Block-wise transfers in CoAP: Extension for Reliable Transport (BERT)

Document Type Replaced Internet-Draft (individual)
Last updated 2016-06-10
Replaced by draft-ietf-core-coap-tcp-tls
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


CoAP (RFC7252) is a RESTful transfer protocol for constrained nodes and networks, originally using UDP or DTLS over UDP as its transport. Basic CoAP messages work well for the small payloads we expect from temperature sensors, light switches, and similar building-automation devices. CoAP's Block protocol (draft-ietf-core-block) allows transferring larger payloads over limited-size datagrams -- for instance, for firmware updates. CoAP over TCP and TLS (draft-ietf-core-tcp-tls) enables the use of extended, but not unlimited, size messages. The present specification, Block-wise transfers in CoAP: Extension for Reliable Transport (BERT), extends the block protocol in a simple way to be able to make use of these larger messages over a reliable transport.


Carsten Bormann (

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