Re: [Netconf] schema capabilities in hello

[Jan Lindblad <[e-mail]>]

Mikael,

> I received a question I couldn't answer. It was regarding capabilities exchange in hellos:
> 
> https://tools.ietf.org/html/rfc6241#section-8
> 
> It seems common way of doing this is to list all schemas as "capabilties". The person asking the question said one vendor did not list all schemas in capabilities, and one NMS they were trying out relied on the schemas being listed in the hello, for discovery.
> 
> Looking at above URL from the NETCONF RFC, one might imply that it only talks about netconf capabilities, not what schemas it supports. Yet, most implementations seem to list all schemas in their hellos.

NETCONF does not require this, but YANG 1.0 does. See RFC 6020 sec 5.6.4.

> So which one is correct here? My immediate reaction is that it's kind of "bloated" to list 1000 schemas (or more) in the hello, and that the schemas supported is something that shouldn't need to be exchanged every time one connects to the device.

Right. This development has been noted by the NETCONF and NETMOD WGs as well, so in YANG 1.1 this is radically changed. Instead of listing all namespaces in hello, they are listed in a YANG data structure called ietf-yang-library. See RFC 7950 sec 5.6.4 and RFC 7895.

/jan