Shulou(Shulou.com)06/03 Report--

Network reference model

1. OSI reference model

1. OSI seven-layer model

OSI (Open system interconnection Open Systems Interconnection)

ISO (International Standard Organization) International Organization for Standardization

The seven layers of the network

From bottom to top, there are physical layer, data link layer, network layer, transport layer, session layer, presentation layer, application layer.

2. A brief introduction to the functions of OSI layer 7

Layering function

An interface between the application layer network service and the end user

Presentation, security, compression of presentation layer data

Session layer establishes, manages, terminates calls

The transport layer defines the protocol port number over which data is transmitted, as well as control and error checking

The network layer carries on the logical address search to realize the path selection between different networks.

The data link layer has the functions of establishing logical connection, finding hardware address, error checking, etc.

Establish, maintain and disconnect physical connections in the physical layer

3. Explain the functions of the seven layers of OSI.

(1) physical layer

How ① uses physical signals to represent data 0 and 1

Can ② data transmission be carried out in both directions at the same time?

How to establish and terminate the connection between the two sides of ③ communication

④ physical interface characteristics.

(2) data link layer

① data frame encapsulation structure

Physical addresses of the ② source and destination

③ data verification function.

(3) Network layer

① packet encapsulation structure

Logical addresses of ② source and destination parties

③ chooses the route according to the logical address of the packet header.

(4) Transport layer

Communication between ① user processes; ② is a connecting link between the preceding and the following.

(5) session layer

① establishes a session relationship between users

(6) presentation layer

① defines the syntax and semantics of conveying information

② encoding and decoding, compression and decompression, encryption and decryption

(7) Application layer

① provides an interface with users.

II. TCP/IP protocol suite

1. OSI model and TCP/IP model.

(1) TCP/IP four-layer model

Network interface layer, network layer, transport layer, application layer

(2) the TCP/ IP five-layer model is more used in the actual network.

Physical layer, data link layer, network layer, transport layer, application layer

2. The composition of TCP/IP protocol suite.

(1) TCP/IP is a collection of protocols, so it should be strictly called TCP/IP protocol suite.

Layer defined protocol

Application layer HTTP FTP TFTP SMTP SNMP DNS

Transport layer TCP UDP

Network layer ICMP IGMP IP ARP RARP

Physical layer, data link layer protocols defined by the underlying network

Data encapsulation and transmission

III. Data encapsulation and unencapsulation

1. Data encapsulation process

2. Data unpacking process

3. Protocol data Unit (PDU)

IV. The process of data transmission in the network

1. The corresponding relationship between equipment and layer

2. Communication between layers

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