Subject: RE: [Dime] Summary of 3588bis Issues Status

From: "STURA, Marco, VF-IT" <[email-masked]>
Date: Tue, 18 Jul 2006 16:27:14 +0200

Hi Victor,

>This topic is issue #2&5 and refers to what app id 
>should "application session level" messages defined in the base
protocol 
>(STR/STA, ASR/ASA, RAR/RAA, ACR/ACA) use. The current consensus in the 
>meeting and more likely in this list as well is that it MUST carry the 
>app id of the application using it.

Could you bring some light on the reasons behind this consensus? I
thought the discussion in the old AAA list was toward a consensus on
using Appl ID 0 at least for the ASR/ASA Diameter common messages.

Regards
Marco

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From: Victor Fajardo <[email-masked]>
Date: Tue, 18 Jul 2006 10:53:09 -0400

Hi Marco,

The main reason (and people can correct me if i'm wrong) is that these 
messages belong to the session/application using them and it is 
better/easier to co-relate these messages to the said application. Since 
the base protocol really defines two sets of messages, one set is for 
session/application usage and another for peer connectivity, it is also 
semantically correct for the the session message to carry the app id of 
the session.

In addition, for implementations, it is more practical to look at the 
app id in the header to determine the application that a message belongs 
to ... and rightfully so. In my opinion, ASR belongs to this category 
even if it is server directed. It maybe a little bit confusing for 
relays with cannot resolve a route via destination-host to look at an 
ASR with an app id of 0.

hope this helps,
victor

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 18 Jul 2006 15:14:27 -0400

I thought the main issue is how to route Diameter base protocol
messages carrying a Session-Id AVP (i.e., messages associated with a
particular session) along the same path on which the
application-specific messages that were used for establishing that
session traversed *when stateful agents are on the path*.

If there is no stateful agent on the path, I think using application
Id = 0 for all Diameter base protocol messages can work regardless of
whether it is better/easier or not.   

Yoshihiro Ohba

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From: Victor Fajardo <[email-masked]>
Date: Tue, 18 Jul 2006 15:29:30 -0400

Hi,
> session traversed *when stateful agents are on the path*.

Mmm.. this maybe for issue 4. Though comments for all issues are
welcomed as well. The current discussion is for Issue 2&5. It has to do
with what app id should be present in common diameter messages. During
the meeting as well as in the list, several people commented that it was
preferable for session level messages (ASR,STR etc) to use the app id of
the application and the rest should use 0.

best regards,
victor

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 18 Jul 2006 16:26:40 -0400

> the application and the rest should use 0.

Then I am not much convinced with the use of app id of the application
for session level base protocol messages, because existing XML
dictionary in Open Diameter is using app id 0 for them.  Why should a
working implementation need to be changed?

Yoshihiro Ohba

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From: Victor Fajardo <[email-masked]>
Date: Tue, 18 Jul 2006 16:41:29 -0400

Hi Ohba,
> working implementation need to be changed?

I guess this is the main reason why there is a need for clarification.
Because existing implementations does have interoperability problems.
Some implementations sets the app id to 0 while other don't and this
seems to have caused some issue during the last interop.

best regards,
victor

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 18 Jul 2006 17:04:56 -0400

> the application and the rest should use 0.

Let me point out that the issue I indicated above is not the same as
issue 4, because issue 4 is about explicit routing while the above issue
applies to hop-by-hop routing as well.

Yoshihiro Ohba

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From: "Tolga Asveren" <[email-masked]>
Date: Tue, 18 Jul 2006 17:49:29 -0400

Hi Yoshihiro,

AFAICS, the toplogoy I posted today (one relay and two proxies) won't work
properly if App-Id = 0 is used.

    Thanks,
    Tolga

> -----Original Message-----
> From: Yoshihiro Ohba [mailto:[email-masked]]
> Sent: Tuesday, July 18, 2006 3:14 PM
> To: Victor Fajardo
> Cc: [email-masked]; STURA, Marco, VF-IT
> Subject: Re: [Dime] Summary of 3588bis Issues Status
>
>

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From: Yoshihiro Ohba <[email-masked]>
Date: Tue, 18 Jul 2006 19:04:00 -0400

> properly if App-Id = 0 is used.

If the proxies in the topology are stateful agents, then you are right.

If the proxies are stateless agents, then routing based on
Destination-Host AVP will just work fine for routing common messages
used for *established sessions*, even with app-id=0, because only 
the end nodes mantains the session states in this case.

Yoshihiro Ohba