What are the protocols for the structure and function of OSI and TCP/IP layers?

( 1) OSI seven-layer modelLayer function in OSI TCP/IP protocol family Application layer file transfer, e-mail, file service, virtual Terminal tftp,http,snmp,ftp,smtp,dns,telnet presentation layer data format, code conversion, data encryption no protocol session layer Release or establish contact with other Contacts No protocol Transport layer provides end-to-end interface TCP,UDP Network layer for packet selection routing Ip,icmp,rip,ospf,bgp,igmp Data link layer transport address frame and error detection function Slip,cslip,ppp,arp, The RARP,MTU physical layer transmits data on the physical medium in the form of binary data iso2110,ieee802,ieee802.2 (2) protocol for TCP/IP five-tier modelApplication Layer Transport Layer Network layer Data Link layer physical layer Physical Layer:Repeaters, hubs, and the twisted pair we usually talk about are also working on the physical layer Data Link layer:Network Bridge (now rarely used), Ethernet switch (second layer switch), network card (actually the NIC is half working on the physical layer, half working at the data Link layer) Network layer:Routers, layer three switches Transport Layer:Four-layer switch, also has a router working on layer four
T the CP (transmission Control Protocol) and UDP (User Datagram Protocol) protocols belong to the Transport layer protocol. TCP provides reliable data transmission in IP environment, and it provides services including data transfer, reliability, effective flow control, full duplex operation and multiplexing. Send through connection-oriented, end-to-end, and reliable packets. Popularly said, it is to send the data in advance to create a connected channel, and then send data, and UDP does not provide the IP reliability, flow control or error recovery function. In general, TCP corresponds to the application of high reliability requirements, and UDP corresponding to the requirements of low reliability, transmission economy applications. TCP-supported application protocols are: Telnet, FTP, SMTP, etc. the application layer protocol supported by UDP mainly includes: NFS (Network File system), SNMP (Simple Network Management Protocol), DNS (primary Domain Name System), TFTP (Universal File Transfer Protocol), etc. The TCP/IP protocol is independent of the low-level data link layer and the physical layer, which is also an important feature of TCP/IP First layer: Physical layer (Physicallayer)Specifies the mechanical, electrical, functional, and process characteristics of the communication equipment used to establish, maintain and dismantle physical link connections. Specifically, the mechanical characteristics of the network connection required to plug-in specification size, PIN number and arrangement of the situation, etc. the electrical characteristics of the transmission of the bit stream on the physical connection on the line signal level of the size, impedance matching, transmission rate distance limit, etc. function characteristic is to assign the exact signal meaning to each signal first, The function of each line between DTE and DCE is defined, and the specification defines a set of operating procedures for bit-stream transmission using a signal line, which refers to the creation, maintenance, and exchange of information in physical connection, which is the series of actions that DTE and DCE double on each circuit. In this layer, the unit of data is called the bit (bit). Typical canonical representatives belonging to the physical layer definition include: Eia/tia RS-232, Eia/tia RS-449, v.35, RJ-45, etc. Second layer: Data link layer (datalinklayer)On the basis of providing the bit-stream service in the physical layer, the data link between adjacent nodes is established, and the data frame (frame) is transmitted without error on the channel through error control, and the action series on each circuit is carried out. The data link layer provides reliable transmission on unreliable physical media. The functions of this layer include: Physical address addressing, data framing, flow control, data error checking, re-sending, etc. In this layer, the units of the data are called frames. The Data Link layer protocol includes: SDLC, HDLC, PPP, STP, Frame Relay, and so on.   The third layer is the network layerThere may be many data links between the two computers that communicate in the computer network, or they may go through many communication subnets. The task of the network layer is to select the appropriate inter-network routing and switching nodes to ensure the timely transmission of data. The network layer consists of a packet of frames provided by the data link layer, which encapsulates the network layer header, which contains the logical address information-the network address of the source site and destination site address. If you're talking about an IP address, then you're dealing with layer 3rd, which is the "packet" problem, not the 2nd "frame". IP is part of the 3rd tier problem, and there are routing protocols and address resolution protocols (ARP). Everything about routing is handled in this 3rd layer. Address resolution and routing are important purposes of layer 3. Network layer can also realize congestion control, Internet interconnection and other functions. At this level, the unit of data is called a packet (packet). Network layer protocol representatives include: IP, IPX, RIP, OSPF, and so on. The fourth layer is the transport layer that processes the informationThe Data unit at Layer 4th is also known as a packet (packets). However, when you talk about specific protocols such as TCP, there are special terms, the TCP data unit is called segment (segments) and the UDP protocol data unit is called "Datagram (datagrams)". This layer is responsible for getting all the information, so it must keep track of the fragmentation of data units, the packets arriving in order of chaos, and other risks that may occur during transmission. The 4th layer provides an end-to-end (end-user to end-user) transparent, reliable data transfer service for the upper layers. The transparent transmission refers to the specific details of the transmission layer shielding the communication transmission system in the communication process. The Transport Layer protocol includes: TCP, UDP, SPX, and so on. The fifth layer is the session layerThis layer can also be called the meeting layer or the dialogue layer, in the conversation layer and above the high level, the data transmission unit is no longer named, but collectively referred to as the message. The session layer does not participate in specific transports, it provides mechanisms for establishing and maintaining communication between applications, including access validation and session management. If the server verifies that the user is logged in, it is done by the session layer. The sixth layer is the presentation layerThis layer mainly solves the problem of the grammatical representation of the support information. It transforms the data to be exchanged from the abstract syntax appropriate for a user into the transfer syntax appropriate for internal use within the OSI system. That is to provide a formatted representation and Transform data service. Data compression and decompression, encryption and decryption are the responsibility of the presentation layer. layer Seventh Application layerThe application layer provides an interface for operating system or network applications to access network services. The application layer protocol includes: Telnet, FTP, HTTP, SNMP, and so on.