Making TCP More Robust to Long Connectivity Disruptions (TCP-LCD) (RFC6069)
Original Publication Date: 2010-Dec-01
Included in the Prior Art Database: 2010-Dec-14
Internet Society Requests For Comment (RFCs)
A. Zimmermann: AUTHOR [+2]
Connectivity disruptions can occur in many different situations. The frequency of connectivity disruptions depends on the properties of the end-to-end path between the communicating hosts. While connectivity disruptions can occur in traditional wired networks, e.g., disruption caused by an unplugged network cable, the likelihood of their occurrence is significantly higher in wireless (multi-hop) networks. Especially, end-host mobility, network topology changes, and wireless interferences are crucial factors. In the case of the Transmission Control Protocol (TCP) [RFC0793], the performance of the connection can experience a significant reduction compared to a permanently connected path [SESB05]. This is because TCP, which was originally designed to operate in fixed and wired networks, generally assumes that the end-to-end path connectivity is relatively stable over the connection's lifetime.
Internet Engineering Task Force (IETF) A. Zimmermann Request for Comments: 6069 A. Hannemann Category: Experimental RWTH Aachen University ISSN: 2070-1721 December 2010
Making TCP More Robust to Long Connectivity Disruptions (TCP-LCD)
Disruptions in end-to-end path connectivity, which last longer than one retransmission timeout, cause suboptimal TCP performance. The reason for this performance degradation is that TCP interprets segment loss induced by long connectivity disruptions as a sign of congestion, resulting in repeated retransmission timer backoffs. This, in turn, leads to a delayed detection of the re-establishment of the connection since TCP waits for the next retransmission timeout before it attempts a retransmission.
This document proposes an algorithm to make TCP more robust to long connectivity disruptions (TCP-LCD). It describes how standard ICMP messages can be exploited during timeout-based loss recovery to disambiguate true congestion loss from non-congestion loss caused by connectivity disruptions. Moreover, a reversion strategy of the retransmission timer is specified that enables a more prompt detection of whether or not the connectivity to a previously disconnected peer node has been restored. TCP-LCD is a TCP sender- only modification that effectively improves TCP performance in the case of connectivity disruptions.
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/rfc6069.
Zimmermann & Hannemann Experimental [Page 1]
RFC 6069 Making TCP More Robust to LCDs December 2010
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