Re: [Idr] Clarifications on draft-ietf-idr-segment-routing-te-policy

[Ketan Talaulikar <[e-mail]>]

Hi Zhenqiang Li,

The deployment design that you describe can achieve the optimization that
you desire by using outbound route policy on the RR to each of its
neighbors. The spec does not prevent an implementation from providing a
policy knob to achieve the behavior you desire.

Also, consider a deployment design with hierarchical RRs. Would your
proposed change not break BGP propagation?

Personally, I do not think we should change the base BGP propagation
mechanism for such scenarios. BGP is basically a p2mp distribution protocol
and we need to be careful how far we bend it for other purposes.

Thanks,
Ketan


On Sat, Apr 8, 2023 at 6:51 AM [e-mail] <
[e-mail]> wrote:

> Hello Ketan,
>
> I understand the objective and the current text do satisfy the objective.
> What I point out is the issue the objective has and the current text should
> be refined.
>
> suppose a  RR has 100 peers, and 10 SR policies are to be configured on
> each peer. Follow the current text, RR will reflect 1000 SR policies to
> each peer and only 1% is needed.
>
> ------------------------------
> Best Regards,
> Zhenqiang Li
>
> [e-mail]
>
>
> *From:* Ketan Talaulikar <[e-mail]>
> *Date:* 2023-04-06 18:29
> *To:* [e-mail]
> *CC:* draft-ietf-idr-segment-routing-te-policy.authors
> <[e-mail]>; [e-mail];
> idr-ads <[e-mail]>; idr-chairs <[e-mail]>
> *Subject:* Re: Clarifications on draft-ietf-idr-segment-routing-te-policy
> Hi Zhenqiang Li,
>
> The objective was not to change the base BGP decision process or the BGP
> propagation rules for this SAFI. I hope that explains the current text.
>
> Thanks,
> Ketan
>
>
> On Thu, Apr 6, 2023 at 1:53 PM [e-mail] <
> [e-mail]> wrote:
>
>> Hello authors and all,
>>
>> Hope it is not too late to make clarifications on this draft.
>>
>> This draft says one or more IPv4 address format route target extended
>> community attached to the SR Policy advertisement and that indicates the
>> intended headend of such an SR Policy advertisement.
>> And a BGP node advertises a received SR Policy NLRI to its IBGP neighbors according
>> to normal IBGP propagation rules.
>>
>> Here a BGP node can be a RR(Route Reflector) which will reflect all the
>> SR Policies to its IBGP peers regardless of the route target attached to
>> the policies. So the IBGP peer node as the headend will receive lots of
>> policies that are not intended for it because those policies have no route
>> target that indicates the received peer node.
>>
>> In my opinion, the rules for RR to reflect SR policy with route target
>> SHOULD be enhanced. RR SHOULD reflect related policies to relevant peers
>> according to the route target attached to the policies.
>>
>> ------------------------------
>> Best Regards,
>> Zhenqiang Li
>>
>> [e-mail]
>>
>>