Shulou(Shulou.com)06/01 Report--

Computer Network Overview

local area network: small coverage, self-maintenance equipment connection 100 meters, bandwidth 100M,1000M.

wide area network

Internet ISPs have their own computer rooms to provide Internet access to Internet users

user accesses a web page

Packets, frames

DNS name resolution

IP addresses determine where packets go.

MAK (physical address) decided to be taken aback.

Server responds to client web pages

The server caches packets, one by one sent to the client, and the client caches them one by one. One by one, pieced together data packets are displayed

OSI reference model

Application layer: All programs that generate data traffic. (Notepad writing is not an application layer.) Access to web pages belongs to application layer)

Presentation layer: whether encryption or compression is performed before transmission Binary ASSCII

Session Layer: View *** netstat -n

Transport Layer: Reliable Transmission Unreliable Transmission Flow Control

Network layer: responsible for selecting the best path planning IP address

Data Link Layer: Start and End of Frame Transparent Transmission Error Check No Error Correction

Physical Layer: Interface Standards Electrical Standards How to transmit faster speeds over physical links

OSI Reference Model Troubleshooting Network Errors

1. Physical Layer Failure: View Connection Status Send and Receive Packets

2。Data link layer failure: MAC address conflict ADSL (gross) arrears network speed can not agree computer connected to the wrong VLAN

3. Network layer failure: misconfigured My IP address subnet mask misconfigured My gateway router is not configured to reach the destination address Gateway

4. Application layer (application layer, presentation layer, session layer) failure: application configuration error.

OSI Reference Model and Network Security

1. Physical Layer Security Disconnect or disable unused switch cable ports

2. Data link layer security: ADSL(Mao) account password Data link layer security VLAN switch port binding MAC address

3. Network layer security: Use ACL on router to control packet traffic Computer firewall

4. Application-level security: Develop applications without vulnerabilities

FCS error check

computer network performance

The rate at which hosts connected to a computer network transmit data bits over digital channels,data rate or bit rate.

Units b/s, kb/s,Mb/s,Gb/s How many bits per second.

Bandwidth: In data communications, the highest data rate that can be transmitted on a digital channel. b/s. etc.

3 Throughput: The amount of data passing through a network per unit time. b/s. such

4 Delay:

5 Delay bandwidth:

6 Round trip time: ipconfig pi ip address

7 Utilization:

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