---- Original Message -----
From: "Ladislav Lhotka" <[email protected]>
To: "t.petch" <[email protected]>; "Susan Hares" <[email protected]>;
"'Edward Crabbe'" <[email protected]>; <[email protected]>
Sent: Thursday, April 24, 2014 3:27 PM
> "t.petch" <[email protected]> writes:
> > ----- Original Message -----
> > From: "Susan Hares" <[email protected]>
> > To: "'t.petch'" <[email protected]>; "'Edward Crabbe'"
> > <[email protected]>; <[email protected]>
> > Sent: Wednesday, April 23, 2014 5:21 PM
> >> Tom:
> >>
> >> 100% agree with your comments. I2RS cares whether it is read-only
or
> >> read-write. My work toward the revision found:
> >>
> >> - RBNF RBNF did not even allow you a place to r/w or r-only or
> > permissions
> >> (needed for security, but that's my next draft).
> >> - The yang tree I wrote was r-w for config, but did not express the
> > ro-only
> >> tree. I wanted some feedback to figure out why I had 2 write 2
trees.
> >> (your telling me it is a yang short-coming).
> >
> > Sue
> >
> > That is a feature of YANG. Spend half a day on the netmod WG
archives
> > for 1H2013, particularly May and June and for interfaces-cfg, and
all
> > will be clear.
> >
> > As Ladislav said on 2May13,
> >
> > "In the current model, the operational state data are not present
unless
> > the corresponding entry in the "interface" list is *configured*. So,
> > what I have in mind is a data tree like this: ..."
> >
> > That is, 'config false' nodes under a 'config true' node do not get
> > instantiated in the data model unless and until the 'config true'
node
> > is configured. So if you have the one routing table, you will be
unable
>
> This issue only affects 'config false' data appearing in the subtree
of a 'config true' node.
> In my opinion, such a data organisation should be generally avoided,
and that's why we now have configuration and state data in separate
trees.
>
> > to see the routes learnt via BGP - 'config false' - unless and until
you
> > configure the table by creating a static route - 'config true'.
>
> Note this has never been the case in the ietf-routing module. Routing
tables (later renamed to ribs) were always "pure" state data and the
default rib for every address family is supposed to be present
independently of any configuration.
>
> >
> > It is a tenet of YANG so fundamental, so basic, that I know of
nowhere
> > where it is written down:-(
>
> Please see the definitions of system-controlled versus user-controlled
list entries in sec. 4.1 of draft-ietf-netmod-routing-cfg-13.
Lada
I find the I-D slightly inconsistent and incomplete on this matter.
I find it inconsistent in its definition of user-controlled entry.
s2.1 " user-controlled entry: An entry of a list in operational state
data
("config false") ... "
versus
s4.1 " Additional entries may be created in the configuration by the
user
via the NETCONF protocol. These are so-called user-controlled
entries. "
where configuration means, to me, configuration which is then not
operational state.
Also in s4.1 " Deleting a user-controlled entry from the configuration
list results .........."
suggests to me again that user-controlled entries can appear in the
configuration.
Given the length and quantity of discussion on this issue over the
years, I think that precision is called for. I am easy as to whether
user-controlled entries can appear in configuration and operational
state, or only in operational state, but think that the I-D needs to be
precise and consistent. If you take the latter option, then you
probably need a new term to describe entries in a configuration list
that correspond to entries in an operational state list in order to
specify the interactions arising from operations on the entry in the
configuration.
Separately, most discussions, although not all I-Ds, split two ways,
into configuration and state and may then subdivide state into
operational state and read-only statistics. This I-D seems not to allow
for read-only statistics, and seems to use state and operational state
interchangeably. Again, I think that precision is called for. I2RS may
be interested in statistics.
And the point I first raised, of when state is instantiated in the data
model, I do not see covered here (not that I was too hopeful that it
would be:-(
As you say, above,
> This issue only affects 'config false' data appearing in the subtree
of a 'config true' node.
but given the quantity of discussion arising from it a year ago, I still
think that it is a pitfall that should be written down.
I keep this on the I2RS list since I imagine that these issues may arise
as and when YANG is used to create I2RS models.
Tom Petch
<snip>
> I also think think is no idiosyncrasy of YANG, just the way how most
systems and their CLIs work.
>
> Lada
>
> >
> > Tom Petch
> >
> >> Ladislav Lhotka, CZ.NIC Labs
> PGP Key ID: E74E8C0C
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