U.S. patent application number 11/853597 was filed with the patent office on 2007-12-27 for ethernet-to-atm interworking that conserves vlan assignments.
Invention is credited to Stephen L. Holmgren, David Kinsky, John Babu Medamana, Mateusz W. Szela.
Application Number | 20070297420 11/853597 |
Document ID | / |
Family ID | 38535842 |
Filed Date | 2007-12-27 |
United States Patent
Application |
20070297420 |
Kind Code |
A1 |
Holmgren; Stephen L. ; et
al. |
December 27, 2007 |
ETHERNET-TO-ATM INTERWORKING THAT CONSERVES VLAN ASSIGNMENTS
Abstract
Interworking of first and second networks (12, 14) is
accomplished by an interworking facility (30) that serves to map
the destination address in first frames received from the first
network into second destinations addresses compatible with the
second network. To conserve such mapping the assignments, the first
network encapsulates information frames (32) received from one or
more sites associated with a first customer into jumbo frames (34)
that have a generic address associated with that customer. At the
interworking facility, the individual frames are stripped from the
jumbo frame and routed to corresponding destinations in the second
network.
Inventors: |
Holmgren; Stephen L.;
(Little Silver, NJ) ; Kinsky; David; (High Bridge,
NJ) ; Medamana; John Babu; (Colts Neck, NJ) ;
Szela; Mateusz W.; (Hillsborough, NJ) |
Correspondence
Address: |
AT&T CORP.
ROOM 2A207
ONE AT&T WAY
BEDMINSTER
NJ
07921
US
|
Family ID: |
38535842 |
Appl. No.: |
11/853597 |
Filed: |
September 11, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10134569 |
Apr 26, 2002 |
7277442 |
|
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11853597 |
Sep 11, 2007 |
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Current U.S.
Class: |
370/397 |
Current CPC
Class: |
H04L 61/106 20130101;
H04L 12/462 20130101; H04L 61/6022 20130101; H04L 29/12877
20130101; H04L 61/604 20130101; H04L 29/12839 20130101; H04L
12/4645 20130101 |
Class at
Publication: |
370/397 |
International
Class: |
H04L 12/56 20060101
H04L012/56 |
Claims
1. A method for communicating information frames from at least one
of a first plurality of sites associated with a customer to at
least one of a second plurality of sites associated with the
customer wherein said one first site is served by a first network
and each second site is served by a second network, comprising:
receiving first information frames in a first network from said one
first site and encapsulating the first information frames into a
jumbo frame having a generic address of a first format that
identifies said customer; receiving at an interworking facility the
jumbo frame and separating therefrom the first information frames,
each first information frame having a first destination address of
a first format specifying a corresponding one of said plurality of
second sites to which each first information frame is destined, the
first destination address being in said first format compatible
with said first network, and made available by the interworking
facility by resolving destinations available to said one first site
through the second network; forming, for each first information
frame, a second information frame of a second format compatible
with the second network; and mapping the first destination address
of each first information frame to a second destination address
specifying in the second format to which the second information
frame is destined.
2. The method of claim 1, wherein each first information frame
comprises an Ethernet frame.
3. The method of claim 2, wherein the jumbo frame comprises an
Ethernet frame.
4. The method of claim 1, wherein each second information frame has
an ATM format.
5. The method of claim 3, wherein the generic address comprises a
portion of a data field comprising part of the jumbo frame.
6. A method for communicating information frames from at least one
of a first plurality of sites associated with a customer to at
least one of a second plurality of sites associated with the
customer, wherein said one first site is served by an Ethernet
network and each second site is served by a High Speed Packet
network, comprising: receiving Ethernet frames in a first network
from said one first site and encapsulating the Ethernet frames into
jumbo Ethernet frames having a generic address that identifies said
customer; receiving at an interworking facility one of the jumbo
frames and separating therefrom the Ethernet frames, each having a
first destination address of an Ethernet format specifying a
corresponding one of plurality of second sites to which each
Ethernet frame is destined, the first destination address being of
said Ethernet format and made available by the interworking
facility by resolving destinations available to said one first site
through the second network; forming, for each Ethernet frame, a
second frame of a second format compatible with the second network,
and mapping the first destination address of each Ethernet frame to
a second destination address specifying in the second format to
which the second frame is destined.
