CDL - Section 10 - Employing Model-Driven Programmability Flashcards
REVIEW: Protocols v Data Models
One misconception is that data models are used to exchange data, which is not the case. Instead, protocols such as Network Configuration Protocol (NETCONF) and RESTCONF send JSON/XML encoded documents, that are governed by a given model.
Models focus on what is the content and not so much on how it is exchanged – that is what protocols do i.e RESTCONF/NETCONF.
Data Models - define the syntax and semantics, including constraints of working with the API; the 2 main models are XML and JSON
Protocols - how the data is exchanged; the 3 core protocols are NETCOFN, RESTCONF, gRPC
What is NETCONF?
What protocol does NETCONF travel over?
Provides a formal and generally interoperable means of opening a secure management session with a network device.
Exposes an API for querying data and performing config changes.
TLS or SSH, but mainly & more commonly over SSH
What are all NETCONF operations encoded with?
XML
They are also described in the YANG language.
What is YANG?
YANG is the standardized modeling language used with NETCONF
It is used to define configuration and operational state data models, operational functions, and notifications that are transported within NETCONF commands.
YANG is used to model both configuration data and state data of network elements
What is RESTCONF?
What encoding does it support?
→ RESTCONF is a REST-like protocol that provides a mechanism over HTTP for accessing data that is defined in NETCONF datastores and modeled in YANG.
RESTCONF is a subset of NETCONF that exposes YANG Models via a REST API.
While NETCONF uses XML encoding only, RESTCONF supports both JSON and XML.
REVIEW: Netconf v Restconf
RESTCONF does not support all the NETCONF operations, but it supports most. Granular commands like config locking, startup config, confirmed commits, etc. are not supported.
While NETCONF only uses/supports XML encoding, RESTCONF supports both JSON and XML.
NETCONF + HTTP/HTTPS = RESTCONF
What is a Software Development Kit (SDK)?
What is a Yang Dev Kit (YDK)?
SDK - A collection of useful tools that are used for developing software or applications.
(YDK) - The main goal of YDK is to reduce the learning curve for interfacing with YANG-based APIs, such as NETCONF and RESTCONF.
What is Model-Driven Programmability?
Programmability that fully decouples transport, protocol, and encoding from the model being used.
The model then becomes the definition of what can be done on a device that is completely decoupled from the encoding method.
What is NXOS Programmability?
What is it typically used for?
The Cisco NX-OS open platform allows for programmatic access to Cisco Nexus platforms.
It is used for Day0 provisioning, config management, pulling data, etc.
What is NX-API CLI?
RPC-style API that allows for programmatic access to Nexus switches.
→ Allows admins to have the CLI available off-box; i.e traditional methods are managing the DC switching via CLI on the box
→ It sends commands to the device, wrapped in HTTP and HTTPS, but receives structured data back
What is NX-API REST?
The next-generation API for the Cisco Nexus platform in that it supports sending and receiving objects in the API payload.
No CLI involved (like with the NX-API CLI), it only works with structured data back & forth – XML or JSON wrapped in HTTP/HTTPS.
** JSON/XML payloads are sent to the device in the HTTP request and received from the device in the response.
What is a Management Information Tree (MIT)?
All information about the switch, including configuration and state data, is stored in a hierarchical tree in the form of objects.
Every object in the tree can be directly accessed via the REST API.
What are the 3 methods supported by NX-API REST?
GET
DELETE
POST
