MetaRing—A Full-Duplex Ring with Fairness and Spatial Reuse

Abstract

We describe the design principles of a ring network with spatial bandwidth reuse. Our goal is to provide the same functions of existing LAN/MAN designs that do not permit spatial reuse and concurrent transmission. A distributed fairness mechanism for this architecture, which uses low latency hardware control signals, is presented. The basic fairness mechanism can be extended for implementing multiple priority levels and integration of asynchronous with synchronous traffic. The ring is full-duplex and has two basic modes of operation: buffer insertion mode for variable size packets and slotted mode for fixed size packets or cells. As a result, this architecture is suitable for a wide range of applications and environments. Concurrent access and spatial reuse enable the simultaneous transmissions over disjoint segments of a bidirectional ring, and therefore, can increase the effective throughput, by a factor of four or more. The efficiency of this architecture does not degrade as the bandwidth and physical size of the system increases. The combination of a full-duplex ring, spatial reuse, reliable fairness mechanism and the exploitation of the recent advent in fiber-optic technology are the basis for the MetaRing network architecture. This network has been prototyped at the IBM T. J. Watson Research Center, and will also be deployed within the AURORA Testbed that is part of the NSF/DARPA Gigabit Networking program. © 1993 IEEE