Re: [Pce] WG Last Call for draft-ietf-pce-binding-label-sid-07 (and Code Point Allocation)

Gyan Mishra <> Sun, 28 March 2021 23:25 UTC

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From: Gyan Mishra <>
Date: Sun, 28 Mar 2021 19:24:55 -0400
Message-ID: <>
To: Siva Sivabalan <>
Cc: "Chengli (Cheng Li)" <>, "Stone, Andrew (Nokia - CA/Ottawa)" <>, "" <>, "" <>, "" <>
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Subject: Re: [Pce] WG Last Call for draft-ietf-pce-binding-label-sid-07 (and Code Point Allocation)
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After further review with Siva the use case is for connecting SR islands
over RSVP-TE core.

So this is for stitching SR-TE on the edge islands binding SID to core
RSVP-TE tunnel.

One major gap  of RSVP-TE is the VRF / VPN coloring capability that in
order to achieve per VRF coloring mapping of VRF to a discrete TE tunnel
requires a separate loopback and static routes to egress PE so it does not
scale.  So for as many RSVP mapped tunnels that exist you need that many
loopbacks and static routes for the next hop rewrite to the RSVP tunnel
next hop.

So this Major gap is filled with SR VRF and app flow coloring capability
that with SR-TE Policy BSID bound to candidate path can provide the
scalability per VRF coloring.

So at the edges you may have many 100s of colored RSVP tunnels but as the
core does not scale you can not provide a 1-1 mapping of SR-TE tunnel to
RSVP tunnel.  So you would have many to 1 mappings of SR-TE tunnels to
single or aggregate.

So in my mind to only way the BSID would come into play is if you could do
a 1-1 mapping of SR-TE tunnel to RSVP tunnel.  Technically that is not

For PCE to compute end to end path in this scenario does RSVP-TE require
the BSID for the stitching even if a many SR-TE colors to single RSVP-TE
tunnel mapping. I would not think so.

If we think that for PCE to build the end to end path even for the end to
end path in this scenario requires BSID binding to the RSVP-TE single path
to make contiguous end to end then I agree technically we do need to make
this inclusive of RSVP-TE.

I think we need to clear this up and if this use case is really not
feasible then we should remove any mention of BSID use with RSVP-TE tunnel.

Kind Regards


On Sat, Mar 27, 2021 at 3:05 PM Siva Sivabalan <> wrote:

