language: en

A Protocol for Efficient Transfer of Data over Fiber/Cable Systems

Dolors Sala John O. Limb
School of Electrical College of Computing and Computer Engineering Georgia Institute of Technology
Atlanta, GA 30332-0280
E-mail: (dolors,limb)@cc.gatech.edu

Abstract A revolution is occurring in the scope and range of information, communication and education services that will be made available to schools, libraries, town-halls, clinics and, most importantly, residences. These services will be provided initially, primarily over hybrid fiber-cable systems, either by telephone companies or cable companies. The old cable plant is being upgraded and used in totally new ways. The topology and physical characteristics of the upstream channel present new challenges for efficient channel access. We present a media access protocol that efficiently transfers data on this channel. A primary goal in the design was to keep the portion of the protocol resident in the station as simple as possible. Thus we use centralized control located in the cable head-end and minimize intelligence in the station. We refer to this protocol as Centralized Priority Reservation or CPR. A station wishing to transmit sends a request to the head-end using a contention channel. The head-end acknowledges the request and then schedules the request, informing the station by means of a grant message when to transmit. The protocol performs well under heavy load. Performance is affected little by the number of stations, the speed of the system and the physical length of the system.

1 Introduction