Hi Sasha,
Although we are providing the same or better functionality, we never had 
mimicking the RFC 4292 MIB structure as a requirement. IMO, this would be a 
mistake since SNMP doesn’t allow nesting of tables while YANG, OTOH, supports 
arbitrary nesting of schema. We really must exploit this key advantage in our 
models.

Thanks,
Acee

From: Alexander Vainshtein <[email protected]>
Date: Wednesday, April 3, 2019 at 3:14 AM
To: Acee Lindem <[email protected]>, Ladislav Lhotka <[email protected]>
Cc: Routing WG <[email protected]>, "[email protected]" <[email protected]>
Subject: RE: Doubts about static routes in RFC 8349 (was: Doubts about static 
routes in RFC 8022)

Acee,
Lots of thanks for a prompt response with a highly relevant pointer.

I will read 
draft-ietf-rtgwg-yang-rib-extend<https://tools.ietf.org/html/draft-ietf-rtgwg-yang-rib-extend-01>
 and probably send more questions.

Meanwhile, could you please explain the rationale for changing the data model 
that has been defined in RFC 4292 (where both the destination prefix and the 
next hop have been parts of the index in the appropriate MIB table) ?

The side effect of this change is  that it is not backward-compatible with 
multiple existing RFC 4292-compliant RIB implementations:

-          Retrieval of such a RIB using YANG requires a stateful mapper that 
merges multiple RIB entries with the same destination prefix and different 
“simple” NH into a single entry with the next-hop-list

-          Configuration of a single static route that uses the next-hop-list 
requires a mapper that splits such a list into multiple 4292-compliant routes 
(simpler than merge, but still non-trivial IMHO).

Regards,
Sasha

Office: +972-39266302
Cell:      +972-549266302
Email:   [email protected]

From: Acee Lindem (acee) <[email protected]>
Sent: Tuesday, April 2, 2019 7:45 PM
To: Alexander Vainshtein <[email protected]>; [email protected]
Cc: [email protected]; [email protected]
Subject: Re: Doubts about static routes in RFC 8349 (was: Doubts about static 
routes in RFC 8022)

Hi Sasha,
You are correct that there is no per-next-hop preference in the current model. 
However, this is included in the augmentation in 
draft-ietf-rtgwg-yang-rib-extend.
Thanks,
Acee

From: Alexander Vainshtein 
<[email protected]<mailto:[email protected]>>
Date: Tuesday, April 2, 2019 at 9:53 AM
To: Acee Lindem <[email protected]<mailto:[email protected]>>, Ladislav Lhotka 
<[email protected]<mailto:[email protected]>>
Cc: Routing WG <[email protected]<mailto:[email protected]>>, 
"[email protected]<mailto:[email protected]>" 
<[email protected]<mailto:[email protected]>>
Subject: Doubts about static routes in RFC 8349 (was: Doubts about static 
routes in RFC 8022)

Hi all,
I have noticed that 8022 has been obsoleted by RFC 8349. But it has exactly the 
same problem.

Regards,
Sasha

Office: +972-39266302
Cell:      +972-549266302
Email:   
[email protected]<mailto:[email protected]>

From: Alexander Vainshtein
Sent: Tuesday, April 2, 2019 3:57 PM
To: '[email protected]' <[email protected]<mailto:[email protected]>>; '[email protected]' 
<[email protected]<mailto:[email protected]>>
Cc: '[email protected]' <[email protected]<mailto:[email protected]>>; '[email protected]' 
<[email protected]<mailto:[email protected]>>
Subject: Doubts about static routes in RFC 8022
Importance: High

Acee, Ladislav and all,
I have serious doubts regarding the data model for static routes in RFC 8022.

As I see it, the data model defined in this document does not support multiple 
routes with common destination, different next hops and different route 
preferences.

This is because only route destination is considered as the key in the RIB in 
Appendix A of RFC 8022., while route preference is a per-route read-only leaf 
in the data model.

In particular (and this was my original problem) , it is possible to configure 
a static route with multiple next hops (using the next-hop-list construct) 
using the data model defined in RFC 8022, but all the next hops in this 
construct would have the same preference. AFAIK, many (if not all) deployed 
implementations support ability to configure static routes with the same 
destination, different next hops and different preferences, so that one of 
these next hops would act as a protection of the other.

For the reference, this problem does not exist in the standard MIB for the RIB 
(RFC 4292), because it includes both the route destination and its next hop in 
the list  of indices in the corresponding MIB.

What, if anything, did I miss?

Regards, and lots of thanks in advance,
Sasha

Office: +972-39266302
Cell:      +972-549266302
Email:   
[email protected]<mailto:[email protected]>


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