RE: Correction: RE: [PCN] Architecture draft - probing section & general updates.

["Georgios Karagiannis" <[e-mail]>]

Hi all

I agree with Joe that the architecture and the selection of PCN marking
approach needs to take into consideration that probing may be part of
some
solutions/deployments and that details will be defined at some future
time.

Best regards,
Georgios


On 10/19/2007, "Jozef Babiarz" <[e-mail]> wrote:

>I agree with Anna, and would like to add that the marking mechanism in
>core network needs to work equally well when ingress-egress aggregates
>passing through bottleneck router have small or large number of flows.
>Choosing marking approach that only works for one case is not that
>useful, at lest to me and my customers that are interested in PCN.
>
>On the probing issue, there are many (two+) methods currently defined
>and some already used in IP networks as well new methods that could be
>defined for possible use with PCN for admission control. I'm OK with
>deferring the selection of already defined protocol(s) or definition of
>new probing protocol until later date. However, I believe strongly that
>the architecture and the selection of PCN marking approach needs to take
>into consideration that probing may be part of some
>solutions/deployments and that details will be defined at some future
>time. 
>
>Regards, Joe
>email:[e-mail]
>Telephone:[phone]
>-----Original Message-----
>From: Anna Charny (acharny) [mailto:[e-mail]] 
>Sent: October 19, 2007 9:25 AM
>To: Anna Charny (acharny); Lars Eggert
>Cc: [e-mail]
>Subject: Correction: RE: [PCN] Architecture draft - probing section &
>general updates.
>
>A typo in my previous message: I meant to say the charter does NOT
>restrict the low ingress-egress aggregation.  Edited the appropriate
>sentense below...
>
>Anna
>
>> -----Original Message-----
>> From: Anna Charny (acharny) 
>> Sent: Friday, October 19, 2007 9:23 AM
>> To: 'Lars Eggert'
>> Cc: Hancock, Robert; [e-mail]; [e-mail]
>> Subject: RE: [PCN] Architecture draft - probing section & 
>> general updates.
>> 
>> Hi Lars,
>> 
>> On the low agfgregation point, please see below: 
>> 
>> > -----Original Message-----
>> > From: Lars Eggert [mailto:[e-mail]]
>> > Sent: Friday, October 19, 2007 8:58 AM
>> > To: Anna Charny (acharny)
>> > Cc: Hancock, Robert; [e-mail]; [e-mail]
>> > Subject: Re: [PCN] Architecture draft - probing section & general 
>> > updates.
>> > 
>> > On 2007-10-16, at 21:55, ext Anna Charny (acharny) wrote:
>> > > Yes, Robert's is a fair concern to which no obvious 
>> solution is in 
>> > > sight. Different equipment might use different algorithms 
>> and might 
>> > > use different fields for ECMP load-balancing under different 
>> > > circumstances.
>> > > IMHO this is a killer argument of why the use of probing for 
>> > > discovering the state of ECMP paths should not be 
>> considered within 
>> > > the scope of PCN WG.
>> > 
>> > Agreed.
>> > 
>> > > There remains a question of whether probing can/should be
>> > considerd to
>> > > probe the path regardless of the ECMP issue.  I see most of
>> > its value
>> > > in flash crowd situations in combination with low ingress-egress 
>> > > agregation.
>> > 
>> > I note that scenarios with low aggregation aren't in scope of the
>> > charter:
>> > 
>> >    The initial scope of the PCN WG is restricted by the following
>> >    assumptions:
>> > ...
>> >    (C) the number of flows across any potential aggregation 
>> bottleneck
>> >    is sufficiently large for stateless, statistical mechanisms
>> >    to be effective
>> 
>> Actually,  I did not mean low aggregation *at the 
>> bottleneck*, which is what the charter seems to restrict.  
>> Rather I meant the case when the bottleneck has high 
>> aggregation, but traffic on that bottleneck comes from a 
>> large number of ingress-egress pairs, each having very low 
>> aggregation levels.  I believe technically the charter does  NOT 
>> put any explicit restrictions on the scope for ingress-egress 
>> aggregation. 
>> 
>> Perhaps the WG should consider whether it is reasonable to 
>> impose  restrictions on the *ingress-egress* aggregation 
>> levels as well.  An argument can be made that in practice a 
>> large number of ingress-egress pairs may only have a few 
>> flows, even when the bottleneck aggregations are large. 
>> 
>> The decision on whether low ingress-egress aggregation level 
>> is in scope seems to be important for choosing among the 
>> various approaches proposed to the WG, as some of them are 
>> substantially more sensitive to the low ingress-egress 
>> aggregations than others (e.g. single marking does not 
>> perform well at very low levels of aggregation, as we showed 
>> at the last meeting).  
>> 
>> Perhaps an explicit discussion on the assumptions regarding 
>> the expected levels of ingress-egress aggregations is needed 
>> on the list? 
>> 
>> Towards that discussion, my personal view is that in the long 
>> range ignoring low levels of ingress-egress aggregation 
>> levels will severely limit the viability/usefulness of the 
>> technology.  However, perhaps as an initial step it would be 
>> OK to assume moderate to high aggregation levels, as long as 
>> a clear path is visible on how to address low aggregations in 
>> the future within the scope of defined behaviors.  But I 
>> think it is important to have a clear consensus on this point. 
>> 
>> Anna 
>> 
>> > 
>> > Lars
>> > 
>
>
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