PLNOG19 - Krzysztof Mazepa - Yang Development Kit – stwórz swój pierwszy program obsługujący urządzenia Cisco IOS XR/XE dzięki ułatwieniom jakie oferuje YDK

Krzysztof Mazepa
Consulting Systems Engineer
26 września 2017, Krakow
Yang Development Kit
– stwórz swój pierwszy program
obsługujący urządzenia Cisco
IOS XR/XE (i nie tylko) dzięki
ułatwieniom jakie oferuje YDK.
ydk.io

• Wprowadzenie
• Data Models
• Management Protocols
• Model-Driven APIs
• Demonstration
• Resources
• Conclusion
Agenda
Większość materiałów w tej prezentacji pochodzi z sesji Santiago Alvarez’a
BRKSPG-2303 Model-driven programmability for Cisco IOS XR.pdf

© 2017 Cisco and/or its affiliates. All rights reserved. Cisco Public 3
Motivations for Network Programmability
• Speed and scale demand software
automation and data analytics
• Rapid innovation as competitive
advantage
• One network operator per 1000s /
10000s of complex network devices

Controller
Orchestrator
Controller
Orchestrator
Device Programmability
Data Plane
Control Plane
Management Plane
App
Controller
Orchestrator
Data Plane
Control Plane
App
Data Plane
App

Model-Driven Programmability Stack
Encoding XML JSON GPB
Protocol NETCONF gRPCRESTCONF
Models
APIs
Apps
Model-Driven APIs
YANG Development Kit (YDK)
YANG Models
(native, open)
App App App
SSH HTTPTransport
Model-Driven
Configuration
Model-Driven
Telemetry

Benefits of Model-Driven Programmability
• Model based, structured, computer
friendly
• Multiple model types (native,
OpenConfig, IETF, etc.)
• Models decoupled from transport,
protocol end encoding
• Choice of transport, protocol and
encoding
• Model-driven APIs for abstraction and
simplification
• Wide standard support while leveraging
open source

Data Models
• Data (config and operational) and actions
(RPCs) in a tree structure
• Self-documented and shipped with devices
• Cisco IOS XR supports ~300 YANG
models (native and open) in release 6.2.1
• OpenConfig support includes BGP, routing
policy, interfaces, MPLS, telemetry, VLAN,
platform, RIB, local routing and terminal
device
• Native models provide most coverage
• OpenConfig and IETF models are mapped
to native models
Native / Common OpenConfig / IETF

Cisco IOS XR Native Data Models
• Provide most comprehensive coverage for device functionality
• Approximately ~300 models in XR 6.2.1 (700+ YANG files)
• A single model defines either configuration (cfg), operational state (oper) or an
action (act)
• Cisco-IOS-XR-ipv4-bgp-cfg.yang
• Cisco-IOS-XR-ipv4-bgp-oper.yang
• Cisco-IOS-XR-ipv4-bgp-act.yang
• Models posted at
• https://github.com/YangModels/yang/tree/master/vendor/cisco/xr
• https://github.com/YangModels/yang/tree/master/vendor/cisco/xe
• https://github.com/YangModels/yang/tree/master/vendor/cisco/nx

OpenConfig Data Models
• Operator group pursuing more dynamic and programmable networks
• Currently focused on vendor-neutral data models (YANG)
• Models designed by operators for operators
• Model coverage still limited, but model development rapidly evolving
• IOS XR 6.2.1 supports
• BGP, routing policy, RIB, local routing
• Interfaces, VLAN
• MPLS
• Telemetry
• Platform
• Terminal device (optical)
• Other new models in active development

Native vs Open Data Models
• Native data models provide most
configuration and operational
coverage
• Open models mapped to native data
models
• Departures from open models
specified as deviation module
Native Model
Open
Model
Native device
config/oper
data
Mapped
config/oper
data
Deviations

Native Data Models
Model Mapping
Open Data Models
Internal Datastore
Management Protocol
Model-Driven APIs
YANG Development Kit (YDK)
Open Model Mapping in IOS XR
• Model mapping converts open model
data to native model data and vice
versa
• Support for mapping config and
operational data (including telemetry)
• Single view of config and operational
data in internal datastore
• Planning to enable user defined
mapping (Model Mapping SDK)
Reference slide

YANG
• Modeling language for networking
• Defines data hierarchy (config or oper) and
RPCs
• Main node types
• Leaf – node with name, type and value (no
children)
• Leaf list – sequence of leafs (no children)
• Container – node that groups nodes and has
no type or value
• List – Series of data instances generally with
one or more keys
• Models extended through augmentations
• Unsupported nodes specified as deviations
Leaf
Node without type/value
Node with a type/value
Leaf list
Container List
key
Reference slide

