Subject: [Lsr] I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt

From: [email-masked]
Date: Mon, 12 Jul 2021 09:12:10 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Link State Routing WG of the IETF.

        Title           : Flexible Algorithms: Bandwidth, Delay, Metrics and Constraints
        Authors         : Shraddha Hegde
                          William Britto A J
                          Rajesh Shetty
                          Bruno Decraene
                          Peter Psenak
                          Tony Li
	Filename        : draft-ietf-lsr-flex-algo-bw-con-01.txt
	Pages           : 27
	Date            : 2021-07-12

Abstract:
   Many networks configure the link metric relative to the link
   capacity.  High bandwidth traffic gets routed as per the link
   capacity.  Flexible algorithms provides mechanisms to create
   constraint based paths in IGP.  This draft documents a generic metric
   type and set of bandwidth related constraints to be used in Flexible
   Algorithms.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-lsr-flex-algo-bw-con/

There is also an htmlized version available at:
https://datatracker.ietf.org/doc/html/draft-ietf-lsr-flex-algo-bw-con-01

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-lsr-flex-algo-bw-con-01

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: "Les Ginsberg (ginsberg)" <[email-masked]>
Date: Tue, 13 Jul 2021 15:39:22 +0000

Draft authors -

I note that the new version has altered the advertisement of the Generic Metric sub-TLV so that it is no longer supported in the ASLA sub-TLV.
This is in direct violation of RFC 8919/8920.

For example, https://www.rfc-editor.org/rfc/rfc8919.html#section-6.1 states:

"New applications that future documents define to make use of the advertisements defined in this document MUST NOT make use of legacy advertisements."

Flex-algo is a "new application" in the scope of these RFCs.

Please correct this error.

Thanx.

   Les

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From: Peter Psenak <[email-masked]>
Date: Wed, 14 Jul 2021 10:40:00 +0200

Hi,

I'm the co-author of this draft and I have tried to convince the rest of 
the co-authors that encoding the new Generic Metric sub-TLV only as a 
application independent value is wrong. Unfortunately, my efforts have 
failed. As a result, although unwillingly, I have to express my opinions 
here and let the WG decide.

1) The usage of the Generic Metric sub-TLV is likely going to be 
associated with the applications, Flex-algo being the first one. Generic 
Metric sub-TLV can not be used by IGP's native calculation. So having 
Generic Metric being encoded only in legacy TLV does not make much sense.

2) TE-metric is defined as application specific attribute by
RFC 8919/8920 and can be advertised in ASLA. The application specific 
value advertisement of TE-metric has been already proved in the field. 
Generic Metric is semantically very similar to TE-metric, so I see no 
reason why application specific encoding should not be supported.

3) Flex-algo specification mandates the usage of the ASLA attributes and 
all of the attributes that we are using for flex-algo so far are encoded 
in ALSA. Encoding the Generic Metric outside of ALSA violates that 
principle.

4) RFC 8919/8920 violation brought by Les below.

thanks,
Peter

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From: Jeff Tantsura <[email-masked]>
Date: Fri, 16 Jul 2021 20:55:25 -0700

+1 Les.

Cheers,
Jeff