Subject: [Sip] New draft on mid-dialog failover and proxy discovery in SIP outbound

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 13 Oct 2006 11:16:46 -0400

I've just submitted a new draft that proposes a solution for outbound 
proxy discovery and mid-dialog failover with SIP outbound. I hinted at 
this solution last IETF meeting. The mechanism requires no state 
replication in edge proxies, no DNS changes or configurations (if 
anythign it simplifies it further from even normal SIP), is backwards 
compatible with home proxies that don't support it, and allows folks to 
continue to place stuff into record-routes and see it back again for 
mid-dialog requests that get routed to backups.

As an interesting side effect, the mechanism also results in TCP/TLS 
connection reuse which *does* work through NAT (unlike the existing 
connect-reuse draft which does not), and addresses many of the problems 
identified in Vijay's domain-certs document. It allows SIP proxies to 
work more like the web model where you just need a single cert like 
'proxies.example.com' for the entire cluster and no other hostname or IP 
address except this one is used.

I admit its not an easy read; the mechanism itself is not too hard to 
describe or implement; its much more complicated to explain why it works.

Until it appears in the archives you can pick it up at:
http://www.jdrosen.net/papers/draft-rosenberg-sip-outbound-discovery-mid-dialog-00.txt

Thanks,
Jonathan R.
-- 
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
[email-masked]                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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From: "Jeroen van Bemmel" <[email-masked]>
Date: Tue, 17 Oct 2006 20:49:14 +0200

Jonathan,

2 questions and 1 minor remark:

1) Why would the REGISTER bounce a second time (305), after receiving 401? 
The request being retried is the one constructed after having received the 
305, so shouldn't it already contain the proper Route headers?

2) For proxy 3, wouldn't the UA use a new reg-id?

(minor remark: several ';lr' missing in Path and Route URIs)

Regards,

Jeroen

Jonathan Rosenberg wrote:
> compatible with home proxies that don't support it, and allows folks
> to continue to place stuff into record-routes and see it back again
> for mid-dialog requests that get routed to backups.
>
> connect-reuse draft which does not), and addresses many of the
> problems identified in Vijay's domain-certs document. It allows SIP
> proxies to work more like the web model where you just need a single
> cert like 'proxies.example.com' for the entire cluster and no other
> hostname or IP address except this one is used.
>