(1) Personal information:
Name: Peng Chen Student Number: 201 821 121 039 Class: calculated 1812
1 Purpose
- Using different network router.
- Use the command line router.
- By grabbing HTTP packets, TCP connection establishment of the analysis process.
2 Experimental content
Use Packet Tracer, properly configure the network parameters, by crawling HTTP packets, analyzes the TCP connection establishment procedure.
- Establish a network topology
- Configuration parameters
- Ethereal
- Analysis of the data packet
3. The test report
(1) establish a network topology
(2) Configuration Parameters
. A PC side configuration parameters:
. B server configuration parameters:
. C router configuration parameters:
Configuration, activation port:
First, according to the instruction: Router> enable to enter privileged mode
Router # config t Enter the global configuration mode
Router (config) #interface Fa 0/0 Ethernet interface 0/0
Router (config-if) #ip address 192.168.1.40 255.255.255.0 add IP addresses
Router (config-if) #no shutdown activation port
Router (config-if) #exit return to the previous
Router (config) #interface Fa 0/1 Ethernet interface 0/1
Router (config-if) #ip address 192.168.2.40 255.255.255.0 add IP addresses
Router (config-if) #no shutdown activation port
3. capture, analyze TCP connection establishment
(1) Ethereal
( 2 ) the TCP to establish a connection diagram:
（3）分析序号和确认号的变化
PC先向Server端发送连接请求报文，同部位为1，选择一个初始序号为x(seq=x),Client进入SYN_SENT状态;Server收到请求报文后进行回复确认确认报文段中，SYN=1，ACK=1，确认号ack=x+1，随机产生一个值seq=m，并将该数据包发送给Client以确认连接请求，Server进入SYN_RCVD状态；PC收到Server端的服务进程的报文后发出确认信息。
（4）解答：为什么连接建立需要第三次握手
答：为了防止已失效的连接请求报文段突然又传送到了服务端，因为产生错误；若没有三次握手，则连接建立成功，服务器会等待这一无效连接发送数据，造成资源浪费。若采用三次握手，则PC端不会再向服务器发送发送确认应答信息，连接不会被建立。