Subject: RE: [Sip] RE: [Sipping] Loose Routing Proposal

From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 7 Sep 2001 12:18:58 -0400

-----Original Message-----
From: Sean Olson (EUS) [mailto:[email-masked]]
Sent: Friday, September 07, 2001 10:55 AM
To: 'Juha Heinanen'; Miguel A. Garcia
Cc: Rosen, Brian; 'Cullen Jennings'; [email-masked]'
Subject: [Sip] RE: [Sipping] Loose Routing Proposal

>[Moved to SIP mailing list] 
>There are several additional constraints 
>that make the 3GPP problem a little more 
>difficult. 
>1) The UA doesn't know what it's home 
>   proxy is. The home proxy is chosen 
>   dynamically for the UA by the home 
>   network based on the required 
>   capabilities needed to fulfill the 
>   user's service profile. 

I think there are really two separate use cases for the loose routing, and
that these are being confused. Remember, the definition of loose is that
there can be intermediate hops between the ones specified.

In one use case, I want some intermediate domain in the path of a message.
The specific server doesn't matter; a selection can be done by an upstream
proxy through SRV computations, for example. Any server in the intermediate
domain will do. I think this is the case for the "i'm visiting a hotel and
need my outbound calls through my home domain". 

In another use case, I need to go through a SPECIFIC proxy, that I've
learned previously. Presumably this is because it has some state specific to
me, established through whatever means I learned about it previously. I
don't care about intermediate hops, but I need to eventually hit THAT proxy.
This is the case for regular record-routed invites, where a called party may
need to send a re-INVITE through an outbound proxy not on the route list,
for example (Juha's original case). Its also the case for 3gpp, since they
have selected a particular proxy as a result of a previous transaction.

Now, in the case of 3gpp, I happen to think that the error was selecting a
particular proxy at registration time in the first place. I assume that
"capabilities required to fulfill the users profile" are things like
features and applications - call screening, etc. that need to be applied to
outbound calls. Trigger conditions for applications like this are frequently
not just subscriber specific, but also dependent on things like called party
and other dynamic criteria. Therefore, to me, it makes more sense to
partition users into sub-domains statically, either based on direct mappings
(which can be cached in a proxy) or algorithmicly. Within a sub-domain, the
call can be routed to any proxy. Each proxy has the triggering conditions
for applications for all users in the sub-domain. Based on those, it may
route a call to an application server for processing, using the
hub-and-spoke model that Jorgen describes in his draft he just posted.
Trigger conditions are also fairly static and can therefore be cached.

This eliminates the need for database dips at all for call setup, and also
eliminates the need for the path header or pre-recording anything. The user
in the visited domain knows his home domain, home.com, and it is sufficient
to use a loose route to get the request to his home. The architecture I
describe above handles the rest.

Maybe someone can clarify why that was not found to be sufficient by the 3g
guys? A related question is this - don't you need to dip the HSS anyway for
incoming calls, to find out which proxy the user is associated with? So you
are eliminating this extra DB load in only half the cases anyway (note that
my proposal above completely eliminates the need for a DB dip).

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com

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From: Nathan Nelson <[email-masked]>
Date: Fri, 7 Sep 2001 13:03:41 -0400

Jonathan Rosenberg wrote:
>>Therefore, to me, it makes more sense to
>>(which can be cached in a proxy) or algorithmically. Within a sub-domain,
the
>>for applications for all users in the sub-domain.

If you put users in a sub-domain it would initially provide relief but now
the service provider has to manage multiple sub-domains and consensually
update records and create new sub-domain names to correspond with additional
users and/or applications.  If the sub-domains are not closely monitored
than you have the same issue as in a domain just with a <something.> in
front.  Sounds like a operation issue in time.

Thx,
Nate Nelson

-----Original Message-----
From: Jonathan Rosenberg [mailto:[email-masked]]
Sent: Friday, September 07, 2001 12:19 PM
To: Sean Olson; 'Juha Heinanen'; Miguel A. Garcia
Cc: Rosen, Brian; 'Cullen Jennings'; [email-masked]'
Subject: RE: [Sip] RE: [Sipping] Loose Routing Proposal

-----Original Message-----
From: Sean Olson (EUS) [mailto:[email-masked]]
Sent: Friday, September 07, 2001 10:55 AM
To: 'Juha Heinanen'; Miguel A. Garcia
Cc: Rosen, Brian; 'Cullen Jennings'; [email-masked]'
Subject: [Sip] RE: [Sipping] Loose Routing Proposal

-Jonathan R.

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