[multipathtcp] Multipath TCP Address advertisement 2/5 - Reliability

Fabien Duchêne <fabien.duchene@uclouvain.be> Wed, 03 August 2016 15:42 UTC

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Subject: [multipathtcp] Multipath TCP Address advertisement 2/5 - Reliability
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As agreed in Berlin during IETF96, I'm sending a series of emails to
discuss the different contributions proposed

This is the part 2/5 : reliability.

In RFC6824, ADD_ADDR options can be attached to segments carrying data
or pure acknowledgements.
In practice, notably given the length of ADD_ADDR with IPv6 addresses
and the HMAC, it is very likely that they will be often sent as pure
This implies that ADD_ADDR are sent unreliably, which could be
problematic when the ADD_ADDR is required to allow the establishment of
additional subflows, as in load balancing scenarios. 
We propose to rely on the "E" (Echo) flag in the ADD_ADDR option.
This echo flag is used to acknolwedge a received ADD_ADDR by echoing it.
If the acknowledgement is not received, the ADD_ADDR option will be
retransmitted up to N times.