Subject: [AAA-WG]: Re: Response routing?

From: Patrice Calhoun <[email-masked]>
Date: Mon, 12 Feb 2001 07:56:17 -0800 (PST)

> Hi,
> 
> Tell me if I'm wrong, but I thought that routing responses from a 
> Diameter node was based on (as in -18 Base draft):
> 
> 1) If there are Route-Record AVPs in the request (Query) message, the 
> last Route-Record AVP is used as the first HOP destination of the reply. 
> So the Route-Record AVPs are used until the last proxy before the 
> originator of the request. However, from there, what AVP is used for 
> routing to the originator node?

What I do, is that the first hop inserts a Proxy-State AVP. In the
Proxy-State-Info AVP, I include the FQDN of the originator of the request.
Then I add my Record-Route AVP.

> 
> 2) If there is no Route-Record AVPs in the request, then the reply is 
> sent back to the originator of the request using the Host-Name AVP of 
> the request as the destination. However, this routing is done at the IP 
> level only, right?
Not using the Host-Name AVP. I insert the value of the Host-Name AVP in my
Proxy-State-Info AVP. I am not sure what you mean by IP level only, though.
This is all application level routing.

> The STA (in the -18 draft of the Base protocol) defines the 
> Routing-Realm AVP in its list of optional AVP in its message structure. 
> This is very confusing to me, since it suggests that replies might not 
> have to go through the same proxies. I guess responses should never use 
> the Routing-Realm AVP.

That is correct, and I need to fix that up. Thanks for pointing this error out
to me.

> 
> I thought that Proxy-State AVPs were not used for routing, or are they? 
> Are we suggesting that each proxy defines a Proxy-State AVP or keeps an 
> internal state so that it knows how to route back messages to the 
> originator?

A proxy can put pretty much whatever it wants in the Proxy-State AVP. Right
now, my code just adds the FQDN, but in the future I may need to also insert
additional data. The Proxy-State is not used for routing per-say, but if one
puts the information needed to route the message, then it could be.

However, the use of the Proxy-State is implementation specific.

> Can we really have a stateless proxy?, or is it a proxy that forwards a 
> Proxy-State AVP?
my proxy is currently stateless.

PatC