the
network on the subscriber's virtual circuit. At the Ethernet level,
this transmission appears as a broadcast message. The L3/4 ATM
switch 19, however, will recognize that the packet is not a PPPoE
communication and route the cells carrying the packet into the
vertical services domain 13. Typically, a DHCP server is coupled to
the vertical services domain network 13, for example as part of the
carrier's administrative network or systems 33. The DHCP server
somewhere on the vertical services domain 13, 33 will answer that
broadcast request by selecting and providing an available one of
the private IP addresses from the carrier's pool of available
addresses. The message with the assigned address will go back to
the L3/4 ATM switch 19 for insertion into the virtual circuit and
transport back to the requesting device 25.
[0121] The particular end-user's device 25 uses the assigned
private IP address as its source address, for all of its
communications with the vertical services network 13, so long as it
remains on-line for the present session. When the overall session
ends and the end-user device 25 goes completely off-line, the DHCP
server returns the private IP address to its pool of available
addresses, for reassignment to another user as the next user comes
on-line.
[0122] As noted, the user equipment 25 receives a private IP
address from the DHCP server. The addresses of services on the
vertical services domain also are private IP networks. Because
these addresses are private, they are accessible only to equipment
within that domain and the data network 10. Consequently, the
devices are not accessible to hackers or the like coming in through
the public Internet.
[0123] This dynamic assignment of IP addresses allows the carrier
to limit the number of IP addresses used to the number of users
actively connected through the ISP's host to the Internet. The use
of private IP addresses allows the user equipment to communicate
with the vertical services domain utilizing a normal IP-Ethernet
protocol stack.
[0124] For the as-desired Internet access service, for example
using a PPP or similar protocol, IP addresses are administered
through the ISPs. The PPPoE protocol preserves or emulates the
traditional dial-up approach to ISP access. However, the PPPoE
approach does utilize Ethernet and follows Ethernet standards, for
example, involving processing of certain broadcast messages.
[0125] The user can select an ISP of choice, and her data equipment
25 will initiate a selective session through the Ethernet layer on
the network 10 to access the equipment 31 of the selected ISP
network 11, in a manner directly analogous to a dial-up modem call
through an ordinary telephone network. Hence at a time after
initial activation through the networks 10 and 13, the user may
activate a browser or other program for using the wide area
internetwork service. This activates a second protocol stack, which
includes the PPP protocol and the PPPoE shim. The user selects an
ISP, and the data equipment initiates communication through the
network 10 to the PPPoE equipment 31 of that ISP.
[0126] The IP addresses used by each ISP are public network type IP
addresses. To the ISP, the pool of available public IP addresses
also is a limited resource. Accordingly, each ISP prefers to assign
IP addresses on a dynamic basis, only to those users actually
on-line at any given time. Typically, as part of each initial
access operation for a PPPoE session, the user's equipment 25 and
the PPP terminating equipment 31 of the ISP conduct a handshaking,
to establish data communications therebetween. As part of this
operation, the user's device transmits a broadcast request for a
public IP network. The broadcast message, in PPPoE goes through the
virtual circuit to the gateway router 29 and through the router and
cell relay network 30 to the ISPs PPPoE equipment 31. Although it
is a broadcast message, the network effectively limits transport
thereof to the virtual circuit going to the ISPs PPPoE equipment
31, that is to a domain separate from the vertical services network
domain 13.
[0127] The ISP host equipment 31 initiates a procedure to assign
the user's computer 25 a numeric Internet Protocol (IP) address
from the pool of available public addresses and sends a PPPoE
message containing that address back to the subscriber's device 25.
When the session ends and the user goes off-line, the ISP host can
reassign the address to another user, as the next user comes
on-line.
[0128] This dynamic assignment of IP addresses allows the ISP to
limit the number of public IP addresses used to the number of users
actively connected through the ISP's host to the Internet. The
end-user equipment will implement a second protocol stack, carrying
PPPoE communications. The PPP protocol will allow the end-user
equipment to obtain and utilize the public IP address for
communications going to and from the public internetwork.
