Imagine that two hosts, A and B are communicating over a TCP connection and Host B has already received all bytes up through byte 87. Suppose A sends B two segments, one immediately after the other. The first segment has 19 bytes. The second segment has 100 bytes. In the first segment, the sequence number is 88, the source port is 4321 and the destination port is 80. B will send an ACK whenever it receives a segment from A.
a) In the second segment sent from A to B, what are the sequence number, source port and destination port?
b) If the segments arrive in-order at B, what are the same values (sequence number, source port and destination port) in both of the acknowledgment segments?
c) If the second segment arrives before the first, what are the values in the acknowledgements?
d) Suppose the two segments are received properly, in order. But, the first acknowledgement is lost and the second acknowledgement arrives after the first timeout interval. There is no other loss. Draw a sequence diagram, much like I did in the slides, showing all of the segments and acknowledgements in this scenario. For each segment, list the sequence number and number of bytes. If the segment is an acknowledgement, list the acknowledgement number.
2) Encapsulation
Draw an IP packet, with all of it’s format fields. Provide values wherever possible. This particular packet is going from your computer (use your own IP address) to Baidu.com’s webserver at 220.181.57.216. This packet holds a TCP segment in the payload. The TCP segment is carrying an HTTP request for the www.baidu.com index page (index.html). Draw all of the fields, using as many proper numbers as possible. If you don’t know what the number would be, provide an estimate of a potentially correct value.
3) IP Addresses
What is the binary value of the IP address 220.181.57.216?