Subject: [Sip] RE: [Sipping] draft-mahy-sipping-connect-reuse-reqs-00

From: "Sean Olson" <[email-masked]>
Date: Tue, 9 Jul 2002 09:42:28 -0700

Good point. Is this is a request or a demand by the client to re-use
the connection? I think we need the possibility for the client to
*demand* that the connection be re-used. There may also be situations
where re-use is just an optimization.

/sean

-----Original Message-----
From: Christer Holmberg [mailto:[email-masked]] 
Sent: Tuesday, July 09, 2002 9:41 AM
To: Sean Olson; Gonzalo Camarillo; [email-masked]; [email-masked];
[email-masked]
Subject: Re: [Sipping] draft-mahy-sipping-connect-reuse-reqs-00

Another comment,

I also think it is important to remember that there MAY be scenarios,
especially if a connection is used for multiple sessions, where one
wants to use separate connections per each direction - even if the
client indicates he wants to use the same connection for the response.
Just to think of before the MUSTs are added...

Regards,

Christer Holmberg
Ericsson Finland

Christer Holmberg wrote:

> Hi Sean,
>
> > Is this really out of scope for this draft? Naturally
> > the more re-use you make of the connection, the more benefit you get

> > from re-use ;-)
>
> Of course, but in that case it should be mentioned in the draft :)
>
> The only thing the draft currently talks about the problem how to make

> sure a single connection is used for both directions, per session - 
> which is a separate issue from reusing connections for multiple 
> sessions.
>
> And, since I don't think any draft currently talks about the reuse of 
> connections for multiple sessions (bis talks about keeping the 
> connection open to make sure the transaction uses the same 
> transaction), maybe it could be added to the connect-reuse draft?
>
> Just some thoughts...
>
> Regards,
>
> Christer Holmberg
> Ericsson Finland
>
> >
> >
> > /sean
> >
> > -----Original Message-----
> > From: Christer Holmberg [mailto:[email-masked]]
> > Sent: Tuesday, July 09, 2002 6:30 AM
> > To: Gonzalo Camarillo
> > Cc: Sean Olson; [email-masked]; [email-masked]; [email-masked]
> > Subject: Re: [Sipping] draft-mahy-sipping-connect-reuse-reqs-00
> >
> > Hi,
> >
> > RFC3261/bis-9 mainly talks about using a single connection (or, one 
> > in each
> > direction) for a single transaction, and the connect-reuse draft 
> > talks about being able to use a single connection for messages in 
> > both direction, for a single session. Sometimes, however, when we 
> > talk about "reuse of connection" we mean when a single connection 
> > (or, one in each
> > direction) is used for multiple sessions. I think it would be a good
> > idea to mention that that kind of "reuse" is out of the scope of the
> > draft. Otherwise the draft subject should more clear indicate what
kind
> > of reuse it refers to...
> >
> > Of course, once a single connection is established, according to the

> > connect-reuse draft, it MAY be used for multiple sessions, but 
> > that's not the scope of the draft, so...
> >
> > Regards,
> >
> > Christer Holmberg
> > Ericsson Finland
>
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---

From: Christer Holmberg <[email-masked]>
Date: Thu, 11 Jul 2002 10:10:46 +0300

Hi,

I think it is important to think of who is allowed to "demand" what. Can we
always assume the client makes the final decission? What if the server - for
whatever reason - doens't want to/isn't able to reuse the connection? Shall
it send some kind of error response to the request where the "demand" is
specified, or shall it be allowed to use another, or establish a new,
connection? Shall the server be allowed to "demand" a re-use of connection,
even if the client didn't? How does this affect backward compability, if the
indicators aren't understood by all the nodes? Do we need
Supported/Require/Proxy-Require tags?

Regards,

Christer Holmberg
Ericsson Finland

---

From: Rohan Mahy <[email-masked]>
Date: Thu, 11 Jul 2002 07:43:47 -0700

Hi,

The current wording is that connection reuse is part of a request which 
can be rejected.  I need to understand Sean's use case a little better, 
but I suspect this will need to remain a request, because the request 
might not be authorized.  I guess the key question is what do you do  if 
the request can't be handled?  do you reject with an error message or 
handle the SIP request anyway (ignoring the connection reuse).  perhaps 
this is what Sean meant.  We probably should have an indication that the 
alias is optional or required.  Of course, required handling would also 
imply a Proxy-Require/Require which I was trying to avoid....

thanks,
-rohan

---

From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 15 Jul 2002 00:08:23 +0900

> where re-use is just an optimization.

Yes, I agree.

My main reason for indicating that a connection MUST be reused is NATs. 
If I open a connection from my UA to the proxy through a NAT, I will 
only be able to receive incoming traffic on that connection. Therefore, 
reuse for incoming messages is a MUST, rather than just an optimiziation.

Another way to think about this is that the alias is "scoped". In the 
case of mandatory reuse, the alias is only defined on the element to 
which the request was sent. I suppose this means that its the 
responsibility of that element to make sure that requests addressed to 
that alias by some other entity get routed to that element first.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.            72 Eagle Rock Avenue
Chief Scientist                         First Floor
dynamicsoft                             East Hanover, NJ 07936
[email-masked]                 FAX: (973) 952-5050
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http://www.dynamicsoft.com

---

From: Christer Holmberg <[email-masked]>
Date: Mon, 15 Jul 2002 01:50:55 +0300

Hi,

We should also look from the other direction, and remember that node
establishing the connection may also be a proxy forwarding an INVITE to a SIP
UA, requiring the connection to be reused in both direction for the purpose
of "saving" connections. Or, it may of course be a NAT. So, from that point
of view it is good that the client can make the reuse "decission".

However, I also think it is good if the called party, receiving the INVITE,
can require the connection to be used. For example, a single-session SIP UA
making a call may not care if it has to establish one or two connections. It
may, however, send the INVITE to a proxy, and/or a NAT, which again does
require the connection to be reused, so it should be able to do so.

I also think it is important to have a look how the solution will affect the
reuse of connections for multiple sessions (IF eg some extra parameters are
needed for that, or if some clarifications are needed).

Regards,

Christer Holmberg
Ericsson Finland