TCP/IP detailed--Basic concept __tcp-ip

Many manufacturers produce various models of computers that run on different operating systems, but the TCP/IP protocol family allows them to communicate with each other. TCP/IP is not a protocol, but a general name of a protocol family, which contains the IP protocol, IMCP protocol, TCP protocol, HTTP,FTP and so on, the computer has these, that is, the model system and other different situations to communicate with each other.

TCP/IP protocols are generally considered to be a four-tier protocol system with each layer responsible for different functions. The following figure.

Link layer: Device Driver and phone number
Network layer: The process of grouping activities in the network layer, such as the selection of groups. Ip,icmp,igmp.
Transport Layer: Provides end-to-end communication for applications on two host computers. TCP (Transmission Control Protocol), UDP (User Datagram Protocol).
Application layer: Handles specific application details. Telnet, FTP, SMTP, SNMP. some basic concepts.

Internet address (IP address)

Each interface on the Internet must have a unique IP address, 32bit long. Divided into unicast, broadcast, multicast. These IPs are allocated by the Internet Information Center (InterNIC), and the allocation of host numbers is the responsibility of the system administrator.

The data unit that TCP passes to the IP is called the TCP message segment. The data units that IP passes to the network interface layer are called IP datagrams. The bit streams transmitted over Ethernet are called frame.

In order to distinguish who came from the information, IP in the first deposit a length of 8bit value, 1 represents the IGMP protocol, 2 represents the IGMP protocol, 6 represents the TCP protocol, 17 represents the UDP protocol.

TCP and UDP use the bit port number to identify the application. Any TCP/IP implementation provides services that use the port number between well-known 1~1023, such as the TCP port number for FTP 21,telnet the TCP port number of the server is 23,tftp 69. The large multiport slogan corresponds to the information in the file/etc/services. The server uses a well-known port number, and the client uses the port number that is temporarily set.

Domain Name System

The domain Name system is a distributed database that provides the host name (URL) to be converted into IP services.

Rfc

A standard document used to record Internet specifications, protocols, processes, etc. Basic Internet communication protocols are described in detail in the RfC file.

Port

Ports include physical ports and logical ports.
The physical port is the interface between the physical devices used to connect.
Logical ports are the ports that are logically used to differentiate services. The ports in the TCP/IP protocol are logical ports that differentiate between different services through different logical ports. The port of one IP address is numbered by 16bit and can have up to 65,536 ports. The port is marked by the port number, and the port number is only an integer, ranging from 0 to 65535. Generally speaking of the closure of a port is actually at the IP level with this number of IP packets to filter out.

Application Programming Interface

Commonly used two application programming interfaces: Socket and TLI (Transport Layer interface).