Computer network seven-layer protocol model "Open Systems Interconnect Reference Model", known as the OSI/RM model (open System interconnection/reference models)

Seven layer protocol model of computer network

Ryan Time: October 7, 2013

I. Physical layer (physical layers)

The lowest or first layer of the OSI model, which specifies the mechanical, electrical, functional, and process characteristics of activating, maintaining, and shutting down communication endpoints, provides a physical medium for the upper layer protocol to transmit data.

At this level, the Protocol data unit is bit (bit).

Typical canonical representatives belonging to the physical layer definition include: RS-232, RS-449, RS-485, USB2.0, IEEE-1394, XDSL, x.21, v.35, RJ-45, etc.

The interconnected devices on the physical layer include: hubs , repeaters (Repeater), etc.

Data link layers (Datalink layer)

The second layer of the OSI model, which controls communication between the network layer and the physical layer, is the main function of providing 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.

At this level, the Protocol data unit is frame.

Representatives of the Data Link layer protocol include: LLC, SDLC, HDLC, MAC, PPP, STP, Frame Relay, CSMA/CD, CSMA/CA, and so on.

The interconnected devices at the data link layer include: Bridge , switch , etc.

Logical Link Control LLC (Logical link controls) protocol

Synchronous Data Link Control SDLC (Synchronous Data Link controls) protocol

High-level Data link Control HDLC (high-level Data Link controls) protocol

Multi-access Control Mac (multiple access controls) protocol

Peer-to-peer protocol PPP (point-to-point Protocol)

Spanning Tree Protocol stp (Spanning tree Protocol)

Carrier-Monitored multi-access CSMA/CD with collision detection (Carrier sense Multiple Access with collision Detection)

Carrier-listening multi-access Csma/ca with Collision avoidance (Carrier sense multiple access with collision avoidance)

Third, network layer

The third layer of the OSI model, whose main function is to translate the network address into the corresponding physical address, and decide how to route the data from the sender to the receiver. The functions of this layer include: routing data packets between subnets, congestion control and Internet interconnection.

At this level, the Protocol data unit is a packet (packet).

Network layer protocol representatives include: IP, ARP, IPX, DDP, RIP, OSPF, RARP, ICMP, IGMP, NetBEUI, etc.

The interconnection devices at the network layer include: routers (Router) , etc.

Internet Protocol IP (Internet Protocol)

Address Resolution Protocol ARP (addr Resolution Protocol)

Internet Packet Switching protocol IPX (Internetwork Packet Exchange Protocol)

Datagram Transport Protocol DDP (Datagram Delivery Protocol)

Routing Information Protocol RIP (Routing information Protocol)

Open Shortest-circuiting by Precedence protocol OSPF (Open shortest Path first)

Reverse Address Translation Protocol Rarp (Reverse addresses Resolution Protocol)

Internet Control Message Protocol ICMP (Internet Controls message Protocol)

Internet Groups Management Protocol IGMP (Internet Group Management Protocol)

NetBEUI (NetBIOS Extended user internet,netbios Subscriber Extension Interface Protocol)

X 25 (a packet switching network protocol)

Ethernet (Ethernet protocol)

Microsoft implementation of Nwlink--ipx/spx Transfer Protocol

Iv. Transport Layer (Transport layers)

The most important layer in the OSI model is the first end-to-end, that is, the host-to-host hierarchy. Its main function is to segment the upper data and provide end-to-end, reliable, or unreliable transmissions. In addition, the transport layer also handles end-to-end error control and flow control issues.

At this level, the Protocol data unit is a data segment (segment).

The Transport Layer protocol includes: TCP, UDP, SPX, and so on.

Transmission Control Protocol TCP (transmission-Protocol)

Subscriber Datagram Protocol UDP (user Datagram Protocol)

Sequence packet switching protocol SPX (sequenced Packet Exchange Protocol)

Name Binding protocol NBP (name binding Protocol)

ATP (AppleTalk Transaction Protocol)--apple Company's network protocol family for managing sessions

V. Conversation layer (Session layers)

The fifth layer of the OSI model, which manages session processes between hosts, is responsible for establishing, managing, and terminating sessions between processes. Its main function is to establish a communication link, keep the session process communication links unblocked, using the data to insert a checkpoint to synchronize the dialogue between two nodes, determine whether the communication is interrupted and the communication is interrupted when the decision from where to resend.

Vi. presentation layers (Presentation layer)

The sixth layer of the OSI model, the translator between the application and the network, is responsible for transforming the upper layer data or information to ensure that one host application layer information can be understood by another host's application. The data transformation of the presentation layer includes data decryption and encryption, compression, format conversion, and so on.

VII. application level (Application layer)

The seventh layer of the OSI model, which provides an interface for operating system or network applications to access network services. The term "Application layer" does not refer to a particular application running on the network, the services provided by the application layer include file transfer, file management, and e-mail information processing.

Representatives of the application layer protocol include: FTP, Telnet, SMTP, TFTP, HTTP, POP3, NNTP, IMAP4, HTTPS, SNMP, DNS, SMB, BOOTP, NFS, NCP, etc.

The interconnect devices at the application layer include: gateways , etc.

File Transfer Protocol FTP (Transfer Protocol) with port number 21;

Remote Terminal Protocol Telnet (remotes Terminal Protocol) with port number 23;

Simple Mail Transfer Protocol SMTP (easy Mail Transfer Protocol) with a port number of 25;

The Simple File Transfer Protocol tftp (Trivial file Transfer Protocol) with a port number of 69;

Hypertext Transfer Protocol HTTP (Hypertext Transfer Protocol) with a port number of 80;

Postoffice Protocol POP3 (Post Office Protocol) with a port number of 110;

Network News Transfer Protocol NNTP (Transport Protocol) with a port number of 119;

Internet Mail Access Protocol (IMAP4), the port number is 143;

Secure Sockets Layer Hypertext Transfer Protocol HTTPS (hypertext Transfer Protocol over Secure Socket Layer) with port number 443;

Easy Network Management Protocol SNMP (simple web Management Protocol)

Domain Name Service protocol DNS

Server Message Block protocol SMB (Server message, block Protocol)

Bootstrap protocol BOOTP (Bootstrap Protocol)

Network File System NFS

Network Core protocol NCP (NetWare core Protocol)

X 500 (a Directory Service System protocol)

AFP (AppleTalk File protocol)--apple Company's network protocol family for exchanging files

Computer network seven-layer protocol model "Open Systems Interconnect Reference Model", known as the OSI/RM model (open System interconnection/reference models)