U.S. patent application number 09/887658 was filed with the patent office on 2003-03-06 for method of establishing logical connections in a synchronous digital communications network, as well as network elements and management system.
Invention is credited to Heuer, Volkmar.
Application Number | 20030046416 09/887658 |
Document ID | / |
Family ID | 26039921 |
Filed Date | 2003-03-06 |
United States Patent
Application |
20030046416 |
Kind Code |
A1 |
Heuer, Volkmar |
March 6, 2003 |
METHOD OF ESTABLISHING LOGICAL CONNECTIONS IN A SYNCHRONOUS DIGITAL
COMMUNICATIONS NETWORK, AS WELL AS NETWORK ELEMENTS AND MANAGEMENT
SYSTEM
Abstract
A method of establishing logical connections in a synchronous
communications network (SDH) comprising a plurality of at least
partially interconnected network elements (NE1, NEn; CC1-CC3) and
designed for the transmission of data packets containing a
destination address involves monitoring destination addresses of
the data packets to be transmitted, determining the traffic volume
between the individual network elements (NE1, NEn; CC1-CC3) with
the aid of the destination addresses, and determining an optimized
configuration of logical connections based on the traffic volume
and existing logical connections. In this manner, the
communications network is adapted to the current traffic situation,
and the transmission capacities of the network are utilized in the
best possible manner. The monitoring is advantageously done in at
least part of the network elements, while the determination of the
traffic volume and the optimized configuration is performed by a
central management system (TMN).
Inventors: |
Heuer, Volkmar; (Ditzingen,
DE) |
Correspondence
Address: |
WARE FRESSOLA VAN DER SLUYS &
ADOLPHSON, LLP
BRADFORD GREEN BUILDING 5
755 MAIN STREET, P O BOX 224
MONROE
CT
06468
US
|
Family ID: |
26039921 |
Appl. No.: |
09/887658 |
Filed: |
July 30, 2001 |
Current U.S.
Class: |
709/232 ;
709/238 |
Current CPC
Class: |
H04Q 11/0478 20130101;
H04J 2203/0098 20130101; H04J 2203/0075 20130101; H04J 3/1617
20130101 |
Class at
Publication: |
709/232 ;
709/238 |
International
Class: |
G06F 015/16; G06F
015/173 |
Claims
1. A method of establishing logical connections in a synchronous
digital communications network (SDH) comprising a plurality of at
least partially interconnected network elements (NE1, NEn; CC1-CC3)
designed for the transmission of data packets each containing a
destination address, said method comprising the steps of:
monitoring the destination addresses of the data packets to be
transmitted; determining a current traffic volume between the
individual network elements (NE1, NEn; CC1-CC3) with the aid of the
destination addresses; determining an optimized configuration of
logical connections based on the traffice volume and existing
logical connections; and updating the logical connections in the
synchronous digital communications network (SDH) with the optimized
configuration.
2. A method as claimed in claim 1 wherein the determination of the
optimized configuration and the updating of the logical connections
are performed periodically.
3. A method as claimed in claim 1 wherein the the data packets are
packets structured in accordance with the Internet protocol.
4. A method as claimed in claim 1 wherein the monitoring of the
destination addresses is performed in at least part of the network
elements (NE1, NEn; CC1-CC3) of the synchronous digital
communications network.
5. A method as claimed in claim 1 wherein the determination of the
traffic volume and the determination of an optimized configuration
are made by a central management system (TMN) of the synchronous
digital communications network (SDH).
6. A method as claimed in claim 1 wherein in addition, the source
addresses are monitored and a charge for transmitted data packets
is determined therefrom.
7. A method as claimed in claim 1 or 6 wherein data packets with
predetermined source or destination addresses are given a higher
priority during transmission.
8. A method as claimed in claim 1 wherein the determination of the
optimized configuration is also based on experience gained in
cyclically occurring traffic situations.
9. A network element (NE1, NEn; CC1-CC3) for a synchronous digital
communications network (SDH) comprising a plurality of at least
partially interconnected network elements and designed for the
transmission of data packets, said network elements (NE1, NEn;
CC1-CC3) comprising: means for monitoring destination addresses of
the data packets to be transmitted; and an interface to a central
management system (TMN) for sending messages (MTL) containing the
destination addresses of the data packets to be transmitted and for
receiving instructions (ANW) relating to logical connections to be
switched, the central management system (TMN) being provided for
establishing the logical connections in the communications network
(SDH).