YANG Model Example
container community-sets {
description “Container for community sets";
list community-set {
key community-set-name;
description "Definitions for community sets";
leaf community-set-name {
type string;
description "name of the community set";
}
leaf-list community-member {
type string {
pattern '([0-9]+:[0-9]+)';
}
description "members of the community set";
}
}
}
community-sets
community-set C-SET1
65172:1,
65172:2,
65172:3
!
65172:10,
65172:20,
65172:30
!
!
YANG CLI

Model Data Example
<community-sets>
<community-set>
<community-set-name>C-SET1</community-set-name>
<community-member>65172:1</community-member>
</community-set>
<community-set>
<community-set-name>C-SET10</community-set-name>
</community-set>
</community-sets>
community-sets
65172:1,
65172:2,
65172:3
!
65172:10,
65172:20,
65172:30
!
!
XML CLI

Model Data Example
community-sets
65172:1,
65172:2,
65172:3
!
65172:10,
65172:20,
65172:30
!
!
{ "community-sets": {
"community-set": [
{ "community-set-name": "CSET1",
"community-member": [
"65172:1",
"65172:2",
"65172:3" ]
},
{ "community-set-name": "CSET10",
"community-member": [
"65172:10",
"65172:20",
"65172:30" ]
}
]
}
}
JSON CLI
Reference slide

XML
NETCONF
NETCONF Protocol Overview
• Rich functionality to manage configuration
and operational (state) data
• Operations defined as RPCs (request /
reply) in XML
• Client/app initiate request towards
server/device
• Supports running, candidate and startup
configurations
• Capability exchange during session
initiation
18
YANG
SSH

Main NETCONF Protocol Operations
Operation Description
get-config Retrieve all or part of a specified configuration
edit-config
Loads all or part of a specified
configuration (merge, replace, create, delete,
remove)
copy-config Create or replace an entire configuration datastore
get
Retrieve all or part of running configuration and device
operational data
get-schema Retrieve device schema (model)
lock Lock entire configuration datastore (e.g. candidate)
unlock
Remove lock on entire configuration datastore (e.g.
candidate)
close-session Request graceful session termination
Reference slide

NETCONF Edit-Config Operations
Merge Merge configuration with existing configuration (default)
Replace Replace configuration with existing configuration
Create
Create configuration if non-existent. Otherwise, return
error. (non-idempotent*)
Delete
Delete configuration if non-existent. Otherwise, return
error. (non-idempotent)
Remove
Remove configuration. Ignore if configuration non-
existent.
* Cannot be applied multiple times without changing the result beyond the initial application
Reference slide

Cisco gRPC
CLIJSON
YANG
HTTP/2
Overview of gRPC on Cisco IOS XR
• Google RPC provides a general
(open source) RPC framework
• Interface definition in Cisco IOS XR
specifies device operations
• Functional subset of NETCONF
• Simple client development
• High performance
21
Reference slide

Protocol Operations in Cisco IDL
GetConfig Retrieve configuration
MergeConfig Merge configuration
DeleteConfig Delete configuration
ReplaceConfig Replace configuration
CommitReplace Replace entire configuration
GetOper Retrieve operational data
CliConfig Merge configuration data in CLI format
ShowCmdTextOutput Retrieves CLI show-command output data
Reference slide

Model-Driven APIs
• Simplify app development
• One-to-one correspondence between
model and class hierarchy
• Abstract protocol, transport, encoding,
modeling language
• API generated from YANG model
• Rich data validation
• Multi-language (Python, C++, Ruby,
Go, etc.)
YANG Model
Class Hierarchy
(Python, C++, Go)

YANG Development Kit
Services
Providers
Cisco
IOS XR
Models
OpenConfig
Models
IETF
Models
Services
Providers
YDK-Py
Python
YDK-Cpp
C++
Cisco
IOS XE
Models
Cisco
IOS XR
Models
OpenConfig
Models
IETF
Models
Cisco
IOS XE
Models

YDK API Structure
• Models group Python APIs created for
each YANG model
• Services perform operations on
model objects (interface)
• Providers implement services
(implementation)
26
Models
(BGP, IS-IS, etc)
Services
(CRUD, NETCONF, Codec, Executor, etc.)
Providers
(NETCONF, Codec, etc.)

Reference slide

YDK Client-Side Validation
• Client will automatically perform local
validation based on model constraints
• Check between type of data: config (read-
write) and state (read-only)
• Type check (enum, string, etc.)
• Value check (range, pattern, etc.)
• Semantic check (key
uniqueness/presence, mandatory leafs,
etc.)
• Model deviation check (unsupported leafs,
etc.)
Application
(client)
Device
(server)

A YDK-Py “Hello World” Using OpenConfig BGP
# Cisco YDK-Py OC-BGP “Hello world”
from ydk.services import CRUDService
from ydk.providers import NetconfServiceProvider
from ydk.models.openconfig import openconfig_bgp as oc_bgp
if __name__ == "__main__":
provider = NetconfServiceProvider(address=10.0.0.1,
port=830,
username=“admin”,
password=“admin”,
protocol=“ssh”)
crud = CRUDService() # create CRUD service
bgp = oc_bgp.Bgp() # create oc-bgp object
bgp.global_.config.as_ = 65000 # set local AS number
crud.create(provider, bgp) # create on NETCONF device
provider.close()
exit()
# End of script
module: openconfig-bgp
+--rw bgp
+--rw global
| +--rw config
| | +--rw as
| | +--rw router-id?
| +--ro state
| | +--ro as
| | +--ro router-id?
| | +--ro total-paths?
| | +--ro total-prefixes?
...