[0129] The switch 19 will limit transport of other types of PPPoE
broadcast messages to the link to the PPPoE concentrator 31, in a
manner similar to that described above for the PPPoE address
request. The switch 19 also limits transport of non-PPPoE broadcast
messages to the vertical services domain network 131, both for the
address request message and for other types of broadcast requests.
As such, the logical circuit to the PPPoE concentrator 31 becomes
the conduit to one broadcast domain for upstream PPPoE messages;
and the vertical services network 13 defines a second broadcast
domain for upstream messages of other Ethertypes.
[0130] As noted, the end-user equipment 25 will implement two
protocol stacks, a native stack without PPPoE and a second stack
with PPPoE and a shim. In actual operation, both the native stack
with other Ethernet protocols and the wide area stack with PPP and
the PPPoE shim often will be active at the same time. The software
in the data equipment 25 will utilize one stack or the other
depending on whether the user selected a link, e.g. a URL, relating
to the wide area internetwork or the vertical services domain. For
example, a browser may display a page with embedded links. If a
link is to a service on the vertical services domain, the embedded
address will be a private address on the vertical services domain.
Selection of such a link causes the device 25 to use the native
Ethernet stack (without PPP or PPPoE) and the private address.
Hence the L3/4 ATM switch 19 routes the request triggered by
selection of the link to the vertical services domain 13. In
contrast, if the link is to a service on the public Internet or
other network 11, the embedded address will be a public IP address.
Selection of such a link causes the end-user device 25 to use the
PPP and PPPoE stack and the public address. Hence the L3/4 ATM
switch 19 routes the request triggered by selection of the link
over the virtual circuits to the PPPoE equipment 31 of the
currently selected access provider network 11.
[0131] Services provided on the vertical services domain therefore
appear as simple IP data services, albeit using the appropriate
address space. Virtually any communication service provider may
access the vertical services network 13 and through it the
carrier's local customer base simply by providing an IP interface
for coupling appropriate equipment to the vertical services
network.
[0132] In addition to vertical services, the carrier continues to
provide agreed access services to the equipment of the ISPs, in a
manner analogous to current practices. For example, the carrier may
provide its Internet access service to a subscriber on a monthly
subscription basis, at one of several available rates corresponding
to the grade of internet access service (and thus the rate of
communication to/from the ISP) selected by the customer's
subscription.
[0133] In an enhanced service offering, the broadcast provider
could offer a convenient navigation interface from a web server.
The server could be on the vertical services network, but
preferably is on the wide area Internet 11. With a PPPoE session
active, the user can surf to the provider's server and view
information about available programming. The user might select a
current broadcast program by `clicking` on a URL link in the
provider's web-based information. Although provided through the
wide area Internet 11, the URL would actually contain the private
IP address for the desired broadcast program available from the
vertical services network 13. Selection of such a URL therefore
would generate a message to the appropriate server on the vertical
services network 11 to initiate the above discussed procedure to
allow the user to `join` the selected broadcast. A similar
methodology might also enable a provider to offer menu, selection
and order/billing services from the Internet 11, to provide
pay-per-view or video on-demand type services from the vertical
services domain network 13.
[0134] For on-demand content service, such as the downloading of
movies, music, games, on-line books, and other bulk on-demand data,
the content provider can store such data in a local content server
32 in the vertical services domain 13, as shown in FIG. 4B. In one
embodiment, a user might download content stored on the local
content server 32 by entering a URL or selecting a web-based link
to the vertical services domain (without PPP or PPPoE) directing
the download request to the local content server 32. As described
above, the content will be transmitted to the end user through the
VSI ATM switch 19, DSLAM 17, and ATU-R 23.
[0135] Certain aspects of the invention relate to distribution of
content to or from such a server 32 in the vertical services
domain. The content stored on the local content server 32 can, in
one embodiment, be distributed to the local content server 32 from
a hub site 24 separated from the central office 15 by a
transmission line 27. It is often desirable to distribute content
in this manner for many reasons. One such reason is that it is
often desirable for content to be distributed or updated
frequently. For example, if the content is a movie in a digital
format and end users want the most recently released movies, the
content on the local content server 32 must be updated often to
include the most recently released movies in digital format.
