Subject: [PCN] Open issue in the termination algorithm

From: Michael Menth <[email-masked]>
Date: Tue, 09 Feb 2010 16:35:36 +0100

Hi all,

the current flow termination method is as follows.

A)
1. The egress node restarts the measurement interval if it detects 
excess-traffic-marked packets after long time.
2. The new PCN feedback is signalled to the decision point.
3. The decision point triggers the measurement of the ingress rate.
4. The ingress returns the ingress rate to the decision point.
5. The decision point calculates the termination rate by
a) TR=ingress-rate - not-marked-rate - threshold-marked-rate (dual marking)
b) TR=ingress-rate - (not-marked-rate * u) (single marking)
6. The decision point terminates flows with an overall rate of  the 
termination rate TR.

The restart of the measurement interval in 1) is needed to avoid 
underestimated not-marked-rates and threshold-marked-rates in 5) when 
the computation of TR uses the rates from the same PCN feedback that 
triggered the measurement at the ingress node.

B)
However, if we require that the PCN feedback used in 5) must be younger 
than the one that triggered the measurement of the ingress-rate, then we 
do not longer need the restart of the measurement interval in 1). This 
does not lead to extra delay compared to A) because traffic cannot be 
terminated earlier than the ingress-rate is available and in the 
meantime, new PCN feedback has arrived. This has two advantages:
i) Simplified control because egress may measure periodically
ii) Earlier termintion because termination is triggered at most but 
mostly earlier than 1 measurement interval after the arrival of the 
first ETM packet at the egress node.

C)
Another option:
1) measurement at egress node starts with arrival of first ETM packets
2) ingress nodes send ingress rates periodically
3) decision point must use ingress rate which is older than pcn feedback 
+ RTT
This is a bit faster but requires restart of measurement intervals at 
the egress node.

BUT: avoiding underestimated non-marked-rates and threshold-marked-rates 
works only for dual marking because with single marking packets may be 
excess-traffic-marked already in the presence of AR-pre-congestion. 
Therefore, I think option B) is most reasonable. What's your opinion?

I think it would be good if we could fix that issue in the next revision 
of the edge behavior drafts.
http://tools.ietf.org/html/draft-ietf-pcn-cl-edge-behaviour-01
http://tools.ietf.org/html/draft-ietf-pcn-sm-edge-behaviour-01

Regards,

    Michael

-- 
Dr. Michael Menth, Assistant Professor
University of Wuerzburg, Institute of Computer Science
Am Hubland, D-97074 Wuerzburg, Germany, room B206
phone: (+49)-931/31-86644 (new), fax: (+49)-931/31-86632 (new)
mailto:[email-masked]
http://www3.informatik.uni-wuerzburg.de/research/ngn

---

From: <[email-masked]>
Date: Wed, 10 Feb 2010 08:40:48 +0100

Hello Michael,

while I'm not with a vendor and no supporter of load reduction by 
termination, it seems to me, that B) is the simplest option. 
That's why I'd favour it.

my 2 cents,

Ruediger

Deutsche Telekom Netzproduktion GmbH
Zentrum Technik Einführung
Rüdiger Geib
Heinrich-Hertz-Straße 3-7, 64295 Darmstadt
+49 6151 628-2747 (Tel.)
+49 251 7985 209 (Fax)
http://www.telekom.com

Erleben, was verbindet.

Deutsche Telekom Netzproduktion GmbH
Aufsichtsrat: Dr. Steffen Roehn (Vorsitzender)
Geschäftsführung: Dr. Bruno Jacobfeuerborn (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 09, 2010 4:36 PM
To: pcn
Subject: [PCN] Open issue in the termination algorithm

Hi all,

A)

B)

C)
Another option:

Regards,

    Michael

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

---

From: <[email-masked]>
Date: Thu, 18 Feb 2010 15:11:53 -0000

I don't object to this - but how do you make sure that it is younger?:-
> than the one that triggered the measurement of the 
> ingress-rate,  

> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of [email-masked]
> Sent: 10 February 2010 07:41
> To: [email-masked]; [email-masked]
> Subject: Re: [PCN] Open issue in the termination algorithm
> 
> 
> Hello Michael,
> 
> 3. The decision point triggers the measurement of the ingress 
> rate. 4. The ingress returns the ingress rate to the decision 
> point. 5. The decision point calculates the termination rate by

Regards,

    Michael

phone: (+49)-931/31-86644 (new), fax: (+49)-931/31-86632 (new) mailto:[email-masked]

---

From: Michael Menth <[email-masked]>
Date: Fri, 19 Feb 2010 22:33:24 +0100

Hi Phil,

> I don't object to this - but how do you make sure that it is younger?:-

1. Decision point receives from egress PCN feedback indicating potential 
termination
2. Decision point triggers ingress to perform ingress measurement
3. Decision point receives from egress next PCN feedback indicating 
potential termination
4. Decision point receives from ingress the sent PCN rate

The PCN feedback in 3 is younger than the PCN feedback in 1. Is there 
something I have overlooked?

Regards,

    Michael

>> Behalf Of Michael Menth
>> ingress-rate, then we