draft-ietf-intarea-frag-fragile-04.txt   draft-ietf-intarea-frag-fragile-05.txt 
Internet Area WG R. Bonica Internet Area WG R. Bonica
Internet-Draft Juniper Networks Internet-Draft Juniper Networks
Intended status: Best Current Practice F. Baker Intended status: Best Current Practice F. Baker
Expires: May 31, 2019 Unaffiliated Expires: July 15, 2019 Unaffiliated
G. Huston G. Huston
APNIC APNIC
R. Hinden R. Hinden
Check Point Software Check Point Software
O. Troan O. Troan
Cisco Cisco
F. Gont F. Gont
SI6 Networks SI6 Networks
November 27, 2018 January 11, 2019
IP Fragmentation Considered Fragile IP Fragmentation Considered Fragile
draft-ietf-intarea-frag-fragile-04 draft-ietf-intarea-frag-fragile-05
Abstract Abstract
This document describes IP fragmentation and explains how it reduces This document describes IP fragmentation and explains how it reduces
the reliability of Internet communication. the reliability of Internet communication.
This document also proposes alternatives to IP fragmentation and This document also proposes alternatives to IP fragmentation and
provides recommendations for developers and network operators. provides recommendations for developers and network operators.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 31, 2019. This Internet-Draft will expire on July 15, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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4.8. Blackholing Due To Filtering . . . . . . . . . . . . . . 13 4.8. Blackholing Due To Filtering . . . . . . . . . . . . . . 13
5. Alternatives to IP Fragmentation . . . . . . . . . . . . . . 14 5. Alternatives to IP Fragmentation . . . . . . . . . . . . . . 14
5.1. Transport Layer Solutions . . . . . . . . . . . . . . . . 14 5.1. Transport Layer Solutions . . . . . . . . . . . . . . . . 14
5.2. Application Layer Solutions . . . . . . . . . . . . . . . 15 5.2. Application Layer Solutions . . . . . . . . . . . . . . . 15
6. Applications That Rely on IPv6 Fragmentation . . . . . . . . 16 6. Applications That Rely on IPv6 Fragmentation . . . . . . . . 16
6.1. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.1. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.3. Packet-in-Packet Encapsulations . . . . . . . . . . . . . 17 6.3. Packet-in-Packet Encapsulations . . . . . . . . . . . . . 17
6.4. Licklider Transmission Protocol (LTP) . . . . . . . . . . 17 6.4. Licklider Transmission Protocol (LTP) . . . . . . . . . . 17
7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 18 7. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 18
7.1. For Application Developers . . . . . . . . . . . . . . . 18 7.1. For Application and Protocol Developers . . . . . . . . . 18
7.2. For System Developers . . . . . . . . . . . . . . . . . . 18 7.2. For System Developers . . . . . . . . . . . . . . . . . . 18
7.3. For Middle Box Developers . . . . . . . . . . . . . . . . 18 7.3. For Middle Box Developers . . . . . . . . . . . . . . . . 18
7.4. For Network Operators . . . . . . . . . . . . . . . . . . 18 7.4. For Network Operators . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19 11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 20 11.2. Informative References . . . . . . . . . . . . . . . . . 21
Appendix A. Contributors' Address . . . . . . . . . . . . . . . 23 Appendix A. Contributors' Address . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
Operational experience [Kent] [Huston] [RFC7872] reveals that IP Operational experience [Kent] [Huston] [RFC7872] reveals that IP
fragmentation reduces the reliability of Internet communication. fragmentation reduces the reliability of Internet communication.
This document describes IP fragmentation and explains how it reduces This document describes IP fragmentation and explains how it reduces
the reliability of Internet communication. This document also the reliability of Internet communication. This document also
proposes alternatives to IP fragmentation and provides proposes alternatives to IP fragmentation and provides
recommendations for developers and network operators. recommendations for developers and network operators.
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that are larger than the path MTU so that more data can be conveyed that are larger than the path MTU so that more data can be conveyed
between the application and the kernel in a single system call. between the application and the kernel in a single system call.
For example, the Licklider Transmission Protocol (LTP) [RFC5326] For example, the Licklider Transmission Protocol (LTP) [RFC5326]
which is in current use on the International Space Station (ISS) uses which is in current use on the International Space Station (ISS) uses
UDP datagram sizes larger than the path MTU to achieve acceptable UDP datagram sizes larger than the path MTU to achieve acceptable
levels of performance even though this invokes IP fragmentation. levels of performance even though this invokes IP fragmentation.
7. Recommendations 7. Recommendations
7.1. For Application Developers 7.1. For Application and Protocol Developers
Protocol developers SHOULD NOT develop new protocols that rely on IP Developers SHOULD NOT develop new protocols or applications that rely
fragmentation. However, they MAY develop new protocols that rely on on IP fragmentation. When a new protocol or application is deployed
IP fragmentation when no viable alternative exists. in an environment that does not fully support IP fragmentation, it
SHOULD operate correctly, either in its default configuration or in a
specified alternative configuration.
Developers MAY develop new protocols or applications that rely on IP
fragmentation if the protocol or application is to be run only in
environments where IP fragmentation is known to be supported.
Legacy protocols that depend upon IP fragmentation SHOULD be updated Legacy protocols that depend upon IP fragmentation SHOULD be updated
to break that dependency. However, in some cases, there may be no to break that dependency. However, in some cases, there may be no
viable alternative to IP fragmentation (e.g., IPSEC tunnel mode, IP- viable alternative to IP fragmentation (e.g., IPSEC tunnel mode, IP-
in-IP encapsulation). In these cases, the protocol will continue to in-IP encapsulation). In these cases, the protocol will continue to
rely on IP fragmentation. rely on IP fragmentation but should only be used in environments
where IP fragmentation is known to be supported.
Some legacy protocols may be able to break their dependency upon IP Protocols may be able to avoid IP fragmentation by using a
fragmentation by using a sufficiently small MTU (e.g. The protocol sufficiently small MTU (e.g. The protocol minimum link MTU),
minimum link MTU), disabling IP fragmentation, and ensuring that the disabling IP fragmentation, and ensuring that the transport protocol
transport protocol in use adapts its segment size to the MTU. Other in use adapts its segment size to the MTU. Other protocols may
legacy protocols may deploy a sufficiently reliable PMTU discovery deploy a sufficiently reliable PMTU discovery mechanism
mechanism (e.g., PLMPTUD). However, some legacy protocols will not (e.g.,PLMPTUD).
be able to break their dependency on IP fragmentation at all.
7.2. For System Developers 7.2. For System Developers
Software libraries SHOULD include provision for PLPMTUD for each Software libraries SHOULD include provision for PLPMTUD for each
supported transport protocol. supported transport protocol.
7.3. For Middle Box Developers 7.3. For Middle Box Developers
Middle boxes SHOULD process IP fragments in a manner that is Middle boxes SHOULD process IP fragments in a manner that is
compliant with RFC 791 and RFC 8200. In many cases, middle boxes compliant with RFC 791 and RFC 8200. In many cases, middle boxes
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