电子档案袋
一、实验目的
1.通过wireshark抓包理解应用层TCP协议。 二、实验器材
1.PC机电脑一台。
2.Wireshark软件。
三、实验内容
1．依照Wireshark Lab 提供的实验步骤完成实验。 2．回答实验中的问题。
四、实验操作实践与步骤
2. A first look at the captured trace
1. What is the IP address and TCP port number used by the client computer (source) that is transferring the file to gaia.cs.umass.edu? To answer this question, it’s probably easiest to select an HTTP message and explore the details of the TCP packet used to carry this HTTP message, using the “details of the selected packet header window”
无级调速器2. What is the IP address of gaia.cs.umass.edu? On what port number is it sending and receiving TCP segments for this connection?
If you have been able to create your own trace, answer the following question:
3. What is the IP address and TCP port number used by your client computer (source) to transfer the file to gaia.cs.umass.edu?
3. TCP Basics
4. (1)What is the sequence number of the TCP SYN segment that is used to initiate the TCP connection between the client computer and gaia.cs.umass.edu? (2)What is it in the segment that identifies the segment as a SYN segment?
(1) SYN sequence number =0
(2) What is in the red region of the figure above identifies the segment as a SYN segment.
5. (1)What is the sequence number of the SYNACK segment sent by gaia.cs.umass.edu 双活接球阀to the client computer in reply to the SYN?(2) What is the value of the ACKnowledgement field in the SYNACK segment? How did gaia.cs.umass.edu辊道窑 determine that value? What is it in the segment that identifies the segment as a SYNACK segment?
(1)SYNACK sequence number =0, ACKnowledgement=1大孔
树脂吸附
(2)ACKnowledgement value= initiate sequence number of the
TCP SYN segment+1油炸锅
(3)What is in the red region of the figure above identifies the segment as a SYN segment.
6. What is the sequence number of the TCP segment containing the HTTP POST comma
nd? Note that in order to find the POST command, you’ll need to dig into the packet content field at the bottom of the Wireshark window, looking for a segment with a “POST” within its DATA field.
The sequence number of the TCP segment containing the HTTP POST command is 1.
7. Consider the TCP segment containing the HTTP POST as the first segment in the TCP connection. (1)What are the sequence numbers of the first six segments in the TCP connection (including the segment containing the HTTP POST)? (2)At what time was each segment sent? When was the ACK for each segment received?(3) Given the difference between when each TCP segment was sent, and when its acknowledgement was received, what is the RTT value for each of the six segments?(4) What is the EstimatedRTT value (see page 249 in text) after the receipt of each ACK? (5)Assume that the value of the EstimatedRTT is equal to the measured RTT for the first segment, and then is computed using the EstimatedRTT equation on page 249 for all subsequent segments.
