Re: [Lsr] [mpls] Comments on draft-ietf-mpls-spring-entropy-label

Hi,

Please see inline (MSD section).

Hope this clarifies, thanks!

Cheers,

Jeff

[jeff] both IGP drafts have identical description of the BMI-MSD:

“Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS labels a node is capable of imposing, including all service/transport/special labels.”

PCEP draft supports only a subset of overall MSD functionality and in general it is expected that this info would come from IGPs(BGP-LS).

However the functoriality provided by PCEP is inline with the  BMI-MSD definition in the IGP drafts, at the node granularity only though. 

3. Section 5 introduces the MSD concept. I wonder whether this concept is aligned with the MSD concept as defined in the PCEP-SR draft or the MSD concept as defined in the IGP-MSD draft. In PCEP-SR draft, it said "
The "Maximum SID Depth" (1
   octet) field (MSD) specifies the maximum number of SIDs (MPLS label
   stack depth in the context of this document) that a PCC is capable of
   imposing on a packet.

In the IGP-MSD draft, it said "
MSD of type 1 (IANA Registry), called Base MSD is used to signal the
   total number of SIDs a node is capable of imposing, to be used by a
   path computation element/controller.  "

If I understand it correctly, the MSD in this draft==the MSD in PCEP-SR draft==the Base MSD (i.e., the MSD of type 1), No?

[SLI] Today, the two IGP drafts does not seem to agree on the definition
ISIS says:” Base MPLS Imposition MSD (BMI-MSD) signals the total number of MPLS
   labels a node is capable of imposing, including all

   service/transport/special labels.”
OSPF says:” MSD of type 1 (IANA Registry) is used to signal the number of SIDs a
   node is capable of imposing, to be used by a path computation

   element/controller and is only relevant to the part of the stack

   created as the result of the computation.”

MSD is just MSD is defines a maximum number of labels to be pushed. This is the definition we use and it is compliant with the one used in PCEP-SR:
“The "Maximum SID Depth" (1
   octet) field (MSD) specifies the maximum number of SIDs (MPLS label

   stack depth in context of this document) that a PCC is capable of

   imposing on a packet.”

As we also say: “This includes any kind of labels (service, entropy, transport...).”, we are compliant with the BMI-MSD defined in IS-IS.

Best regards,

Xiaohu
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