Subject: [SIP] Forking proxy and OPTIONS

From: "Vijay K. Gurbani" <[email-masked]>
Date: Fri, 01 Sep 2000 10:58:35 -0500

All:

What should the behavior of a forking proxy be when the very first
request it gets from it's upstream client is an OPTIONS request.  Let's 
assume that the callee has been registered with multiple Contacts at the 
proxy.

Should the proxy treat the OPTIONS as it does INVITEs and spawn several
downstream requests? 

Thanks,

- vijay
-- 
Vijay K. Gurbani  [email-masked] [email-masked] [email-masked]
Internet Software Group/Intelligent Network and Instant Messaging
Lucent Technologies/Bell Labs Innovations, 263 Shuman Blvd, Rm 1A-413
Naperville, Illinois 60566  Voice: +1 630 224 0216 Fax: +1 630 713 0184

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From: Jonathan Rosenberg <[email-masked]>
Date: Fri, 01 Sep 2000 17:31:01 -0400

> Should the proxy treat the OPTIONS as it does INVITEs and spawn several

It can fork in parallel or sequential, as it would for invite. The
overall request processing is largely no different; the differences
relate to retransmission rules and handling of multiple 200 OK (all sent
upstream for INVITE, only one for anything else, including OPTIONS).

-Jonathan R.

-- 
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
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From: "Vijay K. Gurbani" <[email-masked]>
Date: Fri, 01 Sep 2000 16:58:26 -0500

I asked:

> request it gets from it's upstream client is an OPTIONS request.  
> Let's assume that the callee has been registered with multiple 
> Contacts at the proxy.
> 
> Should the proxy treat the OPTIONS as it does INVITEs and spawn 
> several downstream requests?

Jonathan Rosenberg replied:

> relate to retransmission rules and handling of multiple 200 OK (all 
> sent upstream for INVITE, only one for anything else, including 
> OPTIONS).

Jonathan:

Right; that's what I thought.  But (there's always a "but"), how does
the proxy make the determination which "200 OK" to send upstream? FCFS?
What if the "200 OK" send upstream is not from the desired recepient?
A later "200 OK" which gets to the proxy from the desired recepient will
be silently discarded.

Realistically speaking, I am not sure how often this will happen, or
indeed if it is worth the discussion.  Just happened to run into this
problem while re-doing some of my code; I'm thinking of implementing 
FCFS for all it is worth.

Thanks,

- vijay

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From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 03 Sep 2000 00:17:47 -0400

> A later "200 OK" which gets to the proxy from the desired recepient will

FCFS. Remember, the methods here are not seeking to INVITE a user; so, I
am not 
sure there is really a useful definition of "desired recipient".

> indeed if it is worth the discussion. 

For BYE, never with the bis draft, since its routing is handled by Route
headers. Similarly for INFO. OPTIONS can be sent as the "initial"
request, and thus might fork. The result is that you get back one of the
possible several capabilities. REGISTER might fork, but this is unlikely
since it is not targeted at a user, but rather a domain.

-Jonathan R.