The rules and regulations which should be followed to communicate data on a network are called network protocols. The OSI Model and any other network communication models, provided only a conceptual framework for communication between computers, but the model itself does not provide specific methods of communication. Actual communication is defined by various communication protocols. In data communication, a network protocol is a formal set of rules and data structure that directs how computers and other network devices exchange information over a network. In other words, protocol is a standard procedure and format that two data communication devices must understand, accept and use to be able to talk to each other
In modern protocol design, network protocols are “layered” according to the OSI 7 layer model or similar layered models. Layering is a design principle which divides the protocol design into a number of smaller parts, each accomplishes a particular sub-task, and interacts with the other parts of the protocol only in a small number of well-defined ways. Layering also permits familiar protocols to be adapted to unusual conditions. Networks have certain rules, called Protocols, to send the receive data, and it is defined in the network software. The most common of them are explained as under:
Currently, this is the most commonly used protocol. It uses a high-speed network cable and bus topology, so it is relatively simple receive data, they must follow a set of rules about when to communicate otherwise, two or more computers could transmit at the same time causing lost messages. Before transmitting the data, a node listens” to find out if the cable is in use. If so, the node must wait. When the cable is free from other transmission, the node can begin transmitting immediately. This process is also known as CSMA/CD (Carrier Science Multiple Access with Collision Detection. If by chance, two nodes transmit data at the same time, the message collide. When a collision occurs, a special message, lasting a fraction of second, is sent out over the network to indicate that is jammed. Each node stops transmitting, waits a random period of time, and then transmits again. Since the wait period for each node is random, it is unlikely that they will begin transmitting at the same time again.
It is closely associated with IBM, works on the concept of ring network topology and a token (a kind of electronic signal). The method of controlling access to the shared network cable is called token passing. Only one token is available on the network. When a node on the network wishes to transmit, it first captures the token, only then it can transmit data. When the node has sent its message, it releases the token back to the network. Since only one token is circulating around the network, only one device is able to access the network at a time. Thus no collision occurs but the only disadvantage is its slow data transfer rate.
ARCnet (Attached Resource Computer Network)
The ARCnet has both a topology and networking technology all its own. It uses either twisted-pair wire or coaxial cable, and the star topology is informed with hubs attached to the network.
The original ARCnet protocol was very slow, but it became popular because it was inexpensive, reliable, and easy to set up and to expand. Fast ARCnet increased the transmission rate to 100 Mbits per second and includes the capability to use fiber optic cable.
TCP/IP (Transmission Control Protocol)
TCP/IP is the protocol used by every computer on the Internet. A protocol is a set of rules and procedures that defines how computer receive and transmit data over the network. Every computer on the Internet must have TCP/IP configured. TCP/IP ensures a reliable connection between the computers communicating over the Internet. It also defines a mechanism through which every computer on the Internet is identified separately. TCP/IP software differs for different computers but is always present the same interface to the network. It does not matter if the system on the other end is a supercomputer, a mainframe, minicomputer or microcomputer; as long as it is using TCP/IP, it can send and receive data through the Internet.
ISDN(Integrated Services Digital Network):
ISDN is a set of international communication standers for software control of transmitting voice, video, and data simultaneously as digital signals over twisted-pair telephone lines. Basic rate ISDN provides better quality than analog connections and more reliable digital connections at higher speeds than those offered by analog connections.
DSL (Digital Subscriber Line)
DSL provide high speed, digital data transmission from homes and businesses over existing telephone lines. The existing lines are analog and the transmission is digital, so modems are necessary with DSL technology. DSL is a popular alternative to ISDN.