RE: [Sip] moving UDP support out of the core SIP document

[hisham.khartabil@nokia.com]

Moving UDP to another document, downgrading it to a MAY in the SIP base document or whatever will not achieve anything, IMO. UA implementations will still have it (its easier to start with UDP when implementing SIP). Proxies MUST still support it.

We either deprecate it from the spec or leave it as is.

Regards,
Hisham

> -----Original Message-----
> From: ext Vijay K. Gurbani [mailto:vkg@lucent.com]
> Sent: Thursday, October 24, 2002 6:27 PM
> To: Rohan Mahy
> Cc: sip@ietf.org
> Subject: Re: [Sip] moving UDP support out of the core SIP document
> 
> 
> Rohan Mahy wrote:
> > Hello Everyone,
> > 
> > I wanted to share some thoughts that I had about removing 
> UDP from the 
> > core SIP document when we go to draft standard. 
> [...]
> > Obviously UDP is still very attractive in wireless networks 
> (due to RTT 
> > issues) and in other typically private networks with 
> well-understood 
> > delay and loss characteristics. To make most 
> implementations simpler 
> > however, I am proposing that we make unreliable transports (UDP and 
> > DCCP) of SIP optional in User Agents, and that we put the 
> UDP-specific 
> > mechanism (ex: much of the complication of the transaction 
> layer for 
> > handling retransmissions) in a separate Draft Standard document.  
> 
> Making UDP optional is fine, but I think it should stay in the core
> SIP specification.  Over the years, the SIP state machines for
> INVITE and non-INVITE transactions have evolved keeping multiple
> transports in mind.  The sourrounding text and the FSM figures
> (Figure 5, 6, 7, and 8 in rfc3261) at this point in time are well
> specified and, I beleive, well understood by the SIP community in
> general.
> 
> Divorcing UDP transport from the core spec to another RFC raises other
> questions:
> 
>    1/ Since proxies are optional in SIP and a UA can initiate
>       a session directly with its peer, will a UDP-only UA
>       insert a "Require: udp" in the request?
> 
>    2/ Issues such as reassembly, UDP response growing
>       larger than the request, etc. still remain.
> 
> If it is a choice between deprecating UDP entirely or moving it to
> another RFC, I would choose the latter.  But so long as we tacitly
> support UDP, it would be nice to have it in the base document (maybe
> degrade it to a MAY instead of a SHOULD).
> 
> Regards,
> 
> - vijay
> -- 
> Vijay K. Gurbani  vkg@{lucent.com,research.bell-labs.com,acm.org}
> Wireless Networks Group/Internet Software and Services
> Lucent Technologies/Bell Labs Innovations, 2000 Lucent Lane, Rm 6G-440
> Naperville, Illinois 60566     Voice: +1 630 224 0216
> 
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