1. “with-defaults” capability in NETCONF
Balazs Lengyel, Ericsson
Andy Bierman
draft-ietf-netconf-with-defaults-03
IETF-76 Hiroshima, 2009 November

2. Problem Different network elements handle defaults differently
We want flexible and predictable behavior
We must leave optionality as we can’t force the world to converge
Default data may or may not be stored in the datastore

3. Define Default Default data: Data that is
Defined as default in YANG
Set or used by the network element
Not set by the manager
Explicit default: data set by the manager with a real management operation to its YANG default value
e.g. using <edit-config>, CLI, SNMP, GUI

4. Examples of a Server Provided Data
DEFAULT data CAN be:
- documented as yang default and stored in datastore
- documented as yang default and not stored in datastore
Server created REAL data CAN be
- documented as yang description and stored in datastore,
may or may not be essential for the workings of the system
- factory default setting used after initial load or delete-config
Server provided data CAN NOT be:
- documented as yang description and not stored in datastore

5. Effects of a default Is it part of the datastore?
How the node really works
What is returned in <get-config>/<get>?
With-defaults report-all/trim/explicit
Does <edit-config> create/delete succeed or fail?
Intentionally left undefined to accommodate differing existing nodes
Are non-presence containers present?
Must/When/Reference constraints?
Defaults always considered

6. Default Handling in the Real World
Report all: All default data is always reported.
Trim: Values are not reported if they match the default.
Explicit: Report values if they are explicitly set.
One of the above based on user choice
Etc.

7. Thank you for your response
Receive 439 s on 10 pages of content
More then 20 times the amount of the original text

8. Changes Changed definition of default data !!!!!!!
XSD and YAM marked <CODE BEGINS>…<CODE ENDS>

9. Open Issues Shall we make this mandatory as report-all is important?No
Shall the basic mode be configurable?
Yes, add it to Netconf-Monitoring data model?

10. Open Issues Shall we make explicit mandatory
No, it requires a change in the underlying database
1 bit of extra storage is cheap, BUT adapting an existing database and handling logic is EXPENSIVE
Makes adapting existing device to Netconf much more costly
Ericsson would hate you for it 

11. Open Issues
Shall we make 3 features/capabilities instead of using parameters
No this is more simple
Shall we speak of operations/operation replies instead of rpcs/rpc-replies?
No, other drafts/rfcs also speak about rpc- replies, why introduce new terminology
Yes, it is more correct

12. Open Issues Shall we wait for YANG and 4741bis to make YANG mandatory?
Yes: Andy, Juergen, Phil, Martin, Lada
No it might take a long time especially 4741bis

13. Thank You