TCP and Stream Control Transmission Protocol (SCTP) RTO Restart (RFC7765)
Original Publication Date: 2016-Feb-01
Included in the Prior Art Database: 2016-Feb-12
Internet Society Requests For Comment (RFCs)
P. Hurtig: AUTHOR [+3]
TCP and SCTP use two almost identical mechanisms to detect and recover from data loss, specified in [RFC6298] and [RFC5681] for TCP and [RFC4960] for SCTP. First, if transmitted data is not acknowledged within a certain amount of time, a retransmission timeout (RTO) occurs and the data is retransmitted. While the RTO is based on measured round-trip times (RTTs) between the sender and receiver, it also has a conservative lower bound of 1 second to ensure that delayed data are not mistaken as lost. Second, when a sender receives duplicate acknowledgments or similar information via selective acknowledgments, the fast retransmit algorithm suspects data loss and can trigger a retransmission. Duplicate (and selective) acknowledgments are generated by a receiver when data arrives out of order. As both data loss and data reordering cause out-of-order arrival, fast retransmit waits for three out-of-order notifications before considering the corresponding data as lost. In some situations, however, the amount of outstanding data is not enough to trigger three such acknowledgments, and the sender must rely on lengthy RTOs for loss recovery.
Internet Engineering Task Force (IETF) P. Hurtig Request for Comments: 7765 A. Brunstrom Category: Experimental Karlstad University ISSN: 2070-1721 A. Petlund Simula Research Laboratory AS M. Welzl University of Oslo February 2016
TCP and Stream Control Transmission Protocol (SCTP) RTO Restart
This document describes a modified sender-side algorithm for managing the TCP and Stream Control Transmission Protocol (SCTP) retransmission timers that provides faster loss recovery when there is a small amount of outstanding data for a connection. The modification, RTO Restart (RTOR), allows the transport to restart its retransmission timer using a smaller timeout duration, so that the effective retransmission timeout (RTO) becomes more aggressive in situations where fast retransmit cannot be used. This enables faster loss detection and recovery for connections that are short lived or application limited.
Status of This Memo
This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.
This document defines an Experimental Protocol for the Internet community. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7765.
al. Experimental [Page 1]
RFC 7765 TCP and SCTP RTO Restart February 2016
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