How to Get YDK-Py
Native Virtual Cloud
Install Python
Install YDK
Download ydk-py-samples
Install Vagrant
Install Virtualbox
Download ydk-py-samples
YANG Development Kit Sandbox

CRUD service
NETCONF provider
NETCONF
service
Codec service
deviations
Service
improvements
Better
error
handling
Bundles
(core, XR,
OC, IETF)
YDK Releases
C++
support
Bundle
updates0.3.0
Mar 2016
0.4.0
Apr 2016
0.4.1
May 2016
0.4.2
Jun 2016
0.5.0
Aug 2016
https://github.com/CiscoDevNet/ydk-gen/releases
Python 3
Bundle
updates
0.5.1
Oct 2016
0.5.2
Dec 2016
0.5.3
Jan 2017
RESTCONF
OpenDaylight
0.5.4
Mar 2017
0.5.5
Jun 2017
PyPi install
Bundle
updates
IOS XE
bundle

• Path API
• Additional providers (e.g. Google RPC, Cisco NSO)
• Additional services (e.g. Google RPC)
• Additional languages (e.g. Go, etc)
• Additional encodings (e.g. YAML, GPB)
• Telemetry support
• Model-mapping support
Future Work Items

Testbed Topology (dCloud)
R2R1
Out-of-band
network
lo0
172.16.255.1/32
g0/0/0/0
172.16.1.0/31
lo0
172.16.255.2/32
IS-IS L2 (Area 49.0001)
198.18.1.127/24 s
198.18.1.12/24
g0/0/0/0
172.16.1.1/31
198.18.1.11/24
NETCONF NETCONF
YDK App
Controller

Resources
Model-driven programmability @ Cloud-Scale Networking
• Model-Driven Programmability (http://goo.gl/x3GZDB)
Programmability @ XR Docs
• Tutorials (https://xrdocs.github.io/programmability/tutorials)
• Blogs (https://xrdocs.github.io/programmability/blogs)
Configuration guide
• Cisco IOS XR programmability configuration guide for ASR 9000 series router (http://goo.gl/8dYUeK)
• Cisco IOS XR programmability configuration guide for NCS 5500 series router (http://goo.gl/cnYPw7)

Resources
YDK Portal
• YDK at DevNet (http://ydk.io)
YDK Sample Apps
• YDK-Py sample apps (https://github.com/CiscoDevNet/ydk-py-samples) - Over 700 apps!
• YDK-Cpp sample apps (https://github.com/CiscoDevNet/ydk-cpp-samples ) - Coming soon
Sandboxes
• dCloud YANG Development Kit sandbox (https://goo.gl/RPpBvL)
• Ubuntu YDK Vagrant box (https://git.io/vaw1U)
Support
• Cisco support community (https://communities.cisco.com/community/developer/ydk)

Resources (cont.)
YDK Documentation
• YDK-Py docs (http://ydk.cisco.com/py/docs)
• YDK-Cpp docs (http://ydk.cisco.com/cpp/docs)
GitHub
• YDK Python API – YDK-Py (https://git.io/vaWsg)
• YDK-Py sample apps (https://git.io/vaw1U)
• YDK C++ API – YDK-Cpp (https://git.io/v1Cst) - alpha
• YDK-Cpp sample apps (https://git.io/v14Qh) - coming soon

Resources (cont.)
Conferences
• CiscoLive 2017 Las Vegas - BRKSPG-2303 Model-driven programmability for Cisco IOS
XR (www.ciscolive365.com)
• NANOG 68: Ok, We Got YANG Data Models. Now What? (http://youtu.be/2oqkiZ83vAA )
• LinuxCon NA 2016: Simplifying Network Programmability Using Model-Driven APIs
(https://goo.gl/W6tH2X)

• Model-Driven Programmability
• Speed and scale through
automation
• Rich and flexible in terms of
models, transports and encodings
• NETCONF
• Rich, mature protocol
• Relies on XML encoding
• Google RPC
• Cisco interface definition (device
operations)
• Supports JSON and unstructured data
(CLI)
• High performance
• Model-Driven APIs
• Simplify app development
• Abstract transport and encoding
Let’s Recap

PLNOG19 - Krzysztof Mazepa - Yang Development Kit – stwórz swój pierwszy program obsługujący urządzenia Cisco IOS XR/XE dzięki ułatwieniom jakie oferuje YDK

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