Subject: RE: Definition of QI was: Re: [NSIS] WG requirements draft

From: "Vlora Rexhepi (ELN)" <[email-masked]>
Date: Tue, 26 Feb 2002 17:42:58 +0100

Hi Alban,

As I already mentioned it so many times by now :-), I do 
apologise to all of you for this repetition...But I really think 
that the problem is not only the definitions but the whole model
as I do not consider it as a general one and as the requirements
are heavily dependent on these entities.
Changing the definition as you propose does not really solve 
the problem. 
I would rather prefer that the NSIS QoS requirements are not 
derived/related to this model or any other model, but are based 
on typical scenarios/use cases.

Some more comments inline:

|> A question related to the definition of QI:
|> The QoS Initiator is located in "the end system or within some
|> part of the network, such as the edge router for an access
|> network, or even an application layer proxy" and is used to
|> communicate with higher layers. What does this mean for any other
|> node, e.g. interior node? Can the QI be part of the interior node?
|
|Marcus said on the list : "In todays RSVP you exactly have one QoS
|controller and initiator on each node".
|I understand here that the QoS controller receives signaling, while QoS
|initiator sends it. If this is true, I would say that the figure 1 of
|the WG draft could modified in order to be inline. Instead of :
|
|
|            |         |        ...............
|            |         |        . QoS Control .
|            V         |        . Information .
|       +----------------+      ...............     +----------------+
|   --->|                |------------------------->|                |->
|       |                |      QoS signalling      |                |
|       | QoS Initiator  |     (request/query,      | QoS Controller |
|       |                |   response/error etc.)   |                |
|   <---|                |<-------------------------|                |<-
|       +----------------+                          +----------------+
|        ^              |                            ^              |
|
|I believe we could have:
|
|
|            |         |        ...............
|            |         |        . QoS Control .
|            V         |        . Information .
|       +----------------+      ...............     +----------------+
|       |                |------------------------->|QoS        /    |->
|       |                |      QoS signalling      |Controller/     |
|       | QoS Initiator  |     (request/query,      |         /  QoS |
|       |                |   response/error etc.)   |        /initi- |
|       |                |<-------------------------|       /  -ator |<-
|       +----------------+                          +----------------+
|        ^              |                            ^              |
|
Your proposal brings up the point I was trying to make that it will 
be quite difficult to map these entities into functions of real network 
entities and satisfying the QoS requirements at the same time. 

|Vlora, I think that could answer your question (in case of an RSVP
|network). 
But, doing this is contradictory to the definition of QI. 

|To conclude, in order to make things clear, I would propose a small
|update of the QoS initiator and controller definition, without changing
|its meaning -at least the one I understood-.
|I would propose to add at the beginning of the definition for QoS
|controller and initiator: "role of an entity responsible for...". The
|same entity (an RSVP node) could have both roles.
Than, in this case the NSIS signalling protocol will have problems
satisfying certain QoS requirements defined in the [NSIS] WG draft.

Regards,
Vlora

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---

From: [email-masked]
Date: Tue, 26 Feb 2002 18:52:42 +0100

Hi Vlora

> Changing the definition as you propose does not really solve

Vlora, I just wanted to propose a more clear definition, to answer your
question wih QI and interior nodes. I don't think I changed the meaning.
Marcus can agree, or disagree.

> on typical scenarios/use cases.

Yes, let's make use cases. We'll see if the terminology can still apply. 
Following a use case methodology, you must first define the system, and
an actor. So I identify 3 types of use cases:
1- system= a network, the actor= a terminal, and in this case, the
terminal plays the role of a QoS initiator 
2- system= a network, the actor is another network,
3- system= a network, the actor is a trusted application located in this
network (e.g. a SIP proxy etc..., playing the role of a QoS initiator) 
I don't see more general use cases, they covers everything we talked
about, don't they?
I think starting we these 3 families of use cases, we can do a lot of
work.

> |the WG draft could modified in order to be inline. Instead of :

Why?

> satisfying certain QoS requirements defined in the [NSIS] WG draft.

Really? Which ones? 
(But I would also add for my defense that I may have misunderstood the
QI definition.)

Best regards

-- 
Alban Couturier
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