CoAP Simple Congestion Control/Advanced

Document Type Expired Internet-Draft (core WG)
Authors Carsten Bormann  , August Betzler  , Carles Gomez  , Ilker Demirkol
Last updated 2020-09-10 (latest revision 2018-02-21)
Replaces draft-bormann-core-cocoa
Stream Internet Engineering Task Force (IETF)
Intended RFC status Informational
Expired & archived
pdf htmlized (tools) htmlized bibtex
Additional Resources
- Working Group Repo
- Mailing list discussion
Stream WG state WG Document
Revised I-D Needed - Issue raised by WG
Document shepherd Jaime Jimenez
Shepherd write-up Show (last changed 2018-02-12)
IESG IESG state Expired (IESG: Dead)
Action Holders
Consensus Boilerplate Unknown
Telechat date
Responsible AD Mirja Kühlewind
Send notices to Jaime Jimenez <>

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


CoAP, the Constrained Application Protocol, needs to be implemented in such a way that it does not cause persistent congestion on the network it uses. The CoRE CoAP specification defines basic behavior that exhibits low risk of congestion with minimal implementation requirements. It also leaves room for combining the base specification with advanced congestion control mechanisms with higher performance. This specification defines more advanced, but still simple CoRE Congestion Control mechanisms, called CoCoA. The core of these mechanisms is a Retransmission TimeOut (RTO) algorithm that makes use of Round-Trip Time (RTT) estimates, in contrast with how the RTO is determined as per the base CoAP specification (RFC 7252). The mechanisms defined in this document have relatively low complexity, yet they improve the default CoAP RTO algorithm. The design of the mechanisms in this specification has made use of input from simulations and experiments in real networks.


Carsten Bormann (
August Betzler (
Carles Gomez (
Ilker Demirkol (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)