Subject: [PCN] Few suggestions/comments on draft-charny-pcn-comparison

From: Francois Le Faucheur <[email-masked]>
Date: Mon, 10 Dec 2007 16:03:48 +0100

Hello,

A few suggestions/comments (from a quick read):

	* I found sections 1-10 of this document very helpful to try get my  
head around the various approaches in a consistent/comprehensive  
manner. I hope this document continues to be progressed.

	* While I understand the document does not (yet) try to weigh the  
different "comparison Criteria", I think it would be worth pointing  
out a few salient points like:
			(i) when discussing/comparing the "type of metering & marking": it  
may be worth pointing out that "Excess-rate-marking" is a very common  
mechanism supported on many (if not all) modern router Hardware  
today, while any other metering/marking flavor is probably not so  
commonly supported today. This seems like a significant consideration  
with respect to possible PCN introduction.
			(ii) when discussing/comparing the "rate measurement at boundary  
nodes": it may be worth pointing out that a scheme that does NOT  
require "rate measurement at boundary nodes" would result in  
considerable simplification.
			(iii) when discussing "parameter configuration", the I-D only  
discusses the "network-wide" parameters (that are only applicable to  
SM). Thus, it kind-of suggests that SM may be a little more complex  
to configure than the other schemes. However, the I-D omits to  
discuss all the other parameters that are likely to be much much  
harder to fine-tune (probably making the configuration of the single  
SM network-wide parameter appear as piece of cake). Those other  
parameters should also be discussed.

	* when discussing 3SM (in section 4.3 and section 9), it would be  
very useful to characterize 3SM performance WITH and WITHOUT rate  
measurement at boundary node. As stated above, if the 3SM scheme  
works well without rate measurement at boundary node, that would be a  
significant benefit of that scheme. However, when used without rate  
measurement at boundary node, one would expect performance  
degradation (depending on actual scheme this may include under- 
admission and/or high signaling). I think it is the intention of the  
authors to include material on this in future versions. I am looking  
forward to such information helping further assess whether 3SM  
without rate measurement is a viable option.

I hope this is useful.

Francois

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---

From: "Anna Charny (acharny)" <[email-masked]>
Date: Mon, 10 Dec 2007 13:35:33 -0500

Hi Francois,

Thank you for the comments. All makes perfect sense.  

Will try to address in the next version of the draft - although some of
the performance evaluation questions probably reside with simulation
effort drafts... 

Anna 

> -----Original Message-----
> From: Francois Le Faucheur (flefauch) 
> Sent: Monday, December 10, 2007 10:04 AM
> To: PCN IETF
> Subject: [PCN] Few suggestions/comments on draft-charny-pcn-comparison
> 
> Hello,
> 
> 	* I found sections 1-10 of this document very helpful 
> to try get my head around the various approaches in a 
> consistent/comprehensive manner. I hope this document 
> continues to be progressed.
> 
> 	* While I understand the document does not (yet) try to 
> weigh the different "comparison Criteria", I think it would 
> be worth pointing out a few salient points like:
> 			(i) when discussing/comparing the "type 
> of metering & marking": it may be worth pointing out that 
> "Excess-rate-marking" is a very common mechanism supported on 
> many (if not all) modern router Hardware today, while any 
> other metering/marking flavor is probably not so commonly 
> supported today. This seems like a significant consideration 
> nodes": it may be worth pointing out that a scheme that does 
> NOT require "rate measurement at boundary nodes" would result 
> in considerable simplification.
> 			(iii) when discussing "parameter 
> configuration", the I-D only discusses the "network-wide" 
> parameters (that are only applicable to SM). Thus, it kind-of 
> suggests that SM may be a little more complex to configure 
> than the other schemes. However, the I-D omits to discuss all 
> the other parameters that are likely to be much much harder 
> to fine-tune (probably making the configuration of the single 
> SM network-wide parameter appear as piece of cake). Those 
> other parameters should also be discussed.
> 
> 	* when discussing 3SM (in section 4.3 and section 9), 
> it would be very useful to characterize 3SM performance WITH 
> and WITHOUT rate measurement at boundary node. As stated 
> above, if the 3SM scheme works well without rate measurement 
> at boundary node, that would be a significant benefit of that 
> scheme. However, when used without rate measurement at 
> boundary node, one would expect performance degradation 
> (depending on actual scheme this may include under- admission 
> and/or high signaling). I think it is the intention of the 
> authors to include material on this in future versions. I am 
> looking forward to such information helping further assess 
> whether 3SM without rate measurement is a viable option.
> 
> I hope this is useful.
> 
> Francois
> 
>

---

From: Michael Menth <[email-masked]>
Date: Fri, 14 Dec 2007 17:40:31 +0100

Hi Francois,

see inline, please!

