OpenDaylight is getting the ability to subscribe to changes within switches and routers. We need this because continuous, periodic polling of data is not adequate for applications requiring frequent/prompt updates of remote object state. Having such a capability will address problems including: unnecessary processing load on networks, controllers, routers, and applications, and overly high propagation latency where controllers cannot see key network changes quickly enough. The YANG PUBSUB project in OpenDaylight Beryllium addresses these problems by allowing applications to setup customized subscriptions on specific subtrees of YANG datastores in the network. With change-triggered subscriptions, any changes in interesting YANG objects will be pushed to OpenDaylight without any need to explicitly poll the data. Effectively, we are enabling a telemetry solution with customized YANG object delivery by subscriber. More on the capability can be understood from the IETF NETCONF technology specification draft-ietf-netconf-yang-push, or the I2RS requirements draft-ietf-i2rs-pub-sub-requirements.
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