A file of F = 3 x 105bits is distributed to N  The server has an upload rate of us = 1 x 105 bps. Each peer has a download rate of di = 1 x 105 bps and an upload rate of u = 30,000 bps. For N = 1 to 10, and for both client-server and P2P architectures, plot a single graph with minimum distribution time on the y-axis and N on the x-axis. Use a table to show all the values for N = 1 to 10 and use the values to plot the graph. Clearly show the calculation only for N = 1, 2, and 3.

Needham and Schroeder suggest the following variant of their protocol: 1. Alice → Bob : Alice 2. Bob→ Alice: {Alice rand3}kBob 3. Alice → Cathy : {Alice Bob rand₁|{Alice rand3}kBob} 4. Cathy → Alice: {Alice Bob rand₁|ksession|{Alice rand3|ksession}KBob}KAlice 5. Alice → Bob: {Alice rand3|ksession}kBob 6. Bob→ Alice: {rand2}ksession 7. Alice → Bob: {rand2-1}ksession Show that this protocol solves the problem of replay as a result of stolen session keys. Hint: Consider two cases, one in which the attacker does not send an initial message to Bob and one in which the attacker does.

6. Delays. A user in Madagascar, connected to the internet via a 100 Mb/s (b-bits) connection retrieves a 250 KB (B-bytes) web page from a server in Tokyo, where the page references three images of 500 KB each. Assume that the one-way propagation delay is 82 ms and that the user's access link is the bandwidth bottleneck for this connection. a. Approximately how long does it take for the page (including images) to appear on the user's screen, assuming non-persistent HTTP using a single connection at a time? (For this part, you should ignore queueing delay and transmission delays at other links in the network) How long does it take if the connection uses persistent HTTP (single connection)? b. c. Suppose that user's access router has a 4 MB buffer (B-byte) on the link from the router to the user. How much delay does this buffer add during periods when the buffer is full? d. Assume a cache rate of 45% on the information received by the user in Madagascar from the Tokyo server. How does…

1. If the values of user tool frame UT[2] is (0, 0, 0, 0, 0, 0) in the robot system, then UT[2] (a) is not activated in the robot system (b) cannot be used in recording robot point P[n] (c) coincides with default TCP frame (Def-TCP) of the robot in the robot system (d) coincides with robot world frame R in the robot system 2. A frame transformation is given as 4T; = (X,Y,Z,W,P, R) = (0,0,0, –90, 0, 90). The corresponding graphical representation of the given frame transformation is (a) (b) y y

Computer A uses the Go-back-N ARQ protocol to send a 110 Mbytes file to computer B with a window size of 15. Given each frame carries 100K bytes data. How long does it take to send the whole file (the total time taken from A sending the first bit of the file until A receiving the last acknowledgment)? Given that the transmission rate of the link is 500 Mbps and the propagation time between A and B is 15ms. Assume no data or control frame is lost or damaged and ignore the overhead due to header and trailer.

Delays. A user in Madagascar, connected to the internet via a 100 Mb/s (b=bits) connection retrieves a 250 KB (B=bytes) web page from a server in Tokyo, where the page references three images of 500 KB each. Assume that the one-way propagation delay is 82 ms and that the user’s access link is the bandwidth bottleneck for this connection. a.) Approximately how long does it take for the page (including images) to appear on the user’s screen, assuming non-persistent HTTP using a single connection at a time? (For this part, you should ignore queueing delay and transmission delays at other links in the network)b.) Assume a cache rate of 45% on the information received by the user in Madagascar from the Tokyo server. How does this affect your answer in a? Show your work.