Another reason why it is desirable for content to be distributed
through transmission line 27 is that such a distribution can be
automatic and require minimal maintenance by a system administrator
at the central office 15. One of ordinary skill in the art would
recognize other advantages of distributing content from a central
content server 28 to a number of dispersed local content servers
32.
[0136] Typically a hub site 24, housing the gateway router 29,
services several remote central offices 15. The hub site 24 is a
prime location for housing a central content server 28. The central
content server 28 stores content that is to be distributed to the
vertical service domains 13 of the respective central offices 15.
Accordingly, a content provider can maintain the content stored on
the central content server 28 and update the local content servers
32 located at the respective central offices 15 automatically and
periodically. One of ordinary skill in the art would recognize
other obvious locations for a central content server on a
network.
[0137] One disadvantage of automatic updating of content on the
local content servers 32 from the central content server 28, is
that the bandwidth on transmission line 27 between the hub site 24
and the central office 15 is a limited resource. One of ordinary
skill in the art would recognize that it is undesirable for content
distribution to interfere or compromise the guaranteed transmission
rate of subscriber traffic transmitted over transmission line 27. A
solution to this problem, is a mechanism that determines unused
bandwidth over transmission line 27 and only transmits content from
the central content server 28 to the local content server 32 using
bandwidth that is unused by subscriber traffic. It is desirable to
distribute content from a central content server 28 to a local
content server 32, but it is undesirable for such distribution to
interfere with the quality of subscriber traffic. The mechanism
described above only distributes content using unused bandwidth of
transmission line 27 having the advantage of distributing content
without interfering with the quality of subscriber traffic.
[0138] FIG. 4C is an exemplary illustration of bandwidth
utilization, in terms of time, for exemplary transmission line 27.
On the y-axis 70, the bandwidth utilization is expressed from 0 to
100%. On the x-axis 68, time is expressed in the units of hours,
from 0 to 24. As one of ordinary skill in the art would appreciate,
the subscriber traffic 62 varies over time and at times is close to
utilizing 100% of the bandwidth of transmission line 27. However,
at other times subscriber traffic does utilize less than the entire
bandwidth of transmission line 27. One aspect of the present
invention includes a mechanism within the architecture of the hub
site 24 and the central office 15 to monitor the bandwidth
utilization of subscriber traffic 62. Using bandwidth utilization
information, content distribution 64 can be implemented over
bandwidth unused by subscriber traffic 62. Content distribution 64
fills up the bandwidth of transmission line 27 when subscriber
traffic 62 utilizes less than 100% of the bandwidth of the
transmission line 7.
[0139] It is important to note that region 66 of FIG. 4C is
bandwidth reserved for content distribution. Normally this reserved
bandwidth 66 is minimal and merely serves the purpose of
maintaining sessions between the central content server 28 and
local content servers 32 for content distribution 64. The
"as-available" bandwidth may use up to the entire capacity of the
link 27 when and if available; or the network may impose a maximum
rate limit on the content distribution circuit, e.g., Mb/s.
[0140] The mechanism for distributing content from the central
content server 28 to the local server 32 must utilize a congestion
mechanism to prevent data loss and utilize unused bandwidth. One
such congestion mechanism is Transmission Control Protocol (TCP).
TCP employs a window based end-to-end congestion control mechanism
to recover from segment loss and also avoid congestion collapse. In
one exemplary embodiment, the central content server 28 is in
communication with the gateway router 29 and the local content
server 32 is in communication with the VSI ATM switch 19. This
particular mechanism for distributing content from the central
content server 28 to the local content server 32 is contained in
the gateway router 29 and the VSI ATM switch 19, which are both ATM
devices capable of prioritizing data transmission.
