Multiplex communications – Pathfinding or routing – Switching a message which includes an address header
Reexamination Certificate
1998-03-06
2001-11-20
Chin, Wellington (Department: 2731)
Multiplex communications
Pathfinding or routing
Switching a message which includes an address header
C370S258000, C370S404000
Reexamination Certificate
active
06320860
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to asynchronous transfer mode (ATM) and, more particularly, to ATM unidirectional path switched ring switching criteria.
2. Discussion of Related Art
Various methods of implementing ATM rings were documented in a Fujitsu paper “Ring Survivability in ATM Networks” presented by Jonathan A. Morgan at the National Fiber Optic Engineers (NFOCE) Conference in June of 1995. However, a solution to provide fast switching independent of the cell traffic was not described. ATM unidirectional path switched ring switching criteria must be independent of cell traffic rate and must be compatible with variable bit rate (VBR) and with Virtual Paths (VPs) set-up but with no traffic.
SUMMARY OF INVENTION
An object of the present invention is to provide ATM path switched ring switching criteria.
According to the present invention, a selection method for selecting a path in an asynchronous transfer mode (ATM) unidirectional path switched ring comprises the steps of (a) defining ring segments as different ring paths originating at a same ATM virtual path (VP) ring input and terminating at a same ATM VP ring output wherein a ring segment includes all ring nodes from the ring input to the ring output, (b) determining a preferred ring segment according to a switching criterion that is independent of cell traffic rate, and (c) group switching all VPs which transit the preferred ring segment determined in step (b).
According further to the present invention, the step of determining comprises the steps of computing a running average of a sum of path bit-interleaved-parity (BIP) error counts for each ring segment and selecting the preferred ring segment as the one having the lowest BIP error count.
The basic idea of the present invention is to base the VP cell ring switching on a criterion that is independent of cell traffic rate, that is compatible with variable bit rate (VBR) and with virtual paths (VPs) set-up but with no traffic. Such a criterion is, according further to the invention, a “ring segment” BIP. As mentioned, an ATM VP ring segment may be defined as originating at the ATM VP ring input at a ring entry node and terminating at the ATM VP ring output at a ring exit node. A ring segment BIP may be composed of the path BIP error counts of multiple synchronous optical network (SONET)/synchronous digital hierarchy (SDH) paths over the ring segment from the ring segment input to the ring segment output.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawing.
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“Cell Loss Priority (CLP) Method of Virtual Path (VP) Protection”, N. Shimada et al, Contribution to T1 Standards Project—T1X1.5/96-133; T1S1.5/96- , NEC America, Inc., Oct. 1996, pp. 1-9.
Alcatel
Chin Wellington
Pham Brenda H.
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