[mpls] Re: Working Group Last Call for draft-ietf-mpls-spring-lsp-ping-path-sid (was Re: Working Group Last Call on draft-xp-mpls-spring-lsp-ping-path-sid)

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Hi Greg,

If the question is how the "headend" information is carried in the BGP signaling, accordingly to https://datatracker.ietf.org/doc/html/draft-ietf-idr-sr-policy-safi  section 1, there're several cases:
1）Typically, a SR Policy Controller defines the set of policies and advertises them to policy headend routers, such an advertisement may be sent on a BGP session to that headend. So the BGP peer address indicates the headend in this case.
2) Alternatively, a router (i.e., a BGP egress router) advertises SR Policies representing paths to itself. In this case, it is possible to send the policy to each headend over a BGP session to that headend.  The headend is still indicated by the  BGP peer address in this case.
3) In some situations, it is undesirable for a controller or BGP egress router to have a BGP session to each policy headend. To make this possible, an attribute needs to be attached to the advertisement that enables a BGP speaker to determine whether it is intended to be a headend for the advertised policy. This is done by attaching one or more Route Target Extended Communities to the advertisement. So the route target extended community indicates the headend in this case.

Yao


Original


From: GregMirsky <[e-mail]>
To: 肖敏10093570;
Cc: [e-mail] <[e-mail]>;[e-mail] <[e-mail]>;[e-mail] <[e-mail]>;
Date: 2024年08月20日 11:42
Subject: [mpls] Re: Working Group Last Call for draft-ietf-mpls-spring-lsp-ping-path-sid (was Re: Working Group Last Call on draft-xp-mpls-spring-lsp-ping-path-sid)

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Hi Xiao Min,yes, Quan's information is helpful but the relationship between the ASSOCIATION object of the SR Policy and flow charts in https://datatracker.ietf.org/doc/draft-ietf-pce-sr-path-segment/ is not yet clear to me. I hope that we Quan will clarify that. In the meantime, perhaps you can clarify the scenario when the source of the SR Policy is BGP.

Regards,
Greg





On Mon, Aug 19, 2024 at 8:17 PM <[e-mail]> wrote:


Hi Greg,

Thanks for the further clarification on your concern.
Please see inline.

Original

From: GregMirsky <[e-mail]>
To: Tarek Saad <[e-mail]>;
Cc: [e-mail] <[e-mail]>;MPLS Working Chairs <[e-mail]>;[e-mail] <[e-mail]>;
Date: 2024年08月20日 07:32
Subject: [mpls] Re: Working Group Last Call for draft-ietf-mpls-spring-lsp-ping-path-sid (was Re: Working Group Last Call on draft-xp-mpls-spring-lsp-ping-path-sid)

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Dear All,
I paused to arrange my concerns about the draft and put them in front of you more clearly. Below is what it came to:

The purpose of Target FEC Stack TLV in LSP echo request, as I understand it, is to verify consistency between the data plane and the control plane view of the data plane. That is why the sender of an echo request with Target FEC Stack TLV includes a sub-TLV that, from the sender's perspective, sufficiently represents the control plane information associated with the verifiable label.
[XM]>>> Yes, that's correct.


If the above is correct, I move to the next point. All sub-TLVs in the Target FEC Stack TLV must be validated. The validation process is sub-TLV-specific. This draft defines the validation process, using PCEP as an example, as follows:


*  Validate that the signaled headend, color, end-point,
originator ASN, originator address, and discriminator
defined in [I-D.ietf-pce-segment-routing-policy-cp]
and [I-D.ietf-pce-sr-path-segment], for the PSID,
matches with the corresponding fields in the received
SR Candidate Path's PSID sub-TLV.
Now, my question: What is meant as validation of Headend?

The reason for my question above is that I cannot find that the identity of the Headend is included in PCEP constructs defined for the configuration of an SR Policy. Am I missing something in PCE-related specifications, or must they be enhanced to convey the identity of the SR Policy's Headend?
[XM]>>> As PCEP expert Quan has responded to you, there is *Headend* included in PCEP for SR Policy.

There's a possible way to use information already available in the IP-encapsulated echo request message and source IP address. Personally, I would consider such a check a security measure rather than validation, but how would validation work if no IP/UDP encapsulation of the echo request is used?
[XM]>>> Considering there is *Headend* included in PCEP for SR Policy, the information in the header of echo request is not needed.


I hope that I made my concern more evident now. I welcome your comments and questions.
[XM]>>> Yes, your concern is more evident to me. Hope the responses can resolve your concern. :-)

Cheers,
Xiao Min

Regards,
Greg








On Tue, Aug 6, 2024 at 10:13 AM Tarek Saad <[e-mail]> wrote:



Hi WG,
 
I am correcting a mistake to reference to the WG adopted draft (as opposed to the individual draft for the same document). Sorry for the confusion.
 
Regards,
Tarek
 


From: Tarek Saad <[e-mail]>                                                      
 Date: Tuesday, August 6, 2024 at 9:53 AM
 To: [e-mail] <[e-mail]>
 Cc: MPLS Working Chairs <[e-mail]>, [e-mail] <[e-mail]>
 Subject: Working Group Last Call on draft-xp-mpls-spring-lsp-ping-path-sid



Dear WG,
 
This email starts a two-week working group last call for draft-ietf-mpls-spring-lsp-ping-path-sid.
 
Please indicate your support or concern for this draft. If you are opposed to the progression of the draft to RFC, please articulate your concern. If you support it, please indicate that you have read the latest version, and it is ready for publication in your opinion. As always, review comments and nits are most welcome.
 
Please send your comments to the mpls wg mailing list ([e-mail])
If necessary, comments may be sent unidirectional to the WG chairs.
 
Note, currently there are no IPR disclosures against this document. 
 
This poll runs until August 20, 2024.
 
Thank you,
Tarek (for the MPLS WG co-chairs)
 






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