Internet Protocols :
By the term protocol, we mean the set of rules of standards designed to enable computers to be connected with one another and to exchange information among them with very little error. A protocol can describe low-level details of machine-to-machine interfaces (e.g., the order in which bits and bytes are sent across a wire) or high-level exchange between allocation programs (e.g., the way in which two programs transfer a file across the internet).
The five most commonly used internet protocols are :
- Internet Protocol (IP): The Internet Protocol (IP) is the primary network protocol used on the internet, developed in the 1970s. On the internet and many other networks, IP is often used together with the Transport Control Protocol (TCP) and referred to interchangeably as TCP/IP.
IP supports unique addressing for computers on a network. Most networks use the Internet Protocol version 4 (IPv4) standard that features IP addresses four bytes (32 bits) in length. The newer Internet Protocol version 6 (IPv6) standard features address 16 bytes (128 bits) in length.
The Internet Protocol (IP) is a network-layer (Layer 3) protocol that contains addressing information and some control information that enables packets to be routed. IP is documented in RFC 791 and is the primary network-layer protocol in the Internet protocol suite, Along, with the Transmission Control Protocol (TCP), IP represents the heart of the internet protocols.
- Internet Control Message Protocol (ICMP): ICMP is a message control and error-reporting protocol between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP) datagrams, but the messages are processed by the IP software and are not directly apparent to the application user.
- Transmission Control Protocol: TCP is a set of rule (protocol) used along with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. While IP takes care of handling the actual delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.
For example, when an HTML file is sent to you from a Web server, the Transmission Control Protocol (TCP) program layer in that server divides the file into one or more packets, numbers the packets, and then forwards them individually to the IP program layer. Although each packet has the same destination IP address, it may get routed differently through the network.
TCP is known as a connection-oriented protocol, which means that a connection is established and maintained until the message or messages to be exchanged by the application program at each end have been exchanged. TCP is responsible for ensuring that a message is divided into the packets that IP manages and for reassembling the packets back into the complete message at the other end. In the Open Systems Interconnection (OSI) communication model, TCP is in layer 4, the Transport layer.
- User Datagram Protocol (UDP): UDP is a connectionless protocol that works at the transport layer. UDP transports datagrams but does not acknowledge their receipt. UDP also uses a port address to achieve datagram delivery, but this port address is simply a pointer to a process, not a connection identifier, as it is with TCP. The lack of overhead makes UDP faster than TCP. Hence, a sender wishing to send a small message and does not care much about the reliability of UDP.
UDP gives a connectionless service. Each user datagram sent by UDP in an independent datagram. There is no relationship between the various user datagrams and does not inform the sender the same.
UDP gives a connectionless service. Each user datagram sent by UDP is an independent datagram. There is no relationship between the various user datagrams even when they are coming from the same source process and going to the same destination program. The user datagrams are not numbered. Moreover, each user datagram can travel a different path.
Each request must be small enough to fit into one user datagram. Only those processor send-ing short messages need to use UDP because it cannot cut messages into small segments.
5.Address Resolution Protocol (ARP): address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP address) into a physical machine address that is recognized by the local network.
When an incoming packet destined for a host machine on a particular local area network arrives at a gateway, the gateway asks the ARP program to find a physical host or MAC address that matches the IP address. The ARP program looks in the ARP cache, and if it finds the address, and sent to the machine. If no entry is found for the IP address, ARP broadcasts a request packet in a special format to all the machines on the LAN. If one machine knows that it has that IP address associated with it. ARP updates the ARP cache for future reference and then sends the packet to the MAC address.
Since protocol details differ for each type of local area network, there are separate ARP Requests for Comments (RFC) for Ethernet, ATM, Fiber Distributed-Data Inter-face, HIPPI, and other protocols.
There is a Reverse ARP (RARP) for host machines that do not know their IP address. RARP enables them to request their IP address from the gateway’s ARP cache.