Network Models and Categories of Network Protocols

Network Models

There are two main types of network models Client/Server & Peer-to-Peer.

(1) Client/Server

This arrangement involves a server, which is a computer that controls the network. In particular, a server has the hard disks holding shared files/databases and often shared quality printer, which can be used by all nodes. The clients are all the other computers on the network. Under this arrangement, the server usually does processing. Client/server has attracted a lot of attention because a well-designed system reduces the volume of data traffic on the network and allows faster response at each node. (Also, since the server does most of the heavy work, less expensive computers clients can be used as nodes.

(2) Peer-to-Peer

All computers in a peer to peer arrangement have equal status. No one has control over others. With all files and peripheral devices distributed across several computers, users share each other’s data devices as needed. The main disadvantage in this approach is lack o speed as most peer-to-peer networks slow down under heavy use. Its main disadvantage is the lack of security.

(3) Hybrid

Many networks are hybrid i.e. a combination of both client/server and peer to peer approaches. This takes the advantages of both the above mentioned models.

Categories of Network Protocols

As we know that “The set of rules for exchange of data between computers connected in a network is called network protocols or communication protocols”. The communication protocols are generally divided into two categories named De Facto protocols & De Jure protocols

(1) De Facto Protocols

De Facto protocols are those protocols, which just happened because of historical development. These protocols were developed without any formal plan. These protocols were developed in the early days of computers networking.

De Facto Organizations


The most important De Facto organization involved in establishing communication standards and protocols is CCITT (Consultative Committee for International Telegraph and Telephone). CCITT is a United Nations agency, responsible for defining standards for telephone, telegraph and data communications. One of the most important standards formulated by CCITT is known as X.25 standard, which is one of the most common standards used in Wide Area Networks (WAN).

ii – IBM (International Business Machines)

SNA (System Network Architecture) protocols is an example of De Facto protocol. The IBM developed this protocol in 1974 for its mainframe computers. It is still being used by a large number of organizations all over the world.

(2) De Jure Protocols

De Jure protocols are those protocols, which were properly researched, designed and finally published as a ‘standard’. Such standards are usually researched and published by large international organizations.

De Jure Organizations:


ISO stands for International Standards Organization. It is an international organization concerned with the issuance of standards in various fields. It also publishes communication standards.


IEEE stands for Institute of Electrical and Electronic Engineers. It is the largest organization in the world that defines communication standards. It defines the standards in the field of electrical engineering and computing.

The 802 Project Model of IEEE:

In the late 1970s, when LANs first began to emerge as a potential business tools, the IEEE realized that there was a need to define certain LAN standards. To accomplish this task, the IEEE launched what became known as project 802, named for the year and the month it began (1980, February).

There are three major communication protocols, which were developed by the IEEE.

  • Ethernet (IEEE 802.3)
  • Token Bus (IEEE 802.4)
  • Token Ring (IEEE 802.5)


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