Stateful Observation in CoAP
draft-ma-core-stateful-observe-02

Abstract

The Observe Option allows a CoAP client to observe changes in the state of resources and obtain a current representation of the last resource state. To be an observer of an origin server's resources, the client is required to register its interest with the server. A successful registration will make the client added into the server's observation list, while a failed one MAY drive the client to re- register. However, repeated and frequent re-registrations cannot guarantee the client to eventually become an observer of the target server. In the case that the server is unable or unwilling to accept an observer, the time-intensive re-registrations will just bring redundant messages in the constrained network and considerable energy consumption on both the client and the server. This memo defines a new CoAP option, State, for providing stateful observation on the resources of CoAP servers. By observing the state of the server in terms of the Observe Option, a client can explicitly learn when the server will not actively reject an observation registration, and then can wisely performs the re-registration. This avoids the potential registration flooding that causes considerable network overhead and energy consumption on the constrained nodes.

Authors

Changsha Ma
Peilin Hong
Kaiping Xue

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