Subject: [PCN] Flow termination at ingress or egress: multipath concerns

From: Michael Menth <[email-masked]>
Date: Tue, 24 Mar 2009 12:25:56 +0100

Hi Toby, Phil, and all,

what information is required for fow termination? I guess it's
* per-flow termination priorities (= policy info)
* flow rates to know what's a fat video or a slim voice call. Is that 
info continuously measured or provided by traffic descriptors?

Measured-rate flow termination signals when flow termination is required 
and also how much traffic needs to be removed or can remain. Therefore, 
flow rates and information about marked flows it required for a 
reasonable termination decision. In particular, a large number of flows 
possibly needs termination, not just one or two. Therefore, signalling 
the IDs of a handful of marked flows is not enough for MRT. It's the ID 
of many or even all marked flows that must be signalled with MRT.

However, your proposal probably fits better to marked-packet flow 
termination (MPT, aka marked flow termination MFT) that continuously 
triggers the termination of individual marked flows when needed. 
Providing the ID of just one other flow to have a termination choice 
sounds plausible.

The corner case you pointed out is quite interesting: IEAs with marked 
flows that have all low termintion priority (should not be terminated 
when other flows with high termination priority exist, correct me if 
that's right the opposite!).  Potential solution: they need to be 
terminated only upon a second termination request. Maybe the overload is 
removed by that time by the termination of other flows with high 
termination priority that are part of other IEAs.

I think two issues need clarification:
a) Is it a requirement that the ingress takes the flow termination 
decision instead of the egress and why?
b) Can we signal the IDs of recently marked flows from the PCN egress 
node to the PCN ingress node when flow termination is required?

If a) is a requirement, we should be able to do b) to make MRT work with 
multipath routing.

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