Re: [hybi] I-D Action: draft-ietf-hybi-websocket-multiplexing-01.txt
"Arman Djusupov" <arman@noemax.com> Tue, 22 May 2012 11:40 UTC
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From: Arman Djusupov <arman@noemax.com>
To: 'Greg Wilkins' <gregw@intalio.com>, 'Takeshi Yoshino' <tyoshino@google.com>
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Date: Tue, 22 May 2012 14:40:21 +0300
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Cc: hybi@ietf.org
Subject: Re: [hybi] I-D Action: draft-ietf-hybi-websocket-multiplexing-01.txt
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The mux specification does not define an algorithm for calculating the subsequent FC quota to be sent to the remote side. This means that the quota is not required to be a fixed value, it can have a dynamic value taking into account various criteria including the share of the per-connection window space available. If we have to resolve the overallocation and underutilization issue on the protocol level, we would need a more complex flow control protocol that would be able use an optimistic window size and discard/retransmit the frames that would be overbuffered. This would definitely be much more complex and I doubt that it would resolve performance problems. Note that the issues being discussed in the SPDY list are not only SPDY problems, they are present even with TCP/IP intermediaries (with the difference that TCP/IP packets can be discarded and retransmitted later if the link is overloaded). With best regards, Arman From: hybi-bounces@ietf.org [mailto:hybi-bounces@ietf.org] On Behalf Of Greg Wilkins Sent: Tuesday, May 22, 2012 12:12 PM To: Takeshi Yoshino Cc: hybi@ietf.org Subject: Re: [hybi] I-D Action: draft-ietf-hybi-websocket-multiplexing-01.txt I think we should note the discussion happening over in SPDY-dev about their flow control and concerns about it https://groups.google.com/forum/?fromgroups#!topic/spdy-dev/JB_aQPNI7rw Our mux proposal with it's send quotas has effectively the same problem - namely that a fixed quota per channel can cause a significant under utilisation of a fast link, but can also represent a significant over allocation of capacity if many channels are present. I think we need to closely follow that discussion to see what solutions may be developed before we commit to a per channel window flow control. cheers On 20 April 2012 08:08, Takeshi Yoshino <tyoshino@google.com> wrote: Hi all, Here's the ietf -01 version of multiplexing spec. Diff: http://tools.ietf.org/rfcdiff?url2=draft-ietf-hybi-websocket-multiplexing-01 .txt Changes from -00 are: - now multiplex control blocks MUST be interpreted when the entire message containing them has arrived - now the base for delta-encode of handshake is the last AddChannelRequest/Response with Enc=identity - clarified how much the send quota is until receiving reply -- note that this is still open for discussion - a server MUST _Fail the Physical Channel_ when there's inconsistency between Sec-WebSocket-Extensions in AddChannelRequest/AddChannelResponse (e.g. some value that need to be the same for all logical channels is altered) -- another option is to just _Fail the Logical Channel_ - style/readability -- new term "multiplexed connection" to clarify the difference between logical channels (used for both control and transferring multiplexed connection's data) and multiplexed WebSocket connections -- new term "Implicitly Opened Connection" defined to reduce text -- made definition of send quota and quota parameter in Flow Control section more detailed _______________________________________________ hybi mailing list hybi@ietf.org https://www.ietf.org/mailman/listinfo/hybi
- [hybi] I-D Action: draft-ietf-hybi-websocket-mult… internet-drafts
- Re: [hybi] I-D Action: draft-ietf-hybi-websocket-… Takeshi Yoshino
- Re: [hybi] I-D Action: draft-ietf-hybi-websocket-… Greg Wilkins
- Re: [hybi] I-D Action: draft-ietf-hybi-websocket-… Arman Djusupov