[Teas] SVEC objective function in draft-ietf-teas-yang-path-computation-18

Italo Busi <Italo.Busi@huawei.com> Mon, 17 October 2022 08:33 UTC

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From: Italo Busi <Italo.Busi@huawei.com>
To: "teas@ietf.org" <teas@ietf.org>
CC: Carlo Perocchio <carlo.perocchio@ericsson.com>, Dhruv Dhody <dhruv.ietf@gmail.com>, "Belotti, Sergio (Nokia - IT/Vimercate)" <sergio.belotti@nokia.com>, "pce@ietf.org" <pce@ietf.org>
Thread-Topic: SVEC objective function in draft-ietf-teas-yang-path-computation-18
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Date: Mon, 17 Oct 2022 08:33:28 +0000
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Subject: [Teas] SVEC objective function in draft-ietf-teas-yang-path-computation-18
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During WG LC, Dhruv has raised the following comment:
*       For objective-function-type in grouping synchronization-optimization, the use of "default "te-types:of-minimize-cost-path" is a problem, because this OF is not applicable to SVEC. I don't think you need a default here!
We have further discussed offline the issue with Dhruv and Carlo

There is no need to define a default value of objective functions (OFs): OF is entirely optional so if no OF is configured, no OF is required.

It was also noted that IANA maintains a single list of OFs defined by PCE WG:


However, within this list, some objective functions (i.e., MBC, MLL, MCC, MCTD, MSL, MSS, MSN) are applicable only to SVEC while the other objective functions are applicable only to paths.

In YANG, it would be better to have two base identities to separate the objective functions applicable to paths from those applicable to SVEC (like it has been already done for the metric types).

However, the MBC, MLL and MCC objective functions, which are applicable to SVEC, are already defined in RFC8776 together with the other objective functions which are applicable to paths.

In order to resolve this issue, we would propose the following:
1)      remove the default from the SVEC OF indicating in the description of objective-function-type in the container objective-function that, if no OF is configured, no OF is required
2)      deprecate (or obsolete, since it was a mistake) the of-minimize-agg-bandwidth-consumption (MBC), of-minimize-load-most-loaded-link (MLL) and of-minimize-cost-path-set (MCC) objective functions defined in RFC8776 (in the next updated of draft-ietf-teas-rfc8776-update)
3)      define new SVEC  OF identities
4)      move the SVEC metrics and OFs to draft-ietf-teas-rfc8776-update for broader applicability

We would like to get feedbacks from the TEAS WG about this proposal before updating the path computation and te types as proposed


Sergio and Italo