draft-ietf-ipngwg-pmtuv6-03.txt   rfc1981.txt 
INTERNET-DRAFT J. McCann, Digital Equipment Corporation Network Working Group J. McCann
May 23, 1996 S. Deering, Xerox PARC Request for Comments: 1981 Digital Equipment Corporation
J. Mogul, Digital Equipment Corporation Category: Standards Track S. Deering
Xerox PARC
J. Mogul
Digital Equipment Corporation
August 1996
Path MTU Discovery for IP version 6 Path MTU Discovery for IP version 6
draft-ietf-ipngwg-pmtuv6-03.txt Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract Abstract
This document describes Path MTU Discovery for IP version 6. It is This document describes Path MTU Discovery for IP version 6. It is
largely derived from RFC-1191, which describes Path MTU Discovery for largely derived from RFC 1191, which describes Path MTU Discovery for
IP version 4. IP version 4.
Status of this Memo Table of Contents
This document is an Internet-Draft. Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its areas,
and its working groups. Note that other groups may also distribute
working documents as Internet-Drafts.
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.''
To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
ftp.isi.edu (US West Coast).
Distribution of this document is unlimited.
Expiration
November 23, 1996
Contents
Abstract........................................................1
Status of this Memo.............................................1
Contents........................................................2
1. Introduction.................................................3
2. Terminology..................................................3
3. Protocol overview............................................4
4. Protocol Requirements........................................5
5. Implementation Issues........................................6
5.1. Layering...................................................6
5.2. Storing PMTU information...................................7
5.3. Purging stale PMTU information.............................9
5.4. TCP layer actions.........................................10
1. Introduction.................................................2
2. Terminology..................................................2
3. Protocol overview............................................3
4. Protocol Requirements........................................4
5. Implementation Issues........................................5
5.1. Layering...................................................5
5.2. Storing PMTU information...................................6
5.3. Purging stale PMTU information.............................8
5.4. TCP layer actions..........................................9
5.5. Issues for other transport protocols......................11 5.5. Issues for other transport protocols......................11
5.6. Management interface......................................12 5.6. Management interface......................................12
6. Security Considerations.....................................12
6. Security considerations.....................................12
Acknowledgements...............................................13 Acknowledgements...............................................13
Appendix A - Comparison to RFC 1191............................14 Appendix A - Comparison to RFC 1191............................14
References.....................................................14
References.....................................................15 Authors' Addresses.............................................15
Authors' Addresses.............................................16
1. Introduction 1. Introduction
When one IPv6 node has a large amount of data to send to another When one IPv6 node has a large amount of data to send to another
node, the data is transmitted in a series of IPv6 packets. It is node, the data is transmitted in a series of IPv6 packets. It is
usually preferable that these packets be of the largest size that can usually preferable that these packets be of the largest size that can
successfully traverse the path from the source node to the successfully traverse the path from the source node to the
destination node. This packet size is referred to as the Path MTU destination node. This packet size is referred to as the Path MTU
(PMTU), and it is equal to the minimum link MTU of all the links in a (PMTU), and it is equal to the minimum link MTU of all the links in a
path. IPv6 defines a standard mechanism for a node to discover the path. IPv6 defines a standard mechanism for a node to discover the
skipping to change at page 12, line 49 skipping to change at page 12, line 25
when a packet is sent on a path with this flag set, the IP layer does when a packet is sent on a path with this flag set, the IP layer does
not send packets larger than the IPv6 minimum link MTU. not send packets larger than the IPv6 minimum link MTU.
These features might be used to work around an anomalous situation, These features might be used to work around an anomalous situation,
or by a routing protocol implementation that is able to obtain Path or by a routing protocol implementation that is able to obtain Path
MTU values. MTU values.
The implementation should also provide a way to change the timeout The implementation should also provide a way to change the timeout
period for aging stale PMTU information. period for aging stale PMTU information.
6. Security considerations 6. Security Considerations
This Path MTU Discovery mechanism makes possible two denial-of- This Path MTU Discovery mechanism makes possible two denial-of-
service attacks, both based on a malicious party sending false Packet service attacks, both based on a malicious party sending false Packet
Too Big messages to a node. Too Big messages to a node.
