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Suppose a client sends an HTTP request message with the If-modified-since: header. Suppose the object in a server has not changed since the last time a client retrieved the object. Then the server will send a response message with the status code:

304 Not Modified

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none of the above

Consider the minimum time for P2P file distribution, as discussed in Section 2.6. Suppose the upload rate of the server is10 Mbps, the upload rates of all peers is 1 Mbps, and the download rates of all peers is 10 Mbps. Further suppose that there are 100 peers and the file is 100 million bits. The minimum distribution time is

approximately 1,000 seconds

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approximately 1 second

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approximately 10 seconds

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approximately 100 seconds

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SMTP is used to

to define the format of message headers

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to transfer messages from mail server to a user agent

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to transfer messages from one mail server to another

Consider a queue preceding a transmission link of rate R. Suppose a packet arrives to the queue periodically every 1/a seconds. Also suppose all packets are of length L. Then the queuing delay is small and bounded as long as aL < R.

Suppose the hit rate is .5 in a caching example. Calculate the average delay by assuming the time of the requests to be satisfied from cache is 10 milliseconds and the time of the requests still need to be satisfied by the origin servers is 1.2 seconds

none of the above

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between 1.0 and 1.1 seconds

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greater than two seconds

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between 1.2 and 1.3 seconds

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Local DNS name servers

cache resource records, but discard them after a period of time that is on the order of a few days

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