Subject: [PCN] multipath routing

From: Michael Menth <[email-masked]>
Date: Tue, 10 Feb 2009 11:16:26 +0100

Hi all,

the current PCN architecture does not support multipath routing, i.e. 
flows of a single ingress-egress-aggregate can be transmitted over 
different paths. With some modifications this support could be possible.

Is multipath support a desired feature in the future? Or is it of no 
interest since PCN is intended to be used only in single-path routing 
networks or in combination with MPLS?

Is multipath routing an issue at all in operational networks? Input from 
practitioners is highly appreciated.

Regards,

    Michael

-- 
Dr. Michael Menth, Assistant Professor
University of Wuerzburg, Institute of Computer Science
Am Hubland, D-97074 Wuerzburg, Germany, room B206
phone: (+49)-931/888-6644, fax: (+49)-931/888-6632
mailto:[email-masked]
http://www3.informatik.uni-wuerzburg.de/research/ngn

---

From: <[email-masked]>
Date: Tue, 10 Feb 2009 11:40:50 +0100

Hi Michael,

Equal Cost Multipath (ECMP) routing is a feature applied by my company to 
distribute the load more even on core network links. Should PCN ever be 
deployed in our network, ECMP friendliness is a requirement. 
MPLS friendliness is another, and over all strict DiffServ conformance 
is to be respected. From my point of view.

Regards,

Rudiger

Deutsche Telekom Netzproduktion GmbH 
Zentrum Technik Einführung 
Technik Internet Backbone, TE142-19
Ruediger Geib
Heinrich Hertz Str. 3-7
64297 Darmstadt
Tel.: 06151/6282747
Fax: 0251/7985109

Deutsche Telekom Netzproduktion GmbH 
Aufsichtsrat: Timotheus Höttges (Vorsitzender) 
Geschäftsführung: Friedrich Fuß (Vorsitzender), Albert Matheis, Klaus Peren 
Handelsregister: Amtsgericht Bonn HRB 14190 
Sitz der Gesellschaft: Bonn 
USt-IdNr.: DE 814645262

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Michael Menth
Sent: Tuesday, February 10, 2009 11:16 AM
To: [email-masked]
Subject: [PCN] multipath routing

Hi all,

Regards,

    Michael

_______________________________________________
PCN mailing list
[email-masked]
https://www.ietf.org/mailman/listinfo/pcn

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From: Tom Taylor <[email-masked]>
Date: Wed, 18 Feb 2009 19:33:17 -0500

Could you give details of your proposed modification. From private conversation, 
it requires that only excess-traff-marked flows are terminated when flow 
termination has to happen. How would these flows be distinguished from the flows 
that were not excess-traffic-marked?

---

From: Michael Menth <[email-masked]>
Date: Thu, 19 Feb 2009 08:24:17 +0100

Hi Tom and all,

in case of multipath routing, flows of the same ingress-egress-aggregate 
can run over different paths. One path may be SR-precongested, the other 
path not. Then only terminating flows of the SR-precongested path helps 
and other flows should not be terminated. What's needed is that when an 
excess-marked packet arrives, the corresponding flow is marked for a 
while. This information is available at the egress node.  There are two 
alternatives to take advantage of that information:
1) Signalling the IDs of the marked flows to the PCN ingress node which 
is in charge of termination.
2) Shifting the termination process from the ingress node to the egress 
node to avoid this signalling. Teardown messages terminate the flows 
along the path. If direct measured rate termination is used, no PCN 
signalling is required at all.

Note:
1) The unwanted termination of non-marked flows is not a matter of 
accuracy but collateral damage: without this feature, admitted flows are 
terminated that do not run over precongested paths. A quantitative 
analysis of that phenomenon is available in Sect. IV.D of
http://www3.informatik.uni-wuerzburg.de/~menth/Publications/papers/Menth08-Sub-9.pdf 

2) For SM, this feature just mitigates the phenomenon of unwanted 
termination of non-marked flows, but it cannot remove it when one of the 
paths is AR-precongested and the other is SR-precongested.

Regards,

    Michael

Tom Taylor schrieb:
> Could you give details of your proposed modification. From private 
> conversation, it requires that only excess-traff-marked flows are 
> terminated when flow termination has to happen. How would these flows 
> be distinguished from the flows that were not excess-traffic-marked?
>
> Michael Menth wrote:
>> Hi all,
>>
>> Is multipath routing an issue at all in operational networks? Input 
>> from practitioners is highly appreciated.
>>
>> Regards,
>>
>>    Michael
>>

---

From: "Georgios Karagiannis" <[email-masked]>
Date: Thu, 19 Feb 2009 10:12:16 +0100

Hi Tom, Hi Michael

A solution for the ECMP routing issue, which is identical to the multi-path
routing issue, is  described in the 
LC-PCN draft, by using the PCN_Affected_Marking encoding and by supporting
the flow termination features (detection and termination) 
of the  excess-traff-marked flows at the egress.

Best regards,
Georgios

> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Tom Taylor
> Sent: donderdag 19 februari 2009 1:33
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: [PCN] multipath routing
> 
> Could you give details of your proposed modification. From 
> private conversation, it requires that only 
> excess-traff-marked flows are terminated when flow 
> termination has to happen. How would these flows be 
> distinguished from the flows that were not excess-traffic-marked?
> 
> Michael Menth wrote:
> > Hi all,
> >