# Lab 7 ## Lab 7-1 **What is the IP address of the client?** :::info - 192.168.1.100 ![](https://i.imgur.com/wPHC5RB.png) ::: ## Lab 7-2 **Consider now the HTTP GET sent from the client to the Google server (whose IP address is IP address 64.233.169.104) at time 7.109267. What are the source and destination IP addresses and TCP source and destination ports on the IP datagram carrying this HTTP GET?** :::info - src: 192.168.1.100, 4335 - destination:64.233.169.104, 80 ![](https://i.imgur.com/Zft1BCf.png) ::: ## Lab 7-3 **At what time is the corresponding 200 OK HTTP message received from the Google server?** :::info 7.158797 ![](https://i.imgur.com/iV2VObH.png) ::: **What are the source and destination IP addresses and TCP source and destination ports on the IP datagram carrying this HTTP 200 OK message?** ::info - src: 64.233.169.104, 80 - destination: 192.168.1.100, 4332 ![](https://i.imgur.com/JlcWXPq.png) ::: ## Lab 7-4 **Recall that before a GET command can be sent to an HTTP server, TCP must first set up a connection using the three-way SYN/ACK handshake. At what time is the client-to-server TCP SYN segment sent that sets up the connection used by the GET sent at time 7.109267?** :::info 7.075657 ![](https://i.imgur.com/6Rbbkbe.png) ::: **What are the source and destination IP addresses and source and destination ports for the TCP SYN segment?** :::info - src: 192.168.1.100, 4335 - destination: 64.233.169.104, 80 ![](https://i.imgur.com/BbPpEWZ.png) ::: **What are the source and destination IP addresses and source and destination ports of the ACK sent in response to the SYN.** :::info - src: 64.233.169.104, 80 - destination: 92.168.1.100, 4335 ![](https://i.imgur.com/ZCmzAX0.png) ::: **At what time is this ACK received at the client? (Note: to find these segments you will need to clear the Filter expression you entered above in step 2. If you enter the filter “tcp”, only TCP segments will be displayed by Wireshark)** :::info 7.108968 (https://i.imgur.com/ZCmzAX0.png) ::: ## Lab 7-5 **In the NAT_ISP_side trace file, find the HTTP GET message was sent from the client to the Google server at time 7.109267 (where t=7.109267 is time at which this was sent as recorded in the NAT_home_side trace file). At what time does this message appear in the NAT_ISP_side trace file?** :::info 6.069168，看identification field（都是0xa2ac） ![](https://i.imgur.com/NLsmze1.png) ::: **What are the source and destination IP addresses and TCP source and destination ports on the IP datagram carrying this HTTP GET (as recording in the NAT_ISP_side trace file)?** :::info - src: 71.192.34.104, 4335 - destination: 64.233.169.104, 80 ![](https://i.imgur.com/alehvng.png) ![](https://i.imgur.com/NLsmze1.png) ::: **Which of these fields are the same, and which are different, than in your answer to question 7-2 above?** only src IP has changed ## Lab 7-6 **Are any fields in the HTTP GET message changed?** :::info No ::: **Which of the following fields in the IP datagram carrying the HTTP GET are changed: Version, Header Length, Flags, Checksum. If any of these fields have changed, give a reason (in one sentence) stating why this field needed to change** :::info - version: No - Header Length: No - Flags: No - Checksum: Yes ::: ## Lab 7-7 **In the NAT_ISP_side trace file, at what time is the first 200 OK HTTP message received from the Google server?** ::info 6.117570 ![](https://i.imgur.com/EO7m9ZL.png) ::: **What are the source and destination IP addresses and TCP source and destination ports on the IP datagram carrying this HTTP 200 OK message?** :::info - src: 64.233.169.104, 80 - destination: 710192.34.104, 4335 ![](https://i.imgur.com/RL7TxJb.png) ::: **Which of these fields are the same, and which are different than your answer to question 7-3 above?** only destination IP has changed ## Lab 7-8 **In the NAT_ISP_side trace file, at what time were the client-to-server TCP SYN segment and the server-to-client TCP ACK segment corresponding to the segments in question 7-4 above captured?** :::info - client-to-server TCP SYN: 6.035475 - identification is 0xa2aa - server-to-client TCP ACK:6.067775 - identification is 0xf61a ![](https://i.imgur.com/UZxuJvV.png) ![](https://i.imgur.com/sx7VAjO.png) ::: **What are the source and destination IP addresses and source and destination ports for these two segments?** :::info - SYN - src: 71.192.34.104, 4335 - dst: 64.233.169.104, 80 - ACK - src: 64.233.169.104, 80 - dst: 71.192.34.104, 4335 ![](https://i.imgur.com/UZxuJvV.png) ![](https://i.imgur.com/sx7VAjO.png) ::: **Which of these fields are the same, and which are different than your answer to question 7-4 above?** :::info - SYN: the src IP address has changed - ACK: the destination IP address has changed - port numbers are unchanged ::: ## Lab 7-9 **Using your answers to 1-8 above, fill in the NAT translation table entries for HTTP connection considered in questions 1-8 above.** :::info - WAN: 71.192.34.104, 4335 - LAN: 192.168.1.100, 4335 :::