Re: [multipathtcp] Multipath TCP Address advertisement 2/5 - Reliability
Fabien Duchêne <fabien.duchene@uclouvain.be> Wed, 03 August 2016 16:59 UTC
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Subject: Re: [multipathtcp] Multipath TCP Address advertisement 2/5 -
Reliability
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On 03/08/2016 18:11, Alan Ford wrote: > I am neutral on the addition on this flag… We have spare bits, so could easily allocate this. But is it worth it? Although not explicitly written, I believe we had expected senders to send the ADD_ADDR option multiple times. The idea here is, with the load balancing in mind, we *really* want the ADD_ADDR to be delivered, and sending it multiple times doesn't really guarantee that it will be delivered. > If the ADD_ADDR was not echoed, what would the sender do? Retransmit a few times I guess. I also guess it could learn that a path may not support duplicate ACKs with options. Retransmit it a few times, and if not echoed, we could know that it hasn't been delivred. Because there's the case where the ADD_ADDR is received but the client doesn't elect to open a subflow on this address. With the echo bit, if such thing happen basically you would know "ok, he received my add_addr but doesn't want to establish a subflow for now", otherwise you won't be able to tell the difference between a lost ADD_ADDR and this case. I agree with the dupacks with options. > > It could be useful, but I do not feel strongly here… If this were an IETF room, I’d hum weakly ;-) > > Regards, > Alan > >> On 3 Aug 2016, at 16:47, Fabien Duchêne <fabien.duchene@uclouvain.be> wrote: >> >> Hello, >> >> As agreed in Berlin during IETF96, I'm sending a series of emails to >> discuss the different contributions proposed >> inhttps://datatracker.ietf.org/doc/draft-duchene-mptcp-add-addr/ >> >> 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 >> acknowledgements. >> 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. >> >> Fabien >> >> _______________________________________________ >> multipathtcp mailing list >> multipathtcp@ietf.org >> https://www.ietf.org/mailman/listinfo/multipathtcp
- Re: [multipathtcp] Multipath TCP Address advertis… Yoshifumi Nishida
- Re: [multipathtcp] Multipath TCP Address advertis… Alan Ford
- Re: [multipathtcp] Multipath TCP Address advertis… Yoshifumi Nishida
- [multipathtcp] Multipath TCP Address advertisemen… Fabien Duchêne
- Re: [multipathtcp] Multipath TCP Address advertis… Alan Ford
- Re: [multipathtcp] Multipath TCP Address advertis… Yoshifumi Nishida
- Re: [multipathtcp] Multipath TCP Address advertis… Christoph Paasch
- Re: [multipathtcp] Multipath TCP Address advertis… Juliusz Chroboczek
- Re: [multipathtcp] Multipath TCP Address advertis… Fabien Duchêne
- Re: [multipathtcp] Multipath TCP Address advertis… Alan Ford