By the term protocol, we mean the set of rules or standards designed to enable computers to be connected with one another.
The most commonly used internet protocol are:
- Internet Protocol (IP)
- Internet Control Message Protocol (ICMP)
- Transmission Control Protocol (TCP)
- User Datagram Protocol (UDP)
- Address Resolution Protocol (ARP)
TCP/IP is an industry-standard protocol suite for Wide Area Networks (WANs) developed in the 1970s and 1980s by the US Department of Defence (DOD). It is a routable protocol that is suitable for connecting dissimilar system in Heterogeneous Networks. It is the protocol of the worldwide network known as the Internet. At that time, it was called ARPANET (Advanced Research Project Administration Network).
The four DOD Model layers as shown in the figure and the OSI model layer correspond to as follows:
- The network access layers to the physical and data link layers of the OSI model.
- The internet layer corresponds to the OSI network layer.
- Host-to-host layer corresponds roughly to the OSI transport layer.
- The application layer corresponds to the OSI session, presentation and application layers.
An e-mail program enables us to send, receive and manage our messages. However, there are few parameters you must be clear about before you start sending and receiving e-mail messages. Email addresses commonly take this form: username@hostname.
OSI stands for Open System Interconnection model. The OSI model was designed by the International Standard Organisation (ISO). It is a seven layer model.
These layers are:
- Physical Layer:- This layer is responsible for the physical connection between two nodes. This layer transfers the bits stream in the form of signals.
- Data Link Layer:- This layer organized the data in the form of packets. These packets contain header and trailer part. Various information related to data transmission is stored in header and trailer like source address, destination address, packet numbers etc. Header, trailer, and data packets are combine known as a frame.
- Network Layer:- This is the third layer of OSI model and responsible for the routing of packets. It has various protocols for shortest and fastest routing of packets like internet protocol, OSPF etc.
- Transport Layer:- This is the fourth layer of OSI model. It receives the data from the network layer and split this data as requires and passes this data to the session layer. It also ensures that all the PCs arrive at the other end correctly.
- Session Layer:- This layer is the network dialog controller. It was designed to establish, maintain, and synchronized the interaction between the communicating systems.
- Presentation Layer:- The presentation layer was designed to handle the syntax and semantics of the information exchange between the two systems. It was designed for data translation, encryption, decryption and compression.
- Application Layer:- Top layer of the OSI model and works as an interface between the user and the network. All the user interactive application are available on this layer like e-mail, file transfer etc. Various protocols available on this layer are FTP, HTTP, SMTP, etc.