Speaking as WG member:
I agree with Peter and have a couple additional concerns.
1. If metric normalization is to be performed in the IGP domain, the LSA/LSP
originator should
do it rather than having everyone else in the domain do it for the
originator's metrics.
2. The stated goal is to compute more ECMP paths. Did you consider that some
vendors
have implemented UCMP (Unequal Cost MultiPath)?
Thanks,
Acee
> On Nov 6, 2025, at 8:16 AM, Peter Psenak <[email protected]> wrote:
>
> Liyan,
> On 06/11/2025 10:40, Liyan Gong wrote:
>> Hi All,
>> hank you for your valuable comments.
>> To ensure we are fully aligned, we would like to further clarify the
>> considerations behind our proposal.
>> Please feel free to correct us if we have misunderstood any aspect of your
>> suggestion.
>> In designing our approach, we focused on addressing two key aspects:
>> 1. **Parameter Consistency**: Parameters such as metric-step and
>> metric-offset need to be consistent across the network. We observed that any
>> inconsistency in static configuration could lead to incorrect normalized
>> metrics, which might in turn affect path selection.
> there is no need for consistency of these parameters across the network.
> If the configuration consistency is the problem you trying to address, there
> are existing tools for that.
>> 2. **Parameter Optimization**: In dynamic network environments, these
>> parameters may need to be tuned. We think that relying solely on manual
>> reconfiguration in such cases could not only be operationally costly and
>> prone to errors, but also slow down routing convergence, potentially
>> extending periods of network instability.
> similarly, FAD is not a configuration tool, there are existing tools for
> that.
> thanks,
> Peter
>
>> These considerations motivated our proposal, which draws inspiration from
>> the established concept of automatic metric calculation — an approach that
>> addresses similar needs. We believe a protocol-based extension could be a
>> suitable way to resolve these issues while staying consistent with existing
>> mechanisms.
>> We welcome further discussion.
>>
>> Best Regards,
>> Liyan
>>
>> -----邮件原件-----
>> 发件人: Acee Lindem <[email protected]>
>> 发送时间: 2025年11月6日 3:06
>> 收件人: Gyan Mishra <[email protected]>
>> 抄送: Peter Psenak <[email protected]>; [email protected]
>> 主题: [Lsr] Re: draft-gl-lsr-metric-normalize/
>>
>> Speaking as WG Member:
>>
>> Speaking as WG member, I agree with Peter as well.
>>
>> The additional alternative to local metric normalization is to do UCMP
>> (Unequal Cost Mulltipath) route installation which is also a local behavior.
>> Here is one example:
>>
>> https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/routing/79x/b-routing-cg-ncs5500-79x/implementing-ucmp.html
>>
>> You do have assure you don't create loops (e.g., do a feasible successor
>> check as EIGRP does).
>>
>>
>> Thanks,
>> Acee
>>
>>> On Nov 4, 2025, at 11:46PM, Gyan Mishra <[email protected]> wrote:
>>>
>>>
>>> I agree with Peter that this draft is unnecessary.
>>>
>>> Delay metric normalization is common feature implemented by most all SR
>>> vendors to circumvent sub optimal undesired routing where ECMP exists or
>>> TI-LFA backup path is programmed. A single uS differential in ECMP links
>>> can break ECMP as well as TI-LFA.
>>>
>>> This is all local implementation specific and does not require any
>>> standardization.
>>>
>>>
>>> Thanks
>>>
>>> Gyan
>>>
>>>
>>>
>>> On Tue, Nov 4, 2025 at 10:49AM Peter Psenak
>>> <[email protected]> wrote:
>>> Hi,
>>> here are my comments on the draft:
>>> 1. Normalization of the measured latency, or any other PM related value, is
>>> a local behavior on the router. It should really be viewed as a part of the
>>> measurement procedure. The measured value is normalized before it is
>>> advertised.
>>> 2. It is not functionally required for normalization to be used, nor for
>>> its logic/parameters to be synchronized across all routers in the network.
>>> 3. Felx-algo definition (FAD) is not meant to be used as a management
>>> mechanism for distribution of the configuration parameters. There are
>>> exiting provisioning tools available for that.
>>> To summarize, I find the proposals in the draft to be both unnecessary as
>>> well as undesirable.
>>> thanks,
>>> Peter
>>>
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>>
>
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