Re: [hybi] Last Call: <draft-ietf-hybi-thewebsocketprotocol-10.txt> (The WebSocket protocol) to Proposed Standard: request for max frame size

"Len Holgate" <len.holgate@gmail.com> Wed, 13 July 2011 08:22 UTC

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From: "Len Holgate" <len.holgate@gmail.com>
To: "'Greg Wilkins'" <gregw@intalio.com>, "'Francis Brosnan Blazquez'" <francis@aspl.es>
References: <20110711140229.17432.23519.idtracker@ietfa.amsl.com><4E1BD054.7010103@gmail.com><1310480036.26452.329.camel@vulcan.aspl.local> <CAH_y2NF3pxbUJctg7P1qGNR+mvzaw80+Axh6kCYwx93HiQocug@mail.gmail.com>
Date: Wed, 13 Jul 2011 09:22:27 +0100
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Cc: 'Hybi' <hybi@ietf.org>, ietf@ietf.org, draft-ietf-hybi-thewebsocketprotocol@tools.ietf.org
Subject: Re: [hybi] Last Call: <draft-ietf-hybi-thewebsocketprotocol-10.txt> (The WebSocket protocol) to Proposed Standard: request for max frame size
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I agree that this would be very useful. 

Would this be one frame size for both directions, or could it be specified
in each direction? 

I'm a little wary of intermediaries being allowed to adjust this unless
they're only allowed to reduce the amount...

Len
www.lenholgate.com

> -----Original Message-----
> From: hybi-bounces@ietf.org [mailto:hybi-bounces@ietf.org] On 
> Behalf Of Greg Wilkins
> Sent: 13 July 2011 03:54
> To: Francis Brosnan Blazquez
> Cc: Hybi; ietf@ietf.org; 
> draft-ietf-hybi-thewebsocketprotocol@tools.ietf.org
> Subject: Re: [hybi] Last Call: 
> <draft-ietf-hybi-thewebsocketprotocol-10.txt> (The WebSocket 
> protocol) to Proposed Standard: request for max frame size
> 
> Francis et al,
> 
> not also that the protocol does support fragmentation and a 1004 frame
> too large error.
> Even the 1004 error does not carry an indication of what an acceptable
> size is, so the client/tool/intermediary that receives a 1004 will
> either have to fail or guess a smaller frames size - potentially
> binary chopping down to find an acceptable size, which might be sub
> optimal.
> 
> I simple optional header in the handshake declaring the max frame size
> (which intermediaries could adjust) would be very complimentary to the
> existing fragmentation and 1004 features and I can't think of any
> significant down side.
> 
> regards
> 
> On 13 July 2011 00:13, Francis Brosnan Blazquez 
> <francis@aspl.es> wrote:
> > Hi,
> >
> > Recently, I posted [1] that websocket protocol should include an
> > indication about max frame size that is willing to accept 
> the connecting
> > peer.
> >
> > Many pointed this is not an issue because you could use a stream
> > oriented API (like TCP send/recv and others), but that only 
> bypasses the
> > problem (in some cases) not solves it.
> >
> > Websocket protocol is frame based and every frame based protocol
> > designed until now has/need such feature or similar. Even 
> TCP, for those
> > that proposes to use a stream oriented API as a solution, includes a
> > more complex mechanism than a simple max frame size (window 
> based ack),
> > so each party can control/inform the sender. This is critical.
> >
> > A good example for this would be the next. Let suppose you have a
> > constrained memory device (either because it is small or because it
> > accepts a large amount of connections). On that device you deploy a
> > websocket app that only accepts small messages (< 512 bytes, let's
> > say).
> >
> > In this context, you can hard code at your web app (javascript) that
> > must not send messages larger than this size (so you 
> control websocket
> > payload size) and in the case you need to, you must split them
> > properly.
> >
> > However, even with this mechanism, you have no warranty 
> that the browser
> > or an intermediary will join those messages into a single 
> frame, causing
> > your device to receive a bigger message/frame than expected.
> >
> > Assuming this I think we would require either to include a
> > Max-Frame-Size indication (or a really poor solution: to explicitly
> > state on the draft that frames must not be coalesced by 
> intermediaries
> > or browsers).
> >
> > Regards,
> >
> > [1] http://www.ietf.org/mail-archive/web/hybi/current/msg07641.html
> > --
> > Francis Brosnan Blázquez <francis.brosnan@aspl.es>
> > ASPL
> > 91 134 14 22 - 91 134 14 45 - 91 116 07 57
> >
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