V. Pallios, Th. Antonakopoulos and V. Makios:

A High Speed Access Mechanism for a multiservice LAN at 144 Mbps

The 8th European Conference on Electrotechnics, IEEE, Stockholm, Sweden, June 1988, pp. 256-260.

Abstract: A prototype of a high speed access mechanism that performs the required services of the Medium Access Layer (MAC) following the ISO model of OSI, has been implemented and tested. This access mechanism, called Access Control Manager (ACM), is part of the node hardware and software for a multiservide fiber-optics LAN at 144 Mbps. The network traffic includes both stream (circuit switched) traffic and bursty (packet switched) traffic. Therefore a hybrid protocol for the access on the medium is followed based on a Dynamic Asynchronous Time Division Multiplexing (DATDM) scheme. Because of the high speed stream traffic involved, fiber cab 1e has been chosen as the network carrier following an active bus topology and the carrier speed has been set at 144 Mbps. The Physical Layer at the interface with the ACM provides: i) An 8-bit bus that carries information and commands (delimiters) of the hybrid protocol at a rate of 18 Mbytes/sec.  ii) A 4-bit bus that carries commands of the hybrid protocol at a rate of 18 Mbytes/sec.  iii) Control signals related to the previous mentioned buses, e.g. strobes, and status signals, that discriminate between command and information data at the buses.

The first part of the ACM, called Sense channel is responsible for the recognition of the hybrid protocol delimiters, the control of the proper evolution of the frame in conjuction with the node manager, and the recognition of the right of access of the node in which it belong. The second part, called Write Channel, is responsible when it is notified from the Sense channel to add the required hybrid protocol delimiters to the bursty data, to multiplex the stream and bursty data and to synchronize the transmission during the required stuffing periods. Finally the third part of the ACM, called Read channel, is responsible to recognize the hybrid protocol commands, to demultiplex the received information to stream and bursty data, to decapsulate the protocol delimiters, and to pass to the upper layers transparently stream data and bursty data that their address matches the address of the node where it belongs.

The ACM has been built using discrete LSI and MSI components (fast TTL family) because of the required high speed of operation. The prototype has been implemented on three Eurocards using wire-wrap techniques.

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