Re: [mpls] MPLS label and LSE data models

[Xufeng Liu <[e-mail]>]

Hi Greg,

From: Greg Mirsky [mailto:[e-mail]]
Sent: Tuesday, June 6, 2017 2:56 PM
To: Xufeng Liu <[e-mail]>
Cc: Acee Lindem (acee) <[e-mail]>; [e-mail]; [e-mail]; [e-mail]; [e-mail]
Subject: Re: MPLS label and LSE data models

Hi Xufeng,
thank you for helping me with your insight. I have couple follow-up questions:

  *   yes, grouping mpls-label-stack covers LSE though I cannot see why it needs id, sequence identifier. I'd expect the label stack already be properly ordered;
[Xufeng] There are two ways to achieve the ordering: 1) Explicit sequence id, 2) Implicit order of the list items. Personally I feel that the explicit way is more clear and easier to use, but have no strong objection to the implicit way.

  *   if we agree that the mpls-label-stack is ordered list, then figuring out which LSE should have BoS set is indeed benign and may not require to be explicit;
  *   as for Static MPLS LSP I propose:

     *   no need to have outgoing_label and outgoing_labels as the former is special case of the latter;
     *   consider whether to use rt-type:mpls-label-stack rather than rt-type:mpls-label. It gets tricky on transit nodes but we, it seems to me, need operations on TTL and TC being explicit on ingress.
[Xufeng] Thanks for your suggestion. Will pass to the discussion.
Regards,
Greg

On Tue, Jun 6, 2017 at 8:05 AM, Xufeng Liu <[e-mail]<mailto:[e-mail]>> wrote:
Hi Greg,


  1.  As you mentioned, grouping mpls-label-stack is defined in routing-types, so MPLS LSE is covered, right?
  2.  Bottom-of-the-stack flag should not be needed in the model,  because the label stack is a list with sequence ID’s, which tell us the beginning and the end of the stack.
  3.  The discussion on static MPLS LSP has started, but not converged yet. There are still open issues w.r.t. how to model the label stack and stack operations. Any suggestions would be appreciated. Do you have a proposal?
Thanks,
- Xufeng

From: Greg Mirsky [mailto:[e-mail]<mailto:[e-mail]>]
Sent: Monday, June 5, 2017 8:44 PM
To: Acee Lindem (acee) <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Re: MPLS label and LSE data models

Hi Acee,
I think rather of the contrary, Static MPLS LSP must include TC and TTL. And Bottom-of-the-stack flag as well (I don't see it in grouping mpls-label-stack of the ietf-routing-types).

Regards,
Greg

On Mon, Jun 5, 2017 at 4:55 PM, Acee Lindem (acee) <[e-mail]<mailto:[e-mail]>> wrote:
Greg, et al,

From: Greg Mirsky <[e-mail]<mailto:[e-mail]>>
Date: Monday, June 5, 2017 at 6:28 PM
To: "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Cc: Routing WG <[e-mail]<mailto:[e-mail]>>, "[e-mail]<mailto:[e-mail]>" <[e-mail]<mailto:[e-mail]>>
Subject: MPLS label and LSE data models
Resent-From: <[e-mail]<mailto:[e-mail]>>
Resent-To: Yingzhen Qu <[e-mail]<mailto:[e-mail]>>, <[e-mail]<mailto:[e-mail]>>, Acee Lindem <[e-mail]<mailto:[e-mail]>>, Christian Hopps <[e-mail]<mailto:[e-mail]>>, <[e-mail]<mailto:[e-mail]>>
Resent-Date: Monday, June 5, 2017 at 6:28 PM

Dear Authors, et.al<http://et.al>,
I've got a question, or several of them, about data models of MPLS label and MPLS label stack element (LSE). I ahve not followed the discussions and apologize if these already were considered, discussed.
In the Routing Types document I've found that only MPLS label being modeled but not the MPLS LSE. As result, models that use rt-types:mpls-label, e.g. YANG DAta Model for MPLS Static LSPs, defines outgoing labels not as array of LSEs but as array (leaf-list) of MPLS labels. In the latter document I don't see how TTL and Traffic Class (TC) are presented for each of labels in the array. Hence my questions:

  *   should there be data model of MPLS LSE in rt-types (it does have TTL and TC but separately);

  *   should data model of Static MPLS LSP use MPLS LSE model rather than model of only 20 bit-long label.
Where else so you see  a requirement for a label stack with entries that don’t contain TC and TTL? This seems specific to static provisioning of static LSPs rather than a general requirement for ietf-routing-types.

Thanks,
Acee


Appreciate you comments.

Regards,
Greg