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More Accurate ECN Feedback in TCP

Document type: Expired Internet-Draft (individual)
Document stream: No stream defined
Last updated: 2013-12-22 (latest revision 2013-06-20)
Intended RFC status: Unknown
Other versions: (expired, archived): plain text, pdf, html

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IESG State: Expired
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This Internet-Draft is no longer active. Unofficial copies of old Internet-Drafts can be found here:


Explicit Congestion Notification (ECN) is an IP/TCP mechanism where network nodes can mark IP packets instead of dropping them to indicate congestion to the end-points. ECN-capable receivers will feedback this information to the sender. ECN is specified for TCP in such a way that only one feedback signal can be transmitted per Round-Trip Time (RTT). Recently, new TCP mechanisms like ConEx or DCTCP need more accurate ECN feedback information in the case where more than one marking is received in one RTT. This document specifies a different scheme for the ECN feedback in the TCP header to provide more than one feedback signal per RTT. Furthermore this document specifies a re-use of the Urgent Pointer in the TCP header if the URG flag is not set to increase the robustness of the proposed ECN feedback scheme.


Mirja Kuehlewind <>
Richard Scheffenegger <>

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