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

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

On 13/07/2021 17:39, Les Ginsberg (ginsberg) wrote:
> 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
> 
> 
>> -----Original Message-----
>> From: Lsr <lsr-bounces@ietf.org> On Behalf Of internet-drafts@ietf.org
>> Sent: Monday, July 12, 2021 9:12 AM
>> To: i-d-announce@ietf.org
>> Cc: lsr@ietf.org
>> Subject: [Lsr] I-D Action: draft-ietf-lsr-flex-algo-bw-con-01.txt
>>
>>
>> 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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> 
> 