ABSTRACT
As discussed in previous chapters, the physical layer provides physical connection and services to the data link layer, while the data link layer is concerned with the construction of frames, error control, flow control, and the transmission of frames over the physical circuit connection between computers or even between different types of networks. The frames (containing user’s data) may have to go through a number of nodes (computers, networks) which may be connected in different topologies. The network layer entity uses the services of the data link layer and provides services (routing of packets, relaying, congestion control, etc.) to its higher layers (transport) and also to different types of intermediate networks or sub-networks. The primary functions of the network layer are routing, selection of appropriate faults, controlling of overloading or congestion of traffic on communication lines, efficient use of various communication lines, etc. This layer manages network layer connections and provides an end-to-end reliable packet delivery mechanism. This layer provides user-to-user connection for exchange of data between them.
