Frame content independent stripping

摘要

Token rings have the property that a station that transmits a frame on the ring is responsible for removing the frame after it has been delivered to the destination stations. The algorithm to perform the frame removal is called 'Frame Stripping'. Most existing algorithms strip frames based on their content. This is not always adequate. The need for a new algorithm arises from the fact that frames transmitted by a station need not have the station's own address as the source address for a variety of reasons - such as when a bridge transmits a frame or when another address is used as the source address by a station instead of its original station address. This paper discusses a new frame content independent stripping (FCIS) algorithm for token rings.

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The FCIS algorithm counts the number of frames transmitted by the station after capturing the token. In addition, the station places a special delimiter frame at the end of the transmission of frames, before releasing the token. The station then strips all received frames until either the number of frames stripped equals the number of frames transmitted or when either the delimiter frame or a token is received. We demonstrate that the FCIS algorithm has a minimal impact on the performance of the ring. We study the robustness of the algorithm to errors and demonstrate that its reliability is as good as the inherent mechanisms of the token ring.

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The algorithm studied here is very simple to implement and interoperates with other stations not implementing this algorithm. The algorithm places no topological restrictions on the network and has the attractive feature of removing large fragments and no-owner frames.