10. A network element as claimed in claim 9 which is a
crossconnector (CC1-CC3).
11. A management system (TMN) for a synchronous digital
communications network (SDH) comprising a plurality of at least
partially interconnected network elements (NE1, NEn; CC1-CC3) and
designed for the transmission of data packets, said management
system (TMN) comprising: interfaces to the network elements (NE1,
NEn; CC1-CC3) of the synchronous digital communications network
(SDH) for receiving messages (MTL) containing destination addresses
of the data packets to be transmitted and for sending to the
network elements (NE1, NEn; CC1-CC3) instructions (ANW) relating to
logical connections to be switched; means for determining a current
traffic volume between the network elements based on the messages
(MTL) containing the destination addresses of the data packets to
be transmitted; means for determining an optimized configuration of
logical connections between the network elements (NE1, NEn;
CC1-CC3) based on the existing logical connections and the traffic
volume; and means for sending to the network elements (NE1, NEn;
CC1-CC3) instructions (ANW) relating to the logical connections to
be switched in accordance with the optimized configuration.
Description
[0001] This invention relates to a method of establishing logical
connections in a synchronous digital communications network as
claimed in claim 1, to a network element for a synchronous digital
communications network as claimed in claim 9, and to a management
system as claimed in claim 11.
[0002] Data packets, which originate, for example, from local area
networks, are transmitted through data networks to respective
addressees. Such data packets originate particularly from Internet
applications, are structured in accordance with the Internet
protocol (IP), and have a source address and a destination address.
As transmission media (OSI Layer 1) for long-haul data
communications networks, synchronous digital networks based on the
SDH or SONET standards and recommendations are used
(SDH=Synchronous Digital Hierarchy, SONET=Synchronous Optical
Network). This is stated, for example, in RFC 1619 (W. Simpson,
Request for Comments 1619, Internet Engineering Task Force, Network
Working Group, May 1994), which proposes to place data packets to
be transferred over point-to-point links directly in synchronous
transport modules (STM-N) of SDH or synchronous transport signals
(STS-N) of SONET.
[0003] In synchronous digital communications networks, virtual,
i.e., logical, connections can be switched between elements of the
network. This is done manually with the aid of a management system.
The switched logical connections are then used by routers of
different data networks, which provide the gateways to the
synchronous digital communications network, to transmit data
packets.
[0004] Since applications of the Internet, in particular, produce
widely time-varying data quantities (between 0 b/s and a few Mb/s)
which have to be transmitted over the synchronous digital
communications network in the form of IP data packets, the prior
art has the disadvantage that either large transmission capacities
have to be kept available in the communications network, which then
remain unused most of the time, or that bottlenecks occur if
several users want to send large amounts of data
simultaneously.
[0005] In another concept, IP packets are first placed in ATM cells
and then transmitted over virtual channel connections through a
synchronous digital communications network (SDH or SONET). In an
article published by Ipsilon Networks ("IP Switching: The
Intelligence of Routing, the Performance of Switching", Ipsilon
Technical White Paper on IP Switching, February 1996, retrievable
in the Internet at http://www.ipsilon.com/prod-
uctinfo/wp-ipswitch.html), a device (IP Switch) is presented which
combines the functions of an IP router and an ATM switch. This
device is capable of identifying longer-duration sequences of data
packets having the same source and destination addresses, so-called
flows, by means of an address monitor, and to switch suitable
connections for these flows in the hardware. This increases the
throughput of data packets through the IP switch and shortens the
mean switching time. This, too, has the disadvantage that only
predetermined logical connections can be used, which are either
underdimensioned or overdimensioned, depending on the current
payload.
[0006] It is an object of the invention to provide a method whereby
a synchronous digital communications network can be better adapted
to time-varying data traffic. Further objects of the invention are
to provide a network element and a management system for a
synchronous digital communications network which are suited for
carrying out the method.
[0007] The objects are attained by the features of claims 1, 9, and
11, respectively.
