Re: [mpls] MPLS-RT review on draft-ninan-mpls-spring-inter-domain-oam-02

[Mach Chen <[e-mail]>]

Hi Shraddha,

Thanks for considering the comments, looking forward to the revision.

Best regards,
Mach

> -----Original Message-----
> From: Shraddha Hegde [mailto:[e-mail]]
> Sent: Thursday, June 3, 2021 12:30 PM
> To: Mach Chen <[e-mail]>;
> [e-mail]
> Cc: [e-mail]; [e-mail]
> Subject: RE: MPLS-RT review on draft-ninan-mpls-spring-inter-domain-oam-02
> 
> Hi Mach,
> 
> Thanks for the review.
> Pls see inline ...
> 
> 
> Juniper Business Use Only
> 
> -----Original Message-----
> From: Mach Chen <[e-mail]>
> Sent: Wednesday, June 2, 2021 9:29 AM
> To: [e-mail]
> Cc: [e-mail]; [e-mail]
> Subject: MPLS-RT review on draft-ninan-mpls-spring-inter-domain-oam-02
> 
> [External Email. Be cautious of content]
> 
> 
> Hi,
> 
> I am selected as a MPLS-RT reviewer of
> draft-ninan-mpls-spring-inter-domain-oam.
> 
> After review, I think the problem that the draft is trying to address is valid and
> useful. The solution is overall workable. My comments are mainly about Type 3
> and Type 4 segment sub-TLV, I think it's better to address these comments
> before the adoption.
> <Shraddha> Sure.
> 
> Type 3 and 4 sub-TLVs are supposed to be used when the headend/PMS does
> not have the labels or SRGB information of the remote nodes, <Shraddha> yes
> because  these remote nodes lie in a different domain and SRGB information
> may not be available at the headend in some cases.
> 
>  and assume that the receiving node (egress node) can derive the MPLS labels
> according to the IPv4/IPv6 addresses.
> <Shraddha>
> I will add a section with  example of multi-domain network with different SRGB
> and explain how Type 3 and Type 4 Segments can be used while building the
> return path dynamically for traceroute. The key is only the top segment has to be
> Type 3/Type 4 the remaining segments to be of type label. For the Top segment,
> label has to be derived from the SRGB of the receiving node (not someone else's)
> so its expected to be available.
> 
> 
> This assumption may not hold, because given that the headend/PMS does not
> have the information, it is very likely that the receiving node has no the
> information either. So the draft should add more text to clarify the use cases of
> type 3, 4 sub-TLVs, or just remove them.
> <shraddha> I'll add more text to describe clearly how type3/Type 4 should be
> used.
> 
> In addition, given type 3 and 4 have valid use case, the optional SID fields of type
> 3 and 4 are redundant, I think that they should be removed.
> <shraddha> SIDs are optional anyway. I would prefer to keep it in order to be
> consistent with segment routing
> path description.
> 
> Section 4,
> "Below types of segment sub-TLVs are applicable for the Reverse Path
>    Segment List TLV."
> 
> Should the "Reverse Path Segment List TLV" be "Return Path TLV"?
> <shraddha> Good catch. I'll fix it.
> 
> Best regards,
> Mach