Computer network --OSI seven-layer model

Computer network --OSI seven-layer model

A), OSI definition

Of the OSI: Open System Interconnection, Open Systems Interconnection.

Structure: physical layer, data link layer, network layer, transport layer, session layer, layer represents , the application layer. (bottom up)

A role for me now each layer ---.

Two), the physical layer

Action: transfers bit stream standard defines a physical device, e.g., the transmission speed of the network cable type, optical fiber type, a variety of devices to solve the communication needs between the two physical machines.

Data conversion: 010101 the similar binary data is converted to the strength of the current transmission, when the destination after its conversion into binary data of 010101.

Namely: Binary --- "the current strength ----" binary.

Data forms: a bitstream.

Representative: card.

C), a data link layer

Generating data link layer: data transmission incomplete solve the problem.

Action: defines how to format the data, how to control access to the physical medium, there is provided an error detection and error correction, to ensure reliability of data transmission.

Data forms: frames.

Representative: switch.

D), the network layer

Action: to solve the problem point communications between computers, when there are a plurality of communication nodes, how to find a target node, in which case it is necessary to translate the network to network layer address to a physical address corresponding to the data from the routing direction to the recipient.

Data forms: routing packets.

Representative: routing.

Protocol: IP protocol TCP / IP is.

E), the transport layer

Role: When large file transfers, data is too large, the transfer takes too long, network transmission interrupt is generated face data loss problem, this time on the need to transfer data layer will be cut into segments (segment) performed later data transmission to ensure the accuracy and quality of data transmission.

OSI transport layer is the most important one .

Data forms: a packet.

Representative: routing.

Protocols: TCP / IP UDP protocol.

Vi), session layer

Role: communication between the establishment and management applications.

VII), the presentation layer

Role: to solve the communication problem grammar different communication systems.

H), the application layer

Role: the provisions of the same message header templates.

Protocols: TCP / IP http protocol.

Nine), on OSI and TCP / IP

In simple terms, TCP / IP is an implementation of the OSI, OSI is a conceptual model, TCP / IP is a standard framework.

TCP / IP four-layer structure having: a physical layer (OSI physical layer mapping, the data link layer), the network layer, transport layer, an application layer (OSI mapping session layer, presentation layer, application layer).

OS having seven layers: a physical layer, data link layer, network layer, transport layer, session layer, presentation layer, application layer.

J), on TCP / IP

TCP / IP: not a specific protocol, TXP / IP is equivalent to an Internet Protocol group , below also defined a number of protocols, such as: IP / IMCP / TCP / UDP / HTTP .....