[0008] One advantage of the invention is that transmission
capacities can be better utilized for the transmission of data
packets and that the average transmission rate is higher than in
the prior art. Other advantages are that commercially available IP
routers can be used, and that no changes to the equipment of a user
wishing to transmit data packets over the communications network
are necessary.
[0009] In a preferred embodiment of the invention, source-address
monitoring is additionally performed. This makes it possible to
determine charges for transmitted data packets.
[0010] In another preferred embodiment of the invention, data
packets with predetermined source or destination addresses, e.g.,
all data packets from or for an individual, predetermined user, are
given a higher priority during transmission.
[0011] One embodiment of the invention will now be described with
reference to the accompanying drawing, in which:
[0012] FIG. 1 shows two local area networks (LANs) interconnected
by a synchronous digital communications network;
[0013] FIG. 2a shows a configuration of a communications network
for high data traffic between adjacent users; and
[0014] FIG. 2b shows a configuration of a communications network
for high data traffic between users located remote from each
other.
[0015] Referring to FIG. 1, there are shown two local data networks
LAN1, LAN2 which are interconnected by a synchronous digital
communications network SDH and can exchange data packets via this
network. The gateways from the local area networks to the
communications network SDH are provided by routers RTR1, RTR2. Each
of the latter is connected to a network element NE1, NE2 of the
network SDH. Between these two network elements NE1, NE2, a logical
connection exists through the network SDH over which the data
packets to be transmitted are transported. If data packets are to
be transmitted from the first local area network LAN1 to the second
local area network LAN2, they are placed ("packetized") in
synchronous transport modules or subunits of such synchronous
transport modules, so-called virtual containers VC-N (in SDH) or
virtual tributaries VT (in SONET), in the first network element
NE1, and transmitted to the second network element NE2, where they
are unpacketized and passed to the second router RTR2. Besides SDH
and SONET systems, plesiochronous digital hierarchy (PDH)
transmission systems must be regarded as synchronous digital
networks in the sense of the invention.
[0016] A logical connection (frequently also referred to as a
virtual connection) is formed as two network elements periodically
exchange subunits of synchronous transport modules, with the
subunits being switched through other, intermediate network
elements of the communications network SDH without being
repacketized Virtual connections are established by a central
network management system of the synchronous digital network SDH
and have a fixed transmission capacity, i.e., they are permanent
virtual connections.
[0017] A fundamental idea of the invention is to monitor in the
communications network the destination addresses of the data
packets to be transported, to determine therefrom the traffic
volume between the individual network elements of the
communications network, and, based on the traffic volume, to
determine an optimized configuration of logical connections which
is used to update the network. The network is thus adapted to the
current traffic volume, and the transmission capacities of the
network are utilized in the best possible manner. This approach is
particularly suitable for IP data packets of Internet applications,
but it is also applicable to data packets structured according to
other protocols, preferably of OSI Layer 3, such as the IPX
procotol of Novell Inc.
[0018] Particularly advantageously, the monitoring of the
destination addresses is performed in at least part of the network
elements of the synchronous communications network. To this end,
the network elements include means for monitoring the destination
addresses, e.g., an IP address monitor. Alternatively, the use of a
separate address monitor looped into a connection path of the
network is possible. In another preferred embodiment, the
determination of the traffic volume and the determination of an
optimized configuration are performed in a central management
system of the communications network. The network elements notify
the management system of results of the monitoring of the
destination addresses, from which the management system can
determine the traffic volume. Via the interfaces (e.g., a Q
interface) providing the connection between the management system
and the network elements, instructions are then transmitted to the
network elements relating to logical connections to be switched by
the network elements. In this manner, the management system
establishes the logical connections in the network in accordance
with the optimized configuration.
[0019] Advantageously, an optimized configuration is determined
periodically and the logical connections are updated periodically.
This may be done, for example, every day, every hour, or every
minute (pseudo-online), depending on the application.
