Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations
RFC 3135

Document Type RFC - Informational (June 2001; No errata)
Last updated 2013-03-02
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Network Working Group                                          J. Border
Request for Comments: 3135                        Hughes Network Systems
Category: Informational                                          M. Kojo
                                                  University of Helsinki
                                                               J. Griner
                                              NASA Glenn Research Center
                                                           G. Montenegro
                                                  Sun Microsystems, Inc.
                                                               Z. Shelby
                                                      University of Oulu
                                                               June 2001

    Performance Enhancing Proxies Intended to Mitigate Link-Related
                              Degradations

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document is a survey of Performance Enhancing Proxies (PEPs)
   often employed to improve degraded TCP performance caused by
   characteristics of specific link environments, for example, in
   satellite, wireless WAN, and wireless LAN environments.  Different
   types of Performance Enhancing Proxies are described as well as the
   mechanisms used to improve performance.  Emphasis is put on proxies
   operating with TCP.  In addition, motivations for their development
   and use are described along with some of the consequences of using
   them, especially in the context of the Internet.

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Types of Performance Enhancing Proxies  . . . . . . . . . . . .  4
   2.1 Layering . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.1.1 Transport Layer PEPs . . . . . . . . . . . . . . . . . . . .  5
   2.1.2 Application Layer PEPs . . . . . . . . . . . . . . . . . . .  5
   2.2 Distribution . . . . . . . . . . . . . . . . . . . . . . . . .  6
   2.3 Implementation Symmetry  . . . . . . . . . . . . . . . . . . .  6
   2.4 Split Connections  . . . . . . . . . . . . . . . . . . . . . .  7

Border, et al.               Informational                      [Page 1]
RFC 3135          PILC - Performance Enhancing Proxies         June 2001

   2.5 Transparency . . . . . . . . . . . . . . . . . . . . . . . . .  8
   3. PEP Mechanisms  . . . . . . . . . . . . . . . . . . . . . . . .  9
   3.1 TCP ACK Handling . . . . . . . . . . . . . . . . . . . . . . .  9
   3.1.1 TCP ACK Spacing  . . . . . . . . . . . . . . . . . . . . . .  9
   3.1.2 Local TCP Acknowledgements . . . . . . . . . . . . . . . . .  9
   3.1.3 Local TCP Retransmissions  . . . . . . . . . . . . . . . . .  9
   3.1.4 TCP ACK Filtering and Reconstruction . . . . . . . . . . . . 10
   3.2 Tunneling  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   3.3 Compression  . . . . . . . . . . . . . . . . . . . . . . . . . 10
   3.4 Handling Periods of Link Disconnection with TCP  . . . . . . . 11
   3.5 Priority-based Multiplexing  . . . . . . . . . . . . . . . . . 12
   3.6 Protocol Booster Mechanisms  . . . . . . . . . . . . . . . . . 13
   4. Implications of Using PEPs  . . . . . . . . . . . . . . . . . . 14
   4.1 The End-to-end Argument  . . . . . . . . . . . . . . . . . . . 14
   4.1.1 Security . . . . . . . . . . . . . . . . . . . . . . . . . . 14
   4.1.1.1 Security Implications  . . . . . . . . . . . . . . . . . . 15
   4.1.1.2 Security Implication Mitigations . . . . . . . . . . . . . 16
   4.1.1.3 Security Research Related to PEPs  . . . . . . . . . . . . 16
   4.1.2 Fate Sharing . . . . . . . . . . . . . . . . . . . . . . . . 16
   4.1.3 End-to-end Reliability . . . . . . . . . . . . . . . . . . . 17
   4.1.4 End-to-end Failure Diagnostics . . . . . . . . . . . . . . . 19
   4.2 Asymmetric Routing . . . . . . . . . . . . . . . . . . . . . . 19
   4.3 Mobile Hosts . . . . . . . . . . . . . . . . . . . . . . . . . 20
   4.4 Scalability  . . . . . . . . . . . . . . . . . . . . . . . . . 20
   4.5 Other Implications of Using PEPs . . . . . . . . . . . . . . . 21
   5. PEP Environment Examples  . . . . . . . . . . . . . . . . . . . 21
   5.1 VSAT Environments  . . . . . . . . . . . . . . . . . . . . . . 21
   5.1.1 VSAT Network Characteristics . . . . . . . . . . . . . . . . 22
   5.1.2 VSAT Network PEP Implementations . . . . . . . . . . . . . . 23
   5.1.3 VSAT Network PEP Motivation  . . . . . . . . . . . . . . . . 24
   5.2 W-WAN Environments . . . . . . . . . . . . . . . . . . . . . . 25
   5.2.1 W-WAN Network Characteristics  . . . . . . . . . . . . . . . 25
   5.2.2 W-WAN PEP Implementations  . . . . . . . . . . . . . . . . . 26
   5.2.2.1 Mowgli System  . . . . . . . . . . . . . . . . . . . . . . 26
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