hw2 photos

hw2 photos - P19. P20. P21. -. I ...'.-x, d. Repeat the...

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Unformatted text preview: P19. P20. P21. -. I ...'.-x, d. Repeat the above for a source and desi- Compare the intra—continent and __ Consider the throughput example corresf. suppose that there are M client—server _ i R for the rates of the server links, client other links have abundant capacity and that _ network besides the traffic generated by the M client's-*7 general expression for throughput in terms of Rs, Re, R, t . g _ , ' . '. Consider Figure 1.19(b). Now suppose that there are M paths " ' . . server and the client. No two paths share any link. Path k (k = 1 f I. , sists of N links with transmission rates Rf, Rf, . . . R". If the se ’ . . q ‘ con“ use one path to send data to the client what is the nivaxim flit-“i:r only ’ “m Oughput that the server can achieve? If the server can use all M paths to send . _ .. . . the maxrmum throughput that the server can achieve? ta. What Is Consider Figure 1.19(b). Suppose that each link between the serve client has a packet loss probability p, and the packet loss probabilitri these links are Independent. What is the probability that a packet csffor gem-*- u. _ from the server to the client, then the server will re-transmit the packet. On average, how many times will the server re-transmit the packet in order for the client to successfully receive the packet? P22. Consider Figure l.l9(a). Assume that we know the bottleneck link along the path from the server to the client is the first link with rate Rs bits/see. Suppose we send a pair of packets back to back from the server to the client, and there is no other traffic on this path. Assume each packet of size L bits, and both a. What is the packet inter-arrival time at the destination? That is, how much time elapses from when the last bit of the first packet arrives until the last bit of the second packet arrives? b. Now assume that the second link is the bottleneck link (i.e., RC < RS). Is it possible that the second packet queues at the input queue of the second link? Explain. Now suppose that the server sends the second packet T sec- onds after sending the first packet. How large must T be to ensure no queuing before the second link? Explain. P23. Suppose you would like to urgently deliver 40 terabytes data from Boston to Los Angeles. You have available a 100 Mbps dedicated link for data transfer. Would you prefer to transmit the data via this link or instead use FedEx over- c. Can a client open three or more sim - ultaneous connections ' ' server? Wlth a given d. Filth: a server or a client may close a transport connection between them 11.r elt er one detects the connection has been idle for some time. Is it pos— srble that one slde .starts closmg a connection while the other side is trans- nuttmg data Vla this connection? Explain. P7, Suppose Within your Web browser you click on a link to obtain a Web page. The IP address for the associated URL is not cached in your local host, so a DNS lockup is necessary to obtain the IP address. Suppose that n DNS servers are Visited before your host receives the IP address from DNS; the successive visits incur an RTT of RTT 1, . . ., RTT”. Further suppose that the Web page associated with the link contams exactly one object, con51st1ng of small amount of HTML text. Let R'IT0 denote the RTT between the local hos and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object? P8. Referring to Problem P7, suppose the HTM ' . Neglecting trans L file references eight very smal mission times, how much time elapses with n - . -i nrrrm with nn narallel TCP connections? DNS lookupOiS: necessary to obtain the IP address. Suppose that n DNS servers are visited before your host receives the IP address from DNS' the successrve wsrts incur an RTT of R'I'Tl, . . ., RTT . Further suppose that the Web page assocmted with the link contains exact]; one object. consisting of a small amount of HTML text. Let RTTO denote the RTT between the local host and the server containing the object. Assuming zero transmission time of the object, how much time elapses from when the client clicks on the link until the client receives the object? P8. Referring to Problem P7, suppose the HTML file references eight very small objects on the same server. Neglecting transmission times, how much time elapses with a. Non-persistent HTTP with no parallel TCP connections? b. Non-persistent HTTP with the browser configured for 5 parallel connections? 