The Cisco DNA Center (now Catalyst Center) Northbound API allows external applications and orchestrators to interact with the controller. Its key characteristics include:

1. Referred to as Intent API: Cisco officially designates its northbound interface as the "Intent API" because it allows high-level business intent to be translated into network configurations.
2. RESTful API based on HTTP methods: It follows standard REST architecture, utilizing standard HTTP verbs like GET, POST, PUT, and DELETE to perform operations.
3. Uses JSON exclusively: The API typically mandates Content-Type: application/json for requests and returns data in JSON format, distinguishing it from XML-based APIs.

Why others are incorrect:

• Supports NETCONF, SSH, SNMP: These are Southbound protocols used by the controller to communicate with network devices, not Northbound APIs used by applications to talk to the controller.
• Multivendor focus: While limited third-party support exists via SDKs, the primary focus of DNA Center and its specific Northbound API is the management of Cisco Catalyst, Nexus, and Aironet infrastructure, not a generic multivendor focus.

Cisco DevNet. "Cisco DNA Center Intent API - Overview." Cisco Developer Network. The documentation explicitly states: "The Cisco DNA Center Intent API is a northbound REST API... The API allows you to use HTTPS verbs (GET, POST, PUT, DELETE) and JSON structures to discover and control your network."

Cisco Systems. "Cisco DNA Center Platform User Guide, Release 2.3.3." Chapter: Cisco DNA Center Platform Overview. Mentions the exposure of the platform via the Intent API for external integration.

Cisco Systems. "Cisco Digital Network Architecture Center (DNA Center) Data Sheet." Describes the platform's programmability via "Intent-based APIs."