7. The method of claim 6, wherein the jumbo frame comprises an
Ethernet frame.
8. The method of claim 6, wherein each second frame has an ATM
format.
9. The method of claim 6, wherein the generic address comprises a
portion of a data field comprising part of the jumbo frame.
10. A system for communicating information frames from at least one
of a first plurality of sites associated with a customer to at
least one of a second plurality of sites associated with the
customer, wherein said one first site is served by an Ethernet
network and each second site is served by a High Speed Packet
network, comprising: means for receiving Ethernet frames in a first
network from said one first site and encapsulating the Ethernet
frames into jumbo Ethernet frames having a generic address that
identifies said customer; means for receiving at an interworking
facility one of the jumbo frames and separating therefrom the
Ethernet frames, each having a first destination address of an
Ethernet format specifying a corresponding one of plurality of
second sites to which each Ethernet frame is destined, the first
destination address being of said Ethernet format and made
available by the interworking facility by resolving destinations
available to said one first site through the second network; means
for forming, for each Ethernet frame, a second frame of a second
format compatible with the second network, and means for mapping
the first destination address of each Ethernet frame to a second
destination address specifying in the second format to which the
second frame is destined.
11. The system of claim 10, wherein the jumbo frame comprises an
Ethernet frame.
12. The system of claim 10, wherein each second frame has an ATM
format.
13. The system of claim 10, wherein the generic address comprises a
portion of a data field comprising part of the jumbo frame.
Description
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 10/134,569, filed Apr. 26, 2002, (currently
allowed). The aforementioned related patent application is herein
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] This invention relates to a technique for interworking
Ethernet and ATM networks by mapping Ethernet Virtual Local Area
Network (VLAN) identifiers (tags) to ATM network Permanent Virtual
Circuits (PVCs).
[0004] 2. Background Art
[0005] Presently, communication service providers, such as
AT&T, offer high-speed Asynchronous Transport Mode (ATM)
Virtual Private Network (VPN) service to customers. Each ATM-based
VPN customer utilizes one or more Permanent Virtual Circuits (PVCs)
to route data among different locations (endpoints), each typically
located at a separate edge of an ATM network. In practice, traffic
originating at an endpoint passes to an edge device on the ATM
network for transmission to the network core, which in turn,
transmits such traffic to an edge device serving the destination
end point. While the edge devices may run one or more different
protocols, including ATM or Frame Relay, the network core typically
utilizes the ATM protocol. In this environment, ATM PVCs constitute
a point-to-point network topology.
[0006] Currently, there exists a large embedded base of Ethernet
Local Area Networks (LANs). Advances in Ethernet technology have
led to the development of Metropolitan Area Networks (MANs) that
afford access to the Internet and some limited access to VPNs.
Ethernet-based MANs offer significant cost advantages on a per port
basis, as compared to Frame Relay and ATM networks. Many VPN
customers would like the opportunity to use an Ethernet-based MAN
to access their ATM-based VPNs but have not had the ability to do
so because of interworking issues. The protocol associated with
Ethernet is different than that associated with ATM. Ethernet is a
broadcast protocol within level 2 (the data link layer) of the
well-known 7-layer OSI model, whereas ATM and Frame Relay is a
point-to-point circuit-type protocol within level 2. Ethernet is
designated as a broadcast protocol within level 2 because
information in an Ethernet network travels in both directions and
passes by all devices on the path. A device that recognizes the
information intended for itself (as opposed to another device) will
pull the information from the network.
[0007] U.S. patent application Ser. No. 10/016,019, filed Dec. 12,
2001 in the names of Stephen L. Holmgren, David Kinsky, John Babu
Medamana and Mateusz Szela, and assigned to AT&T (incorporated
by reference therein) describes a technique for interworking
Ethernet to ATM networks. An interworking facility receives frames
from a first network that are destined for the second network. Each
such frame destined for the second network includes not only the
payload, but also a destination address indicative of the endpoint
in the second network destined to receive the information in the
payload. The destination address is obtained by initially resolving
the destinations available to the source, including those available
through the second network. In practice, the interworking facility
establishes a set of pseudo addresses in a format compatible with
the first network that correspond to destinations in the second
network so that the source can address an information frame using
its own protocol for a destination that actually lies in the second
network without concerning itself with the protocol employed in the
second network. In the case where the first information frame comes
from a source in an Ethernet-based network, the first information
frame will have a Virtual Local Area Network (VLAN) tag associated
with the address of the destination. On the other hand, if the
information frame comes from a source in an ATM network, the frame
will include a VPN Virtual Circuit Identifier (Vel), herein after
referred to as a Permanent Virtual Circuit (PVC) that corresponds
to the address of (e.g., the network path to) the destination in a
format compatible with the ATM network, even though the destination
lies in another network having a different protocol.
