-----Original Message-----
From: hybi-bounces(_at_)ietf(_dot_)org
[mailto:hybi-bounces(_at_)ietf(_dot_)org] On
Behalf Of Greg Wilkins
Sent: 13 July 2011 03:54
To: Francis Brosnan Blazquez
Cc: Hybi; ietf(_at_)ietf(_dot_)org;
draft-ietf-hybi-thewebsocketprotocol(_at_)tools(_dot_)ietf(_dot_)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(_at_)aspl(_dot_)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(_dot_)brosnan(_at_)aspl(_dot_)es>
ASPL
91 134 14 22 - 91 134 14 45 - 91 116 07 57
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