overview of tcp/ip

Overview of TCP/IP:

The TCP/IP protocol suit was developed prior to the OSI model. The TCP/IP protocol suit was defined as having four layers: host-to-network, internet, transport and application. TCP/IP is a hierarchical protocol made up of interactive modules, each of which provides a specific functionality.

The term hierarchical means that each upper level protocol is supported by one or more lower level protocols. At transport layer TCP/IP defines three protocols: (TCP) Transmission Control Protocol, UDP (User Datagram Protocol), and (SCTP) Stream Control Transmission Protocol. At physical and data link layers, TCP/IP does not define any specific protocol. It supports all the standard and proprietary protocols. At the network layer, TCP/IP supports the Internetworking Protocols. IP, in turn uses four supporting protocols: ARP(Address Resolution  Protocol), RARP(Reverse Address Resolution Protocol), ICMP (Internet Control Message Protocol), and IGMP(Internet Group Message Protocol). Addressing: Four level of addresses are used in an internet employing TCP/IP protocols:

1. Physical address: It is also called link address, is the address of a node as defined by its LAN WAN. It is included in the frame used by the data link layer. It is the lowest level address. The size and format of these addresses vary depending on the network. For example Ethernet uses a 5 byte(48bit) physical address that is imprinted on the network interface card.

2. Logical Address: these address are necessary for universal communications that are independent of underlying physical networks. Physical addresses are not adequate in an internetwork environment where different networks can have different address formats. A universal addressing system is needed in which each host can be identified uniquely, regardless of the underlying physical network. The logical address in the Internet is currently a 32 bit address that can uniquely define a host connected to the Internet. No two publicly addressed and visible hosts on the Internet can have the same IP address.

3. The IP address and the physical address are necessary for a quantity of data to travel from a source to the destination host. However, arrival at the destination host is not the final objective of data communications on the Internet. Today computers are devices that can run multiple processes at the same time. The end objective of Internet communication is a process communicating with another process. For these processes to receive data simultaneously, we need a method to label the different processes. In other words they need addresses. In the TCP/IP architecture, the label assigned to a process is called a port address. A port address in TCP/IP is 16 bits in length.

4. Specific Address: Some applications have user friendly addresses that are designed for that specific address. Examples include the email address (vineetkathuria2000@yahoo.com) and the URL www.netsetgo.co.in the addresses however get changed to the corresponding port and logical addresses by the sending computer.