Third experiment: using a TCP connection is established Packert Tracer analysis process

     1. The experiment

• Using different network router
• Use the command line router
• By grabbing HTTP packets, TCP connection establishment process analysis

  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. The establishment of the network topology
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    2. Configuration Parameters

• ip address of the client is 192.168.1.42, 192.168.1.43 gateway

  ip-address server is 192.168.2.43, 192.168.2.42 gateway

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  Command interpreter:

  enable: enter the privileged EXEC mode

  configure terminal: Enter the global configuration mode 

  interface + Interface Name: Select the appropriate router interface

  p address: ip address configuration for the interface

  no shutdown: Activation Interfaces

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  3. capture, analyze TCP connection is established processes

• 1. Ethereal
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  2.TCP link

• 1. Draw a schematic diagram of the TCP connection establishment
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  2. Analysis of changes in numbers and acknowledgment numbers

• When intended to establish a TCP connection, it sends a connection request packet to the server TCP segments, time synchronization bit SYN = 1 header, while selecting an initial sequence number seq = x. In this case, the client is the SYN_SENT state;
• After the server receives the connection request packet, if they agree to establish a connection, it sends an acknowledgment to the client. In the acknowledgment segment should SYN bit and ACK bits are set to 1, ack acknowledgment number equal to x + 1, while the initial sequence number seq = y;
• After the client receives the acknowledgment server, but also gives an acknowledgment to the server, the acknowledgment ACK is set 1, ack = y + 1, their number segments of seq = x + 1.

• 3. Answer: Why we need a third connection establishment handshake

• In order to prevent the connection request has failed segment server suddenly spread, resulting in an error.

  4. expand 

• no