Network protocols are usually divided into different levels of development, each layer are
responsible for different communication functions. A protocol suite, such as TCP / IP, is
a combination of a plurality of protocols on different levels of a group. TCP / IP are generally considered
to be a four-layer protocol system as 1--1 in FIG.
Each layer is responsible for different functions:
1) Link layer, sometimes called the data link layer or the network interface layer,
typically includes an operating system device driver and the computer
in the corresponding network interface card. They are processed together with details of the physical interface cable (or any other transmission medium) is.
2) the network layer, sometimes called the Internet layer processes the packet in the network, for example, routing of the packet. In the
TCP / IP protocol suite, including the network layer protocol IP protocol (Internet Protocol), ICMP protocol (I nternet Internet control
system protocol packet), and the IGMP protocol (I nternet Group Management Protocol).
3) transport layer mainly provides end to end communication application on both hosts. In the TCP / IP protocol suite, there are two
different transmission protocols: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
TCP provides a highly reliable data communication to two hosts. All it does it comprises the application to the data packets
to an appropriate tile to the network layer below, acknowledgment packets received, provided the final confirmation packet transmission timeout clock
and the like. Since the end of the transport layer provides a highly reliable communication, the application layer can ignore all these details.
On the other hand, UDP, compared with the application layer provides a very simple service. It just called datagram packet
Sent from one host to another host, but does not guarantee that the packets reach the other end. Any required reliability
of the layer must be provided by the application.
Both transport layer protocols each have different purposes in different applications, as will be seen later.
4) The application layer is responsible for handling specific application details. Almost a variety of TCP / IP implementation The following are some
Universal application:
• Telnet remote login.
• FTP file transfer protocol.
• SMTP Simple Mail Transfer Protocol.
• SNMP SNMP