A comparison of two token-passing bus protocols

ABSTRACT

A well known disadvantage of standard token-passing in ring and bus networks is the waste of channel bandwidth often seen in lightly loaded or asymmetric systems. It is possible to make use of the broadcast mechanism in token bus systems to distribute nearly up-to-date information about the state of individual stations to the entire system. One such scheme involves the determination of a randomly varying set of more active stations. These stations are given a chance to form a second logical ring above the standard logical ring that characterizes the token bus. The transmission cycles of the system can thus be made to alternate between standard token-passing and transmission cycles, and the cycles of token-passing and transmission within the logical ring of more active stations. We assume that each station makes at most one transmission when given the chance to transmit. For Poisson arrivals and otherwise general input distributions, the cycle-time distribution of the token is derived for each kind of cycle. An important random variable is the random token turnaround time seen by individual stations. For lightly loaded stations this time tends to be larger than for heavily loaded stations. The distribution of this random time, simple performance measures, and a comparative measure of stability, showing the adaptive scheme to be more stable than the standard, are obtained.

REFERENCES

• Buxw81: W. Bux, "Local-area subnetworks: a performance comparison," IEEE Trans. Commun., pp. 1465- 1473, October 1981.
• Buxw84: W. Bux, "Performance issues in local-area networks," IBM Journal, Vol. 23, No. 4, 1984.
• Cart70: B. Carter, On the Probability Distribution of Rational Functions of Independent H-Function Variates, Ph.D. thesis, University of Arkansas, 1970.
• Cinl75: E. Cinlar, Introduction to Stochastic Processes, Prentice-Hall, Inc., 1975.
• HeSo82: D.P. Heyman and M. J. Sobel, Stochastic Models In Operations Research, Volume I, McGraw-Hill, Inc., 1982.
• IEEE84: IEEE Standard 802.4, Token Passing Bus Access Method and Physical Layer Specifications, 1984.
• ECMA83: Standard ECMA-90: Local Area Networks Token bus (Broadband), September 1983.
• Klei76: L. Kleinrock, Queueing Systems, Volume i1: Computer Applications, John Wiley & Sons, 1976.
• Kueh79: P.J. Kuehn, "Multiqueue Systems with Nonexhaustive Cyclic Service," B.S.T.J., 58, No. 3, pp. 671-698, March 1979.
• Loyn62: R.M. Loynes, "The stability of a queue with non-independent inter-arrival and service-times," Camb. Philos., 58, 3, pp. 497-520, 1962.
• ReNi85: V.I. Rego and L. M. Ni, "A Queueing Model for Token-Passing Computer Networks," submitted to journal for publication, 1985.
• ReHu85a: V.J. Rego and H. D. Hughes, "Modelling an Adaptive Token-Passing Protocol," IEEE Global Telecommunicatio~ Conference , New Orleans, Dec. 1985.
• ReHu85b: V.J. Rego and H. D. Hughes, "Stability And Performance of Adaptive Token-Bus Networks," Submitted, 1985.
• Stal84: W. Stallings, "Local Network Performance," IEEE Communications Magazine, pp. 27-36, Feb. 1984.
• Stro83: Norman C. Strole, "A Local Communications Network Based on Interconnected Token-Access Rings: A Tutorial," IBM J. of Research & Development, Vol. 27, No. 5, September 1983.
• Twee83: R.L. Tweedie, "The existence of moments for stationary Markov chains," J. Appl. Prob., 20, pp. 191-196, 1983
• Wolf82: R.W. Wolff, "Poisson Arrivals See Time Averages," Opns. Res., 30, pp. 223-231, 1982.

INDEX TERMS

Classification:
  C. Computer Systems Organization
  C.1 PROCESSOR ARCHITECTURES
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.5 Local and Wide-Area Networks
          Subjects: Buses

General Terms:
Performance, Standardization, Verification