Re: [PCN] PCN WG last call for draft-ietf-pcn-architecture-05.txt

[<philip.eardley at bt.com>]

{ > So the question is about adding to the draft:
{ > A model where the egress measures marks coming from all the
{ > ingresses, and makes admission decision based on that.
{ >
{ > Before adding anything about this to the draft, I'd like to
{ > understand if this is a genuine practical, understood option
{ > (if so, OK), or if it's a theoretical possibility or one not
{ > well understood.
{ > (there are many things in the latter category that aren't
{ > mentioned in the draft.)
{ >
{ > Questions are why this is interesting, why is it better than
{ > the models already well-known, are there comparative analysis
{ > /simulations?
{ 
{ Georgios: It is interesting because is more scalable than the
{ ingress-egress-aggregation model and
{ because the level of flow aggregation (and thus the level of
statistical
{ aggregation)
{ that can be achieved is higher than in the IEA case.

I don't really believe either of these claims. 
On scalability, what's the scenario? Eg imagine a core network with 100
or so gateway pcn-nodes. Whether an egress node is recording marking
info per ingress node (100 pieces of info) or recording it whatever the
ingress (1 piece of info) - is this really a significant scaling
difference? Especially when you remember that the PCN-ingress-nodes keep
per flow state for policing purposes.

On aggregation, I actually think the opposite is true. In your case, you
can get a focused overload: many flows happen to focus on a particular
link and then all flows through the congested link fail
catastrophically. With PCN (ie ingress-egress-aggregates) the finer
grained info should prevent this happening. So your scheme has to be
more cautious about how much traffic it admits (eg by setting the
PCN-threshold-rate lower).


{ 
{ 
{ >
{ > I suppose I've got 2 general issues:
{ > [1] every time something is added, overall the document
{ > becomes harder to understand, more daunting to read & it
{ > looks less like the WG has consensus.
{ 
{ Georgios: I think that the sentence proposed by you, 

it most certainly wasn't proposed by me

see below (with an
{ addition from my side)
{ is clear enough:
{ "An aggregation model where the egress measures marks coming from all
the
{ ingresses, and makes admission decision based on that."

my point was different. It wasn't about the clarity or not of the
sentence.

{ 
{ 
{ > [2] this is an INFO doc. People are free to invent ways of
{ > using the standards pieces other than the architecture draft
{ > says, and indeed in ways not yet dreamt of.
{ 
{ Georgios: I am not sure if this is always true, that is why I would
{ like to see somethink like the sentence given above.

What I wrote seems true. Indeed, in general if subsequent experience
shows that Info docs haven't captured important ways in which Stds docs
are being used in practice, then docs get revised. 

{ 
{ Best regards,
{ Georgios
{ 
{ 
{ >
{ > Phil.
{ >
{ > { -----Original Message-----
{ > { From: pcn-bounces at ietf.org [mailto:pcn-bounces at ietf.org] On
{ > Behalf Of { Georgios Karagiannis { Sent: 27 August 2008 08:54
{ > { To: 'Steven Blake'
{ > { Cc: pcn at ietf.org
{ > { Subject: Re: [PCN] PCN WG last call for
{ > draft-ietf-pcn-architecture-05.txt
{ > {
{ > { Hi Steven
{ > {
{ > { > -----Original Message-----
{ > { > From: Steven Blake [mailto:slblake at petri-meat.com] { >
{ > Sent: woensdag 27 augustus 2008 6:18 { > To: Georgios
{ > Karagiannis { > Cc: pcn at ietf.org { > Subject: RE: [PCN] PCN
{ > WG last call for { > draft-ietf-pcn-architecture-05.txt
{ > { >
{ > { > On Tue, 2008-08-26 at 16:11 +0200, Georgios Karagiannis wrote:
{ > { >
{ > { > > Hi Steven
{ > { > >
{ > { > >
{ > { > > Please see in line!
{ > { > >
{ > { > >
{ > { > > > -----Original Message-----
{ > { > > > From: Steven Blake [mailto:slblake at petri-meat.com] {
{ > > > > Sent: dinsdag 26 augustus 2008 14:46 { > > > To:
{ > Georgios Karagiannis { > > > Cc: pcn at ietf.org { > > >
{ > Subject: Re: [PCN] PCN WG last call for { > > >
{ > draft-ietf-pcn-architecture-05.txt
{ > { > > >
{ > { > > > On Tue, 2008-08-26 at 11:44 +0000, Georgios Karagiannis
wrote:
{ > { > > >
{ > { > > > > Hi Phil, Hi all
{ > { > > > >
{ > { > > > > Here are some  comments on the PCN architecture draft:
{ > { > > > >
{ > { > > > > 1) Thank you for clarifying the bullet in Setion
{ > 3.2 about flow { > > > > termination.
{ > { > > > >
{ > { > > > > 2) From what I understand the PCN architecture
{ > draft { > > > mentions that PCN { > > > > supports only the
{ > trunk (ingress-egress-aggregate) and not the { > > > > HOSE model.
{ > { > > > > Is the PCN architecture draft excluding solutions
{ > that { > support the { > > > > HOSE model? If not, please
{ > emphasize in the PCN { > architecture draft { > > > > that
{ > "solutions that are based on other types of flow { > > >
{ > aggregation than { > > > > the ingress-egress-aggregate
{ > method of flow { > aggregation, are not { > > > > excluded
{ > from the PCN WG activities."
{ > { > > >
{ > { > > > Actually they are, by our charter.
{ > { > >
{ > { > > I have not seen that the PCN charter excludes other
{ > types { > of aggregation.
{ > { >
{ > { > Well, I checked, and you are correct (mea culpa).
{ > { Georgios: No problem
{ > {
{ > { >
{ > { > > Please note
{ > { > > that I am refering to the HOSE model where the traffic
{ > sent { > by one or { > > more than one ingresses towards one
{ > egress is aggregated at the { > > egress. In this way higgher
{ > traffic aggregation can be accomplished { > > than in the
{ > situation that the pipe/trunk { > (ingress-egress-aggregate)
{ > { > > is used, where the traffic sent by only one ingress in
{ > aggegated at { > > the egress.
{ > { >
{ > { > Typically the "hose" model refers to point-to-multipoint
{ > { > traffic flow, not multipoint-to-point.
{ > { Georgios: Typically yes, but in this case we refer to
{ > bandwidth allocation { in a multipoint-to-point fashion.
{ > {
{ > { >
{ > { >
{ > { > Regards,
{ > { >
{ > { > // Steve
{ > { >
{ > {
{ > {
{ > { _______________________________________________
{ > { PCN mailing list
{ > { PCN at ietf.org
{ > { https://www.ietf.org/mailman/listinfo/pcn
{ >
{ 

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