Subject: [PWE3] draft-ietf-pwe3-fc-encap-06.txt Last Call

From: Stewart Bryant <[email-masked]>
Date: Tue, 23 Oct 2007 13:22:37 +0100

This is the start of WG last call for:

Encapsulation Methods for Transport of Fibre Channel 
frames Over MPLS Networks 

http://www.ietf.org/internet-drafts/draft-ietf-pwe3-fc-encap-06.txt

Last Call will end 9th November 2007.

Please read the draft and provide feedback to the list.

Thanks

Stewart

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From: [email-masked]
Date: Tue, 23 Oct 2007 14:36:47 -0400

This draft has congestion control issues.  The authors should be
commended for use of TFRC, but TFRC is used with an absolute rate
floor called the Committed Information Rate (CIR).  When CIR > 0,
the FC PW behaves like a fixed bandwidth PW up to the CIR (uses
CIR bandwidth regardless of losses), and is TCP friendly only
for the bandwidth that exceeds the CIR.

This is a potential problem if the network capacity has fallen
to the point that the use of CIR bandwidth by the FC PW is a
contribution to congestion - that CIR bandwidth usage is
non-reactive to drops, e.g., the last sentence in Section
6.1.2 says:

	The sender SHALL continue to transmit data at
	the CIR, as long as the conditions do not change (i.e.,
	the network continue being congested).

In other words, the FC PW will continue to send traffic at the
CIR no matter what the network conditions.  I believe the recent
discussion about what could be done for congestion control for
fixed- bandwidth/non-reactive pseudo wires applies to the
FC PW usage of CIR bandwidth.  To start with, see:

http://www1.ietf.org/mail-archive/web/pwe3/current/msg09208.html

Thanks,
--David
----------------------------------------------------
David L. Black, Senior Technologist
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email-masked]        Mobile: +1 (978) 394-7754
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> -----Original Message-----
> From: Stewart Bryant [mailto:[email-masked]] 
> Sent: Tuesday, October 23, 2007 8:23 AM
> To: pwe3
> Cc: Danny McPherson
> Subject: [PWE3] draft-ietf-pwe3-fc-encap-06.txt Last Call
> 
>