[0141] In one exemplary embodiment, a logical circuit is
provisioned in the gateway router 29 and in the VSI ATM switch 19
for the download traffic between the servers 28 and 32. The
provisioning for this logical circuit specifies a guaranteed
minimum rate or bandwidth 66 for "keep-alive" purposes, so that the
servers may maintain session communications. The provisioning for
this logical circuit also provides an additional transport capacity
on an "as available" service, to allow the circuit to access and
utilize otherwise unutilized capacity. There may be a set maximum
for this "as available" service, or the circuit may be allowed
access up to the maximum otherwise unutilized capacity 64, at any
given time, on the link 27 between the gateway router 29 and the
VSI ATM switch 19. In this manner, the gateway router 29 and
possibly the VSI ATM switch 19 will throttle the content
transmissions from the server 28 to only consume otherwise
available bandwidth as shown at 64.
[0142] In an initial implementation, the logical communication
circuit between the servers 28 and 32 is an ATM Permanent Virtual
Circuit (PVC) between the servers 28 and 32, that is to say
extending through the gateway router 29 and the link 27 and at
least to the access switch 19. The provisioning for this ATM
circuit specifies the minimum rate or bandwidth 66 for "keep-alive"
purposes and the "as available" capability to access additional
bandwidth. In one embodiment, the ATM PVC circuit is provisioned as
an Unspecified Bit Rate plus (UBR+) service between the gateway
router 29 and the VSI ATM switch 19. The UBR+ service is
essentially a low-priority unspecified bit rate service, with
certain enhanced features, such as intelligent cell drop and early
packet discard. Of note for purposes of discussion here, one of the
enhanced features of UBR+ is that it may be provisioned with a
minimum rate or service guarantee.
[0143] Those skilled in the art will recognize that different
network implementations may utilize different mechanisms to control
congestion and allocate some combination of guaranteed bandwidth
and unspecified or as-available bandwidth for the circuit between
the servers used for content distribution. For example, it would be
possible to provision two circuits, one with low constant bit rate
(CBR) service, the other with normal Unspecified Bit Rate (UBR)
service. The servers, however, would be configured to treat the two
ATM PVC circuits as one aggregate pipe. If router 29 supports QoS
mechanisms of the type described above with respect to service
control through the switch 19, another alternative is to utilize
those mechanisms in the router 29 and/or the switch 19, to
implement the desired combination of minimum guaranteed rate and
as-available service for the content distribution circuit.
[0144] One skilled in the art would also recognize the content can
be distributed from a local content server 32 to a central content
server 28 in the same manner as discussed above. One example of
when this is desirable, is when the content provider is an end user
25 served through central office 15. Such a content provider would
upload content to the local content server 32 in the respective
central office 15, and then the content would be distributed from
the local content server 32 to the central content server 28. The
central content server 28, in turn, re-distributes that content to
other local content servers 32, at other remote central offices
15.
[0145] In one exemplary embodiment, the present invention is a
software product for replicating content data from a server 28 at a
hub site 24 to servers 32 at a respective central office 15. The
software product comprises at least one machine readable medium and
programming code carried by the at least one machine readable
medium for execution by at least one computer. The programming code
includes a congestion mechanism and a first transmitting mechanism.
The congestion mechanism allows for the determination of unused
bandwidth on a portion of a common link of a network over which the
hub site and the central office communicate.
[0146] In one embodiment of the software product, the congestion
mechanism is Transmission Control Protocol (TCP) utilized by
servers 28 and 32. The congestion mechanism may also rely on UBR+
service or other capabilities through the switches as outlined
above. The first transmitting mechanism causes the hub site server
to transmit content to a second server, via the otherwise unused
bandwidth, e.g. as TCP over UBR+ATM transport.
[0147] The programming code may further comprise a second
transmitting mechanism for causing transmission of content data
stored at the central office, e.g. on server 32, to the customer.
More particularly, the second transmitting mechanism may cause the
transmission of the content data stored at the central office to a
VSI ATM switch 19 at the central office 15. The second transmitting
mechanism then causes the integration of the content data with
other data being transmitting to the customer through the ATM
switch 19 in the central office 15 to the customer equipment 25,
essentially as described above relative to FIGS. 1 and 2. The
second transmitting mechanism may cause the distribution of the
integrated data to the customer through a multiplexer.
[0148] In one embodiment, the software product runs on a server and
a gateway router within the hub site and/or the local server and
VSI ATM switch of the central office. However, one of ordinary
skill in the art would realize that the software product could run
from other computer hardware devices within or proximate to the hub
site and/or the gateway router. Alternate embodiments of the hub
site are discussed later with respect to FIG. 7.
