Question

Consider the figure below, for which there is an institutional network connected to the Internet. Suppose that the average (upload or download) object size is 1 Mbytes. Also suppose that the amount of time it takes from when the router on the Internet stde of the access link forwards an HTTP request until it receives the response is 3 seconds on average. Answer questions (28)-(30) Origin server Origin servers Public Internet Public intenet 15 Mbps access link 15 Mbps access link 100 Mbps LAN 100 Mbps LAN- Institutional cache Institutional network institutional network Figure 2: Bottleneck between an institutional network and the Internet

Parts 28, 29, and 30

Answer 1

Dear,

R11 The TCP connection oriented protocol and UDP is connectionless protocol. It sends datagrams and does not manage connection, re transmission, or data sequencing. HTTP, FTP, SMTP, and POP3 named protocols assumes the presence of a sequenced, loss-free data stream transport For protocols that can stand losing data or prefer a data pacing strategv other than what TCP provides, UDP is a better choice. Hence, TCP provides this service whereas UDP doesn't Streaming audio and video services where the data streams are designed to endure data losses can sometimes do better with the more lightweight UDP protocol. R12 FTP uses two parallel TCP connections, one connection for sending control infomation such as a request to transfer a file, and another connection for actually transferring the file Because the control information is not sent over the same connection that the file is sent over, FTP sends control information out of band P1 The total amount of time to get the IP address is Once the IP address is known RIT, elapses is to set up the TCP connection and another RITelapses to request and receive the small object. The total response time is 2RTI +RTI.RTT P9 a) ? 900000 bits 15000000 bps 0.06 sec ? β= 0.06 secrequest * 15 request/sec = 0.9 ?/(1-2β)= 0.06 sec / ( 1-09 )-0.6 Total average response time= 0.6 + 2-2.6sec b) The traffic intensity on the access link is reduced by 40% since the 40% of the requests are satisfied within the institutional network. Thus the average access delay is 0.06 [ 1-0.0.91 0.1304 sec. The response time is approximately zero if the request is satisfied by the cache The average response time is 0.1304 sec + 2 sec = 2.1304 sec for cache misses So the average re sponse time is 0.4 * 0 sec +0.6* 2.1304-127824 sec. Thus the average response time is reduced from 2.6 sec to 1.27824 sec.