Re: [lisp] 6833bis - NMR with locator count !=0

["Victor Moreno (vimoreno)" <[e-mail]>]

> On Aug 22, 2017, at 10:22 AM, Dino Farinacci <[e-mail]> wrote:
> 
> Here are some of my comments Victor.
> 
>> Would be mainly conveying the RLOCs of the feasible PETRs dynamically.
> 
> Anything or anyone can register mapping entries to the mapping database as long as they are authenticated with the map-server. So I believe you can achieve what you want with NO spec changes or additions to the protocol.

That would be great, we’ve been trying and haven’t had luck.

> 
>> As PETRs are brought on-line in the network, they can be configured/added in the Mapping System, rather than touching a multitude of ITRs.
> 
> Meaning you do not want ITRs to have to configure PETRs. That makes a ton of sense for scale and management reasons.

Correct, we are looking at 1000s of ITRs in some of these networks.
> 
>> This would also allow a more elegant definition for the support of a default exit to the Internet in the Extranet case defined in the lisp-vpn draft. In this scenario, the RLOC record would convey the RLOC of the PETR plus the IID to which the Internet connects at the PETR.
> 
> An ITR has no idea where a packet really ends up. So if its encapsulating to an ETR at the destination site or a PETR that decaps and sends the packet many “native” hops to a non-EID destination, then so be it.

Correct, what is of interest is to have some sense of the likelihood of the mapping received changing and allow the ITR to check again. We are looking at the NMR as one way to indicate back to the ITR the nature of the mapping. Because the ITR can differentiate clearly between an NMR and a Positive MR, it can choose to treat the mappings differently. For example (maybe this is implementation specific) the cache-TTL assigned to the mapping received in an NMR may be in the order of minutes, vs. a mapping from a positive MR having a TTL in the order of hours..

> 
> I would not call these negative map-replies though. By definition, from the spec, a negative map-reply is a map-reply with an RLOC-count of 0. 

What I am after is a map reply with the characteristics of an NMR (short TTL, dynamically calculated covering prefix for non-EID destination), but an RLOC-count > 0. If there is a way to encode this with a Positive MR, then we are covered. 

> 
> What many implemenationsn do is when they get a map-reply with an RLOC set of 0, they then decide, via configuration to encapsulate to a list of xTRs. Those xTRs are PETRs (by definition of the implementation).

We are trying to avoid the “decide, via configuration, to encapsulate to a list of xTRs”, but still have the ITR give the map-cache a short TTL. 

> 
> It could be useful to write up a very short draft indicating a “dynamic use-case for PETRs”. But check the Interworking RFC to make sure we didn’t cover this, in some form (even brief) in that spec.

I can do that if it helps. It would be very very brief.

-v

> 
> Cheers,
> Dino
> 
>> 
>> -v
>> 
>>> On Aug 21, 2017, at 11:12 PM, Joel M. Halpern <[e-mail]> wrote:
>>> 
>>> Can you explain what information you are conveying with the RLOCs?  I think we would need a clear use case before changing the spec.
>>> 
>>> Yours,
>>> Joel
>>> 
>>> On 8/22/17 2:07 AM, Victor Moreno (vimoreno) wrote:
>>>> Dear WG,
>>>> As we put some of our specifications to the test in deployments, we have found the ability to return RLOCs dynamically in an NMR to be compelling in a variety of deployment scenarios. Particularly in Networks with multiple Internet exit points.
>>>> What are the thoughts of the group on allowing NMRs with a locator count !=0?
>>>> One option to indicate that a map-reply is an NMR could be to assign one of the reserved bits as an NMR flag.
>>>> Would like to gauge the inclination of the WG before proposing text/edits.
>>>> -v
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