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NETMOD Architecture
Phil Shafer
[email protected]
IETF 72
Components of NETMOD
• YANG
– Data modeling language and semantics
– Hierarchy of nodes
– Constraints on those nodes
• Mapping rules of YANG to XML
– Content on the wire
• YIN (XML-based syntax for YANG)
– Semantically equivalent, fully reversible, XML-based syntax
• Same content, different format: more "<"s and ">"s
– YIN is simply the data model in an XML syntax
• Can be manipulated using existing XML tools (e.g., XSLT)
• Mapping rules of YANG to DSDL
– Including annotations for DSDL to preserve top-level semantics
• Standard type library for use by YANG
– yang-types.yang in draft-netmod-yang
Building Network Mgmt
Solutions with YANG
• NETCONF content defines two players:
• Clients (Managers, Applications)
• Servers (Agents, Devices)
• NETCONF content can be handled in two
ways:
• Specific: hardcoded
• Generic: driven by meta-data
• YANG modules define machine-readable,
human-oriented models which support the
needs of all four areas
Where does YANG fit?
Tells the app developer what
the data can be modeled
Specific App
Generic App
Tells the app's XML handler
how to parse/build content
Defines XML on the wire
Generic Device
Tells the device parser how
to parse/build content
Specific Device
Tells the device developer
what the model requires
Things you can generate from YANG
• IDL Code generators (stubs)
– Structure/Object definitions
– Serializers, deserializers, etc
– Specific code to enforce constraints
• Database table definitions (SQL "create table" statements)
• Meta-data
– Drive CLI operation (completion, validation, etc)
– Drive database instance creation
• Documentation
– API Docs
– Release notes
• UI Definitions
– Support for Web pages
• XSLT, XUL, SVG, VRML
Building Network Mgmt
Solutions with YANG
Some selected use cases:
1)
2)
3)
4)
Device developer / native implementation
On-device DSDL validation
Generic browser
VPN application developer
First Step:
Write the YANG Module
YANG
Modules
• Models are written in YANG
• Both standard and proprietary
content are supported
• YANG is canonical form of model
Use Case #1:
Device developer
YANG
Modules
• Developer reads the models
• Write code to support the
model
– Uses model's hierarchy
– Enforces model's constraints
Device
Impl
• Transforms model view into
device implementation, if
needed
Use Case #2:
On-device DSDL validation
YANG
Modules
Config
DSDL
Schema
Files
Device
• Compile YANG using toolset
• Generate DSDL schema files
• Device uses schema to
validate configuration data
– As data arrives in NETCONF
operations, it can be checked
– At validation time (commit), the
entire config can be validated
• DSDL can enforce hierarchy
and many YANG constraints
Use Case #3:
Generic Browser
YANG
Modules
YIN files
App
Config
XSLT files
• Compile YANG using toolset
• Generate YIN files
• Use XSLT to transform YIN
into XSLT files
• Use XSLT files to generate
web pages for web-based
config browser
– Config -> [XSLT] -> XHTML
Use Case #4:
VPN Application
YANG
Modules
• Developer reads the models
• Write code to support the model
– Uses model's hierarchy
– Enforces model's constraints
VPN App
Impl
• Transforms model into user-oriented
view of VPNs
• Uses generic YANG/ NETCONF
library to send/recv data from the
device, but uses VPN-cognoscent
code to manipulate config data
Deliverables
• Architecture document
• Informational RFC
• YANG data modeling language and semantics
– P roposed Standard
• Mapping rules of YANG to XML
– Proposed Standard
• YIN (XML-based syntax for YANG)
– Proposed Standard
• Mapping rules of YANG to DSDL
– Proposed Standard
• Standard type library for use by YANG
– Proposed Standard