IP Fragmentation Considered Fragile
draft-bonica-intarea-frag-fragile-02

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Internet Area WG                                               R. Bonica
Internet-Draft                                          Juniper Networks
Intended status: Best Current Practice                          F. Baker
Expires: December 12, 2018                                  Unaffiliated
                                                               G. Huston
                                                                   APNIC
                                                               R. Hinden
                                                    Check Point Software
                                                                O. Troan
                                                                   Cisco
                                                                 F. Gont
                                                            SI6 Networks
                                                           June 10, 2018

                  IP Fragmentation Considered Fragile
                  draft-bonica-intarea-frag-fragile-02

Abstract

   This document provides an overview of IP fragmentation.  It explains
   how IP fragmentation works and why it is required.  As part of that
   explanation, this document also explains how IP fragmentation reduces
   the reliability of Internet communication.

   This document also proposes alternatives to IP fragmentation.
   Finally, it provides recommendations for application developers and
   network operators.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 12, 2018.

Bonica, et al.          Expires December 12, 2018               [Page 1]
Internet-Draft          IP Fragmentation Fragile               June 2018

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  IP Fragmentation  . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Links, Paths, MTU and PMTU  . . . . . . . . . . . . . . .   3
     2.2.  Upper-layer Protocols . . . . . . . . . . . . . . . . . .   5
   3.  Requirements Language . . . . . . . . . . . . . . . . . . . .   7
   4.  IP Fragmentation Reduces Reliability  . . . . . . . . . . . .   7
     4.1.  Middle Box Failures . . . . . . . . . . . . . . . . . . .   7
     4.2.  Partial Filtering . . . . . . . . . . . . . . . . . . . .   8
     4.3.  Suboptimal Load Balancing . . . . . . . . . . . . . . . .   8
     4.4.  Security Vulnerabilities  . . . . . . . . . . . . . . . .   9
     4.5.  Blackholing Due to ICMP Loss  . . . . . . . . . . . . . .  11
       4.5.1.  Transient Loss  . . . . . . . . . . . . . . . . . . .  12
       4.5.2.  Incorrect Implementation of Security Policy . . . . .  12
       4.5.3.  Persistant Loss Caused By Anycast . . . . . . . . . .  13
     4.6.  Blackholing Due To Filtering  . . . . . . . . . . . . . .  13
   5.  Alternatives to IP Fragmentation  . . . . . . . . . . . . . .  14
     5.1.  Transport Layer Solutions . . . . . . . . . . . . . . . .  14
     5.2.  Application Layer Solutions . . . . . . . . . . . . . . .  15
   6.  Applications That Rely on IPv6 Fragmentation  . . . . . . . .  16
     6.1.  DNS . . . . . . . . . . . . . . . . . . . . . . . . . . .  16
     6.2.  OSPFv3  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     6.3.  Packet-in-Packet Encapsulations . . . . . . . . . . . . .  17
   7.  Recommendations . . . . . . . . . . . . . . . . . . . . . . .  17
     7.1.  For Application Developers  . . . . . . . . . . . . . . .  17
     7.2.  For Network Operators . . . . . . . . . . . . . . . . . .  17
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  18