While the Open Networking Foundation defines OpenFlow as the first standard communications interface between the control and forwarding layers of an SDN architecture, it may not remain the predominating protocol.
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With all of its promise, OpenFlow also poses a slew of challenges from scalability to security. Most troubling, network vendors must create supporting switching in order for OpenFlow to take hold industry wide.
While most network vendors have already developed OpenFlow-based equipment, they're also designing SDN architectures that use alternate communication methods -- including existing networking protocols, such as MPLS and NETCONF.
We rounded up five SDN protocols to know other than OpenFlow.
1. Border Gateway Protocol (BGP) is a protocol used for exchanging routing information between gateway hosts in a network of autonomous systems. This protocol is often used between gateway hosts on the Internet and it is also considered a standardized exterior gateway protocol. BGP is often also classified as either a path vector protocol or a distance-vector protocol. In the network, each gateway host typically has its own router. The routing table contains a list of known routers, the addresses they can reach, and a cost metric associated with the path to each router; in turn, this allows for the best available route to be chosen.
Vendors are looking to use BGP in hybrid software-defined networking. Some argue that the southbound protocol in an SDN architecture is less important than the operational agility and programmability that SDN offers, with or without OpenFlow. As a result, vendors identified BGP as an SDN protocol with potential to enable network programmability promised by SDN.
2. NETCONF is an Internet Engineering Task Force (IETF) network management protocol. It provides an administrator or network engineer with a secure way to configure a firewall, switch, router, or other network device. It is based on remote procedure call (RPC) and was designed to resolve issues that exist with the Simple Network Management Protocol and Command-Line Interface protocols, as they relate to the configuration of network devices.
The Open Networking Foundation (ONF) recently embraced NETCONF and made it mandatory for the configuration of OpenFlow-enabled devices. The specification, called OF-CONFIG, requires that devices supporting it must implement the NETCONF protocol as the transport.
3. Extensible Messaging and Presence Protocol (XMPP) is a protocol that's based on Extensible Markup Language. Its intended use is for instant messaging and online presence detection. The protocol functions between or among servers and facilitates near-real-time operation. XMPP has recently emerged as an alternative SDN protocol to OpenFlow in hybrid SDN networks and can be used by the controller to distribute both control plane and management plane information to the server endpoints. It manages information at all levels of abstraction, down to the flow.
4. Open vSwitch Database Management Protocol (OVSDB) is an OpenFlow configuration protocol that is meant to manage Open vSwitch implementations. Open vSwitch is a virtual switch that enables network automation and the support of standard management interfaces and protocols, such as NetFlow. The protocol also supports distribution across multiple physical servers.
In an Open vSwitch implementation, a control cluster contains managers and controllers that use the OVSDB protocol to supply configuration information to the switch database server. Controllers use OpenFlow to specify details of packet flows through the switch. Each manager and controller can direct multiple switches, and each switch can receive directives from multiple managers and controllers.
5. MPLS Transport Profile (MPLS-TP) is the transport profile for Multiprotocol Label Switching. MPLS-TP is designed to be used as a network layer technology in transport networks. The protocol extensions to MPLS are being designed by the IETF based on requirements provided by service providers. The protocol will be a connection-oriented packet-switched (CO-PS) application that offers a dedicated MPLS implementation by removing features that aren't relevant to CO-PS applications and adding devices that provide support of critical transport functionality.
The Open Networking Foundation proposed changes to MPLS that include the use of the standard MPLS data-plane with a simpler control-plane based on SDN and OpenFlow. By having a simplified control plane that de-coupled from the data plane, the ONF argues that it's able to globally optimize services, make services more dynamic, and create new services by programming networking applications on top of the SDN controller.