CS610 Final Term Short Notes Lectures 23-45

CS610 Short Notes final term · Lec 23 to 45 · Website Link:

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Lecture No. 23

INTERNETWORKING: CONCEPTS, ARCHITECTURE AND PROTOCOLS

The Motivation for Internetworking

No single networking technology is best for all needs. A large organization with diverse networking requirements needs multiple physical networks. If the organization chooses the type of network that is best for each task, the organization will need several types of networks.

The interconnection of two or more networks, usually local area networks so that data can pass between hosts on the different networks as though they were one network. This requires some kind of Router or Gateway.

THE CONCEPT OF UNIVERSAL SERVICE:

The chief problems with multiple networks are as follows:

• A computer attached to a given network can only communicate with other computers attached to the same network.
• In the 1970s large organizations began to acquire multiple networks. Each network in the organization formed island. Employees needed to choose a computer appropriate for each task. So they needed multiple screens, keyboards and computers.

UNIVERSAL SERVICES:

A communication system that supplies universal services allows arbitrary pairs of computers to communicate. Universal service is desirable because it increases individual productivity.

UNIVERSAL SERVICES IN A HETEROGENEOUS WORLD:

Extension techniques such as bridging cannot be used with heterogeneous network because of incompatible packet formats.

INTERNETWORKING: Despite the incompatibilities among networks, researchers have devised a scheme that provides universal service among heterogeneous networks called ‘internetworking’. It uses both hardware and software.

Physical Network Connection with Routers

A router is a special-purpose system dedicated to the task of interconnecting networks. A router can interconnect networks that use different technologies, including different media, physical addressing schemes, or frame formats.

Internet Architecture

Organizations seldom use a single router to connect its entire network for two reasons.

•  Because the router must forward each packet, the processor in a given router is insufficient to handle the traffic.
•  Redundancy improved internet reliability.

An Internet consists of a set of networks interconnected by routers. The internet scheme allows each organization to choose the number and type of network, the number of routers to use to interconnect them, and the exact interconnection topology.

Achieving Universal Services

The goal of internetworking is universal service across heterogeneous networks. To provide this service all computers and routers must agree to forward information from a source on one network to a specified destination. The task is complicated as frame formats and addressing schemes may differ. The key is universal protocol software (TCIP/IP).

A Virtual Network

A virtual network is shown in the figure that TCP/IP software provides to users and applications.

LAYERING AND TCP/IP PROTOCOLS: LONG

TCP/IP protocols are organized into five conceptual layers. Although some layers of the TCP/IP reference model correspond to layers of the ISO reference model,