The X25 Network Access Protocol

Abstract

The protocols used in a computer network are the mechanisms by which the various entities: nodes, hosts, processes, and users, exchange information in a secure and controlled manner. Because of the number of entities involved, communications protocols are structured into layers, each layer having its own specific protocol. The purpose of a layer is to carry out communication for a higher layer using lower layers as carriers. Each layer allows communication between two similar entities, for example node to node, host to host, user to user. The boundaries between layers has been the subject of considerable debate in standards committees throughout the Western world. Various networks already implemented have defined their own protocols and therefore their own layers. New networks are trying to match the currently agreed layer architecture so that intercommunication will be possible through standard mechanisms.