Re: [PCN] Redundant aggregate reservations: draft-ietf-tsvwg-rsvp-pcn-03

Tom Taylor <tom.taylor.stds@gmail.com> Sat, 17 November 2012 19:41 UTC

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Date: Sat, 17 Nov 2012 14:41:13 -0500
From: Tom Taylor <tom.taylor.stds@gmail.com>
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To: Bob Briscoe <bob.briscoe@bt.com>
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Cc: PCN IETF list <pcn@ietf.org>, anuragb@cisco.com, tsvwg@ietf.org, rsvp-dir@ietfa.amsl.com
Subject: Re: [PCN] Redundant aggregate reservations: draft-ietf-tsvwg-rsvp-pcn-03
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Stepping back a bit here, I have to question your definition of an 
ingress-egress aggregate. When you say it is composed of all flows with 
the same next hop, what sort of topology are you assuming? The 
definition makes sense only if the next hop entity is an egress node.

If that is not the case, then I would say an ingress-egress aggregate is 
defined as the set of all flows where the RESV message comes from the 
same egress node.

On 16/11/2012 3:03 PM, Bob Briscoe wrote:
> Tom,
>
> The edge behaviour RFCs attempted to abstract over any signalling
> protcol, but I think they ended up being biased towards the ITU way of
> doing things, rather than an abstraction that encompassed both RACF and
> RSVP, which was probably too ambitious.
>
> Is you piggy-backing draft effectively what I am describing -
> piggy-backing on e2e signalling?
>
> I don't believe we need any more abstract drafts if that's what you mean
> - we need to focus on RSVP specifically now. We could perhaps re-boot
> from Francois's original draft.
>
>
>
> Bob
>
> At 22:09 15/11/2012, Tom Taylor wrote:
>> OK, I guess I see your point. I was too focussed on the calculations
>> that are done at the Decision Point.
>>
>> It makes me wonder if I should revive that piggy-backing edge
>> behaviour draft I once started.
>>
>> On 15/11/2012 4:02 PM, Bob Briscoe wrote:
>>> Tom,
>>>
>>> The RSVP message I'm proposing doesn't say "Never mind the SESSION in
>>> this message, I'm related to every flow with the same first hop". It
>>> says "These are the marking probabilities for the SESSION in this
>>> message". Then the PCN-ingress (not the message) infers that all other
>>> flows that share the same aggregate will share the same marking
>>> probability, because PCN marking on interior nodes is random and
>>> unbiased.
>>>
>>> It's a subtle distinction, but it preserves the semantics of RSVP
>>> messages, without the three disadvantages of setting up an RSVP
>>> aggregate that I mentioned.
>>>
>>> You will have seen from the rest of the message that I have not rejected
>>> the concept of aggregation, I am merely saying that the PCN-ingress and
>>> PCN-egress can hold the concept internally.
>>>
>>>
>>> Bob
>>>
>>> At 16:42 15/11/2012, Tom Taylor wrote:
>>>> I'm not sure the semantics of the PCN information -- particularly as
>>>> it relates to flow termination -- are correct without some sort of
>>>> concept of aggregation. Or can you really define an RSVP object that
>>>> has semantics "Never mind the SESSION in this message, I'm related to
>>>> every flow with the same first hop"?
>> ...
>
> ________________________________________________________________
> Bob Briscoe,                                BT Innovate & Design
>