From the computer networking point of view, a packet is referred to a planned data unit. But certain computer communication links such as point to point communication don’t support data packets. In such cases, data is simply transmitted as an array of bytes or characters etc over the medium. Anyway, transformation of data into packets is a good way to achieve better bitrate of a communication medium in the course of sharing data amongst the users.
Well! You can say that packet is the central unit of an information transmission process within a network system. Typically, networks are using the TCP/IP (communication protocol) set of rules between the communicating computer devices. And according to IP protocol rules, information should be divided in the form of packets. But a packet will contain the subdivision of data (to be broadcast) as well as the receiver’s address (destination of that data). This is also considered as the packet-switching technology and according to which a data packet is consisted on two different types of information:
- control information included: source address, destination address and error detection codes(checksums) etc
- payload (user data)
That means the principal internet communication protocol IP is used to pass the datagram packets from one machine to another over the internetwork with the assistance of internet protocol suite. IP as a primary protocol resides over internet layer of that Suite and is fulfilling the task of to hand over the datagrams from the source user to the destination user with the help of their addresses. Moreover, IP is defining the addressing techniques and datagram encapsulation structures as well. “Encapsulation” is a process in which each packet is further labeled along with a header (containing meta-data) so delivery of these tagged packets becomes possible.
But IP protocol was designed to provide a connectionless datagram service (according to the original data transmission control plan). Its 1st version is now referred to as IPv4 (internet protocol version 4) while second version IPv6 (internet protocol version 6) is the growing deployment all over the world. The key benefit of this connectionless model is actually that, all packets in the course of transmission are forwarded ahead independent of their accompanied other packets. So in case of a link or else router failure, these packets are speedily switched to another path.
An IP protocol definition is exhibited that it is a connectionless, thus, it is an unreliable protocol. That is because it doesn’t care about either a packet is reached to its destination or not. Moreover, an IP protocol knows nothing about connections, port numbers and data sequences. But its sole job is to transmit and route packets to their destinations. In short, IP packets are self-governing units. A packet always has a header along with a data field. The header contains addresses and other routing information. In other words, an IP header contains the following fields: header length, service type, source and destination IP addresses and data. You can regard a packet as a letter and think about the header as an envelope while the data field is anything or anyone place inside that envelope.