Technical Report CS0642

Authors: R. Cohen and A. Segall
Abstract: In this paper we address tile issue of dynamic management of isochronous bandwidth in integrated rings. We propose a new scheme that allows dynamic maintenance, allocation and release of the isochronous bandwidth, achieving the following properties: (1) The scheme is flexible since it permits the stations to bundle together several low-speed isochronous channels to form one high-speed isochronous channel. Thus, integration of isochronous traffic with different bandwidth requirements is supported. (2) The acquiring of isochronous channels by ring stations, as well as their release, are cheap, fast and simple processes. The main reason rests with the fact that there is no need to communicate with other stations for this purpose. (3) The acquiring and release processes are decentralized. This means that each station can acquire or release channels by local actions. Thus, problems caused by a failure of a management station, when such a station exists, are reduced. (4) The overhead bandwidth required by the scheme is negligible. (5) The allocation rate is not affected by the number of stations in the ring or by the number of stations that require isochronous channels at the same time. This property is very important in High Speed Local and Metropolitan Area Networks with a dynamic number of stations, up to several thousands. The main principle behind the new scheme is to divide the isochronous bandwidth into fixed length slots and to maintain the available channels in each slot as a linked list. The paper presents a mechanism to recover from transmission errors and station failures that may interfere with the proper operation of the new scheme. The main concepts of the paper are applicable to the FDDI-II networks also.
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