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

Basic Overview of computer Network

I. computer network

Hardware

Software: realizing resource sharing and information transmission

Second, the function of computer network

Data communication, resource sharing, increase data reliability, improve system processing capacity

III. Network protocols and standards

1. Protocol: a set of rules that control data communication.

2. Standard: the rule of consensus can be understood as standard

ISO (International Organization for Standardization) created the OSI (Open Systems Interconnection) model in network communication.

IV. OSI

1. International Organization for Standardization (ISO)

Open Systems Interconnection reference Model OSI

OSI is an open architecture that divides the network into seven layers

2. Protocol layering

In order to reduce the complexity of network design, the protocol is designed in layers.

Fifth, the meaning of OSI seven-layer reference model.

Application layer: an interface between network services and end users

Presentation layer: the representation of data, such as encryption and compression.

Session layer: establish, manage, and abort sessions, such as breakpoint continuation.

Transport layer: define the protocol port number of data transmission, as well as flow control and error checking, to achieve the interconnection of programs, reliable and unreliable transmission.

Network layer: carries on the logical address addressing, realizes the communication between different networks, defines the IP address, chooses the best path for data transmission, and the router works in the network layer.

Data link layer: establishing logical connection, hardware address addressing, error checking and other functions, data communication through MAC address, frame packaging, frame transmission, frame synchronization. The switch operates at the data link layer.

Physical layer: establish, maintain and disconnect the physical connection, define the interface and media, and realize the transmission of bit stream.

VI. Data unpacking process

In the process of transmission, the data is encapsulated from the upper layer to the lower layer, and the receiver is de-encapsulated from the bottom layer to the top layer.

VII. Composition of the TCP/IP protocol family

Application layer: HTTP, https, FTP, TFTP, SMTP, pop3, SNMP, DNS, telnet

Transport layer: TCP, UDP

Network layer: ICMP, IGMP, IP, ARP, RARP

8. PDU (Protocol data Unit)

Transport layer segment

Network layer packet packet

Data Link layer frame frame

Physical layer bit bit

IX. Equipment at the corresponding level

Application layer-- computer

Transport layer-firewall

Network layer-Router

Data Link layer-switch

Physical layer-network card

The number system of computers

1. Decimal number system

Composed of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Representation () 10 or letter D

2. Binary

Binary is based on two numbers, only 0 and 1

Representation () 2 or letter B

3. Hexadecimal

The hexadecimal base is 16.

The first ten numbers are 0 to 9, followed by A, B, C, D, E and F, representing 10, 11, 12, 13, 14 and 15, respectively.

Representation () 16 or letter H

11. IP address

1. Default subnet mask

The subnet mask is used to distinguish the network bits from the host bits of the IP. The network bits are represented by a continuous 1, and the host bits are represented by a continuous 0.

2. Network ID

The IP address of the network bits remains the same, and the host bits are represented by consecutive zeros.

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