[0008] Upon receipt of the first information frame at the
interworking facility, the facility forms a second frame (which
includes the payload) in a format compatible with the second
network. The interworking facility maps destination address of the
first frame to a second destination address compatible with the
second network. Thus, for example, the VLAN tag in an originating
Ethernet frame is mapped to a VPN PVC in an ATM frame and vice
versa. Mapping the destination address from a format compatible
with the first information frame to a format compatible with the
second information frame allows routing of the second frame,
including the information embodied in its payload. to the
destination.
[0009] As described above, the interworking technique of the
aforementioned U.S. patent application Ser. No. 10/016,019 permits
interworking of Ethernet to Frame Relay or ATM networks by mapping
Ethernet VLANs to ATM PVCs and vice versa. While this technique
works well, most large Frame Relay and ATM customers typically
enjoy hundreds if not thousands of PVCs per access link whereas the
VLAN ID space within an Ethernet frame is limited to 12 bits (4096)
values, thus limiting mapping.
[0010] Thus, there is a need for a technique for expanding the VLAN
ID space to enhance Ethernet-to-ATM interworking.
BRIEF SUMMARY OF THE INVENTION
[0011] Briefly, there is provided a method for interworking two
different networks to allow communication of information frames
there between by mapping the address format of one network into the
other network while conserving mapping assignments. In a preferred
embodiment, a first network serves at least one of a first
plurality of sites associated with a particular customer while the
second network serves at least one of a plurality of second sites
associated with the same customer. To facilitate interworking of
the two networks, the first network receives information frames
from the first site destined for one or more of the second sites
and encapsulates each individual frame into jumbo frames that have
a generic address of a first format that identifies the customer.
An interworking facility receives each jumbo frame and extracts the
encapsulated individual frame that each has a first destination
address that specifies, in a first format compatible with the first
network, the corresponding one of the plurality of second sites
destined to receive the individual frame. The interworking facility
makes such first destination addresses available by resolving
destinations (i.e., second sites) available to each first site
through the second network. For each individual frame extracted
from a jumbo frame, the interworking facility forms a second frame
of a format compatible with the second network and maps the first
destination address to a second destination address compatible with
the second network, so that the second network, upon receipt of the
second frame, can route the frame to a corresponding one of the
second sites.
[0012] The above-described method advantageously allows for
interworking of a VLAN network to a Frame Relay or ATM network
while conserving VLAN assignments. By encapsulating individual VLAN
frames from a first site destined for each of a plurality of second
sites of the same customer into jumbo frames having a single
generic address associated with that customer, the large number of
VLAN ID assignments otherwise needed for mapping is greatly
reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 depicts a block schematic diagram of a network
architecture for practicing the method of the invention;
[0014] FIGS. 2A and 2B depict the relationship between an
individual frame from a first network within the network
architecture of FIG. 1 and a jumbo frame into which the first frame
is encapsulated.
DETAILED DESCRIPTION
[0015] FIG. 1 illustrates a schematic diagram of a network
architecture 10 in accordance with an illustrative embodiment of
the invention for interworking a first and second networks 12 and
14, respectively, while minimizing address mapping assignments in
the manner discussed below. In the illustrated embodiment of FIG.
1, the network 12 takes the form of an Ethernet Metropolitan Area
Network or the like operated by an Ethernet Service Provider (ESP)
that provides Ethernet network service to at least one site 16
associated with a particular customer, hereinafter designated as
Customer A. In practice, the network 12 may serve a plurality of
separate sites (not shown) of Customer A as well as one or more
sites of other customers (not shown). A site 16 on the Ethernet
network 12 can easily route traffic, in the form of Ethernet
information frames. to other sites of the same customer within the
Ethernet network by appropriately setting a Virtual Local Access
Network (VLAN) identifier in each Ethernet frame.
