Subject: [AAA-WG]: Comments: draft-belinchon-aaa-diameter-mm-app-01.txt

From: "Jayshree Bharatia" <[email-masked]>
Date: Tue, 8 Jul 2003 17:30:15 -0500

Hello Miguel,

I have the following comments on draft-belinchon-aaa-diameter-mm-app-01.txt.

Global: 
- Since the description in this draft is specific to SIP, I like to suggest
new title 
  for this draft as "Diameter for SIP Based Multimedia Application".
- Another  suggestion is to include new "User De-registration" scenario as
section 
  3.6 so that usages of commands RTR and RTA become more clear.
Section:2 (Second paragraph)
- Reword the paragraph "However, this document...between SIP and Diameter". 
  Something is missing from this paragraph.
Section 3 (Second paragraph)
- The draft says that Figure 1 provides general overview of the integration
of
  the SIP architecture with the AAA architecture but the next paragraph says
  that it is related to specific SIP server configuration. If UAR/UAA and
  LIR/LIA are applicable to just edge routers, it should be reflected in
this
  model clearly.
Section 3.1 and 3.2 (general)
- I don't see much difference between the scenarios discussed in section 
  3.1-"Diameter server authenticate the user" and section 3.2 -"SIP server 
  authenticate the user". There are just couple of steps (13 and 14) which
are  
  different from the description of these sections. Since these scenarios
  are discussed in different context, it's better to show which commands are
  used for what purpose and consolidate the description.
Section 5.1
- In Open Issue Note, you have mentioned User-Name AVP being the mandatory
  parameter. I would think that UAR may be used for other SIP Requests as
well
  (other than REGISTER). In those cases, do we have private id available
also?
  Additionally,  I would think that it will be better to mention what value
will
  be assign to SIP-Public-User-Identity parameter in case of non-3GPP usage.
- This section says that the Diameter server must include either the address
of
  the SIP server  or the capability needed by the SIP server. Does it mean
that
  requesting SIP server always have capability to derive next hope based on
the
  capabilities received from the AAA? Why do we have this additional 
  requirement. 

Regards,
Jayshree

---

From: "Miguel A. Garcia" <[email-masked]>
Date: Wed, 09 Jul 2003 10:03:09 +0300

Hi Jayshree:

Thanks a lot for your comments. See answers inline.

Jayshree Bharatia wrote:
> Hello Miguel,
> 
> I have the following comments on 
> draft-belinchon-aaa-diameter-mm-app-01.txt.
> 
> Global:
> - Since the description in this draft is specific to SIP, I like to 
> suggest new title

The thing is that the RFC editor does not allow to have acronyms in the 
title (other than well known protocols such us IP, TCP, UDP). So your 
suggestion will become:

"Diameter for Session Initiated Protocol (SIP) Based Multimedia Application"

And I think when a reader gets the sentence will be lost to find out 
whether this is a Diameter application, a SIP extension or something else.

I would rather keep the current title, unless I hear another proposal that 
is easy to read.

> - Another  suggestion is to include new "User De-registration" scenario 
> as section

Yes, I agree. Actually, section 3.5 deals with registration termination. I 
believe this section should contain a couple of flows showing examples of 
RTR/RTA.

>   Something is missing from this paragraph.

Certainly. What is missing is a "mandate" word, so the text should read:

"... nor this document mandates any particular sequence of events between 
SIP and Diameter."

> - The draft says that Figure 1 provides general overview of the 
> integration of

UAR/UAA and LIR/LIA are not only applicable to SIP edge proxies. They are 
"typically" used by SIP edge proxies, by we don't mandate to be supported 
exclusively in SIP edge proxies.

Actually, the application provide means (commands, AVPs) to differentiate 
SIP edge proxies from non SIP edge proxies. However, both edge and non edge 
proxies will need to support the complete set of commands and AVPs, since 
there is only one Diameter application.

So that is the reason why the figure discusses two different SIP proxies 
that, due to their role, use only a subset of the commands. But you could 
configure the SIP proxy to change role. So all commands have to be 
supported in all proxies.

>   authenticate the user". There are just couple of steps (13 and 14) 
> which are 

I think it is important to highlight the difference between these two 
scenarios. 3.1 is more aligned with the AAA architecture, where a Diameter 
server is authenticating users. This is the main role of the AAA server. 
Section 3.2 describes a scenario that is used in 3GPP, where the Diameter 
server delegates authentication to the SIP server.

I believe both scenarios have different values in different networks. From 
the point of view of the application, we just want to provide the means to 
use either of the scenarios. 3GPP has chosen to go for scenario 3.2, but 
other networks will most likely use scenario 3.1.

Please, let me know exactly what is missing. I am able to add any 
clarification to the text.

>   parameter. I would think that UAR may be used for other SIP Requests 
> as well

I agree with you. I am sure that the username AVP will not be available in 
general, in all requests. It might be get acquiered, but that requires the 
SIP proxy to challenge the user.

So this open issue is just an action point to make the AVP optional and 
discuss what are the procedures in the Diameter server when the AVP is not 
present in the UAR.

>   Additionally,  I would think that it will be better to mention what 
> value will

This is not dependent on 3GPP or not-3GPP. The SIP-Public-User-Identity is 
what in normal SIP is called an Address Of Record (AOR). In an INVITE 
request, the SIP AOR comes in the Request-URI. In a REGISTER request it 
comes in the To field.

The 4th paragraph in section 5.1 should answer your concern:

    The SIP or SIPS URI to be registered is conveyed in the
    SIP-Public-User-Identity AVP (Section 7.8). Typically this SIP or
    SIPS URI is found in the To header field value of the SIP REGISTER
    request that triggered the Diameter UAR message.

And that makes me think that the SIP-Public-User-Identity should be renamed 
to SIP-AOR (Address of Record) to align the terminology with SIP...

> - This section says that the Diameter server must include either the 
> address of
>   the SIP server  or the capability needed by the SIP server. Does it 
> mean that
>   requesting SIP server always have capability to derive next hope based 
> on the

Here I am lost. Are you still discussing section 5.1??? Which paragraph are 
you referring to??? I don't find the text you mention.

Thanks a lot for reviewing the text. Please, keep on posting additional 
comments.

Regards,

     Miguel

-- 
Miguel-Angel Garcia                     Oy LM Ericsson AB
                                         Jorvas, Finland
mailto:[email-masked]     Phone:  +358 9 299 3553
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