Subject: [Sip] Connection: Keep-Alive

From: "Christian Stredicke" <[email-masked]>
Date: Wed, 12 Nov 2003 16:59:45 -0600

Hi There!

The discussion today about moving to TCP transport layer and the
consequences on NAT raises the question if we should define a header
that asks the proxy explicitly to keep the TCP connection open. As far
as I see this has not been defined yet. 

I see two possibilities:

1) Implicit: The proxy detects that client cannot be reached by the
address which it is using (using the received or rport parameter in the
top via). 

2) Explicit: The client explicitly requests this. This could be done
with the famous Connection header, maybe as a parameter in the top via.

In any case the behavior of the UAC as well as the proxy needs to be
(re)defined, I think the current TCP specification does not allow a
permanent connection.

Any thoughts on this?

CS
--
Christian Stredicke
tel:+49.30.39833.401 (ENUM & PSTN)
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---

From: "Vijay K. Gurbani" <[email-masked]>
Date: Wed, 12 Nov 2003 22:14:18 -0600

> as I see this has not been defined yet. 

I've discussed this in a I-D I presented at the Atlanta IETF.
See
http://www.ietf.org/internet-drafts/draft-jain-sipping-persistent-conn-reqs-00.txt
on some ways to do so.  That I-D builds on Rohan's connection-reuse
draft and fills in a couple of gaps in it.  Namely the longevity
aspects of the connection and the neediness of a client in
requesting a persistent connection.

> with the famous Connection header, maybe as a parameter in the top via.

Section 8 of that I-D describes some ways to explicitly signal
the intent.

> (re)defined, I think the current TCP specification does not allow a

At the Atlanta IETF, it was decided that we will open a bug
against rfc3261 to provide more information on TCP connection
handling.  But as I said on the floor then, I believe that we
need to go beyond that; a BCP outlining TCP connection handling
was suggested as an additional venue.  I have not had the time
to do that so far.

Given the current and growing interest in this topic,
maybe we can get together some more heads interested in this
to hammer out a BCP.  We can use the above I-D as a starting
point.  The need for persistent connections will become
pressing as more implementations support TLS.  Despite TLS
session resumption, persistent TLS connections between two
high-volume proxies can be extremely beneficial.

Question to SIP/SIPPING chairs: Is the time ripe for a design
team on this?

Cheers,

- 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

---

From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 13 Nov 2003 02:12:20 -0500

Vijay K. Gurbani wrote:

> handling. 

Well, in particular, it was concluded that signaling "please keep this 
connection open" was not needed at all. Rather, the server should keep 
the connection open as long as it could, and only close it if it ran 
out of resources. Since there was no benefit to closing it prematurely 
(extra costs of setting it up again), and since signaling the desire 
for persistence could not be used to force the server to keep it open 
if the server ran out of resources, the signaling was not needed. 
Indeed, the observation was that many implementations in any case were 
doing this; it was just unclear in the spec.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                600 Lanidex Plaza
Chief Technology Officer                    Parsippany, NJ 07054-2711
dynamicsoft
[email-masked]                     FAX:   (973) 952-5050
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---

From: "Sean Olson" <[email-masked]>
Date: Wed, 12 Nov 2003 23:38:44 -0800

Actually, many implementations are not doing this unfortunately. A BCP is
not a bad idea. 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Jonathan
Rosenberg
Sent: Wednesday, November 12, 2003 11:12 PM
To: Vijay K. Gurbani
Cc: Christian Stredicke; [email-masked]; [email-masked]
Subject: Re: [Sip] Connection: Keep-Alive

Vijay K. Gurbani wrote:

> At the Atlanta IETF, it was decided that we will open a bug against 
> rfc3261 to provide more information on TCP connection handling.

Well, in particular, it was concluded that signaling "please keep this
connection open" was not needed at all. Rather, the server should keep the
connection open as long as it could, and only close it if it ran out of
resources. Since there was no benefit to closing it prematurely (extra costs
of setting it up again), and since signaling the desire for persistence
could not be used to force the server to keep it open if the server ran out
of resources, the signaling was not needed. 
Indeed, the observation was that many implementations in any case were doing
this; it was just unclear in the spec.

-Jonathan R.

_______________________________________________
Sip mailing list  https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol Use
[email-masked] for questions on current sip Use
[email-masked] for new developments on the application of sip