Subject: [ANCP] Question about the ANCP high-level architecture

From: Kais Belgaied <[email-masked]>
Date: Wed, 12 Jul 2006 08:17:22 -0700

Folks,

My question is regarding the following picture of the high level ANCP
architecture:

                                                +--------+
                                                | Policy |
                                                | Server |
                                                +--------+
                                                     |
                                                     |
   +-----+   +-----+   +--------+                 +-----+   +----------+
   | CPE |---| HGW |---|        |                 |     |   |          |
   +-----+   +-----+   | Access |   +---------+   |     |   | Regional |
                       |  Node  |---| Aggreg. |---| NAS |---| Network  |
   +-----+   +-----+   |        |   |  Node   |   |     |   |          |
   | CPE |---| HGW |---|        |   +---------+   |     |   |          |
   +-----+   +-----+   +--------+                 +-----+   +----------+

The policy server is attached to the NAS only.

A couple of observations about the AN:
. it is shared between multiple HGWs that don't know/trust each other
. it is the first candidate for enforcing link sharing policies (e.g. bandwidth
  allocation) between subscribers attached to those HGWs

Such policy is applicable to HGWs connected to the same AN.
There may be other policy information still live in the NAS policy server.
The picture could look more like:

                        +--------+              +--------+
                        |   AN   |              |  NAS   |
                        | Policy |              | Policy |
                        | Server |              | Server |
                        +--------+              +--------+
                            |                        |
                            |                        |
   +-----+   +-----+   +--------+                 +-----+   +----------+
   | CPE |---| HGW |---|        |                 |     |   |          |
   +-----+   +-----+   | Access |   +---------+   |     |   | Regional |
                       |  Node  |---| Aggreg. |---| NAS |---| Network  |
   +-----+   +-----+   |        |   |  Node   |   |     |   |          |
   | CPE |---| HGW |---|        |   +---------+   |     |   |          |
   +-----+   +-----+   +--------+                 +-----+   +----------+

comments?

	Kais

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---

From: [email-masked]
Date: Wed, 12 Jul 2006 17:32:49 +0200

Hi Kais,

see below...

> My question is regarding the following picture of the high level ANCP

do you mean that bandwidth can be shared between 2 subscribers? This can 
also be done by the NAS Policy server I would think. Note that the main 
focus of the WG is DSL, and sharing bandwidth in DSL is rather difficult.

> The picture could look more like:

As mentioned during the meeting, the interaction with the policy server 
has to be further detailed. I do not say that the above architecture is 
invalid but I do not see how it relates to the current framework of 
ANCP. The NAS policy server gives all subscriber information to the NAS, 
which enforces the policies are gives them to the AN via ANCP. If you 
have 2 policy servers, then you must also take care of all possible 
interactions, e.g., AN policy server says that the bandwidth is x Mbps 
while the NAS says y Mbps.

Maybe an Element Management system to the AN can be added because that 
one has some interaction with ANCP.

regards,
Stefaan

---

From: Kais Belgaied <[email-masked]>
Date: Wed, 12 Jul 2006 11:16:03 -0700

[email-masked] wrote:

> do you mean that bandwidth can be shared between 2 subscribers? This 
> can also be done by the NAS Policy server I would 

yes, that's what I mean. I understand the  information about all 
subscribers is available at the  Policy server.

> think. Note that the main focus of the WG is DSL, and sharing 
> bandwidth in DSL is rather difficult.

I'm possibly seeing more sharing in the aggregation node component than 
there actually is with DSL.
I view it as a resource shared between multiple subscribers, therefore 
the AN being the arbitrator for
accessing that resource would be a natural choice.
If in reality (and in the foreseeable future) the model for the 
aggregation node is just a collection of
independent pipes to to the NAS, then, yes the NAS is the first point 
shared access, and the policy
enforcement belongs there.

> As mentioned during the meeting, the interaction with the policy 
> server has to be further detailed. I do not say that the above 
> architecture is invalid but I do not see how it relates to the current 
> framework of ANCP. The NAS policy server gives all subscriber 
> information to the NAS, which enforces the policies are gives them to 
> the AN via ANCP. If you have 2 policy servers, then you must also take 
> care of all possible interactions, e.g., AN policy server says that 
> the bandwidth is x Mbps while the NAS says y Mbps.

I should've clarified: the AN policy database is a subset of the whole 
policy database residing in the NAS policy server.
the AN server caches in the information relevant to subscribers 
connecting through it *only*.
and yes, that'll add a  requirement on the AN to keep the cached version 
in sync with the NAS',

> one has some interaction with ANCP.

makes sense.

    Kais.