Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Patent
1997-12-05
2000-09-26
Ton, Dang
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
370401, H04L 1228, H04L 1256
Patent
active
061251186
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The Telecommunications Infrastructure has structure resulting from fundamental differences between its three component parts--the Access Infrastructure which provides connection to users, the Switching Infrastructure which provides dynamic handling of communication entities (e.g. "calls") and the Transport Infrastructure which interconnects geographically separated segments.
Telecommunications Networks are logical entities mapped onto the infrastructure, illustrated in FIG. 1. A Network can be of any size and may be "bent" into any shape but is limited by the infrastructure: in particular no discontinuities are permissible, which may be interpreted as meaning that the only acceptable topologies are those which will map retrospectively onto the existing infrastructure.
Aspects of a design for a segment of the access layer of an Asynchronous Transfer Mode (ATM) infrastructure conforming to the above definition are described.
SUMMARY OF THE INVENTION
According to the present invention there is provided an ATM Access Network or Segment of an Access-Layer Infrastructure comprising a plurality of subscribers or extensions linked to one or more gateways having ports providing access to/from higher network layers where the linking from the subscribers or extensions to the gateways is by the statistical-multiplexing of ATM cells carried in time-slots formatted onto broadband bearers where a desired gateway is identified by a number carried in the Virtual-Path Identifier field of each ATM cell and the source is identified by a number carried in an additional address field external to the ATM cell but internal to the time-slot, the linking from the gateways to the subscribers or extensions being by means of a distribution switch where the desired subscriber is identified by the number carried in the additional address field and the source is identified by the number carried in the Virtual Path Identifier field of the cell.
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 is a pictorial illustration of a Telecommunications Infrastructure;
FIGS. 2a(i) and 2a(ii) show the upstream and downstream Access-Segment User-Network Interface (UNI) formats respectively for the subscriber interface;
FIGS. 2b(i) and 2b(ii) show the upstream and downstream Access-Segment Slot formats respectively for the subscriber interface;
FIG. 3 shows a diagrammatic model of an ATM infrastructure.
FIG. 4 shows diagrammatically an ATM access node for the present invention;
FIG. 5 shows a diagrammatic representation of a router for the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The two most basic requirements of the access infrastructure are concentration and grooming.
Paths and channels through an ATM network are carried on tracks. A track will only occupy bandwith on the network bearers when it is carrying information; thus the track of a path or channel is a virtual entity which has real existence only when carrying information.
Therefore, within the limits of the fixed-size Virtual-Path and Virtual-Channel address fields carried in the ATM cell header (VPI and VCI fields), it is possible within one segment of an access infrastructure to define permanent virtual-tracks between all of the subscribers and one or more gateways into the upstream switching layer.
Concentration is provided in the upstream direction by statistically-multiplexing the multiplicity of sources onto a single bearer of bandwidth compatible with a good quality-of-service and expected usage. Distribution is provided in the downstream direction by addressing source information to the virtual-track of the required subscriber.
Grooming is provided by the subscriber addressing one of a choice of virtual-tracks accessing two or more separate gateways. Each gateway in a segment of the access infrastructure with a single higher-level network or service on the upstream side and with a group of subscribers within
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Marconi Communications Limited
Sam Phirin
Ton Dang
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