Subject: Re: [Idr] draft-ietf-idr-bgp-ls-segment-routing-ext-08 ( BGP Link-State extensions for Segment Routing )

From: Rajesh M <[email-masked]>
Date: Mon, 3 Sep 2018 05:05:22 +0000

Please find the response inline.

From: Ketan Talaulikar (ketant) <[email-masked]>
Sent: Friday, August 31, 2018 1:21 PM
To: Rajesh M <[email-masked]>; [email-masked]
Cc: Shraddha Hegde <[email-masked]>; Ram Santhanakrishnan <[email-masked]>; Balaji Rajagopalan <[email-masked]>
Subject: RE: draft-ietf-idr-bgp-ls-segment-routing-ext-08 ( BGP Link-State extensions for Segment Routing )

Hi Rajesh,

There is also a problem with your suggestion.

The moment we add protocol to the attribute it can no longer be shared between NLRIs across protocols in any case. So I don't see how it helps in the BGP packing.

I agree with you, we cannot share attributes across OSPF/ISIS.
My suggestion is to add protocol tlv as optional attribute for Node/Link/Prefix attributes. So that backward compatibility is not an issue.

There are several implementations of this draft which are shipping and deployed. So changing encodings in a manner that is not backward compatible is a challenge at this stage.

Thanks,
Ketan

From: Rajesh M <[email-masked]<mailto:[email-masked]>>
Sent: 31 August 2018 11:22
To: Ketan Talaulikar (ketant) <[email-masked]<mailto:[email-masked]>>; [email-masked]<mailto:[email-masked]>
Cc: Shraddha Hegde <[email-masked]<mailto:[email-masked]>>; Ram Santhanakrishnan <[email-masked]<mailto:[email-masked]>>; Balaji Rajagopalan <[email-masked]<mailto:[email-masked]>>
Subject: RE: draft-ietf-idr-bgp-ls-segment-routing-ext-08 ( BGP Link-State extensions for Segment Routing )

Hi Ketan,

Attributes might end Up same even across protocol (OSPF/ISIS). It's not good to make that Assumption.
our suggestion is to : Mandatory add protocol as part of the Node/Link/Prefix attributes to ensure the same.

Thanks
Rajesh

From: Ketan Talaulikar (ketant) <[email-masked]<mailto:[email-masked]>>
Sent: Friday, August 31, 2018 7:18 AM
To: Rajesh M <[email-masked]<mailto:[email-masked]>>; [email-masked]<mailto:[email-masked]>
Cc: Shraddha Hegde <[email-masked]<mailto:[email-masked]>>
Subject: RE: draft-ietf-idr-bgp-ls-segment-routing-ext-08 ( BGP Link-State extensions for Segment Routing )

Hi Rajesh,

Please check inline below.

From: Idr <[email-masked]<mailto:[email-masked]>> On Behalf Of Rajesh M
Sent: 29 August 2018 12:32
To: [email-masked]<mailto:[email-masked]>
Cc: Shraddha Hegde <[email-masked]<mailto:[email-masked]>>
Subject: [Idr] draft-ietf-idr-bgp-ls-segment-routing-ext-08 ( BGP Link-State extensions for Segment Routing )

About section 2.2.1 (Adjacency SID TLV) section 2.2.2 (LAN Adjacency SID TLV):
Here Flags field is specific to OSPF and ISIS. Until we know the protocol we will not be able to decode the received Flags.
[KT] Ack

About section 2.3.1 (Prefix-SID TLV) :
Here Flags field is specific to OSPF and ISIS. Until we know the protocol we will not be able to decode the received Flags.
[KT] Ack

Our understanding is
Protocol cannot be got from Node NLRI Format, Link NLRI Format, Prefix NLRI Format since multiple NLRIs can share same set of BGP-LS attribute.
[KT] This is about packing of BGP-LS updates. Since each BGP-LS NLRI has a unique set of attributes, it is not possible to pack multiple NLRIs in the same update. Doing this for NLRIs across protocol is even harder. The update messages end up being a single NLRI and its attributes. Would you agree? And as an extension we know the protocol when decoding the flags.

Thanks,
Ketan