(a) What information is used by a process running on one host to identify
a process running on another host?
(b) Why does HTTP run on top of TCP rather than on UDP?
(c) Consider an HTTP client that wants to retrieve a Web document at
a given URL. The IP address of the HTTP server is initially unknown.
What transport and application-layer protocols besides HTTP are needed
in this scenario (list all that will be used)?
(d) Consider a short, 10-meter link, over which a sender can transmit at a
rate of 150 bits/sec in both directions. Suppose that packets contain
ing data are 100,000 bits long, and packets containing only control
(e.g., ACK or handshaking) are 200 bits long.
Assume that N parallel connections each get 1=N of the link band
Now consider the HTTP protocol, and suppose that each downloaded
object is 100 Kbits long, and that the initial downloaded object con
tains 10 referenced objects from the same sender.
Firstly, consider parallel downloads via parallel instances of non-persistent
HTTP. Secondly, consider persistent HTTP. Do you expect significant
performance gains over the non-persistent case? Justify and explain
your answer (please clearly show your reasoning and summary calcu
(e) i. The equation for determining the download time for a peer-to
peer file sharing is given below.
Explain what each of the following terms represents (for example:
“The time for one peer to download a single copy of the file”)
ii. Using the same variables (F, u, d) give an equation for the mini
mum download time for a client/server file download.
(f) Consider the network shown in figure 1. The hosts in the left network
are requesting resources using HTTP from the origin servers on the
Internet. 30% of web requests result in a cache hit (the request has
been previously downloaded and can be served from the cache). Each
host (not including the cache) generates a request every 20 seconds
and each request requires the download of 1Mbit. What download
bandwidth is needed on the access link, L1, in order for this HTTP
download traffic to utilise a no more than 80% of the link download
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