Subject: RE: [Sip] draft-jennings-sip-dtls

From: "Francois Audet" <[email-masked]>
Date: Wed, 16 Feb 2005 14:54:59 -0500

I would agree with Jonathan.
 
Yes, some implementations of SIP/TCP have performance issues compared to
SIP/UDP, but not necessarily all of them. 
 
Also, if we need to address the other problems of UDP transport (like
fragmentation, and others), then it is not clear to me that we are saving
much in the first place by using UDP/DTLS instead of TCP/TLS.
 
I'd like to see real data before we add yet another thing we'll have to
implement...

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Cullen
Jennings
Sent: Tuesday, February 15, 2005 20:08
To: Jonathan Rosenberg
Cc: [email-masked]
Subject: Re: [Sip] draft-jennings-sip-dtls

Oops - I meant to put that.... There is pretty much one key thing. No one
has build an single edge proxy that can terminate 100k to 1M connections to
UAs using TLS. In theory it is possible, but in practice it seems hard. The
argument is that this will be easier with DTLS. The issue is not the time it
takes to do the crypto - session resumption deals with that nicely - it just
the issues of dealing with half a million TCP connections to one box. Of
course no one has done it with DTLS either :-)

I believe the argument we made for SCTP was that adding an extensions for
SCTP won't increase the complexity of things that don't support SCTP. 

I agree the UDP/TCP complexity made SIP more complicated and I agree that
sip and sips made things more complicated. I'm not sure I buy that both TLS
and TCP made things more complicated. 

On 2/15/05 7:15 PM, "Jonathan Rosenberg" <[email-masked]> wrote:

Cullen, 

What seems missing to me from this is requirements and problem 
statements. What is DTLS doing for us that we don't get from TLS? 

Though SIP can run over many different transport protocols, I think 
experience over time has shown that more choices here is not necessarily 
a good thing, as SIP has a fair bit of complexity as a result of dealing 
with the differences between UDP and TCP. As such, I don't think its a 
good idea to just add more transport protocols to SIP's list of 
supported ones unless there is a compelling problem that it is solving. 

Thanks, 
Jonathan R. 

Cullen Jennings wrote: 

> 
> Nagendra and I put together a draft on using DTLS with SIP. Until it 
> shows up in the archives you can find it at 
> 
>
http://scm.sipfoundry.org/rep/ietf-drafts/fluffy/draft-jennings-sip-dtls-00.
html
<http://scm.sipfoundry.org/rep/ietf-drafts/fluffy/draft-jennings-sip-dtls-00
.html>  
> 
> (there is a .txt version too) 
> 
> 
> The abstract is: 
> 
>    This draft specifies how to use Datagram Transport Layer Security 
>    (DTLS) as a transport for SIP.  DTLS is a new protocol for providing 
>    TLS security over a datagram protocol. 
> 
> 
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