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

Bob Briscoe <bob.briscoe@bt.com> Thu, 15 November 2012 21:02 UTC

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Date: Thu, 15 Nov 2012 21:02:14 +0000
To: Tom Taylor <tom.taylor.stds@gmail.com>
From: Bob Briscoe <bob.briscoe@bt.com>
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Cc: PCN IETF list <pcn@ietf.org>, karagian@cs.utwente.nl, anuragb@cisco.com, tsvwg@ietf.org, rsvp-dir@ietfa.amsl.com
Subject: Re: [rsvp-dir] [PCN] Redundant aggregate reservations: draft-ietf-tsvwg-rsvp-pcn-03
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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"?
>
>On 15/11/2012 8:07 AM, Bob Briscoe wrote:
>>Georgios, Anurag,
>>
>>Below is the main point of my review, arguing that aggregate
>>reservations are redundant. I'm reviewing as:
>>- a member of the RSVP directorate
>>- one of the early PCN design team
>>- a co-author of draft-lefaucheur-rsvp-ecn-01, on which this draft is
>>based.
>>
>>I would have missed any decision to use aggregate reservations. Pls
>>point me to the relevant discussion (e.g. Subject line / date).
>...

________________________________________________________________
Bob Briscoe,                                BT Innovate & Design