Subject: RE: multiples PAAs

From: <[email-masked]>
Date: Thu, 27 Mar 2003 11:29:29 -0600

> let's try to clarify:
> 
> what are the motivations (if any) for having more than a 
> single PAA in the access network WHEN SEPARATED from EPs (and/or ARs) ?

One possible scenario that has been suggested is that an access network
operator may allow different service providers to install PAAs on their
network. So essentially an airport hotspot network may have a T-Mobil PAA
as well as a Wayport PAA (as an example) on the same network. And it is
upto the PaC to choose the PAA.

Obviously it is a lot simpler to have a single PAA and then allow the PAA
to forward authentication requests to either T-Mobil or Wayport based on
the NAI or other identifiers. 

So while the justification for multiple PAAs is not very strong there is 
no reason to limit this in the protocol design itself. 

> thanks,
> yacine

-Basavaraj

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From: [email-masked]
Date: Fri, 28 Mar 2003 12:03:47 +0100

so far the reasons for having multiples PAAs are:
a) redundancy (a.k.a. fault-tolerance, backup PAA, etc.)
b) administrative coverage (one PAA per ISP)

I would suggest also:
c) distributed authentication (2 PAAs sharing all PaCs load)
d) topological coverage (one PAA per access area)

a combination of any cases should be acceptable.
please feel free to augment, correct or refine this list.

> upto the PaC to choose the PAA.

in this latter case (b), my understanding is that the T-Mobil PAA deals 
with the T-Mobil customers: each (ISP-X) PAA is responsible for 
authenticating a pool of distinct (ISP-X) PaCs.

> no reason to limit this in the protocol design itself. 

who said that ?

thanks,
yacine

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From: Alper Yegin <[email-masked]>
Date: Fri, 28 Mar 2003 11:29:57 -0800

Hello Yacine,

> a combination of any cases should be acceptable.

If you look at the current protocol spec, you'd see only (a) can be handled.
(b), (c), and (d) are not addressed, because we need to understand these
scenarios first. We had a discussion on at least (b) earlier, and it was not
clear if that scenario was really needed. Note that these additional
scenarios all incur extra complexity, hence their inclusion in the solution
requires justification.

alper

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From: [email-masked]
Date: Mon, 31 Mar 2003 12:09:39 +0200

hi Alper,

please see my comments inline:

Alper Yegin wrote:

 > If you look at the current protocol spec, you'd see only (a) can be > 
handled.

indeed the current protocol spec says that only (c) is handled [extract
from the discovery section]:

     There can be multiple PAAs on the link.  The result does not depend
     on which PAA PaC chooses. By default PaC chooses the PAA that sent
     the first response.

this text states clearly that the 2 PAAs plays an identical role =>(c).

can you please elaborate on how you intend to realize (a) without
assuming PAA-PAA communication.

 > scenarios all incur extra complexity, hence their inclusion in the 
solution

may I add that, without saying it clearly, you also had ealier
discussions about (d) for example: when talking about handovers in the
mobility context.

 > alper

thank you,
yacine