TCP latency modeling

Q: How long does it take to receive an object from a Web server after sending a request?

• TCP connection establishment

• data transfer delay

Notation, assumptions:

• Assume one link between client and server of rate R

• Assume: fixed congestion window, W segments

• S: MSS (bits)

• O: object size (bits)

• no retransmissions (no loss, no corruption)

Two cases to consider:

• WS/R > RTT + S/R: ACK for first segment in window returns before window’s worth of data sent

• WS/R < RTT + S/R: wait for ACK after sending window’s worth of data sent

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