Re: [Pce] WG Last Call for draft-ietf-pce-segment-routing-11

[Jonathan Hardwick <[e-mail]>]

Hi Cyril

Many apologies for the delay – please see below.

Cheers
Jon


From: Pce [mailto:[e-mail]] On Behalf Of Cyril Margaria
Sent: 30 January 2018 16:49
To: Dhruv Dhody <[e-mail]>
Cc: [e-mail]
Subject: Re: [Pce] WG Last Call for draft-ietf-pce-segment-routing-11

Hi,

I have the following (hopefully not too late) comments/questions:

Section 5.3 ERO Object

         S: When this bit is set, the SID value in the subobject body is

         null.  In this case, the PCC is responsible for choosing the

         SID value, e.g., by looking up its TED using the NAI which, in

         this case, MUST be present in the subobject.

- What is the associated procedure if the PCC cannot resolve the NAI to a SID? Should there be associated error codes. For instance the PCC may not be able to resolve the NAI  at all or the resolution may fail. In case the PCC does not support the NAI resolution, having this capability part of the capability exchange would improve interop, as the PCE can be capable to provide the SID.

[Jon]
I agree that a capability would be good.  Yes, if the NAI cannot be resolved, it should be rejected.
I have added both of these to the latest draft.
[/Jon]

- If Both S and F are cleared, should the PCC do the NAI resolution and verify that the SID match? Would error codes be needed)

[Jon]
If the SID is a bare label then the NAI may be given to help identify the next hop.  If the SID is an index and NAI is given as well, then the PCC SHOULD use the SID, because it is a more explicit instruction.  The PCE MAY give both SID and NAI for diagnostic / logging purposes.  I don’t think we should require the PCC to validate SID==NAI in that case; it should just use the SID as given.  I will clarify in the draft.
[/Jon]

Thanks,
Cyril


On 30 January 2018 at 01:19, Dhruv Dhody <[e-mail]<mailto:[e-mail]>> wrote:
Hi,

   I had reviewed and given comments on the I-D in the past, which the
   authors had addressed. I found these additional nits/suggestions.
   Apologies for being late by a day.

   Suggestions
   -----------

   Section 1

   (1) Though it is true that a child PCE act as a PCC towards the
   parent PCE, I feel it is not wise to say the opposite, that is a PCC
   is acting as a PCE in this context. I see no advantage to bring up the
   H-PCE in this context. I suggest we remove it.

      A PCE, or a PCC operating as a PCE (in hierarchical PCE
      environment), computes paths for MPLS Traffic Engineering LSPs
      (MPLS-TE LSPs) based on various constraints and optimization
      criteria.

   (2) Since this document is related to MPLS data plane only, it would
   be nice to include a pointer to the SRv6 work in PCEP for the benefit
   of the readers.

   (3) Regarding first mention of PST
   OLD:
      This specification relies on the procedures specified in [I-
      D.ietf-pce-lsp-setup-type].
   NEW:
      This specification relies on the procedures specified in [I-
      D.ietf-pce-lsp-setup-type] for the path setup type for SR.

   Section 3

   (4) Regarding this text -

      SR-TE LSPs
      computed by a PCE can be represented in one of the following forms:

      o  An ordered set of IP address(es) representing network nodes/links:
         In this case, the PCC needs to convert the IP address(es) into the
         corresponding MPLS labels by consulting its Traffic Engineering
         Database (TED).

      o  An ordered set of SID(s).

      o  An ordered set of both MPLS label(s) and IP address(es): In this
         case, the PCC needs to convert the IP address(es) into the
         corresponding SID(s) by consulting its TED.

   Each SR-ERO object can include both SID and NAI (IP address); this
   case is different from the case 3 above, I suggest if some text can
   be added to make things clearer.

   Section 5.1.1

   (5) Why SHOULD in this text?

      A PCEP speaker SHOULD indicate its support of the function described
      in this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the
      OPEN object with this new PST included in the PST list.

   Section 6

   (6) Regarding,

      A PCEP speaker that does not support the SR PCEP capability cannot
      recognize the SR-ERO or SR-RRO subobjects. As such, it MUST send a
      PCEP error with Error-Type = 4 (Not supported object) and Error-Value
      = 2 (Not supported object Type) as per [RFC5440].

   RFC 5440 did not state the behavior for unknown sub-object. My
   suggestion would be -

      A PCEP speaker that does not support the SR PCEP capability and
      thus cannot recognize the SR-ERO or SR-RRO subobjects, it will
      respond according to the rules for a malformed object as per
      [RFC5440].

   Section 7

   (7) Suggest to make Manageability Consideration section as per RFC
   6123

   (8) PCEP-Yang should be mentioned in section 7.2

   Section 8

   (9) Suggest we expand the security consideration section a bit based
   on recent DISCUSSes.


   Nits
   ----

   Section 5.3.1

   s/MUST not/MUST NOT/

   Section 5.3.3

   (2)
   OLD:
      A PCEP speaker that does not recognize the SR-ERO subobject in PCRep,
      PCInitiate, PCUpd or PCRpt messages MUST reject the entire PCEP
      message and MUST send a PCErr message with Error-Type=3 ("Unknown
      Object") and Error-Value=2 ("Unrecognized object Type") or Error-
      Type=4 ("Not supported object") and Error-Value=2 ("Not supported
      object Type"), defined in [RFC5440].
   NEW:
      A PCEP speaker that does not recognize or support the SR-ERO
      subobject in PCRep, PCInitiate, PCUpd or PCRpt messages MUST
      reject the entire PCEP message and MUST send a PCErr message with
      Error-Type=3 ("Unknown Object") and Error-Value=2 ("Unrecognized
      object Type") or Error- Type=4 ("Not supported object") and Error-
      Value=2 ("Not supported object Type"), defined in [RFC5440].

   (3) I agree with Adrian that the ".. not identical" needs to change.
   Since you mean all subobject in ERO must be of SR-ERO type, we should
   just call it that! (also applicable for SR-RRO).

   Thanks!
   Dhruv


> -----Original Message-----
> From: Pce [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Julien Meuric
> Sent: 15 January 2018 15:08
> To: [e-mail]<mailto:[e-mail]>
> Subject: [Pce] WG Last Call for draft-ietf-pce-segment-routing-11
>
> Dear PCE WG,
>
> Best wishes for this new year, full of interoperable specifications. Let
> us begin by resuming our work in progress.
>
> This message starts a 2-week WG last call for draft-ietf-pce-segment-
> routing-11. Please send your feedback on the I-D to the PCE mailing list
> by Monday January 29.
>
> Regards,
>
> Jon & Julien
>
> _______________________________________________
> Pce mailing list
> [e-mail]<mailto:[e-mail]>
> https://www.ietf.org/mailman/listinfo/pce

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