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Unformatted text preview: nd the trailer (7y from the frames before passing them on to the
network layer. The application layer of the receiver's machine finally passes on the
message in its original form to the communicating process on the receiver's node.
Notice that the software of a particular layer on the sending machine conceptually
communicates only with its peer layer on the receiving machine, although
physically it communicates only with the adjacent layers on the sending machine.
This abstraction is crucial to network design.
Interconnecting of two or more networks to form a single network is called
internetworking, and the resulting network is called an internetwork. Therefore, a
WAN of multiple LANs is an internetwork.
Internetworks are often heterogeneous networks composed of several network
segments that may differ in topology and protocol. For example, an internetwork
may have multiple LANs, some of which may have multi-access bus topology
while others may have ring topology; some of these LANs may be using Ethernet technology which others may be using Token Ring technology; and some
segments of the network may be using the IP suite while others may be using
IBM's SNA (System Network Architecture) protocol suite. Internetworking allows
these, relatively unrelated networks to evolve into a single working system. That
is, the goal of internetworking is to hide the details of different physical networks,
so that the resulting internetwork functions as a single . Interconnecting two
networks having the same topology and protocol is simple because the two
networks can easily communicate with each other. However, interconnecting two
dissimilar networks that have different topologies and protocols requires an
internetworking scheme that provides some common point of reference for the two
networks to communicate with each other. That point of reference might be a
high-level protocol common to the two networks, a device that allows
interconnection of different topologies with different physical and electrical
characteristics, or a protocol that allows operating environment differences to be
ignored. The m...
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This document was uploaded on 04/07/2014.
- Spring '14