[0020] FIGS. 2a and 2b show three network elements CC1-CC3 of the
synchronous digital communications network in one embodiment of the
invention, the first and second network elements and the second and
third network elements being physically interconnected by, e.g.,
optical fibers or coaxial cables, but the physical connections are
not shown in the figure. The connections shown are logical
connections. Each of the three network elements is connected via an
interface to a central management system TMN. From the latter they
can receive instructions as to which logical connections have to be
switched internally. Connected to the three network elements
CC1-CC3 are routers RTR1-RTR3, respectively, which provide the
gateways from respective local area networks (not shown) to the
communications network. The router routes data packets from the
local area network connected to it which are destined for an
addressee in another local area network to the network elements
connected to it, where they are packetized in subunits of
synchronous transport modules and transmitted over one of the
logical connections to a further network element.
[0021] According to the invention, the destination address of each
data packet is monitored in the sending network element prior to
the packetizing of the data packet. The result of this monitoring
is passed in the form of a message MTL to the central management
system TMN. It is also possible to combine the results of the
monitoring of two or more data packets to be transmitted and send
them as one message MTL to the management system TMN.
[0022] In the configuration shown in FIG. 2a, there are two logical
connections between every two adjacent network elements, while
there is no logical connection between the two remote network
elements CC1 and CC3. This configuration is suitable for high data
traffic volumes between the adjacent network elements CC1, CC2 and
CC2, CC3. Traffic between remote network elements, i.e., data
packets to be sent from CC1 to CC3, must be depacketized in CC2,
passed to the associated router RTR2, checked there, and returned
to CC2, from where they can then be transmitted to CC3.
[0023] In all three network elements, the destination addresses of
all data packets to be transmitted by the respective network
element are monitored. The results of the monitoring are
communicated as messages MTL to the central management system TMN.
The management system TMN determines the current traffic volume
from these messages, and from the current traffic volume, it
determines an optimized configuration with which the logical
connections in the communications network are then updated. To do
this, the management system sends to the network elements
instructions ANW relating to the logical connections to be switched
by each network element.
[0024] If increased data traffic occurs between the remote network
elements CC1 and CC3, the management system TMN will determine that
a logical connection between the network elements CC1 and CC3 is
necessary for an optimized configuration, and will send to the
network elements CC1-CC3 an instruction ANW to switch the
corresponding connection, i.e., to switch a virtual container
representative of the logical connection from the first network
element CC1 through the second network element CC2 to the third
network element CC3.
[0025] The optimized configuration for data traffic between the
remote network elements CC1 and CC3 is shown in FIG. 2b. The
optimization increases the throughput of IP packets and reduces the
transmission delays through the communications network.
[0026] From the IP routers, such an optimization of the
communications network would not be possible, since the IP routers
have no knowledge of the topology of the network. By contrast,
newly established or no longer existing logical connections can be
automatically identified and used or circumvented by the routers,
for example by the polling method. Therefore, after short
identification times, the transmission network dynamically
optimized by the method according to the invention can be used by
routers for routing.
[0027] Another advantage is that at the gateways to the
communications network, commercially available routers with
commonly used interfaces can be employed, such as routers with E1,
E3, E4, T1, T3, DS1, DS3, OC-n, or STM-n interfaces. The user
equipment need not be modified, either.
[0028] Advantageously, the monitoring of the destination addresses
is performed in crossconnectors which are designed to switch
logical connections in a synchronous digital communications
network.
[0029] Instead of providing network elements with IP monitors for
monitoring the destination addresses, the routers may be provided
with an interface to the central management system for informing
the management about the current traffic situation.
[0030] A further development of the invention consists of
monitoring not only the destination addresses of the data packets,
but also the source addresses. In this manner, charging for the
transmission of data packets can be implemented, for example by
simply counting the transmitted data packets for each source.
[0031] According to another development of the invention, data
packets selected according to predetermined criteria are given
preferential treatment, i.e., higher priority. Such criteria may be
particularly the source or destination addresses of the data
packets. In this manner, a more reliable and faster data link can
be made available to selected users, for example to users paying a
higher tariff.
[0032] According to a further development of the invention,
experience gained in cyclically occurring traffic situations are
taken into account in determining the optimized configuration. Such
experience may be gained, for example, by statistical eveluation
over prolonged periods of time or from the typical behavior of
individual users. For instance, it may be known from observations
that every Sunday night, two users exchange data with a high data
traffic volume. The transmission capacity regularly required for
this transaction is then automatically made available in the form
of a logical connection already shortly before the beginning of the
data transfer and the connection is automatically released after
termination of the transaction.
* * * * *
References