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Re: HTTP over SCTP without chunked encoding

From: Mark Nottingham <mnot@mnot.net>
Date: Wed, 8 Apr 2009 16:38:07 +1000
To: leighton@mail.eecis.udel.edu
Message-Id: <06A70EFB-A85F-4FE5-AD13-C854C8867842@mnot.net>
Cc: ietf-http-wg@w3.org, fred@cisco.com, amer@cis.udel.edu, prenatar@cisco.com
I'm far from an expert in SCTP, but at first glance, this is  
potentially attractive, but slightly more intrusive in the HTTP stack,  
because it's introducing a new way to frame messages, rather than  
reusing exising code to do so.

The current proposals (AIUI) are less intrusive, because at a certain  
point a SCTP stream just looks like a TCP connection.

Now, whether this trade-off is worth it or not is an open question, of  
course. I think most people are focused on the aspects of SCTP that  
relieve the problems experienced with pipelining, and while having a  
more efficient framing mechanism is interesting, it's not low-hanging  
fruit.

Perhaps this should be an open design question in a HTTP-over-SCTP  
draft, to try to get feedback from interested vendors...

Cheers,



On 02/04/2009, at 11:58 AM, leighton@mail.eecis.udel.edu wrote:

> At the recent HTTP WG meeting the subject of HTTP over SCTP was  
> discussed,
> and in particular the question was raised as to whether or not SCTP  
> could
> be used to avoid chunked encoding.  There are two ways to do this,  
> but one
> of them (EXPLICIT_EOR socket option) conflicts with current thinking  
> about
> how best to send HTTP over multiple SCTP streams.  The other  
> approach is
> to use the payload protocol identified or PPID.
>
> The PPID is an optional value that is set by the sender and read by  
> the
> receiver.  The approach would be to define two PPID values  
> (allocated by
> IANA), say HTTP_MESSAGE_PIECE and HTTP_MESSAGE_END.  The sender  
> would set
> the PPID to HTTP_MESSAGE_END for the last sctp_sendmsg() call for the
> current HTTP object, thereby allowing the receiver to identify the  
> end of
> the current HTTP object.
>
> I'm far from being an expert in HTTP, and I would be grateful for  
> feedback
> on the suitability of this mechanism.  Thanks very much.
>
> - Jon Leighton
>
>


--
Mark Nottingham     http://www.mnot.net/
Received on Wednesday, 8 April 2009 06:38:49 GMT

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