Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-02.txt

["John G. Scudder" <[e-mail]>]

Hi Rajiv,

In reviewing draft-ietf-idr-bgp-bestpath-selection-criteria-07, I note section 3 has:

   The mechanism(s) to perform the "path availability" check and the
   selection of particular data plane are a matter of a policy and
   outside the scope of this document.

RS-BFD represents an instance of a specific path availability check and selection of data plane. Based on that, it seems to me the RS-BFD could add something like the following in the introduction:

   [I-D.ietf-idr-bgp-bestpath-selection-criteria] discusses enhancement
   of the route resolvability condition of section 9.1.2.1 of [RFC4271]
   to include next hop reachability and path availability checks.  This
   specification represents in part an instance of such, implemented
   using BFD as the OAM mechanism.

If you have other suggestions for text, please send them.

Thanks,

--John

> On Jul 6, 2017, at 12:54 AM, Rajiv Asati (rajiva) <[e-mail]> wrote:
> 
> Jeff, John,
>  
> I didn’t see the latest -03 addressing the below. Any plans?
>  
> -- 
> Cheers,
> Rajiv  
>  
> From: Rajiv Asati <[e-mail]>
> Date: Sunday, April 16, 2017 at 3:42 PM
> To: Jeffrey Haas <[e-mail]>
> Cc: "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>
> Subject: Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-02.txt
>  
> Hi Jeff,
>  
>  
>>    But more importantly, you'll stop sending it toward your own peering and
>>    attracting blackholed traffic.
> Indeed. That’s key. 
>  
> And it could rely on the route resolvability condition to be appropriately modified, as described in  
> https://tools.ietf.org/html/draft-ietf-idr-bgp-bestpath-selection-criteria.
>  
>>     RS-BFD basically reinvents the same procedure in your draft, simply being
>>     specific about the use of BFD as the dataplane liveness check mechanism.
>>     However, as you note in the RS-BFD draft, we do leave the option for other
>>     mechanisms.
>>  
>>     I suspect the other authors of RS-BFD aren't particular where we pick up our
>>     text for the resolvability condition.  However, if the suggestion is to make
>>    a reference to your draft, you'll need to bring it back from zombie state
>>     and progress it. :-)
>  
> Agreed. It is alive (-07 version). https://tools.ietf.org/html/draft-ietf-idr-bgp-bestpath-selection-criteria-07
> It can be used as a normative reference in your draft. 
>  
> -- 
> Cheers,
> Rajiv Asati
> Distinguished Engineer, Cisco
>  
> -----Original Message-----
> From: Jeffrey Haas <[e-mail]>
> Date: Tuesday, March 14, 2017 at 5:36 PM
> To: Rajiv Asati <[e-mail]>
> Cc: "[e-mail]" <[e-mail]>, "[e-mail]" <[e-mail]>
> Subject: Re: [Idr] I-D Action: draft-ietf-idr-rs-bfd-02.txt
>  
>     Rajiv,
>     
>     On Tue, Mar 14, 2017 at 09:08:24PM +0000, Rajiv Asati (rajiva) wrote:
>     > Is the assumption here that the client routers have routing view limited to what’s provided by the Route Server? If not, then wouldn’t Client Routers benefit from having to invalidate the path learned from the remote client router as soon as the connectivity check failed?
>     
>     This is what I believe the procedure says.  See section 6.
>     
>     > Of course, Client Routers conveying the lack of NLRI reachability per NH to the Route Server, and expecting Route Server to provide a different NHs of the NLRIs, and expecting it to be functional, while still attracting the traffic for unreachable destinations since the Loc-RIB is still pointing to the unreachable NH for the affected NLRIs.
>     
>     The thing that is somewhat different for a IXP environment running a route
>     server than normal eBGP is the low (to zero) likelihood of having a backup
>     path.  If 10/8 was learned from the route server for nexthop 192.0.2.1, and
>     you stop being able to reach that nexthop, removing it from your forwarding
>     (unreachable) is your only choice.
>     
>     You *might* have a source of that path internally.  In that case, you can
>     use it.
>     
>     But more importantly, you'll stop sending it toward your own peering and
>     attracting blackholed traffic.
>     
>     > I wonder whether  https://tools.ietf.org/html/draft-ietf-idr-bgp-bestpath-selection-criteria be useful here.
>     
>     In a sense of good timing, John Scudder had brought this to my attention
>     about an hour ago. 
>     
>     RS-BFD basically reinvents the same procedure in your draft, simply being
>     specific about the use of BFD as the dataplane liveness check mechanism.
>     However, as you note in the RS-BFD draft, we do leave the option for other
>     mechanisms.
>     
>     I suspect the other authors of RS-BFD aren't particular where we pick up our
>     text for the resolvability condition.  However, if the suggestion is to make
>     a reference to your draft, you'll need to bring it back from zombie state
>     and progress it. :-)
>     
>     -- Jeff
>     
>  
>