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TCP Divacks for Hand-overs

Divacks can be used to ramp-up the cwnd in TCP after a vertical handover.

When vertical hand-overs (or even horizontal hand-overs between networks with different levels of congestion) occur, the congestion control state of TCP may need to be adjusted. Right after the handover, the value of TCP's cwnd is adapted to the previous network's capacity. To have feedback about the new network capacity, at least one new RTT has to elapse. It may then take several new RTTs for the congestion control state to update to the actual cwnd the new network can support.

Considering mobile TCP receivers, it may be possible, using ACK division techniques, to ramp-up the remote server to ramp up its cwnd and occupy the network more quickly.

Further attention may need to be paid to the possibility of ramping down the cwnd without causing too much congestion on the new network if its capacity is not as large as the previous one. A work-around could be setting the rwnd at the receiver to the desired value which, if smaller than the sender's cwnd, will limit the throughput. An interesting solution may be to apply an AIMD algorithm on the receiver, and compute a rcwnd which would be sent in place of the normal wnd until it eventually becomes larger. Question: How would the sender update its local cwnd during periods of receiver-controlled CC?

research/divackvho.1265959169.txt.gz · Dernière modification: 2013-11-15 05:04 (modification externe)