Repeat And Request-Tag

Document Type Replaced Internet-Draft (individual)
Authors Christian Amsüss  , John Preuß Mattsson  , Göran Selander 
Last updated 2017-07-01
Replaces draft-amsuess-core-request-tag
Replaced by draft-ietf-core-echo-request-tag
Stream (None)
Intended RFC status (None)
Expired & archived
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IESG IESG state Replaced by draft-ietf-core-echo-request-tag
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document defines two optional extensions to the Constrained Application Protocol (CoAP): the Repeat option and the Request-Tag option. Each of these options when integrity protected, such as with DTLS or OSCOAP, protects against certain attacks on CoAP message exchanges. The Repeat option enables a CoAP server to verify the freshness of a request by requiring the CoAP client to make another request and include a server-provided challenge. The Request-Tag option allows the CoAP server to match message fragments belonging to the same request message, fragmented using the CoAP Block-Wise Transfer mechanism. This document also specifies additional processing requirements on Block1 and Block2 options.


Christian Amsüss (
John Preuß Mattsson (
Göran Selander (

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