Re: [Pce] Question about Originator Address in draft-ietf-pce-segment-routing-policy-cp

[Oscar González de Dios <[e-mail]>]

Thanks Mike,

                Another question/comment.

                The color & endpoint are encoded in the Extended Association ID TLV (defined in RFC 8697. The Extended Association ID TLV is an optional TLV for use in the ASSOCIATION object. The meaning and usage of the Extended Association ID TLV are as per Section 4 of [RFC6780] .

                The content of the Extended Association TLV is defined here. Hence, the content of the TLV as expressed in the draft is only valid when the association type is 6 (segment routing). In other cases, the format would be completely different.

                Typically the content of all PCEP TLVs are well defined without requiring knowledge of the object in which they are carried. Some sort of type is used to determine the content.

                Looking at Section 4 of [RFC6780], the "Extended Association ID: variable, 4-byte aligned
      This field contains data that is additional information to support
      unique identification.  The length and contents of this field is
      scoped by the Association Source.  ".

                There, all association fields are together, so it makes sense. However, as in PCEP RFC 8697 "stripped off" the extended association ID to a TLV... well, we have the problem of having a TLV without any pre-defined format or any way of knowing its content without context...

                Is there any particular reason for this behavior?  Does color & endpoint absolutely need to be part of the Extended Association TLV or could they have their own TLV?

                Best Regards,

                                Oscar

De: Mike Koldychev (mkoldych) <[e-mail]>
Enviado el: viernes, 17 de septiembre de 2021 19:01
Para: Oscar González de Dios <[e-mail]>; [e-mail]; [e-mail]
Asunto: RE: Question about Originator Address in draft-ietf-pce-segment-routing-policy-cp

Hi Oscar,

Yes, I believe your understanding is correct.

Thanks,
Mike.

From: Oscar González de Dios <[e-mail]<mailto:[e-mail]>>
Sent: Friday, September 17, 2021 8:02 AM
To: [e-mail]<mailto:[e-mail]>; [e-mail]<mailto:[e-mail]>
Subject: Question about Originator Address in draft-ietf-pce-segment-routing-policy-cp

Dear PCE WG & draft-ietf-pce-segment-routing-policy-cp authors,

        I have one (easy) question about the SR Policy Candidate Path Identifiers TLV in section 5.2.2.
"Originator Address: Represented as 128 bit value where IPv4 address
   are encoded in lowest 32 bits, part of the originator identifier, as
   specified in [I-D.ietf-spring-segment-routing-policy] Section 2.4."
In [I-D.ietf-spring-segment-routing-policy] Section 2.4. :
"Node Address : represented as a 128-bit value.  IPv4 addresses
      MUST be encoded in the lowest 32 bits, and the high-order bits
      MUST be set to zero."

             I guess an IPv4 Originator address would be encoded as follows: (apologies if the lines do not appear properly)

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             Type              |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Proto. Origin |                    Reserved                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Originator ASN                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   all zeros                                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   all zeros                                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   all zeros                                                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Originator IPv4 Address                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         Discriminator                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


        I ask it because in one interoperability test we are carrying out now, in one implementation the IPv4 address is encoded in the bits right after Originator ASN. Hence... I just want to be sure my understanding is correct to avoid a philosophical discussion :)

        Best Regards,

                Oscar


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