Re: [Isis-wg] Regd encoding of ISIS SRMS range inside BGP-LS

"Stefano Previdi (sprevidi)" <sprevidi@cisco.com> Fri, 16 June 2017 18:12 UTC

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From: "Stefano Previdi (sprevidi)" <sprevidi@cisco.com>
To: idr wg <idr@ietf.org>, "isis-wg@ietf.org" <isis-wg@ietf.org>
CC: "draft-ietf-idr-bgp-ls-segment-routing-ext@ietf.org" <draft-ietf-idr-bgp-ls-segment-routing-ext@ietf.org>, "Ketan Talaulikar (ketant)" <ketant@cisco.com>
Thread-Topic: Regd encoding of ISIS SRMS range inside BGP-LS
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Date: Fri, 16 Jun 2017 18:12:03 +0000
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Subject: Re: [Isis-wg] Regd encoding of ISIS SRMS range inside BGP-LS
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practically speaking, it would be helpful to know if there are any implementations of draft-ietf-idr-bgp-ls-segment-routing-ext and especially the Binding SID TLV.

We’re in the process of updating the draft and in an effort of simplification, we’d like to change the way the ISIS SRMS (SR Mapping Server) is encoded.

The changes we’d like to propose are not backward compatible so it is important to know if any implementation exists.

Thanks for coming back to us.

s.







> On Jun 14, 2017, at 3:22 PM, Ketan Talaulikar (ketant) <ketant@cisco.com> wrote:
> 
> Hello All,
> 
> Needed some clarification from the authors and implementers of BGP-LS on Sec 3.4 of the https://tools.ietf.org/html/draft-ietf-idr-bgp-ls-segment-routing-ext-01#page-26 
> 
> It currently states ...
> 
> 3.4.  Advertisement of a range of IS-IS SR bindings
> 
>   The advertisement of a range of IS-IS SR bindings has following
>   rules:
> 
>      In IS-IS the Mapping Server binding ranges are advertised using
>      the Binding TLV.  The IS-IS Binding TLV is encoded in the BGP-LS
>      Prefix Attribute Range TLV as defined in Section 2.3.5 using the
>      Binding Sub-TLV as defined in Section 2.3.6.  The flags in the
>      Range TLV are all set to zero on transmit and ignored on
>      reception.  The range value from the original IS-IS Binding TLV is
>      encoded in the Range TLV "Range" field.
> 
> My understanding what that the encoding for ISIS is done with Range TLV + Prefix-SID sub-TLV (very similar to how it is specified in Sec 3.3 for OSPF). However the language is indirectly referring to the Prefix-SID sub-TLV by saying  "using the Binding Sub-TLV".
> 
> This may give an impression that the encoding for ISIS is done as Range TLV + Binding TLV + Prefix-SID sub-TLV and differently than done for OSPF. It would be clearer if the ISIS sec 3.4 were to also use similar language as OSPF sec 3.3. Would like to propose something like below:
> 
> 3.4.  Advertisement of a range of IS-IS SR bindings
> 
>   The advertisement of a range of IS-IS SR bindings has following
>   rules:
> 
>      In IS-IS the Mapping Server binding ranges are advertised using
>      the IS-IS Binding TLV
>      ([I-D.ietf-isis-segment-routing-extensions]).  The IS-IS Binding
>      TLV is encoded in the BGP-LS Prefix Attribute Range TLV as defined
>      in Section 2.3.4.
>      The flags in the Range TLV are all set to zero on transmit and
>      ignored on reception.  The range value from the original IS-IS
>      Binding TLV is encoded in the Range TLV "Range" field. The
>      Prefix-SID from the original ISIS Prefix SID Sub-TLV is encoded
>      using the BGP-LS Prefix Attribute Prefix-SID as defined in
>      Section 2.3.1 with the flags set according to the definition in
>     [I-D.ietf-isis-segment-routing-extensions]
> 
> I would also like to check if anyone has implemented the encoding of ISIS SRMS range using the Binding SID TLV.
> 
> Thanks,
> Ketan
>