[0149] Table 2 summarizes the characteristics and requirements of a
number of examples of the types of vertical services that the VSD
network 13 can deliver via the L3/4 ATM switch 19 and the ADSL data
network 10. TABLE-US-00002 TABLE 2 Vertical Service Characteristics
Network Offering of the Service Requirements Voice Local Co-Located
Low latency, low jitter, Services VoIP Gateways, VoIP,
non-correlated packet Unified messaging, loss, and high avail- IP
PBX, IP Centrex ability Video Local VOD Servers High bandwidth, low
On Demand or access to central- jitter, high avail- (Unicast) ized
servers. Supports ability, and low whatever model of packet loss
server deployment/ content delivery mechanism. Multimedia Broadcast
Video; Varies with Broadcast Broadcast Audio; content type and
(Multicast) Satellite Down Link with multicast support; Local
implementation Servers at the edge. Caching Local servers at the
Layer 3/4 Services insertion point, Local visibility delivery
mechanism for generic media objects such as web pages, images,
video files, audio clips, software downloads, etc. Distance
Integrated interactive Low latency, low jitter, Learning video,
voice and data non-correlated packet (EVC) loss, and high avail-
ability Tele- Closed user group with IEEE 802.1Q commuting access
to Transparent LAN Service (TLS).
[0150] The above discussed preferred embodiments implemented the
processing above the layer-2 protocol in an enhanced ATM switch and
focused on implementation over an xDSL network specifically
designed for use of twisted pair wiring to the customer premises.
Those skilled in the art, however, will recognize that the
principles of the present invention are equally applicable to other
types of layer-1 and layer-2 transport/switching technologies as
well as selection based on other protocols above the layer-2
connectivity protocol.
[0151] FIG. 5, illustrates the implementation of the layer 3/4 and
higher switch functionality in a generic access router (AR) 61. The
underlying protocol defining the lowest L2 layer switch
connectivity may utilize ATM or other transport mechanisms, such as
native Ethernet, frame relay, or native IP. The illustration also
teaches the provision of digital subscriber line data communication
between the access router (AR) 61 and a number of customer
premises, using a variety of line technologies. The digital line
technologies include dial-up modems 63, 65 as well as wireless
communications between wireless asymmetrical subscriber loop (WASL)
transceivers 67, 69. The access router (AR) 61 can service
residential customers via these other communication technologies as
well as through the DSLAM 17 and the ATU-R 23 as in the earlier
embodiment. The access router (AR) 61 also serves business customer
router equipment 71, using a variety of fast frame/cell packet
technologies 73-76 and even optical fiber (SONET) 71.
[0152] Those skilled in the art will recognize that even these
examples are limited. For example, the invention may apply to
systems that have previously been considered as pure video
networks, such as a hybrid fiber-coax implementation of a CATV
system with digital video service as well as cable modem
service.
[0153] The access router (AR) 61 will provide one or more types of
logical circuits, implemented in the appropriate layer-2
protocol(s), e.g. ATM, frame relay, etc. Although the links to the
wide area internetwork and the vertical services domain have been
omitted here for simplicity of illustration, the access router (AR)
61 will provide the routing functions to and from the wide area
internetwork and the vertical services domain in a manner similar
to the functionality of the L3/4 ATM switch 19 in the earlier
embodiment. In this regard, the access router (AR) 61 will support
the QoS levels and will enable local insertion of vertical
services.
[0154] FIG. 6 depicts a portion of the network of FIG. 5, showing
the interconnection thereof with the wide area internetwork and the
local vertical services domain. The vertical services network
itself may include a number of routers (R) 73. Through that
network, the access router (AR) 61 provides communications with
services in the VSD that may be purely local, somewhat distributed
or even centralized. True long distance data services, such as chat
rooms, email and web browsing on the public Internet, however, are
considered as Off-Net services, since they are accessed via the
Internet access connection under the associated SLA.
