RFC 2923 (rfc2923) - Page 1 of 15

TCP Problems with Path MTU Discovery

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Network Working Group                                        K. Lahey
Request for Comments: 2923                            dotRocket, Inc.
Category: Informational                                September 2000


                  TCP Problems with Path MTU Discovery

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 (2000).  All Rights Reserved.

Abstract

   This memo catalogs several known Transmission Control Protocol (TCP)
   implementation problems dealing with Path Maximum Transmission Unit
   Discovery (PMTUD), including the long-standing black hole problem,
   stretch acknowlegements (ACKs) due to confusion between Maximum
   Segment Size (MSS) and segment size, and MSS advertisement based on
   PMTU.

1. Introduction

   This memo catalogs several known TCP implementation problems dealing
   with Path MTU Discovery [RFC 1191], including the long-standing black
   hole problem, stretch ACKs due to confusion between MSS and segment
   size, and MSS advertisement based on PMTU.  The goal in doing so is
   to improve conditions in the existing Internet by enhancing the
   quality of current TCP/IP implementations.

   While Path MTU Discovery (PMTUD) can be used with any upper-layer
   protocol, it is most commonly used by TCP;  this document does not
   attempt to treat problems encountered by other upper-layer protocols.
   Path MTU Discovery for IPv6 [RFC 1981] treats only IPv6-dependent
   issues, but not the TCP issues brought up in this document.

   Each problem is defined as follows:

   Name of Problem
      The name associated with the problem.  In this memo, the name is
      given as a subsection heading.





Lahey                        Informational
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