The document discusses strategies for automating network configuration using model-driven approaches and open standards. It provides an overview of exciting developments in software development that could enable more programmatic network configuration. Specifically, it covers NETCONF and YANG standards for automating device configuration and management, and recommends starting with familiarization of OpenConfig models, templated deployments of simple configurations, and using tools like YDK and NCClient to test automations.

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The Path to a Programmable Network
Open Telemetry and Model-Driven Configuration
David Leonard
4-Jul-2019
MyNOG-8, Kuala Lumpur

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3. Overview
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• Motivation
• Exciting news from the world of software development
• Strategies for automation
• Standards
• Demo / teaser

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How it starts

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configure

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configure
configure
configure

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configure
configure
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configureconfigure
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configure

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configure
configure
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configureconfigure
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What have
we wrought?

10. Trouble with configuring via the CLI
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• Configs applied and maintained by hand
• Vendor-specific syntax, ever-changing
• Inconsistent configurations, unexplained special cases
• Configurations are forgotten; until... reactive break-fix model
• Workarounds: brute force, diligence, hard work, RANCID
• Fragile scrapers break on upgrades
• Human-oriented interfaces are for humans

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Manual control
Controlled by
software

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Combining
the reliability of software
with
the low cost of network changes

13. Exciting news from the world of software
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• Agile practices
– Lighter but more intense teamwork
• git + pull requests
– collaborative text editing, focused review
• CI/CD + tests + sandboxes
– safety nets are safer
• DevOps
– the best tools and practices adopted by operations

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programmer

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configure
configure
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1:100

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program
program
program
configure
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configure
1:100

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program
program
configure
configure
configure
configure
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program
1:1000

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Strategies

19. Pre-conditions for automation
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• Inventory: do you have good detail of all devices?
• Requirements: business's expectation of function level; now & plans
• Standards: which model/vocabulary to use in automation
• Telemetry: feedback channels
• Automation: control channels; tooling
• Trust: get experience, confidently predict automation's behaviour
• other: Budget, Stakeholders, Suppliers

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Provisioning Monitoring Security …
Requirements ? ? ? ?
Automation ? ? ? ?
Telemetry ? ? ? ?
Inventory ? ? ? ?
Standards ? ? ? ?
Suppliers ? ? ? ?
Partners ? ? ? ?
Budget ? ? ? ?
Trust ? ? ? ?

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Standards

22. IETF NETCONF
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• 2006 RPC-based protocol for configuring network devices
• "SNMP done right"
• Replaces CLI-based programmatic interfaces (perl/expect over SSH)
• Installs, manipulates configuration
• Can validate config before activation
• Atomic commit/transaction across multiple devices
• Structured message and errors (XML/JSON)

23. NETCONF: XML over SSH
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$ ssh -oHostKeyAlgorithms=+ssh-dss root@ios-xe-mgmt.cisco.com -p 10000 -s netconf
S: <hello> <capabilities> … </capabilities> </hello>
]]>]]>
C: <hello> <capabilities> … </capabilities> </hello>

24. NETCONF: XML over SSH (continued)
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C: <rpc>
<get-config>
<source><running/></source>
</get-config>
</rpc>
S: <rpc-reply>
<data>
<interfaces><interface> <name>eth0</name> <enabled>true<… </interfaces>
</data>
</rpc-reply>
]]>]]>

25. NETCONF landscape
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• YANG – the modeling language for NETCONF
– like MIBs' ASN.1 notation
– IETF provides some basic models, eg RFC8343 "ietf-interfaces"
• NETCONF – the client-server protocol
– NETCONF: sends XML over SSH
– RESTCONF: sends XML or JSON over HTTP
• OpenConfig – the community
– a group of carriers and vendors sharing their YANG models
– more than just "vendor MIBs" (called native models)

26. Where to get YANG models
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• yangcatalog.org
– https://github.com/YangModels/yang (yangcatalog.org)
• openconfig.org
– https://github.com/openconfig/public
• https://github.com/Juniper/yang

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Demo – Getting Started

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Summary

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Suggested approach:
• Get familiar with the OpenConfig models, eg BGP.
Many examples available showing YANG/NX-OS CLI
https://developer.cisco.com/docs/openconfig-yang-release-9-2x/#!ocni-bgp/ocni-bgp
• Try simple templated deployment (interfaces)
http://karneliuk.com/2018/07/openconfig-w-o-and-w-ansible-for-arista-eos-
cisco-ios-xr-and-nokia-sr-os-part-1-interfaces/
• Try same using YDK or NCClient, in Python

32. Additional thoughts
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• The divide-and-conquer NETCONF strategy reflects what we’ve seen at
network operators and in large scale networks
• The “surgical” approach to configuration updates is
– Faster and less disruptive
– Allows for shared control of network devices (multi-tenant)
• Alternate approach is to distribute "complete" configuration files via tools
like Ansible, possibly generated from YANG models
– Reliable, whole-device 'restore'
• Ultimate end game is an Intent Based Network?

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