[0155] Although the embodiments discussed to this point provide a
single local vertical services domain and the public Internet
domain through the ISPs or ISPs, the inventions encompass networks
supporting even more distinct network domains. For example, the
different Ethertype identifiers or other traffic type indicators
can be used to segregate traffic into multiple domains at different
points between the DSLAM and the gateway router. The PC or other
CPE would determine which type to use, and a switch similar to the
VSI switch 19 at the appropriate point along the PVC would
segregate and aggregate the traffic according to Ethertype or the
like. In addition, the distinctions can be based on still higher
types of information from the protocol stack.
[0156] FIG. 7 illustrates a somewhat modified architecture of the
ADN and may be helpful in understanding certain aspects and
alternatives relating to the inventive content distribution as well
as the implementation of more network domains. The drawing shows
two central offices 15.sub.1 and 15.sub.2 and the hub site 24. It
should be noted, however, that the hub 24 typically is located in a
central office, as well. Each of these central offices includes one
or more DLAMS 17, a VSI ATM switch 19 and a local vertical services
domain network 13. In general, these elements provide Internet
access and vertically inserted services through modems (ATU-Rs) 23
to customer premises equipment (not shown here for simplicity of
illustration).
[0157] For example, the first remote central office 15.sub.1
includes one or more DLAMS 17.sub.1 and a VSI ATM switch 19.sub.1.
The DSLAMS 17.sub.1 provide DSL communications to and from the
customer premises modems 23.sub.1. The first remote central office
15.sub.1 also includes a local data network forming the first
vertical services domain 13.sub.1. Data equipment for providing the
vertically inserted services connects to the vertical services
domain 13.sub.1. Of note for purposes of this discussion, the
equipment connected to the vertical services domain 13.sub.1
includes a local content server 32.sub.1, for example for content
downloading as might be used in an on-demand service or the like.
Similarly, the second remote central office 15.sub.2 includes one
or more DLAMS 17.sub.2 and a VSI ATM switch 19.sub.2. The DSLAMS
17.sub.2 provide DSL communications to and from the customer
premises modems 23.sub.2. The first remote central office 15.sub.2
also includes a local data network forming the second vertical
services domain 13.sub.2. Data equipment for providing the
vertically inserted services, such as the local content server
32.sub.2, connects to the vertical services domain 13.sub.2.
[0158] These elements in the remote central offices 15.sub.1 and
15.sub.2 function essentially the same as in the earlier
embodiments, to provide both Internet access services and
vertically inserted services, including content distribution to
customers. In particular, the VSI ATM switches 19.sub.1, 19.sub.2
forward upstream PPPoE traffic over the respective SONET links 27
to the hub office 24 and segregate upstream traffic of at least one
other Ethertype and supply that traffic to the respective vertical
services domain 13.sub.1, 13.sub.2. In the downstream direction,
the VSI ATM switches 19.sub.1, 19.sub.2 aggregate traffic from the
respective vertical services domain 13.sub.1, 13.sub.2 together
with respective customers' Internet traffic in the virtual
circuits, for communication via the DSLAMS 17.sub.1, 17.sub.2 and
modems 23.sub.1, 23.sub.2 to the customer premises equipment.
[0159] As noted, the remote hub site 24 also is within the building
of a central office. The hub office may provide tandem services,
but in most cases, the hub office will also provide at least some
end office services over subscriber links to customer premises.
Accordingly, the office 24 also includes one or more DLAMS 17.sub.3
and a VSI ATM switch 19.sub.3. The DSLAMS 17.sub.3 provide DSL
communications to and from the customer premises modems 23.sub.3.
The hub office 24 also includes at least one and preferably two
local network domains. The first of the local domains in the hub 24
is a local data network forming a third vertical services domain
13.sub.3. Data equipment for providing the vertically inserted
services for example, including a content server 32.sub.3, connects
to that vertical services domain 13.sub.3. In this embodiment, the
content server 32.sub.3 provides local content distribution
services to customer equipment coupled to the ATU-R modems
23.sub.3, in essentially the same manner as provided by the content
servers 32 in the other offices 15. As discussed more later, a
central content server 28 in the office 24 also provides
distribution of content to/from the servers 32.
