A client sends a 200 byte request message to a service, which produces a response containing 5000
bytes. Estimate the total time to complete the request in each of the following cases, with the
performance assumptions listed below:
i) Using connectionless (datagram) communication (for example, UDP);
ii) Using connection-oriented communication (for example, TCP);
iii) The server process is in the same machine as the client.
[Latency per packet (local or remote,
incurred on both send and receive):5 milliseconds
Connection setup time (TCP only):5 milliseconds
Data transfer rate:10 megabits per second
MTU:1000 bytes
Server request processing time:2 milliseconds
Assume that the network is lightly loaded.]
What will be an ideal response?
The send and receive latencies include (operating system) software overheads as well as network delays.
Assuming that the former dominate, then the estimates are as below. If network overheads dominate,
then the times may be reduced because the multiple response packets can be transmitted and received
right after each other.
i) UDP: 5 + 2000/10000 + 2 + 5(5 + 10000/10000) = 37.2milliseconds
ii) TCP: 5 + 5 + 2000/10000 + 2 + 5(5 + 10000/10000) = 42.2milliseconds
iii)same machine: the messages can be sent by a single in memory copy; estimate interprocess data transfer
rate at 40 megabits/second. Latency/message ~5 milliseconds. Time for server call:
5 + 2000/40000 + 5 + 50000/40000 = 11.3milliseconds
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What will be an ideal response?
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