Re: [PCN] PCN termination marking algorithm - consensus?

[<[e-mail]>]

>> such that later on a selection on the algorithms is done.

Actually I think we're now at the stage where we have good consensus on
what the marking algorithms (behaviours) are. So now is the time to
agree it!

 

- For admission, it reflects what's in anna's comparison draft

- For termination, it also reflects what's in anna's comparison draft,
with the added info we now have from michael's emft draft that 3SM
termination system behaviour can be got with the CL marking behaviour (&
a new edge behaviour).

 

> I thought that the idea of the architecture draft is to provide a
description of the architectural options

lars is discouraging this & trying to get us to make the choices now. I
think we can do this for the marking really quite easily. The edge
behaviour may be harder to reach consensus on. 

 

-----Original Message-----
From: Georgios Karagiannis [mailto:[e-mail]] 
Sent: 28 February 2008 13:33
To: Eardley,PL,Philip,CXR9 R; [e-mail]
Subject: RE: [PCN] PCN termination marking algorithm - consensus?

 

Hi Phil

 

My concerns are similar to the previous email that I have sent regarding
admission control.

I would like to have a more clear understanding on what you are
proposing before we can get any consensus!

In my option all options that are currently decribed in the current
version of the archietcture draft will be reduced at the moment that the
encoding method is selected and probably also when the PCN algorithms
used at interior and edges are selected.

I thought that the idea of the architecture draft is to provide a
description of the architectural options that can be used, such that
later on a selection on the algorithms is done.

If that is not the case then the publication of the architecture draft
should be delayed until the above selections are done!

Best regards,

Georgios

 

	 

	
________________________________


	From: [e-mail] [mailto:[e-mail]] 
	Sent: donderdag 28 februari 2008 14:27
	To: [e-mail]; [e-mail]
	Subject: RE: [PCN] PCN termination marking algorithm -
consensus?

	We've got to have *one* metering function for termination (& one
for adm). 

	 

	I thought the idea was that lc-pcn would get into anna's
comparison draft, ie in the same format & the same general level of
understanding of how it works (the latter being a pre-requisite to
getting it in there!). 

	 

	Even so, I looked at the latest lc-pcn & S4.3.1 (interior node &
termination) and it says:

	The PCN-interior-nodes can measure the PHB aggregated PCN
traffic
	   that exceeds a configured-admissible-rate and mark this
excess PCN

	   traffic

	 

	which is exactly what the email below does.

	                          

	Please explain what youre concerned about!

	thanks.

	 

	Phil/

	 

	-----Original Message-----
	From: Georgios Karagiannis [mailto:[e-mail]] 
	Sent: 28 February 2008 13:08
	To: Eardley,PL,Philip,CXR9 R; [e-mail]
	Subject: RE: [PCN] PCN termination marking algorithm -
consensus?

	 

	Hi Phil

	 

	I am not in favour of using the token bucket as the only
metering function that can be used in PCN!

	Regarding the comparison, I think that if you want to base any
decission on it, then 

	the LC-PCN algorithm should also be included in this comparison!

	 

	Best regards,

	Georgios

	 

	 

	 

	 

	 

		 

		
________________________________


		From: [e-mail] [mailto:[e-mail]]
On Behalf Of [e-mail]
		Sent: woensdag 27 februari 2008 14:13
		To: [e-mail]
		Subject: [PCN] PCN termination marking algorithm -
consensus?

		Here also is an attempt for consensus on the termination
marking behaviour.

		 

		 

		 If an interface of the PCN-domain performs PCN
Admission Marking then it performs three functions, which are outlined
in draft-ietf-pcn-architecture as follows:

		 
		   o  Packet classify - decide whether an incoming
packet is a PCN-
		      packet or not.  Another PCN WG document will
specify encoding,
		      using the DSCP and/or ECN fields.
		 
		   o  PCN-meter - measure the 'amount of PCN-traffic'.
The measurement
		      is made as an aggregate of all PCN-packets, and
not per flow.
		 
		   o  PCN-mark - algorithms determine whether to
PCN-mark PCN-packets
		      and what packet encoding is used (as specified in
another PCN WG
		      document).

		 

		These functions are now described in more detail.

		Note: The PCN-node MAY implement these three functions
on either its ingoing or outgoing interfaces. The same choice MUST be
made for every PCN-node in one PCN-domain. 

		[Lars has commented: do we need to allow this choice?]

		 

		Classify function:

		If a packet's ECN/DSCP fields have the value PCN, as
defined in [RFC-encoding], then it MUST be classified as a PCN-packet.
However, if the PCN-packet is already "termination marked", as defined
in [RFC-encoding], then the Meter function SHOULD NOT be performed. (*)

		If a packet's ECN/DSCP fields do not have the value PCN,
as defined in [RFC-encoding], then it MUST NOT be classified as a
PCN-packet.

		 

		Meter function:

		Note: The meter is described as a 'token bucket',
however the implementation is not standardised.

		 

		A packet classified as a PCN-packet MUST be metered as
follows. 

		The interface MUST have:

		[1] a configured bit rate, termed PCN-upper-rate

		[2] a meter for PCN-packets, which MUST have the
following behaviour:

		 

		a token bucket, operating in bits: 

		1A tokens are added at the PCN-upper-rate, to a maximum
TB.size

		1B tokens are removed equal to the size in bits of the
PCN-packet, to a minimum TB.size=0

		2 if TB.fill = 0, then the meter indicates "termination
mark" to the Mark function

		 

		Note: Step 1A can be triggered by a packet and so can be
done at the same time as Step 1B.

		Note: Step 2 can be performed before or after step 1

		 

		The following SHOULD be done (**) instead of Step 2
above (Step 2 is then superfluous).

		if TB.fill < maximum size of PCN-packet, then the meter
indicates "termination mark" to the Mark function

		The "maximum size of PCN-packet" is the MTU in bits of
any PCN-packets in the PCN-domain. 

		Note: Step 1B above is still performed. 

		 

		 

		Mark function:

		If the meter indicates to "termination mark" a
PCN-packet, then:

		the PCN-packet's ECN/DSCP fields MUST be set to the
codepoint "termination marked", as defined in [RFC-encoding]

		 

		 

		(*) Explanation: for CL termination (ie the termination
based on rates, rather than the 3SM termination based on marked pkts),
if the meter counts pkts that are already termination marked then
there'll be over-termination in the event of multiple bottlenecks.
However, since this option is probably more complicated to implement
than a normal classifier (?), I suggest it is a SHOULD.

		 

		(**) Explanation: this captures the point that Michael
makes in
http://www3.informatik.uni-wuerzburg.de/staff/menth/Publications/Menth08
-PCN-MFT.pdf
<http://www3.informatik.uni-wuerzburg.de/staff/menth/Publications/Menth0
8-PCN-MFT.pdf>  & Bob makes in
http://www.ietf.org/internet-drafts/draft-briscoe-tsvwg-byte-pkt-mark-02
.txt
<http://www.ietf.org/internet-drafts/draft-briscoe-tsvwg-byte-pkt-mark-0
2.txt>  Otherwise flows with big pkts get marked more than flows with
small pkts. However, since this option is more complicated to implement
than a normal token bucket, I suggest it is a SHOULD.

		 

		we could also add an example algorithm, such as that in
http://www.ietf.org/internet-drafts/draft-charny-pcn-comparison-00.txt
Fig 10.1
<http://www.ietf.org/internet-drafts/draft-charny-pcn-comparison-00.txt%
20Fig%2010.1>  on page 21.

		 

		Comments?

		phil

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