CSC 425 Problems, Fall 2008

Lage oN Eyre npr rage e © on eager AS ATE Se TowyY TASTE csc 425 pr H. Maaiouf EXTRA PROBLEMS ’ ttn _ , Ue 3 pes 1) You were asked to design a LAN for a site that has 60 PCs.Each PC downloads 20 Dewaload Tif & | MB file every 10 minutes from the Internet Each PC uploads 800 KB every 8 minutes. G20 x0 BF ZL - a) Determine the total traffic on the LAN. . ir bo 4, b) How will you connect these PCs to each others and to the external world? = 16R6ps iu [sel re Explain which interconnection devices you will use. Sketch your LAN. { br iow Tufte a a ab.cr€ Cortouxtese® ; 2) Which of the network fragments (a, b, ¢, d, €) represent’ Rotfiston domains? Do Sy be Ue, - users on network fragments (b) and (c) collide together? And why? If all these = PU Kb we 4 network interconnection devices are Ethernet, give the expected throughput for the ght Taft a devices on the different network fragments (use the information In table 2 below to fill Faw “yn bret depts in table 1. Wha le ? Ye, bide = (6. YP Network Fragment a b c d e Throughput (bps) | QAea%75-Ph, i, » | Sibps sOnbos Bithys Table 1 Nbre of Stations | 3 6 9 Normalized Throughput \ 0.8 0.6 0.4 Table 2 { \ H H eM RA ENTER TRAE AS NTIS AONE S raves header sizes are 20 B for the AL, 30 of p =2 f the frames is 1,000 B. Every frame # : 4 2AM or of a single packet on the _ 824 n side, it is 650 msec (for _ * 260f.. T, is 10 msec. N= 260/008 _ see oc file of 240,000 B. The for the LL. The size © 10 B. Processing time frame); on the destinatio 3) You are transmitting 2 B for the NL and 26 bytes is acknowledged. The ACK size is source side is 50 msec (for the Ack- the L-frame).Transmission rate R is 1OMbps and Propagation delay rope Calculate The Total Time required to transmit the whole file and the Normalized Throughput. 490. 465042 . é ino = 4 2 4) Total Time to Discard a workstation wait until its frame is discarded by the th ( collision and the 3 i cngghpd = L406 Toe sj How long can @ + Gp Cpe) network adapter if this frame encounters 2 consecutives Cothgin ete. transmission attempt was successful? Assume the following: ge whe he — 68 hf ede of the frame is 1518 Bytes and the LAN is an Ethernet LAN. ones 1 ft f=) «The backoff time is always taken as its worst case. ; loons Zs Hint: You need to consider all the possible delays: Transmission delay, _ ise e to recognize a CQ lision and bagroft time. 7 3. -*) let é s Speror) (3x 36«'0 + Br5t2V Ns (2G 12 «80 ) + CExS12 107 5) Roun Trip Time TT) fat heel "Seca! back ff Mbps fink is being set up between earth and a communication fered {25 MB should be trans Supose that a 100! light = 3*10°8 mis. satellite at an altitu from station A 10 station de of 36,000 km. An image file 0 Bon earth. Assume the speed of Calculate the minimum Round Trip Time (RTT) for the link. unt of data already sent when the sender receives the ACK Calculate the amo from the receiver that the first bit has arrived’. * 6) Network Utilization In Figure 2 the bit rate between sender and router is router is 8kpbs. Suppose the sender transmits 10 pac and the RTO (retransmission time out) is 2 times RTT(roun » Calculate the arrival time for the packets at the router and the r arrival time for ACKs at the sender. Fill in the table. Which packets will be unnecessary retransmitted? What is the network utilization? g0kbps and between receiver and kets with 1000 bytes in 1 second d trip time). eceiver and the Receiver Packet Start Send Packet Arrive Packet Arrive ACK Arrive Number (Router) (Receiver Sender y) 4 ( ) a 2 3 t 4 | 4 L 5 L 1 SP] 31o