DESIGN AND IMPLEMENTATION OF A RELIABLE DATAGRAM PROTOCOL

Abstract

With their continuing invasion into every facet of human life, computers have come a long way in a very short time! The ability to access information/resources between physically widely separated computers increases their utility manifold. The need for computer communication has led to the proliferation of computer networks which enable users to access resources and information irrespective of the relative location between the two. It is the communication protocol software that brings a network to life. The TCP/IP protocol suite is the most widely used communication protocol. The transport layer User Datagram Protocol(UDP) of this suite provides unreliable delivery service In this dissertation, a new protocol layer, RDP, has been added above UDP to provide reliability. Using RDP, the user need not worry about packet sequencing, retransmissions, timeouts, duplicate detection etc., all of which would be required if he directly uses UDP. The receiver part of RDP is implemented as a concurrent server process and a receive function, rdprecv, with the server handling the job of receiving and assembling datagrams forming the message. It uses shared memory to communicate the message to rdprecv which then passes it to the recipient user process. The access to the shared memory by the server and rdprecv is controlled by a semaphore. The sending part of RDP is implemented as a function, rdpsend, which contacts the server on the destination machine and transmits messages addressed to processes on that machine.