ECE4110, Internetwork Programming, QUIZ 2 - PRACTICEName (Print) ______________________________Email Address ECE4110, Internetwork Programming, QUIZ 2 - PRACTICESpring 2006Prof. John A. Copeland Practice for April 11, 2006Tel.: 404-894-5177E-Mail: [email protected] This quiz is not open book. One original sheet of hand-written notes may be used. Calculators are ok.ii Answer all questions and show all work to receive full credit. Use back of sheets only if necessary.iii All sub-questions have the same weight.iv Please do not ask the proctors any questions during the exam about exam questions. Part of the test is understanding the question, as written, without supplemental information. If you feel additional data is needed to solve the problem, make (and state) an assumption and then work the problem.v. This is a time-limited test. All papers must be turned in 50 minutes after the start. If you find you are taking more than 10 minutes on a particular problem, move on and come back to that problem after finishing the others. The Georgia Honor Code applies (see last page). The actual test will be about 60% as long as this.Question 1 – TCP with no Congestion.A 100 Mbps network connection has a 100 ms round trip time (RTT). A server begins sending maximum-size packets (afterthe initial SYN-ACK) using Slow Start. The client ACK's every packet (col. 2) or every-other (col.3), and has a receiver-window which holds 16 maximum-size packets. Show how many packets are sent in each RTT period below:Time Period Start (ms) No. Segments, when all ACKed No. Segments, when 1/2 ACKed0 1 1100200300400500600_____________ How long does it take the server to ramp up to maximum transfer rate (ms)._____________ If the maximum packet size is 1000 bytes, what is the maximum transfer rate (bytes/second).How and when is the receiver's maximum segment size (MSS) sent to the sent to the other host? How? _____________________________ When _________________________________________How and when is the receiver's TCP window (WIN) sent to the sent to the other host? ? How? _____________________________ When _________________________________________The last WIN received was 8000, the last ACK number was 12000, and the last TCP segment sent had a SEQ number of 14000. How many more bytes can be sent? ___________________Once those bytes are sent, name three conditions that will allow additional bytes to be sent:a. __________________________ b.____________________________ c. ____________________________A TCP host on an Ethernet LAN receives an MSS of 1460 bytes. It sends IP headers with no options (20 bytes) and TCP headers with 32 bytes (12 bytes for options). What is the maximum number of data bytes (SMSS) it can send per TCP segment? _______________________________________________ECE4110 Quiz 2 PRACTICE p. 1Name (print) ______________________________Question 3 – Bandwidth-Delay Producta. If the round-trip time (RTT) for a dedicated 16 Mbit/s connection to California is 50 ms, what is the bandwidth-delay product of the link? ________________________(bits).b. What is the minimum TCP widow size that will allow this channel to be fully utilized? _______________ (bytes)c. What will the maximum throughput be if the window is half the value in b. above. ____________ (bits/s)d. What will the maximum throughput be if the window is twice the value in b. above. ____________ (bits/s)Question 4 – TCP Response to Congestion - Lost and Out-of-Order PacketsOnce a TCP segment times out, a variable collision window-size is cwnd is used. For consistency, we consider cwnd to govern the number of segments sent during the initial Slow Start mode. SMSS (sender maximum segment size) was called segsize in the class slides, MSS in some of the books. Conditions at the sender may require SMSS to be smaller than the MSS value received for the other TCP host.What places an upper limit on the maximum number of outstanding (sent, but not ACKed) bytes besides cwnd? _________________________After a time-out, the value of cwnd drops to _____________ times the maximum segment size (SMSS or segsize).After a time-out, the value of ssthresh drops to _____________ times the previous value of cwnd.cwnd then grows in _______________ mode until it reaches ssthresh. which is reduced to _______ times the value of ____________ before the time-out.After cwnd reaches ssthresh, cwnd grows linearly by adding SMSS bytes for approximately every __Y__ number of maximum segments sent (ignore the incorrect SMSS/8 term in the slides and book). What is this linear mode (of cwnd increase) called? __________________________For the case where the receiver ACKs every packet, Y = _____________________________ (in terms of cwnd, SMSS)For the case where the receiver ACKs every other packet, Y = _____________________________ (ditto)What is the maximum value of cwnd? ___________________ (or is it moot, see TCP Illustrated, p. 310, rule 1).Does cwnd or win (from the receiver) govern the bytes by (sequence number) that can be sent? ____________________Question 5 – TCP Fast Retransmission and Fast RecoveryAfter a TCP sender receives __________ duplicate ACKs it retransmits the first missing segment.How many additional bytes (at a minimum) can be sent after each additional duplicate ACK is received? ________________How much does cwnd increase after each additional duplicate ACK is received? ________________When does Fast Recovery operation start? ________________________________When FR starts, cwnd is set equal to ___________ x cwnd-before-dup-ACK + _____________ SMSS.In Fast Recovery, how many SMSS bytes are added each RTT is all segments are ACKed (do not use SMSS/8 term): ECE4110 Quiz 2 PRACTICE p. 2 of 4Name (print) ______________________________if all segments are ACKed__________________ if every other segment is ACKed?Question 6– Window Size versus TimeSMSS =1420 bytes, MSS=1420 bytes, RTO = 50 ms, RTT = 30 ms.QuickTime™ and aTIFF (LZW) decompressorare needed to see this picture.What is the Time scale factor, X ? _________________What is the Bytes scale factor, Y ? _________________Identify the cwnd growth modes (Slow Start = SS, Collision Avoidance = CA, Fast Recovery=FR) ?:Mode A ________________Mode B ________________Mode C ________________Mode D ________________Mode E ________________What causes the mode changes ( Start Up = SU, Fast Retransmit = FT, Retransmit Time Out = RTO, ssthresh reached =