[0016] In addition to maintaining one or more sites, such as site
16, on the Ethernet network 12, Customer A may also maintain one or
more sites, such as sites 18,20, and 22, on the network 14. In the
illustrated embodiment, the network 14 takes the form of a High
Speed Packet Service (HSPS) network which routes traffic, in the
Frame Relay or ATM frames, to each of the sites 18, 20, and 22
through an ATM switch 23 via a corresponding one of Permanent
Virtual Circuits 24, 26, and 28, respectively.
[0017] Often, Customer A will have the need to send information
from one of the sites, such as site 16, on the Ethernet network 12,
to one of the sites, such as site 18, on the HSPS network 14.
Unfortunately, the protocol associated with Ethernet is different
than the protocol associated with ATM and Frame Relay, making
direct routing of an Ethernet frame between the networks 12 and 14
impossible. Ethernet is a broadcast protocol within level 2 (the
data link layer) of the well-known 7-layer OSI model, whereas ATM
and Frame Relay is a point-to-point circuit-type protocol within
level 2. Ethernet is designated as a broadcast protocol within
level 2 because information in an Ethernet network travels in both
directions and passes by all devices on the path. A device that
recognizes the information intended for itself (as opposed to
another device) will pull the information from the network.
[0018] Our co-pending U.S. patent application Ser. No. 10/016,019
(incorporated by reference herein) describes a technique for
interworking an Ethernet network such as Ethernet network 12 with
an ATM or Frame Relay network, such as HSPS network 14, by way of
an Ethernet gateway switch 30. At the outset of operation, the
Ethernet gateway switch 30 first resolves for each of source of
Ethernet traffic in the Ethernet network 12 (such as customer site
16) a corresponding Ethernet address for each available site (e.g.,
customer sites 18,20, and 22) within the HSPS network 14. By the
same token, the Ethernet gateway switch 30 resolves, for each of
the customer sites 18-22 corresponding PVC routing addresses for
each site (e.g., site 16) served by the Ethernet network 12. In
actuality, the customer sites 18-22 do not actually have Ethernet
addresses nor does the customer site 16 have a PVC routing address.
Rather, the Ethernet gateway switch 30 resolves (i.e., makes
available) such pseudo addresses so that the customer sites served
by each network effectively appear in the other network.
[0019] After resolving the addresses for the customer sites in each
of the networks 12 and 14, the Ethernet gateway switch 30
facilitates the transmission of traffic from one network to
another. Upon receipt of traffic, in the form of a frame from a
first network (i.e., an Ethernet frame from the Ethernet network
12), the Ethernet gateway switch 30 facility forms a second frame
(e.g., a Frame Relay or ATM frame) compatible with the other
network (e.g., the HSPS network 14). The second frame includes the
information payload from the first frame.
[0020] In forming the second frame, the Ethernet gateway switch 30
maps the destination address of the first frame to a second
destination address compatible with the second network. Thus, for
example, for an Ethernet frame received from the customer site 16
in the Ethernet network 12, the Ethernet gateway switch 30 maps the
VLAN tag to a corresponding PVC for a Frame Relay or ATM frame.
Conversely, upon receipt of a Frame Relay or ATM frame from the
HSPS network 14, the Ethernet gateway switch 30 maps the PVC
associated with that frame to a corresponding VLAN tag compatible
with the Ethernet network 12. Mapping the destination address of
the received frame to a format compatible with the destination
network allows routing of the payload to its destination (i.e., the
corresponding customer site in the destination network).
[0021] To facilitate such address mapping, the Ethernet gateway
switch 30 typically includes one or more tables (not shown) that
cross reference VLAN tags to corresponding PVCs and vice versa. In
a typical Frame relay or ATM network, such as HSPS network 14, a
customer, such as Customer A, may have hundreds if not thousands of
PVCs per access link. On the other hand the VLAN tag within an
Ethernet frame is limited to twelve bits in length, allowing for a
maximum number of 4096 values. Thus, with present day techniques, a
site, such as site 20 in the HSPS network 14, can only map to only
one of 4096 sites in the Ethernet network 12. For a large customer,
mapping to a larger number of sites within the Ethernet network
(>4096) may have value.
