End-to-end Performance Implications of Links with Errors
RFC 3155
Document | Type |
RFC - Best Current Practice
(August 2001; No errata)
Also known as BCP 50
Was draft-ietf-pilc-error (pilc WG)
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Authors | Gabriel Montenegro , Markku Kojo , Nitin Vaidya , Vincent Magret , Spencer Dawkins | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 3155 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group S. Dawkins Request for Comments: 3155 G. Montenegro BCP: 50 M. Kojo Category: Best Current Practice V. Magret N. Vaidya August 2001 End-to-end Performance Implications of Links with Errors Status of this Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract This document discusses the specific TCP mechanisms that are problematic in environments with high uncorrected error rates, and discusses what can be done to mitigate the problems without introducing intermediate devices into the connection. Table of Contents 1.0 Introduction ............................................. 2 1.1 Should you be reading this recommendation? ........... 3 1.2 Relationship of this recommendation to PEPs ........... 4 1.3 Relationship of this recommendation to Link Layer Mechanisms............................................. 4 2.0 Errors and Interactions with TCP Mechanisms .............. 5 2.1 Slow Start and Congestion Avoidance [RFC2581] ......... 5 2.2 Fast Retransmit and Fast Recovery [RFC2581] ........... 6 2.3 Selective Acknowledgements [RFC2018, RFC2883] ......... 7 3.0 Summary of Recommendations ............................... 8 4.0 Topics For Further Work .................................. 9 4.1 Achieving, and maintaining, large windows ............. 10 5.0 Security Considerations .................................. 11 6.0 IANA Considerations ...................................... 11 7.0 Acknowledgements ......................................... 11 References ................................................... 11 Authors' Addresses ........................................... 14 Full Copyright Statement ..................................... 16 Dawkins, et al. Best Current Practice [Page 1] RFC 3155 PILC - Links with Errors August 2001 1.0 Introduction The rapidly-growing Internet is being accessed by an increasingly wide range of devices over an increasingly wide variety of links. At least some of these links do not provide the degree of reliability that hosts expect, and this expansion into unreliable links causes some Internet protocols, especially TCP [RFC793], to perform poorly. Specifically, TCP congestion control [RFC2581], while appropriate for connections that lose traffic primarily because of congestion and buffer exhaustion, interacts badly with uncorrected errors when TCP connections traverse links with high uncorrected error rates. The result is that sending TCPs may spend an excessive amount of time waiting for acknowledgement that do not arrive, and then, although these losses are not due to congestion-related buffer exhaustion, the sending TCP transmits at substantially reduced traffic levels as it probes the network to determine "safe" traffic levels. This document does not address issues with other transport protocols, for example, UDP. Congestion avoidance in the Internet is based on an assumption that most packet losses are due to congestion. TCP's congestion avoidance strategy treats the absence of acknowledgement as a congestion signal. This has worked well since it was introduced in 1988 [VJ- DCAC], because most links and subnets have relatively low error rates in normal operation, and congestion is the primary cause of loss in these environments. However, links and subnets that do not enjoy low uncorrected error rates are becoming more prevalent in parts of the Internet. In particular, these include terrestrial and satellite wireless links. Users relying on traffic traversing these links may see poor performance because their TCP connections are spending excessive time in congestion avoidance and/or slow start procedures triggered by packet losses due to transmission errors. The recommendations in this document aim at improving utilization of available path capacity over such high error-rate links in ways that do not threaten the stability of the Internet. Applications use TCP in very different ways, and these have interactions with TCP's behavior [RFC2861]. Nevertheless, it is possible to make some basic assumptions about TCP flows. Accordingly, the mechanisms discussed here are applicable to all uses of TCP, albeit in varying degrees according to different scenariosShow full document text