Performance evaluation of the FDDI medium access protocol for real-time traffic

Student thesis: Master's Thesis

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Author(s)

  • Hin Ho Peter TSANG

Related Research Unit(s)

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date27 Jun 1998

Abstract

The FDDI Standard specifies a 100 Mbits/sec fiber optic token ring network that has been implemented and widely installed. The FDDI medium access control (MAC) protocol, however, has the inherent deficiency that at most one half of the bandwidth of a FDDI ring can be used to transmit synchronous messages. In a recent paper by K. Shin and Q. Zheng [18], a modification to the FDDI MAC protocol, called FDDI-M, has been proposed to overcome this deficiency. It has been shown through simulations that FDDI-M doubles a ring's ability of supporting synchronous traffic while at the same time achieves a higher throughput for asynchronous traffic than the standard FDDI. This will be useful for building multi-service high-speed network. FDDI ring will be an option to support such high-volume data passing. However, there is no literature research made on this topic except the only one from the Shin and Q. Zheng [18]. More specifically, the timing properties of the FDDI that has been studied extensively before [13,17] should be revisited under this enhanced protocol. In this thesis we study these timing properties of the FDDI-M protocol as well as its performance for real-time video traffic. In addition, a crucial factor for handling the synchronous messages is the synchronous bandwidth allocation (SBA) scheme. The schemes that have been studied in the thesis are full-length allocation scheme, proportional allocation scheme and normalized proportional allocation scheme. Using the worst case achievable utilization (WCAU) as the performance metric, which is the approximation of the least upper bound of the achievable utilization, we evaluate the performance of the SBA schemes in guaranteeing synchronous message deadlines. It is found that the FDDI Standard specifies a 100 Mbits/sec fiber optic token ring network that has been implemented and widely installed. The FDDI medium access control (MAC) protocol, however, has the inherent deficiency that at most one half of the bandwidth of a FDDI ring can be used to transmit synchronous messages. In a recent paper by K. Shin and Q. Zheng [18], a modification to the FDDI MAC protocol, called FDDI-M, has been proposed to overcome this deficiency. It has been shown through simulations that FDDI-M doubles a ring's ability of supporting synchronous traffic while at the same time achieves a higher throughput for asynchronous traffic than the standard FDDI. This will be useful for building multi-service high-speed network. FDDI ring will be an option to support such high-volume data passing. However, there is no literature research made on this topic except the only one from the Shin and Q. Zheng [18]. More specifically, the timing properties of the FDDI that has been studied extensively before [13,17] should be revisited under this enhanced protocol. In this thesis we study these timing properties of the FDDI-M protocol as well as its performance for real-time video traffic. In addition, a crucial factor for handling the synchronous messages is the synchronous bandwidth allocation (SBA) scheme. The schemes that have been studied in the thesis are full-length allocation scheme, proportional allocation scheme and normalized proportional allocation scheme. Using the worst case achievable utilization (WCAU) as the performance metric, which is the approximation of the least upper bound of the achievable utilization, we evaluate the performance of the SBA schemes in guaranteeing synchronous message deadlines. It is found that, in comparison with FDDI, the FDDI-M protocol results in a higher WCAU for the normalized proportional SBA scheme. For the local SBA schemes, full-length allocation scheme and proportional allocation scheme, the WCAU values remain zero. However, for many types of real-time application such as video transmission, some frame loss is acceptable. We explore the performance of FDDI-M for this important class of applications and show that it is superior to that of FDDI even for the local SBA schemes. We also demonstrate an early frame discard strategy that will greatly improve the throughput of the system. he normalized proportional SBA scheme. For the local SBA schemes, full-length allocation scheme and proportional allocation scheme, the WCAU values remain zero. However, for many types of real-time application such as video transmission, some frame loss is acceptable. We explore the performance of FDDI-M for this important class of applications and show that it is superior to that of FDDI even for the local SBA schemes. We also demonstrate an early frame discard strategy that will greatly improve the throughput of the system.

    Research areas

  • Ring networks (Computer networks), Computer network protocols, Fiber Distributed Data Interface (Computer network standard)