[0022] In accordance with present principles, VLAN assignments may
be conserved, yet allow for a large number of such mappings by
stacking Ethernet frames in the following manner. Referring to FIG.
1, a customer site, such as customer site 16, will send individual
Ethernet frames, such as frame 32, into the Ethernet network 12.
Each frame 32 has a VLAN tag as depicted in FIG. 2 that identifies
a corresponding site in the network 14 served by the same customer
to which the frame is destined. In the illustrated embodiment of
FIG. 1, each frame 32 may contain a VLAN tag (e.g. between 20 and
400) as sub-interfaces to different remote sites (Le., different
sites in the network 14). The ESP network 12 advantageously
encapsulates each frame 32 destined for sites in the network 12
associated with the same customer (e.g., customer A) into a
corresponding jumbo frame 34. The jumbo frame 34 has a single VLAN
tag, e.g., 625, identifying the customer (e.g., customer A) whose
sites in the network 14 are destined to receive the individual
frames encapsulated in the jumbo frames. The VLAN 625 terminates on
an ATM interface inside the Ethernet gateway switch 30.
[0023] The Ethernet network 12 routes the jumbo frame 34 to the
Ethernet gateway switch 30 which then removes the encapsulation and
its VLAN tag of 625 (i.e., "pops" the VLAN stack) which identifies
this as a frame for Customer A. The Ethernet Gateway Switch then
performs the requisite address mapping as discussed previously to
map the Ethernet VLAN tag in each original frame 32 to the
corresponding PVC associated with Customer A's site in the network
14 destined to receive that frame. In this way, the large numbers
of VLAN tags needed for mapping to corresponding PVCs are confined
to inside the Ethernet gateway switch 30. The single VLAN 625 can
be used by the Ethernet service provider to carryall of customer
A's different VLANs to the Ethernet gateway switch 30.
[0024] FIGS. 2A and 2B illustrate the relationship between each
individual frame 32 and the jumbo frame 34 into which the
individual frame is encapsulated. As depicted in FIG. 2A, each
frame 32 has a conventional Ethernet format and includes the
following fields and corresponding bit size TABLE-US-00001 Field
Designator Bit Size Preamble 8 Destination Address 6 Source Address
5 VLAN Flag 2 VLAN Priority and Tag ID 2 Type 2 Data field 0-1496
FCS 4
The customer provides input frames using the format shown in FIG.
2A and identifying the customer's different VLANs using multiple
VLAN IDs.
[0025] As depicted in FIG. 2B, the "jumbo" Ethernet frame 34 has a
header format similar to the conventional Ethernet frame 32, and
contains all of the information in the entire original frame.
However, the customer frame 32 is altered by inserting a new VLAN
field (referred to in FIG. 2 as a stackable VLAN field or "S-VLAN"
field) which is used by the Ethernet Service Provider only for that
customer. The jumbo frame 34 now carries VLAN tag information, e.g.
a stackable VLAN tag ID of 625, that is inserted at the location
specified in FIG. 2B. The jumbo frame 34 can now be routed through
the ESP network 12 by only looking at the outer stackable VLAN ID
(this implies that there is only one routing path needed for all of
customer A's VLANs through the ESP network 12).
[0026] As may now be appreciated, encapsulating each individual
frame 32 into a jumbo frame 34 enables the Ethernet network 14 and
the Ethernet gateway switch 30 to utilize a single VLAN to carryall
of Customer A's different VLANs; this process is sometime referred
to as VLAN stacking. The large number of VLANs needed for mapping
to PVCs are thus confined inside the ATM interface in the Ethernet
gateway switch. VLAN stacking, although not an industry standard,
is a capability supported by many current equipment vendors to
address scalability issues within existing VLAN frame tagging
specifications. It should be noted that FIG. 2B depicts only one
known format for enabling VLAN stacking, and that the present
invention is not limited to the particular format used to
encapsulate a customer's input frame.
[0027] The foregoing describes a technique for interworking
Ethernet and ATM networks by mapping Ethernet Virtual Local Access
Network (VLAN) identifiers (tags) to ATM network Permanent Virtual
Circuits (PVCs) while conserving mapping assignments.
[0028] The above-described embodiments merely illustrate the
principles of the invention. Those skilled in the art may make
various modifications and changes that will embody the principles
of the invention and fall within the spirit and scope thereof.
* * * * *