[0160] With respect to the locally served customers, for example
receiving services via the ATU-R modems 23.sub.3, the elements
17.sub.3, 19.sub.3 and 13.sub.3 function essentially the same as in
the earlier embodiments, to provide both Internet access services
and vertically inserted services, including content distribution to
those customers. In particular, the VSI ATM switch 19.sub.3
forwards upstream PPPoE traffic toward the Internet, and switch
19.sub.3 segregates upstream traffic of at least one other
Ethertype and supplies that traffic to the vertical services domain
13.sub.3. In the downstream direction, the VSI ATM switch 19.sub.3
aggregates traffic from the vertical services domain 13.sub.3
together with the respective customers' Internet traffic in the
virtual circuits, for communication via the DSLAMS 17.sub.3 and the
modems 23.sub.3 to the customer premises equipment.
[0161] The hub office 24, however, also implements a number of
centralized functions. As in the earlier embodiments, the hub
office 24 provides the link to the Internet, for example, via a
gateway router 29. The drawing shows the router in dotted line
form, because the use of such router in this embodiment is optional
and may no longer be necessary. Preferably, the VSI ATM switch
19.sub.3 implements the functions previously performed by the
gateway router 29, in addition to the functions discussed above
relative to the switches 19. To this end, the VSI ATM switch
19.sub.3 includes interface cards for trunk connections 27 going
to/from the other switches 19.sub.1, 19.sub.2. The VSI ATM switch
19.sub.3 further includes one or more interface cards for trunk
connection(s) to the public ATM network 30, which provides the
links to the Internet service providers.
[0162] The hub office 24 also provides a convenient location to
implement the network services domain 33 and provide associated
network server(s) 34. The server 34, for example, may provide the
above-discussed DHCP address administration for the ADN carrier's
vertical services. The server 34 also may perform a variety of
network operations in support of the ADN, such as automated
provisioning, downloading of network related software to CPE
devices, automated testing, etc. The central content distribution
server 28 may connect to the vertical services domain 13.sub.3 in
the hub 24; or as shown, that server 28 may connect to the network
services domain.
[0163] The earlier embodiments supported two network domains, one
for Internet services and the other for vertical services. The
embodiment of FIG. 7 implements a traffic-type routing technique,
as an extension of that used in the earlier embodiments, to
implement even more distinct network domains. For example,
different Ethertype identifiers can be used to segregate traffic
into multiple domains at different points in the ADN. Specifically,
the respective end offices implement PPPoE segregation of upstream
traffic on the subscribers' logical circuits, for all traffic going
to the Internet. The PC or other CPE uses a second Ethertype
indicator in traffic destined for the vertical services domain 13
in the respective office 15 or 24. The VSI ATM switch 19 extracts
upstream traffic of an appropriate second Ethertype from the
logical circuits for the respective local subscribers and supplies
that traffic to the network forming the vertical services domain 13
in the respective office.
[0164] The network of FIG. 7 utilizes a third Ethertype for traffic
relating to the network services domain 33. The PC or other CPE
uses the third Ethertype indicator in traffic destined for
equipment in the network services domain 33, such as the network
server 34. The VSI ATM switches 19.sub.1, 19.sub.2 in the remote
central offices 15.sub.1, 15.sub.2, allow this traffic type to pass
upstream over the trunk links 27 in the subscribers' logical
circuits, together with the PPPoE traffic. The VSI ATM switches
19.sub.3, however, extracts upstream traffic of the third Ethertype
from the logical circuits for the respective local subscribers and
supplies that traffic to the network forming the network services
domain 33 in the hub office. The switch 19.sub.3, performs this
Ethertype recognition and traffic segregation both for upstream
traffic received via the trunk links 27 and for traffic of the
local subscribers coming over logical circuits from the ATU-R
modems 23.sub.3. As noted earlier, the traffic type distinctions
can be based on still higher types of information from the protocol
stack.
[0165] The switch 19.sub.3 also aggregates downstream traffic from
the network services domain 33 into the appropriate customers'
logical circuits. The remote switches 19.sub.1, 19.sub.2 allow such
traffic to pass downstream within the respective customers' logical
circuits, in essentially the same manner as downstream traffic
coming from the Internet.
