1. [20pts] Consider the following network path taken by a file of size 2700 bytes from source A to
Suppose the switching delays at B and C are 10 and 30 milliseconds each. All other delays are
negligible. In addition there is a maximum frame size including a frame header at each link. This
information is available from the table below.
Link Maximum Frame size Frame header size
A to B 900 bytes 10 bytes
B to C 512 bytes 12 bytes
C to D 500 bytes 20 bytes
The file is broken down into TCP segments with payload size of 1000 bytes each. Each segment
has a 20 byte header. Each segment is then transmitted over the three links. Obviously the frames
need to be fragmented at the IP layer where a 20 byte IP header is added on to each segment.
Assume a 20 byte IP header.
a) [15pt] Show the Total length, DF, MF and fragment offset fields of the IP header of each
transmitted frame at A, B and C.
Hint: You need to show this only for the first 1000byte TCP segment. The other two segments will
b) [5pts] How long does it take for the file to reach from A to B?
Hint: Calculate the total switching delay for the file.
c) [5pts] Calculate the overhead in transmitting this file from A to B.
Hint: Calculate the total header length divided total bytes sent.
Rubrics: You must answer each part
Write units and show steps – 50%
2. 5) [10 pts] Suppose that the TCP congestion window is set to 18 KB and three duplicate
acknowledgments arrive when the current transmission window size is 22KB. Assume that
the maximum segment size is 1 KB.
a) How big will the transmission window and congestion window be if the next 2 transmission
bursts are all successful?
b) How big will the transmission window and congestion window be if the next 2 transmission
bursts are all successful and then a timeout happens?
|Due By (Pacific Time)||05/20/2014 12:00 pm|
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