Shepherd writeup

1. Summary

The document shepherd is Michael Scharf <>.

The responsible Area Director is Mirja Kuehlewind <>.

This informational memo describes Datacenter TCP (DCTCP). DCTCP is an improvement to TCP congestion control for datacenter traffic that uses Explicit Congestion Notification (ECN). DCTCP as described in this draft is applicable to deployments in controlled environments like datacenters, but it must not be deployed over the public Internet without additional measures. The document is published to document an implementation in the Microsoft Windows Server 2012 operating system. The Linux and FreeBSD operating systems have also implemented support for DCTCP.

Given the limitations of the existing DCTCP specification, which are discussed in the document, the TCPM working group requests publication as informational document.

2. Review and Consensus

The objective of this informational memo is to document an alternative TCP congestion control algorithm that is known to be widely deployed. It is consensus in the TCPM working group that a DCTCP standard would require further work. A precise documentation of running code enables follow-up experimental or standards track RFCs.

The document describes DCTCP as implemented in Microsoft Windows Server 2012. Since the publication of the first versions of the document, the Linux and FreeBSD operating systems have also implemented support for DCTCP. The specification should also enable implementation in other TCP stacks.

The TCPM working group has reviewed the document regarding clarity and comprehensiveness of the protocol specification, e.g. in corner cases. The document has been discussed multiple times in the working group without any major controversy. During the working group last call there have been several detailed reviews, and those comments have been addressed in the most recent version. All in all, there is very strong consensus in the TCPM working group that this document should be published. 

3. Intellectual Property

Each author has stated that their direct, personal knowledge of any IPR related to this document has already been disclosed, in conformance with BCPs 78 and 79.

There is an IPR disclosure for the DCTCP protocol specification (, which declares "Royalty-Free, Reasonable and Non-Discriminatory License to All Implementers". The TCPM working group is aware of this IPR but there have never been concerns.

4. Other Points