[0166] In this manner, the network of FIG. 7 provides Internet
access services, vertical services insertion and network services
in a manner analogous to the earlier embodiments. Certain services,
such as content distribution and network services, however, can be
centralized to at least to some extent in the hub office 24. The
use of a VSI ATM switch 19.sub.3 at the hub 24 also allows
application of the prioritization and queuing for QoS, at the hub
location.
[0167] The preferred embodiment shown in FIG. 7 offers certain
advantages of particular note with respect to the inventive content
distribution. In that embodiment, content is distributed among the
servers 28, 32. The content may be uploaded from a server 32 to the
central content server 28, but most often content is downloaded
from the central server to one or more of the local content servers
32. For this purpose, the network of FIG. 7 provides at least one
logical circuit between the central content server 28 and each of
the local content servers 32.sub.1, 32.sub.2. The servers utilize a
congestion mechanism to prevent data loss and utilize unused
bandwidth, such as Transmission Control Protocol (TCP). Each
logical circuit between two content servers preferably is
provisioned to have a guaranteed minimum rate or bandwidth 66 for
"keep-alive" purposes, as well as an additional "as available"
transport capacity. There may be a set maximum for the "as
available" service, or the circuit may be allowed access up to the
maximum otherwise unutilized capacity 64, at any given time, on the
link 27 between the switch 19.sub.3 and the VSI ATM switch 19.sub.1
or 19.sub.2 in the respective remote office 15 (see FIG. 4C).
[0168] In this regard, it may be helpful to discuss one specific
example of such a circuit between content servers. For that
purpose, consider the circuit between the central content server 28
in the hub site 24 and the first local content server 32.sub.1 in
the remote central office 15.sub.1. The circuit may be an ATM
permanent virtual circuit extending through the hub VSI ATM switch
19.sub.3, the appropriate interoffice link 27 and the first remote
VSI ATM switch 19.sub.1. In one embodiment, the ATM PVC circuit is
provisioned as an Unspecified Bit Rate plus (UBR+) service. The
provisioning for this ATM circuit in the switches 19.sub.1,
19.sub.3 specifies the minimum "keep-alive" rate or bandwidth 66
and the "as available" capability parameters 64.
[0169] The embodiment of FIG. 7, however, also will support a
preferred alternative implementation of the logical circuit between
the central content server 28 and each of the local content servers
32.sub.1, 32.sub.2. In this later embodiment, the circuit again
would extend through the hub VSI ATM switch 19.sub.3, the
appropriate interoffice link 27 and the first remote VSI ATM switch
19.sub.1 and use an ATM PVC. However, the circuit is provisioned as
a normal Unspecified Bit Rate, with no guaranteed minimum. Instead,
the desired rate characteristics are implemented using the
prioritization and queuing mechanisms developed for QoS and
described earlier. At least the hub switch 19.sub.3 applies the QoS
mechanisms to the communications between the servers in such as
manner as to implement the desired available bandwidth service with
a minimum guarantee for transmissions from the central server 28 to
the remote server 32. If appropriate, the switch 19.sub.1 may
provide similar bandwidth regulations using its QoS mechanisms, for
transmissions from the content servers 32.sub.1 to the central
server 28.
[0170] The use of the VSI ATM switch at the hub also provides
another point for cell replication. For example, the switch
19.sub.3 can replicate cells for concurrent transmission to the
remote switches 19.sub.1 and 19.sub.2. The switches 19.sub.1 and
19.sub.2 can supply such content to servers in the associated
vertical services domains 13. Alternatively, the switches 19.sub.1
and 19.sub.2 can further replicate cells for transmission to
currently "joined" customers of a broadcast service.
[0171] While the foregoing has described what are considered to be
the best mode and/or other preferred embodiments of the invention,
it is understood that various modifications may be made therein and
that the invention may be implemented in various forms and
embodiments, and that it may be applied in numerous applications,
only some of which have been described herein. It is intended by
the following claims to claim any and all modifications and
variations that fall within the true scope of the inventive
concepts.
* * * * *