Les,
As I explained in this e-mail chain, my motivation for including max-link
metric is
Option 2 in your description. That is the reason I referred to RFC 3784 text.
We can add text to describe the motivation for max link metric in next revision.
Request WG to provide details If there are other usecases/motivations beyond
what is discussed in this e-mail chain.
Rgds
Shraddha
Juniper Business Use Only
-----Original Message-----
From: Les Ginsberg (ginsberg) <ginsberg=40cisco....@dmarc.ietf.org>
Sent: Monday, January 16, 2023 11:06 PM
To: Shraddha Hegde <shrad...@juniper.net>; Mengxiao.Chen
<chen.mengx...@h3c.com>; lsr@ietf.org
Subject: RE: [Lsr] FW: I-D Action: draft-ietf-lsr-flex-algo-bw-con-04.txt
[External Email. Be cautious of content]
Shraddha -
I think Mengxiao has raised a legitimate point. The use of max-metric to
exclude a link is at best redundant in flex-algo since there are existing ways
to exclude a link. Simply quoting RFC 5305 doesn’t really help in understanding
the motivation of the authors in adding this restriction.
I do not object to this additional restriction, but I think the draft should be
more forthcoming as to why this was introduced. I can think of a couple of
possible reasons:
1)Existing logic in implementations for algo 0 have this restriction. Applying
it to all algos simplifies implementations.
2)As the new generic metric can potentially be used for use cases other than
flex-algo, it makes sense to apply the same restriction.
Perhaps the authors had different motivations...
Please consider adding text that helps the readers to understand why this new
restriction was added.
Les
> -----Original Message-----
> From: Lsr <lsr-boun...@ietf.org> On Behalf Of Shraddha Hegde
> Sent: Sunday, January 15, 2023 9:27 PM
> To: Mengxiao.Chen <chen.mengx...@h3c.com>; lsr@ietf.org
> Subject: Re: [Lsr] FW: I-D Action:
> draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> Hi,
>
> This is the excerpt from the RFC 3784
> " If a link is advertised with the maximum link metric (2^24 - 1), this
> link MUST NOT be considered during the normal SPF computation. This
> will allow advertisement of a link for purposes other than building
> the normal Shortest Path Tree. An example is a link that is
> available for traffic engineering, but not for hop-by-hop routing."
>
> This same usecase applies to flex-algo and generic metric as well.
> Maximum link metric Implies the link is not available for use in
> flex-lago but can be used for other Purposes like SR-TE.
>
> Rgds
> Shraddha
>
>
> Juniper Business Use Only
>
> -----Original Message-----
> From: Mengxiao.Chen <chen.mengx...@h3c.com>
> Sent: Thursday, January 12, 2023 1:18 PM
> To: Shraddha Hegde <shrad...@juniper.net>; lsr@ietf.org
> Subject: RE: [Lsr] FW: I-D Action:
> draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> [External Email. Be cautious of content]
>
>
> Hi Shraddha,
>
> Thank you for replies.
> I think the case of Flex-Algo is different from normal SPF. Flex-Algo
> is used to compute paths based on constraints.
> The topology constraints include whether a link is considered for
> flex-algo calculation. And it is already realized by Node
> Participation, Admin Group and SRLG, as specified in draft-ietf-lsr-flex-algo.
> Could you explain the reason for defining additional Max-Generic-Metric?
>
> Thanks,
> Mengxiao
>
> -----Original Message-----
> From: Shraddha Hegde <shrad...@juniper.net>
> Sent: Thursday, January 12, 2023 12:45 PM
> To: Mengxiao.Chen <chen.mengx...@h3c.com>; lsr@ietf.org
> Subject: RE: [Lsr] FW: I-D Action:
> draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> Hi Chenmengxiao,
>
> Thanks for review and comments.
