1. Henning Schulzrinne Dept. of Computer Science Columbia University
XCON data modeling – NETCONF, RDF and others draft-schulzrinne-sipping-emergency-req-01 draft-sipping-sos
Henning Schulzrinne
Dept. of Computer Science
Columbia University
XCON - IETF 62 (March 2005) - Minneapolis

2. XCON - IETF 62 (March 2005) - Minneapolis
Executive summary
XCON is an instance of a standard problem  avoid the IETF tendency to create one-off protocols
excusable a decade ago, recipe for delay now
Provide both “semantic” (tightly constrained) and user interface-oriented interface
Use XForms where user interface is needed
Consider NETCONF for object content manipulation and state retrieval
XCON - IETF 62 (March 2005) - Minneapolis

3. Data representation models
Document model
structured document
RPC model
set/get variables
Data models
RDF
NETCONF
user-interface oriented
XCON - IETF 62 (March 2005) - Minneapolis

4. “Semantic” description
Tightly described set of properties
No expectation that user interface would directly correspond to each element
No I18N issue  application maps description elements to UI elements in appropriate language
translation into other languages done by client
and may derive some parts through local policy, rather than user input
Well-defined extension policy
XCON - IETF 62 (March 2005) - Minneapolis

5. XCON - IETF 62 (March 2005) - Minneapolis
RDF
“Resource Description Framework (RDF) is a language for representing information about resources in the World Wide Web.”
describing resources in terms of simple properties and property values
XCON - IETF 62 (March 2005) - Minneapolis

6. XCON - IETF 62 (March 2005) - Minneapolis
RDF, cont’d.
W3C RDF primer
XCON - IETF 62 (March 2005) - Minneapolis

7. XCON - IETF 62 (March 2005) - Minneapolis
RDF/XML example
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="
xmlns:contact="
<contact:Person rdf:about="
<contact:fullName>Eric Miller</contact:fullName>
<contact:mailbox
<contact:personalTitle>Dr.</contact:personalTitle>
</contact:Person>
</rdf:RDF>
identifies the thing = subject (a URI)
property = predicate
value = object
W3 RDF primer
XCON - IETF 62 (March 2005) - Minneapolis

8. XCON - IETF 62 (March 2005) - Minneapolis
More about RDF
Generally, “meta data”
RSS is most common usage
Also used in Composite Capabilities/Preferences Profile (CC/PP)
Has schema-like capability to describe vocabularies
Allows trees with nodes and relationships (“is-a”, “has”)
XCON - IETF 62 (March 2005) - Minneapolis

9. XCON - IETF 62 (March 2005) - Minneapolis
RDF: evaluation
Good
limited parameter-value expressiveness
type definition
tools available
Bad:
static document, does not define protocol to get/set elements
would need XCAP, XPath or similar
XCON - IETF 62 (March 2005) - Minneapolis

10. XCON - IETF 62 (March 2005) - Minneapolis
NETCONF
“The NETCONF protocol defines a simple mechanism through which a network device can be managed, configuration data information can be retrieved, and new configuration data can be uploaded and manipulated. The protocol allows the device to expose a full, formal, application programming interface (API).”
Defined to run over HTTP, BEEP, UDP, …
XCON - IETF 62 (March 2005) - Minneapolis

11. XCON - IETF 62 (March 2005) - Minneapolis
NETCONF, cont’d.
content
configuration data
operations
<get-config>
<edit-config>
RPC
<rpc>
<rpc-reply>
application
protocol
BEEP, SSH, SSL
XCON - IETF 62 (March 2005) - Minneapolis

12. XCON - IETF 62 (March 2005) - Minneapolis
NETCONF
Data =
configuration data = writable  <get-config>
state data = read-only, statistics  <get>
Leaves privacy and authentication to transport layer
Supports Xpath and subtree filtering
Supports multiple “data stores”
default <running>
<candidate> allows incremental update + commit
XCON - IETF 62 (March 2005) - Minneapolis

13. XCON - IETF 62 (March 2005) - Minneapolis
NETCONF RPC
<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<rock-the-house xmlns="
<zip-code> </zip-code>
</rock-the-house>
</rpc>
<rpc-reply message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<some-content>
<!-- contents here... -->
</some-content>
</rpc-reply>
XCON - IETF 62 (March 2005) - Minneapolis

14. NETCONF – subtree filtering
<rpc message-id="101" xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<get-config>
<source>
<running/>
</source>
<filter type="subtree">
<top xmlns="
<users/>
</top>
</filter>
</get-config>
</rpc>
XCON - IETF 62 (March 2005) - Minneapolis

15. XCON - IETF 62 (March 2005) - Minneapolis
NETCONF operations
get
Retrieve all or part of state + configuration
get-config
Retrieve all or part of a specified configuration.
edit-config
merge/create/replace/delete; with possible roll-back
copy-config
completely replaces configuration
delete-config
delete a configuration datastore
lock
lock configuration data store
unlock
unlock configuration data store
close-session
graceful termination; releases locks
kill-session
abort connection
XCON - IETF 62 (March 2005) - Minneapolis

16. NETCONF capabilities advertisement
<hello xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
<capabilities>
<capability>
urn:ietf:params:xml:ns:netconf:base:1.0
</capability>
urn:ietf:params:xml:ns:netconf:base:1.0#startup
</capabilities>
<session-id>4</session-id>
</hello>
XCON - IETF 62 (March 2005) - Minneapolis

17. User-interface oriented
Describe suggested rendering on controlling client without client knowing meaning of controls
element names are just labels
e.g., can’t gateway to other systems based on equivalence
user interface can change at any time
Element names are text strings, not XML elements
no schema verification possible
XCON - IETF 62 (March 2005) - Minneapolis

18. User-interface oriented
Client software does not need to understand meaning of terms – just variables and prompts
includes necessary prompts and structure
needs to be translated into different languages by server
Existing work: XForms
Allows use of CSS to render on variety of devices
Allows use of JavaScript for client-side verification
Specifies type of control (“selection”), not rendering (“radio button”, “select list”)
Suggestion: allow as alternate representation
XCON - IETF 62 (March 2005) - Minneapolis

19. XCON - IETF 62 (March 2005) - Minneapolis
XForms example
<h:html xmlns:h=" xmlns="
<h:head>
<h:title>Search</h:title>
<model>
<submission action="
method="get" id="s"/> </model>
</h:head>
<h:body>
<h:p>
<input ref="q"><label>Find</label></input>
<submit submission="s"><label>Go</label></submit>
</h:p>
</h:body>
</h:html>
XCON - IETF 62 (March 2005) - Minneapolis

20. XCON - IETF 62 (March 2005) - Minneapolis
Conclusion
If desired, XForms provides rich user interaction environment
NETCONF provides flexible configuration retrieval mechanism, with extensibility
incremental configuration + commit
stored configurations (startup, running, candidate)
XPath and subtree selection
no constraints on configuration content
XCON - IETF 62 (March 2005) - Minneapolis