Re: [bess] Comments on draft-ietf-bess-mvpn-expl-track-03

[Eric C Rosen <[e-mail]>]

I apologize for the delay in answering this message.

On 12/21/2017 4:22 AM, Xiejingrong wrote:
>
> I have a comment on draft-ietf-bess-mvpn-expl-track-03.
>
> The chap 5.3 of this document said:
>
> Furthermore, if the PTA specifies "no tunnel info", the LIR and LIR-pF
>
> flags in the PTA MUST be passed along unchanged.
>
>    This will ensure that an egress ABR/ASBR only sends a Leaf A-D route
>
>    in response to a "match for tracking" if it is on the path to an
>
>    egress PE for the flow(s) identified in the corresponding S-PMSI A-D
>
>    route.
>
> The issue is as follow:
>
> In a [IngressPE--EgressABR--EgressPE] topology, IngressPE send a 
> Wildcard S-PMSI(*,*) route with PTA(flag<LIR+LIR-pF>), whose NLRI is 
> donated as  SPMSI(type<0/1/2>RD,*,*,IngressPE). This SPMSI route will 
> be relayed by EgressABR to EgressPE with PTA flag untouched. Then 
> EgressPE will generate ONE LeafAD route with 
> NLRI(type<0/1/2>RD,*,*,IngressPE,EgressPE) and RT<EgressABR> and 
> N(N>=0) LeafAD routes with 
> NLRI(type<16/17/18>RD,S,G,IngressPE,EgressPE) and RT<EgressABR>. All 
> according to chap 5.2 of this document.
>
> Then according to chap 5.3  of this document:
>
> IngressABR will only send a Leaf A-D route, It should be the ONE of 
> LeafAD(type<0/1/2RD,*,*,IngressPE,EgressABR) with RT<IngressABR>.
>

In the example above, there is an "EgressABR" but not an "IngressABR".  
So I'm not completely sure that I understand your question.

> Then how should IngressABR deal with the the N(N>=0) LeafAD routes 
> with NLRI(type<16/17/18>RD,S,G,IngressPE,EgressPE) and RT<EgressABR> ?
>
> It is not clarified in RFC7524 either. See chap 7.1 of RFC7524, which 
> only clarify LeafAD route with type<0/1/2>RD.
>
> Should such LeafAD route with type<16/17/18>RD be accepted and 
> installed by EgressABR, and then ‘relay’ back to IngressPE, and thus 
> enable IngressPE explicit tracking inside the ingress “segmentation 
> domain” ?
>

The intention is the following.  Suppose an egress ABR/ASBR satisfies 
the following two conditions:

1. It has installed an S-PMSI A-D route  with the following properties:

- its NLRI has wildcards for S and G,
- its NLRI specifies PE1 as the ingress PE,
- its PTA specifies "no tunnel info" and has LIR-pF set.

2. It has installed one or more Leaf A-D routes whose NLRI specifies 
(S,G) with PE1 as ingress PE

Then the ABR/ASBR should originate a Leaf A-D route (with RD type 
16/17/18) specifying (S,G) with ingress PE1.
The Leaf A-D route would be withdrawn when one of these conditions no 
longer holds.

Does this answer your question?