Multiplex communications – Wide area network – Packet switching
Patent
1990-11-05
1993-03-30
Olms, Douglas W.
Multiplex communications
Wide area network
Packet switching
370 601, H04L 1256
Patent
active
051990270
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication switching system including a switching network with at least one switching element having a plurality of input links and at least one output link, and processing means for calculating the total bandwidth used by virtual paths on said output link from individual bandwidth values contained in path setup cells used for setting up said virtual paths.
2. Description of the Prior Art
Such a communication switching system is already described in the PCT application No. PCT/EP88/00482. In this known switching system the total bandwidth used by the virtual paths on an output link is obtained by calculating the sum of the individual bandwidth values contained in the path setup cells for these paths. A new virtual path is allowed to be multiplexed on the output link only when the thus calculated total bandwidth is smaller than the maximum allowable bandwidth.
The thus calculated total bandwidth may be erroneous due to a fault, for instance because an individual bandwidth value is erroneous, or due to a calculation error, etc. Such a fault may give rise to a traffic overload on the output link or to an undue restriction of the traffic load on this link since the decision to allow or inhibit the multiplexing of a new virtual path on an output link is based on the thus calculated total bandwidth.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a communication switching system of the above type, but wherein the effect of previous, especially temporary errors, on the calculated total bandwidth is reduced.
According to the invention this object is achieved due to the fact that said processing means re-calculate said total bandwidth at least from said individual bandwidth values contained in maintenance cells transmitted on said virtual paths and adjust said calculated total bandwidth in function of said re-calculated total bandwidth.
By thus recalculating the total bandwidth the effect of temporary errors which possibly occurred during a previous calculation is reduced if not eliminated.
Another characteristic feature of the present communication switching system is that the transmission of said maintenance cells is interleaved with that of said path setup cells and that said processing means store said calculated total bandwidth in a first memory and at the start of a recalculation operation copy said calculated total bandwidth from said first memory into a second memory and reset the contents of a third memory, the total bandwidth stored in said second memory and said individual bandwidth values being then used to re-calculate said total bandwidth in a cumulative way and the successive partial results thus obtained being stored in said third memory.
Still another characteristic feature of the present communication switching system is that the transmission of said maintenance cells is also interleaved with the transmission of path release cells containing an individual bandwidth value relating to the virtual path to be released and that said processing means in addition to performing a path release operation process each of said path release cells in the same way as each of said maintenance cells.
Hence, although the normal operation of the system is continued, i.e. although virtual paths may be built up or released and thus give rise to a change of the contents of the first memory, such a change has no effect on the re-calculation operation since the latter makes use of the contents of the second and third memories only. In other words the bandwidth re-calculation is isolated from the normal bandwidth calculation.
DESCRIPTION OF THE DRAWINGS
The above mentioned and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawings wherein:
FIG. 1 represents a communication switching system according to the invention and details
REFERENCES:
patent: 4896316 (1990-01-01), Lespagnol et al.
patent: 4914650 (1990-03-01), Sriram
ALCATEL N.V.
Chin Wellington
Olms Douglas W.
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