> Pls see inline [SH] for replies
>
>
> Juniper Business Use Only
>
> -----Original Message-----
> From: Chenmengxiao <chen.mengx...@h3c.com>
> Sent: Wednesday, January 11, 2023 8:26 AM
> To: Shraddha Hegde <shrad...@juniper.net>; lsr@ietf.org
> Subject: RE: [Lsr] FW: I-D Action:
> draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> [External Email. Be cautious of content]
>
>
> Hi Shraddha,
>
> In the new version, Generic Metric sub-TLV added "A metric value of
> 0xFFFFFFFF is considered as maximum link metric and a link having this
> metric MUST NOT be considered in SPF computation."
> With that I have two questions/suggestions:
> #1 Generic Metric sub-TLV may be used for different kinds of
> metric-type, maximum value can have different meanings. Besides, Admin
> Group rules can be used to exclude a link in Flex-Algo. Why must
> define a global unreachable value?
> [SH] RFC 3784 defined MAX-LINK-METRIC so that links can be advertised
> but not used for normal SPF computation.
> Same case applies here where links are not considered for flex-algo
> calculations but can be used for other reasons inside a flex-algo plane.
>
> #2 According to draft-ietf-lsr-flex-algo, I think it's better to use
> "Flex- Algorithm calculations" instead of "SPF computation".
> [SH]. Agree. Will update .
>
>
> Thanks,
> Mengxiao
>
> -----Original Message-----
> From: Lsr <lsr-boun...@ietf.org> On Behalf Of Shraddha Hegde
> Sent: Tuesday, January 10, 2023 12:43 PM
> To: lsr@ietf.org
> Subject: [Lsr] FW: I-D Action: draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> WG,
>
> New version of the draft has been posted.
> Changes listed below.
>
> 1. Suggested codepoints in IANA section removed 2. Section 2.1 and 2.2
> updated. Metric 0 is allowed. Added below sentence "
> Maximum link metric MUST NOT be used in SPF"
> 3. editorial changes.
>
> Pls review the draft.
>
> Rgds
> Shraddha
>
>
> Juniper Business Use Only
>
> -----Original Message-----
> From: Lsr <lsr-boun...@ietf.org> On Behalf Of internet-dra...@ietf.org
> Sent: Tuesday, January 10, 2023 10:10 AM
> To: i-d-annou...@ietf.org
> Cc: lsr@ietf.org
> Subject: [Lsr] I-D Action: draft-ietf-lsr-flex-algo-bw-con-04.txt
>
> [External Email. Be cautious of content]
>
>
> 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-04.txt
> Pages : 29
> Date : 2023-01-09
>
> 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://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-iet
> f-lsr-
> flex-algo-bw-con/__;!!NEt6yMaO-gk!Db--a1RCey-
> Q7ZXMSpU93MYIPyuVk4YeN_KLhIVN0FsLiqDW8ARDpp485WSQ6jtGcNg-
> iL_V_VJkQ-71AZ8UPWiFZZw$
>
> There is also an htmlized version available at:
> https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/draf
> t-
> ietf-lsr-flex-algo-bw-con-04__;!!NEt6yMaO-gk!Db--a1RCey-
> Q7ZXMSpU93MYIPyuVk4YeN_KLhIVN0FsLiqDW8ARDpp485WSQ6jtGcNg-
> iL_V_VJkQ-71AZ8Use7KjRU$
>
> A diff from the previous version is available at:
> https://urldefense.com/v3/__https://author-
> tools.ietf.org/iddiff?url2=draft-ietf-lsr-flex-algo-bw-con-04__;!!NEt6
> yMaO-
> gk!Db--a1RCey-
> Q7ZXMSpU93MYIPyuVk4YeN_KLhIVN0FsLiqDW8ARDpp485WSQ6jtGcNg-
> iL_V_VJkQ-71AZ8UFI_AgUI$
>
>
> Internet-Drafts are also available by rsync at
> rsync.ietf.org::internet-drafts
>
>
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