D3Q - the dynamic distributed dual queue an optimised distributed queueing protocol

摘要

Interest in Metropolitan Area Networks (MAMs) is gaining momentunt, with the need to ituerconnectLAYsspreadovercities and suburbs covering large areas and involving high data rates. Standards are emerging (eg. IEEE 802.6, FDDI-11) with different architecturej andprotacols. The particular interest in IEEE 802.6 is with the Distributed 12ueueDualBus (DQDB)protocol because ofits granularity and flexibility ofbandwidth allacatioN use oftransfer rates which are consistent with existing telecommunication transmission hierar chies and cmMmlibility with the emergingAsynchronous Transfer Mode (ATM) based B ISDN However, the DQDB protocol does not appear to be the most optimal andefficient solution. A new concept of a Dynamic DisoibuNdDsmiQueut(D3!2)slmedMACprotacolisproposed in this paper whereby, in comparison with DQDB, access delays are reduced and network capacity is increasedi These improve ments are achieved through the employment of dynamic emM slot generators and empty slot transmitters rather than the static 'Frame Generators I of the current DQDB system architecture. The D"12 protocol operates independently of network speed and size and can optimise the capacity ofa network when utilised in a closed ring structure. However, the same protocol can be applied on open ring1bus structures, thereby enabling a. truly integrated systems architecture to be developed. Some advan tages of a closed ring structure versus an open ring structure for MANs are described. Since L@Q and DQDBprotocols are similar and intendedfor the same applications, thefeatures and the reladveperformances of each implementation are indicated.