Subject: [Sipping] Overload requirements

From: David Schwartz <[email-masked]>
Date: Tue, 4 Dec 2007 01:51:44 -0800

Hi John.

I may need to re-read but is there mention anywhere in this  
requirements doc of the ability to inform an upstream element that  
the problem is further downstream and not necessarily at the AD  
returning a 503?

I guess I am asking since I am confused. The draft states ...  
"RFC3261 also instructs proxies to not forward 503 responses upstream  
at SHOULD NOT strength". If we look at figure 3 where there is  
potentially more than one AD what is S1 supposed to pass upstream if  
it gets a 503 from P2? I know that you are differantiating between a  
proxy and a server but the point is that at some point an entity  
(Proxy or Server) cannot forward downstream and needs to notify the  
upstream requester of this. In this case the 503 is appropriate as a  
response and I would like to know upstream (P1 in figure 3) that this  
503 was generated by P2.

Is this covered anywhere in the requirements or is it just a jet- 
lagged  2 AM issue.

D.

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 05 Dec 2007 17:20:10 -0500

David Schwartz wrote:
> Hi John.
> 
> I may need to re-read but is there mention anywhere in this requirements 
> doc of the ability to inform an upstream element that the problem is 
> further downstream and not necessarily at the AD returning a 503?

No.

> 
> I guess I am asking since I am confused. The draft states ... "RFC3261 
> also instructs proxies to not forward 503 responses upstream at SHOULD 
> NOT strength". If we look at figure 3 where there is potentially more 
> than one AD what is S1 supposed to pass upstream if it gets a 503 from 
> P2?

Do you mean, what does P2 pass upstream if it gets a 503 from S1? It 
would convert it to a 500 response.

> I know that you are differantiating between a proxy and a server but 
> the point is that at some point an entity (Proxy or Server) cannot 
> forward downstream and needs to notify the upstream requester of this. 
> In this case the 503 is appropriate as a response and I would like to 
> know upstream (P1 in figure 3) that this 503 was generated by P2.
> 
> Is this covered anywhere in the requirements or is it just a jet-lagged  
> 2 AM issue.

I don't understand what the requirement issue is that is being discussed 
here. As I mention above, current rfc3261 behavior is to reject the 
request with a different response code than the received 503.

Are you suggesting there is a requirement to know about load more than 
one hop away? We had discussed this and rejected it since it is 
extremely hard to do anything useful with that information.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   499 Thornall St.
Cisco Fellow                                   Edison, NJ 08837
Cisco, Voice Technology Group
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