Re: [Netconf] capability exchange

[Phil Shafer <phil at juniper.net>]

Martin Bjorklund writes:
>There is nothing that prevents us from requiring the client to
>advertise foo:1.1, if it is necessary.  So if foo:1.1 changes some
>semantics of foo:1.0, then we can say that the client MUST advertise
>foo:1.1, otherwise the agent will use the semantics of foo:1.0.

Brief history:  when capabilities were introduced, the idea was
that both sides would always advertise all there capabilities and
the overlapping set of capabilities would be what defines the
capabilities of the session.  So if both sides support the a new
revision of a capability, both sides can operate with an understanding
that the other side will do The Right Thing WRT this capability.

Useful, simple, elegant.

But someone objected and this idea turned into a rat's nest, so
during the Great Netconf Purge, this idea was discarded.

The post-Purge idea was that if you want the server to behave
differently, then the new capability should introduce a new RPC or
parameter to explicitly request this new behavior.

Personally, I'd be happy if 4741 reverts this to an "advertise all
your capabilities" strategy, so capabilities can more easily evolve
over time.

Thanks,
 Phil