Telecommunications network

Details Telecommunications network Telecommunications network

1995-07-11

1997-05-06

Chin, Wellington

Multiplex communications

Pathfinding or routing

Switching a message which includes an address header

H04J 326

Patent

active

056278241

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

In United Kingdom Patent Application No. GB 2255257 is described an earlier concept for an Asynchronous Transfer Mode (ATM) self-routing network which may be used for Private Networks, Virtual Private Networks and distributed Local Area Switches in the Public Network. The service is connectionless using a, special format of the address octets i n the cell header; cells are directed to their respective destinations by an Interpreter held in each elemental switch or at each switch input port, depending upon implementation. No overhead is required in the cell Information Field which therefore corresponds to the payload in the ATM layer or a composite network; hence the use of standard adaption-layer formats is not compromised. This application is included herein by reference.
The network is divided into Mini-Networks typically with up to 256 user Network Ports. The size of the address field limits the number of Mini-Networks served to 16. The resultant cell header format is shown in FIG. 1.
It will be seen that such a network is limited to a maximum of 4k (4,096) User Network Ports, although thee use of multiplexers can substantially increase this number.


SUMMARY OF THE INVENTION

According to the present invention there is provided a telecommunications switching network comprising a plurality of sub-networks, each sub-network having a plurality of User Network Ports wherein the Destination and Source addresses in a cell-header carried by a cell switched by the network are each divided into a Port Address part and a Sub-network Address part and wherein the Source Sub-network part is implicit whilst the cell remains in the Source Sub-network and similarly the Destination Sub-network part is implicit from when the cell arrives in the Destination Sub-network, wherein the Source and the Destination Sub-networks are linked via a cross-connect switching device wherein the address formats are changed.


BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example, with reference to the accompanying drawings, in which:
FIG. 1 shows an example of a prior art cell header format;
FIG. 2 shows a variation of the format shown in FIG. 1 with the cross-connect function of the present invention;
FIG. 3 shows a further variation of the format shown in FIG. 1 having a modified cross-connect function;
FIG. 4 shows diagrammatically the paths between users on two mini-networks.
FIGS. 5 and 6 show diagrammatically the transmit and receive functions for a public network link;
FIG. 7 shows diagrammatically the signalling system between peripheral nodes for the present invention;
FIG. 8 shows diagrammatically the use of a Public Network Port address with addresses allocated in site networks.


DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The earlier network, as described above, uses a common address format throughout (apart from changes at the Public Network Port used in mapping to Public Virtual Circuits (PVCs) for inter-site links). This means that the Source Mini-Network address is carried in the source Mini-Network where it is redundant, being implicit, and similarly the Destination Mini-Network address is carried in the destination Mini-Network. FIG. 2 shows how, by eliminating this redundancy, in accordance with the present invention, the address capability may be expanded.
In the figures shaded areas show where changes have been made from the earlier format.
Two slightly different formats are used for the Source and Destination Mini-Networks respectively and, since a Mini-Network is relatively unstructured internally, it is necessary to inform the interpreters which format is being used and this is done by using the least significant bit of the most significant octet of the cell header as a Source/Destination (S/D) format indicator. Within the cross-connect function both Source and Destination Mini-Network identities must be known but, since the total information required to be held exceeds the capacity of the standard cell header format, the function mus

REFERENCES:
patent: 5157654 (1992-10-01), Cisneros
patent: 5315588 (1994-05-01), Kajiwara et al.

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