A Distributed Scheduling Algorithm for Real-Time Communication on Slotted Shared Medium

Algorithms for arbitrating and scheduling transmissions from different transmitters sharing a common access medium arise often in the design of many shared and distributed systems. In this paper we present a distributed algorithm for arbitrating time-constrained transmissions on slotted shared access media. The two most important distinguishing features of our algorithm are: (1) unlike most of the other schemes that guarantee on-time transmission over shared media by centralized preallocation of slots, our algorithm is fully distributed and completely on-line; (2) it eliminates one of the common pitfalls of all slotted systems, that is, allocation in integral multiples of full slots. We derive sufficient conditions for schedulability and show that the proposed scheme achieves high levels of schedulable utilization. We also show that the schedulable utilization increases as the length of the allocation cycle increases and asymptotically approaches the maximum achievable utilization. We present a distributed slot access protocol to realize the proposed algorithm for ring architecture. The protocol can be easily modified for other topologies, such as bus and dual-bus networks. Using illustrative examples we demonstrate the effectiveness of the algorithm.

[1]  Ignas G. Niemegeers,et al.  Performance modelling of the Orwell basic access mechanism , 1987, Computer Communication Review.

[2]  Guy Pujolle.  Local Communication Systems: Lan and Pbx , 1987 .

[3]  Paul M. Chau,et al.  An extension to the SCI flow control protocol for increased network efficiency , 1996, TNET.

[4]  Jay K. Strosnider,et al.  Scheduling real-time communication on dual-link networks , 1992, [1992] Proceedings Real-Time Systems Symposium.

[5]  Qiang Li,et al.  The Scalable Coherent Interface (SCI) , 1996, IEEE Commun. Mag..

[6]  Henning Schulzrinne,et al.  Real-time communication in packet-switched networks , 1994, Proc. IEEE.

[7]  Raj Jain.  Performance analysis of FDDI token ring networks: effect of parameters and guidelines for setting TTRT , 1990, SIGCOMM '90.

[8]  Chung Laung Liu,et al.  Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment , 1989, JACM.

[9]  Biswanath Mukherjee,et al.  A Journey Through the DQDB Network Literature , 1992, Perform. Evaluation.

[10]  Wa Halang,et al.  REAL-TIME SYSTEMS .1. , 1990 .

[11]  Satish K. Tripathi,et al.  On guaranteed delivery of time-critical messages in DQDB , 1994, Proceedings of INFOCOM '94 Conference on Computer Communications.

[12]  Ignas G. Niemegeers,et al.  A Performance Modeling and Evaluation of the Cambridge Fast Ring , 1992, IEEE Trans. Computers.

[13]  Michael Teener,et al.  FDDI-II operation and architectures , 1989, [1989] Proceedings. 14th Conference on Local Computer Networks.

[14]  Kang G. Shin,et al.  On slot allocation for time-constrained messages in DQDB networks , 1995, Proceedings of INFOCOM'95.

[15]  Parameswaran Ramanathan,et al.  Real-time computing: a new discipline of computer science and engineering , 1994, Proc. IEEE.

[16]  Andy Hopper,et al.  The Cambridge Backbone Ring , 1990, Proceedings. IEEE INFOCOM '90: Ninth Annual Joint Conference of the IEEE Computer and Communications Societies@m_The Multiple Facets of Integration.

[17]  Andy Hopper,et al.  The Cambridge Fast Ring Networking System , 1988, IEEE Trans. Computers.

[18]  Shirish S. Sathaye,et al.  Generalized rate-monotonic scheduling theory: a framework for developing real-time systems , 1994, Proc. IEEE.

[19]  Wei Zhao,et al.  Optimal synchronous capacity allocation for hard real-time communications with the timed token protocol , 1992, [1992] Proceedings Real-Time Systems Symposium.

[20]  Floyd E. Ross,et al.  An overview of FDDI: the fiber distributed data interface , 1989, IEEE J. Sel. Areas Commun..