0. Persistent HTTP? P9. Consider Figure 2.12, for whi the Internet. Suppose that the average request rate from the institution’s requests per second. Also suppose that the amount of time it takes from wher the router on the Internet side of the access link forwards an HTTP request 0 APPLICATION LAYER P10. Consider a short, 10-meter link, over which a sender can transmit at a rate of P11. 150 bits/sec in both directions. Suppose that packets containing data are 100,000 bits long, and packets containing only COIltl‘O1 (e-gu ACK or hand- shaking) are 200 bits long. Assume that N parallel connections each get l/N of the link bandwidth. Now consider the HTTP protocol, and suppose that each downloaded object is 100 Kbits long, and that the initial downloaded object contains 10 referenced objects from the same sender. Would parallel downloads via parallel instances of non-persistent HTTP make sense in this case? Now consider persistent HTTP. Do you expect significant gains over the non-persistent case? Justify and explain your answer. the link is Shared by 3013 With four other users. Bob uses parallel instances of non-persistent HTTP, and the other four users - . use 110 - m- out parallel downloads. ‘1 Pel‘SlStent HTTP W1 a. Do Bob’s parallel connections hPln mm M... u r . P26. P27. bacxorr lllwrvzua m “MW... A draws K = O and B draws ; in the exponential backofl' protOCol, the jam signal and the 96-bit time delay. I What is the one-way propagation delay (inCll'ding A and B in seconds? Assume that the signal propagation is 2 * 1'0a b. At what time (in seconds) is A’s packet completely deliv at B? c. Now suppose that only A has a packet to send and that me. are replaced with switches. Suppose that each switch has a 20-bit pmcessjmg delay in addition to a store-and—forward delay. At what time, in seconds, is A‘s packet delivered at B? In the Ethernet standard, a sender pauses 96 bit times between sending consec- utive frames. This pausing time is referred to as inter-frame gap, and it is used to allow a receiving device to complete the processing of a received frame and to prepare for the reception of the next frame. Since the Ethernet standard was specified, there has been a tremendous improvement in technology including the speed of processors, memory, and the Ethernet rates. If the standard were to be rewritten. how would these improvements impact the inter-frame gap? Consider Figure 5.38 in problem P14. Provide MAC addresses and IP addresses for the interfaces at Host A, both routers, and Host F. Suppose H05t A sends a datagram to Host F. Give the source and destination MAC addresses in the frame encapsulating this IP datagram as the frame is transmitted (i) from A to the left router, (ii) from the left router to the right router, (iii) from the right router to F. Also give the source and destination IP addresses in the 11’ a. Figure 1.19 o Throughput for a file ire-.nsfer_frojtn...se-rver to client it receives them. In W bits will onlv leave fl‘m mm..- ‘ L :«n. . A .1“,- 10 Servers Bottleneck link of -ients __ b. A ‘jfthmug-hput: (a) Client downloads a file from j with 10 servers. , g‘ a is again the minimum of R, and He, that is, . -~ _ I \ I V ‘ se of small packets for Voice‘over IP appli- mtmst One of the thaancks 0f 3 small packet size is that a large fraction of Mk h “I”! Mfm‘ '3 mm by overhead bytes. To this end. suppose that the Ne! “Sim 0f P bytes and 5 bytes of header. 3' sending a digitally 6de voice source directly. Suppose the Is encoded at a constant rate of 128 kbps. Assume each packet is (thumb filled before the source sends the packet into the network. The time minim! to fill a packet is the packettutton delay. In terms of L. the packetizmion delay in milliseconds. bi.- deley's greater than 20 mm: can cause a noticeable and W Maurine the packctimkm delay fm’ L a: 1.500 bytes i am ma militant-sired m pack“) midtown 59(me‘1‘14 packet), _ a... WhWfiquafingkwM foralinkmd £5,522ng1,’ IMW,MIWLIS()W. I - 4.Wm.nwmdmamu1|mafize. ...
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hw2 photos - P19. P20. P21. -. I ...'.-x, d. Repeat the...

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