This is an extensible system for SDN, that can be used for multiple networking use cases. It comprises two major drivers in the architecture, which are as follows:

Cloud Computing:

These are primarily private clouds designed for enterprises and service providers, Infrastructure as a Service (IaaS), cloud service providers, and virtual private clouds. These cases involve multi-tenant virtualized data centers where the physical resources (servers, storage boxes, and physical network) are being utilized by all tenants. The physical resources are logically (via virtual machines, virtual storage, and virtual networks) assigned to each individual tenant. The virtualized resources are siloed from one another, except that security policies are created to allow inter-tenant communication or via physical IP VPN or layer two VPN connections.

Network Function Virtualization (NFV) in service providers network:

Value added services are key components in service providers edge networks. Some major service provider edge networks include business edge networks, broadband subscriber management edge networks, and mobile edge networks. This involves the orchestration and management of functions in virtual machines, such as firewalls, deep packet inspection, and WAN optimization.

Components that make up the OpenContrail system are controller and vRouter. The OpenContrail controller is the centralized logical distributed SDN controller that is responsible for providing management, control, and analytics functions of the virtualized network. OpenContrail vRouter is basically the forwarding plane of the distributed router running in the hypervisor of a virtualized server. The physical switches and routers are extended into the virtual overlay network by the vRouter. OpenContrail vRouter can be likened to the open source switches that are available, such as the Open vSwitch, but it has more advanced functionalities such as routing and higher-level switching, from which it derived the name vRouter.

The architecture of OpenContrail can be found in the following diagram:

The preceding architecture comprises various components. These are as follows:

• Northbound REST APIs are primarily utilized by applications. They are used when integrating the OpenContrail with cloud orchestration systems. They are also used by other operators that provide BSS/OSS. They are also utilized to implement web-based GUI.
• Southbound interfaces are used to communicate with the virtualized vRouters and the physical routers and switches.
• East-west interfaces are used to bond with other controllers. The standard BGP present is for the east-west interface, and XMPP is used for the vRouters by the southbound interface. The gateway routers and switches utilize the BGP and NETCONF.