IP Routing Protocols

A CLOSER LOOK AT THE LAYER OPERATIONS

Layered network protocols allow interaction between functionally paired layers in different locations without affecting other layers. This concept aids in distributing the functions to the layers. In the majority of layered protocols, the data unit, such as a message or packet, passed from one layer to another is usually not altered, although the data unit contents may be examined and used to append additional data (trailers/headers) to the existing unit.

Each layer contains entities that exchange data and provide functions (horizontal communications) with peer entities at other computers. For example, in Figure A-3, layer N in machine A communicates logically with layer N in machine B, and the N+1 layers ...