[Idr] Comments and Questions for draft-ietf-idr-bgp-ls-sr-policy

[Jayant Agarwal <[e-mail]>]

Hi Authors,

I have few questions and comments for draft "draft-ietf-idr-bgp-ls-sr-policy" regarding segment list metric sub-TLV.

1. what metric values reported by "SR Segment List Metric Sub-TLV" (section 5.9)?
              a. is this sub-TLV used only to report computed metrics (computed by path computation entity i.e., headend or controller)?
              b. is this sub-TLV can also be used to report real time end to end path delay metrics?

2. If 1.a is TRUE means this metric sub-TLV is used only to report computed metrics (when path computation is successful) then,
              a. We shall explicitly clarify that this metric TLV will not be used to report real time measured end to end path delay metric values.
              b. We shall have some other way to report real time end to end delay metrics (to generalize, any kind of performance metrics). which will be open for future discussions.
c. For TLV type "Min Unidirectional Link Delay [RFC7471]", we shall clarify that this is computed path metric based on IGP minimum link delay metric and not the measured SRTE end to end path delay. SRTE end to end path delay additionally includes delays from each node, queueing etc.

3. If 1.b is TRUE means this metric sub-TLV is used to report both computed metric and real time measured end to end path delay metrics then,
              a. We shall explicitly state and clarify in this section that this metric can be used to report both type of value.
b. We shall also clarify that TLV type "Min Unidirectional Link Delay [RFC7471]" will be used to report computed metric or measured metric or both? because both the values can co-exist for any path at any given moment, and both values may/will be different. And then there is no way to differentiate if this is measured value or computed value.
              c. How to report maximum delay, average delay, and delay variation values for end-to-end path delay?

Thanks
Jayant



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