Re: [netmod] Doubts about static routes in RFC 8349

Martin Bjorklund <mbj@tail-f.com> Wed, 03 April 2019 11:56 UTC

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Subject: Re: [netmod] Doubts about static routes in RFC 8349
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"Acee Lindem (acee)" <acee@cisco.com>; wrote:
> Hi Sasha, 
> 
> On 4/3/19, 7:27 AM, "Alexander Vainshtein"
> <Alexander.Vainshtein@ecitele.com>; wrote:
> 
>     Martin,
>     Lots of thanks for a prompt response.
>     
>     My reading of your response is that, if you need multiple static
>     routes with the same destination but different next hops, you
>     configure them as a single route with next-hop-list, but what you see
>     when you retrieve the RIB may be multiple individual routes, each with
>     its own simple next hop. Or it may be something else, since no keys
>     have been defined in the read-only representation of the RIB.
>     
>     Is my reading correct?
> 
> No - you'd see a single route and next-hop-list with the alternatives
> when it is retrieved.

Do you think it would be a violation of the spec if an implementation
expanded this into several route entries?  If yes, is this specified?


/martin



>  
> Thanks,
> Acee
>  
>     
>     Regards, and lots of thanks in advance,
>     Sasha
>     
>     Office: +972-39266302
>     Cell:      +972-549266302
>     Email:   Alexander.Vainshtein@ecitele.com
>     
>     
>     -----Original Message-----
>     From: Martin Bjorklund <mbj@tail-f.com>; 
>     Sent: Wednesday, April 3, 2019 2:05 PM
>     To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>;
>     Cc: acee@cisco.com; lhotka@nic.cz; netmod@ietf.org; rtgwg@ietf.org
>     Subject: Re: [netmod] Doubts about static routes in RFC 8349
>     
>     Hi,
>     
>     
>     Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>; wrote:
>     > Martin,
>     > 
>     > Lots of thanks for an interesting input.
>     > 
>     > I have noticed that Appendix A in RFC
>     > 8349<https://tools.ietf.org/html/rfc8349#appendix-A>  defines the key 
>     > for static IPv4 and IPv6 unicast routes as “destination-prefix”.
>     
>     Right (to be precise, the key is defined in the YANG models in section
>     8 and 9).
>     
>     
>     > draft-ietf-rtgwg-
>     > yang-rib-extend<https://tools.ietf.org/html/draft-ietf-rtgwg-yang-rib-
>     > extend-01> claims that it augments the model defined in 8349, 
>     > therefore, to the best of my understanding, it uses the same key for 
>     > station IPv4 and
>     > IPv6 unicast routes.
>     
>     Correct.
>     
>     
>     > At the same time Appendix A in this draft does not define any keys for
>     > the read-only RIB.
>     > 
>     > Can you explain this controversy?
>     
>     Not sure there's a controversy.  The static route list is how you
>     configure static routes, and the RIB is the operational state of all
>     routes (static and others).  Two different things.
>     
>     The MIB had a single table to show routes and write routes.  I don't
>     think the persistency of the routes you wrote into the MIB was
>     defined; perhaps these can be viewed as being "static".
>     
>     
>     /martin
>     
>     
>     > 
>     > 
>     > 
>     > Regards, and lots of thanks in advance,
>     > 
>     > Sasha
>     > 
>     > 
>     > 
>     > Office: +972-39266302
>     > 
>     > Cell:      +972-549266302
>     > 
>     > Email:   Alexander.Vainshtein@ecitele.com
>     > 
>     > 
>     > 
>     > -----Original Message-----
>     > From: Martin Bjorklund <mbj@tail-f.com>;
>     > Sent: Wednesday, April 3, 2019 1:34 PM
>     > To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>;
>     > Cc: acee@cisco.com; lhotka@nic.cz; netmod@ietf.org; rtgwg@ietf.org
>     > Subject: Re: [netmod] Doubts about static routes in RFC 8349
>     > 
>     > 
>     > 
>     > Hi,
>     > 
>     > 
>     > 
>     > Alexander Vainshtein
>     > <Alexander.Vainshtein@ecitele.com<mailto:Alexander.Vainshtein@ecitele.com>>
>     > wrote:
>     > 
>     > 
>     > 
>     > [...]
>     > 
>     > 
>     > 
>     > > 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
>     > 
>     > 
>     > 
>     > Note that the "route" list in the rib doesn't have any keys.  This
>     > means that you can report several entries with the same destination
>     > prefix.  So I think that this design is compatible with the MIB
>     > design.
>     > 
>     > 
>     > 
>     > 
>     > 
>     > 
>     > 
>     > /martin
>     > 
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