> Hi Gyan,
> BSID can be allocated for RSVP-TE as well, and yes, there are use-cases
> for that. The proposed PCEP extension is equally applicable to both SR-TE
> and RSVP-TE.
> Thanks,
> Siva
> On Sat, Mar 27, 2021 at 1:40 PM Gyan Mishra <> wrote:
>> I support WG LC advancement of this draft for publication.
>> I see there are a lot of comments related to a mix of verbiage related to
>> MPLS label binding and Binding label SID confusion.
>> Few comments.
>> The draft title states “carrying binding label/sid in PCE based networks”
>> In the abstract it states it is possible to associate a BSID with a RSVP
>> signaled path.
>> I don’t recall any RSVP extension to support concept of BSID usage on an
>> active Candidate Path option ERO.  Can you refer me to the RFC that states
>> how BSID is used with RSVP TE.
>> For more clarity with this draft can we replace
>> s/TE/s/SR as TE nomenclature refers to RSVP-TE and does add confusion
>> where SR is SR.  When mentioned traffic engineered path please spell out or
>> say SR path for clarity.
>> Also the “TE-PATH-BINDING TLV” can we change to “SR-PATH-BINDING TLV”.
>> The word “binding” is very confusing as it’s used interchangeably with
>> label binding and binding SID.
>> So I am thinking a more appropriate name for the TLV would be “SR-TE-BSID
>> TLV”.  Makes it clear and concise the TLV is for SR-TE.
>> Kind Regards
>> Gyan
>> On Fri, Mar 26, 2021 at 9:45 PM Chengli (Cheng Li) <>
>> wrote:
>>> Thanks again for your help!
>>> Cheng
>>> -----Original Message-----
>>> From: Stone, Andrew (Nokia - CA/Ottawa) []
>>> Sent: Saturday, March 27, 2021 2:42 AM
>>> To: Chengli (Cheng Li) <>;;
>>> Cc:
>>> Subject: Re: [Pce] WG Last Call for draft-ietf-pce-binding-label-sid-07
>>> (and Code Point Allocation)
>>> Hi Cheng,
>>> Thanks for clarifying the text in the document. Diff content looks good
>>> to me, much clearer. Consider my comments resolved.
>>> Thanks!
>>> Andrew
>>> On 2021-03-25, 10:49 PM, "Pce on behalf of Chengli (Cheng Li)" <
>>> on behalf of> wrote:
>>>     Hi Andrew,
>>>     Thanks for your comments, please see my reply inline.
>>>     Also, the diff is attached.
>>>     Respect,
>>>     Cheng
>>>     -----Original Message-----
>>>     From: Stone, Andrew (Nokia - CA/Ottawa) [mailto:
>>>     Sent: Saturday, March 20, 2021 4:21 AM
>>>     To:;
>>>     Cc:
>>>     Subject: Re: [Pce] WG Last Call for
>>> draft-ietf-pce-binding-label-sid-07 (and Code Point Allocation)
>>>     Hi all,
>>>     Overall Support WGLC. It's an important document in the world of
>>> SRTE, and the document goes to good lengths to describe the various
>>> scenarios and combinations.
>>>     Only one question I have for the authors and WG, for any further
>>> clarification on the following text (section 4):
>>>       The absence of TE-PATH-BINDING TLV in PCUpd message
>>>        means that the PCE does not specify a binding value in which case
>>> the
>>>        binding value allocation is governed by the PCC's local policy.
>>>     I find the "governed by PCC local policy" a bit too vague and could
>>> lead to implementation interop differences. Assuming a PCInitiated LSP that
>>> been established with a BSID: If the PCE wants to withdraw the binding SID
>>> , I interpret the document as the PCE would send a PCUpdate without the
>>> TLV, but the behaviour is now up to PCC as per that text. if the PCC local
>>> policy/implementation is to do nothing, how can the PCE explicitly
>>> force-remove the BSID with a PCUpdate? In a similar manner, If the PCE does
>>> not want to change the value but PCC local policy is to treat missing TLV
>>> as remove, then PCE should always send the TLV in every PCUpdate (which I'm
>>> okay with) which is not stated, otherwise the local policy/implementation
>>> may interpret it as a removal compared to an implementation which may
>>> interpret it as being okay to not send the TLV on every PCUpdate since
>>> there was "no change".
>>>     In summary: might need a bit of a wording to further detail "PCE
>>> wishes to withdraw" case.
>>>     [Cheng] You are correct, there was some issues with multiple
>>> TE-PATH-BINDING TLV. This has been updated. See the diff.
>>>     The above text has been updated to -
>>>        The absence of TE-PATH-BINDING TLV in PCUpd message means that the
>>>        PCE does not specify a binding value in which case any previous
>>>        allocated binding values are withdraw.
>>>     Further, the PCC's local policy aspect has been seperated out as -
>>>        In the absence of any instruction from the PCE, the PCC's local
>>>        policy dictates how the binding allocations are made for a given
>>> LSP.
>>>     Thanks!
>>>     Thanks!
>>>     Andrew
>>>     On 2021-03-18, 7:09 AM, "Pce on behalf of"
>>> < on behalf of> wrote:
>>>         Hi all,
>>>         This message initiates a 2-week PCE WG Last Call for
>>>         draft-ietf-pce-binding-label-sid-07. Please review and share your
>>>         feedback, whatever it is, using the PCE mailing list. This WGLC
>>> will end
>>>         on Thursday April 1st (no kidding).
>>>         Moreover, we have received a request from the authors for a code
>>> point
>>>         allocation to support interoperability testing.
>>>         RFC 7120 requires to meet the following criteria to proceed:
>>>         b. The format, semantics, processing, and other rules related to
>>>         handling the protocol entities defined by the code points
>>>         (henceforth called "specifications") must be adequately described
>>>         in an Internet-Draft.
>>>         c. The specifications of these code points must be stable; i.e.,
>>> if
>>>         there is a change, implementations based on the earlier and later
>>>         specifications must be seamlessly interoperable.
>>>         If anyone believes that the draft does not meet these criteria,
>>> or
>>>         believes that early allocation is not appropriate for any other
>>>         reason, please send an email to the PCE mailing list explaining
>>> why. If
>>>         the chairs hear no objections by Thursday, March 25th, we will
>>> kick off
>>>         the "early" allocation request.
>>>         Thanks,
>>>         Dhruv & Julien
>>> _________________________________________________________________________________________________________________________
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>> --
>> <>
>> *Gyan Mishra*
>> *Network Solutions A**rchitect *
>> *Email <>*
>> *M 301 502-1347*
>> --


*Gyan Mishra*

*Network Solutions A**rchitect *

*Email <>*

*M 301 502-1347*