Francois Le Faucheur wrote:
>     * I found sections 1-10 of this document very helpful to try get 
> my head around the various approaches in a consistent/comprehensive 
>             (i) when discussing/comparing the "type of metering & 
> marking": it may be worth pointing out that "Excess-rate-marking" is a 
> very common mechanism supported on many (if not all) modern router 
> Hardware today, while any other metering/marking flavor is probably 
> not so commonly supported today. This seems like a significant 
> consideration with respect to possible PCN introduction.
>             (ii) when discussing/comparing the "rate measurement at 
> boundary nodes": it may be worth pointing out that a scheme that does 
> NOT require "rate measurement at boundary nodes" would result in 
>             (iii) when discussing "parameter configuration", the I-D 
> only discusses the "network-wide" parameters (that are only applicable 
> to SM). Thus, it kind-of suggests that SM may be a little more complex 
> to configure than the other schemes. However, the I-D omits to discuss 
> all the other parameters that are likely to be much much harder to 
> fine-tune (probably making the configuration of the single SM 
> network-wide parameter appear as piece of cake). Those other 
> measurement at boundary node. As stated above, if the 3SM scheme works 
> well without rate measurement at boundary node, that would be a 
> measurement at boundary node, one would expect performance degradation 
> (depending on actual scheme this may include under-admission and/or 
> high signaling). I think it is the intention of the authors to include 
> material on this in future versions. I am looking forward to such 
> information helping further assess whether 3SM without rate 
> measurement is a viable option.

Yes, you are right. This is crucial and needs to be done. We're working 
on this issue.

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: "Jozef Babiarz" <[email-masked]>
Date: Mon, 17 Dec 2007 09:58:06 -0500

In my additional review of the PCN Architecture draft, I realized that
there is no mention of how bi-directional flows are handled.

I believe that the PCN Architecture draft needs to discuss and explain
how admission control and flow termination works at high level for
telephony and video conferencing applications and that both, telephony
and video conferencing applications have bi-directional flows. For
admission control a new flow can not be admitted unless the traffic
level on both unidirectional paths is below the PCN-lower-rate. As well
for flow termination, a bi-directional flow is terminated if one of the
unidirectional paths is in excess of PCN-upper-rate. 

Regards, Joe
email:[email-masked]
Telephone:613-763-6098

---

From: "Ingemar Johansson S" <[email-masked]>
Date: Tue, 18 Dec 2007 14:59:37 +0100

Hi

I would say that scenarios like this are covered atleast if SIP is used
as protocol for the session setup as there are features in the protocol
that handles the case that "crap hits the fan". 
I would assume that simular mechanisms exist for other session setup
protocols aswell. Here one can maybe pay some attention to how long it
actually takes to be "admitted" as it may impact of session setup times.
This would require a dialog between the PCN admission protocol and the
session setup protocol but I beleieve that it is more a headache for the
protocol that handles the resource reservation than PCN itself as this
problem is not only related to PCN (similar issues/problem statements
and solutions exist in 3GPP wireless access).

Termination issue:
I believe that this is handled aswell. As a last resort RTP contains a
mechanism that ensures termination after a period of silence in one
direction, SIP also contains mechanisms for (abnormal) teardown.

Ingemar

> From: Jozef Babiarz [mailto:[email-masked]] 
> Sent: den 17 december 2007 15:58
> To: PCN IETF
> Subject: RE: [PCN] Architecture draft- bi-directional flows
> 
> In my additional review of the PCN Architecture draft, I 
> realized that there is no mention of how bi-directional flows 
> are handled.
> 
> I believe that the PCN Architecture draft needs to discuss 
> and explain how admission control and flow termination works 
> at high level for telephony and video conferencing 
> applications and that both, telephony and video conferencing 
> applications have bi-directional flows. For admission control 
> a new flow can not be admitted unless the traffic level on 
> both unidirectional paths is below the PCN-lower-rate. As 
> well for flow termination, a bi-directional flow is 
> terminated if one of the unidirectional paths is in excess of 
> PCN-upper-rate. 
> 
> 
> Regards, Joe
> email:[email-masked]
> Telephone:613-763-6098
> 
> 
>