In the first attack, the false message indicates a PMTU much smaller In the first attack, the false message indicates a PMTU much smaller
than reality. This should not entirely stop data flow, since the than reality. This should not entirely stop data flow, since the
victim node should never set its PMTU estimate below the IPv6 minimum victim node should never set its PMTU estimate below the IPv6 minimum
link MTU. It will, however, result in suboptimal performance. link MTU. It will, however, result in suboptimal performance.
skipping to change at page 15, line 15 skipping to change at page 14, line 35
References References
[CONG] Van Jacobson. Congestion Avoidance and Control. Proc. [CONG] Van Jacobson. Congestion Avoidance and Control. Proc.
SIGCOMM '88 Symposium on Communications Architectures and SIGCOMM '88 Symposium on Communications Architectures and
Protocols, pages 314-329. Stanford, CA, August, 1988. Protocols, pages 314-329. Stanford, CA, August, 1988.
[FRAG] C. Kent and J. Mogul. Fragmentation Considered Harmful. [FRAG] C. Kent and J. Mogul. Fragmentation Considered Harmful.
In Proc. SIGCOMM '87 Workshop on Frontiers in Computer In Proc. SIGCOMM '87 Workshop on Frontiers in Computer
Communications Technology. August, 1987. Communications Technology. August, 1987.
[ICMPv6] A. Conta and S. Deering, "Internet Control Message [ICMPv6] Conta, A., and S. Deering, "Internet Control Message
Protocol (ICMPv6) for the Internet Protocol Version 6 Protocol (ICMPv6) for the Internet Protocol Version 6
(IPv6) Specification", RFC 1885, December 1995 (IPv6) Specification", RFC 1885, December 1995.
[IPv6-SPEC] S. Deering and R. Hinden, "Internet Protocol, Version 6 [IPv6-SPEC] Deering, S., and R. Hinden, "Internet Protocol, Version
(IPv6) Specification", RFC 1883, December 1995 6 (IPv6) Specification", RFC 1883, December 1995.
[ISOTP] ISO. ISO Transport Protocol Specification: ISO DP 8073. [ISOTP] ISO. ISO Transport Protocol Specification: ISO DP 8073.
RFC 905, SRI Network Information Center, April, 1984. RFC 905, SRI Network Information Center, April, 1984.
[ND] T. Narten, E. Nordmark, and W. Simpson, "Neighbor [ND] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", work in progress Discovery for IP Version 6 (IPv6)", Work in Progress.
draft-ietf-ipngwg-discovery-04.txt, February 1996.
[RFC-1191] J. Mogul and S. Deering, "Path MTU Discovery", [RFC-1191] Mogul, J., and S. Deering, "Path MTU Discovery",
November 1990 RFC 1191, November 1990.
[RPC] Sun Microsystems, Inc. RPC: Remote Procedure Call [RPC] Sun Microsystems, Inc., "RPC: Remote Procedure Call
Protocol. RFC 1057, SRI Network Information Center, Protocol", RFC 1057, SRI Network Information Center,
June, 1988. June, 1988.
Authors' Addresses Authors' Addresses
Jack McCann Jack McCann
Digital Equipment Corporation Digital Equipment Corporation
110 Spitbrook Road, ZKO3-3/U14 110 Spitbrook Road, ZKO3-3/U14
Nashua, NH 03062 Nashua, NH 03062
Phone: +1 603 881 2608 Phone: +1 603 881 2608
Fax: +1 603 881 0120
Email: mccann@zk3.dec.com
Stephen E. Deering Fax: +1 603 881 0120
Xerox Palo Alto Research Center Email: mccann@zk3.dec.com
3333 Coyote Hill Road
Palo Alto, CA 94304
Phone: +1 415 812 4839
Fax: +1 415 812 4471
Email: deering@parc.xerox.com
Jeffrey Mogul Stephen E. Deering
Digital Equipment Corporation Western Research Laboratory Xerox Palo Alto Research Center
250 University Avenue 3333 Coyote Hill Road
Palo Alto, CA 94301 Palo Alto, CA 94304
Phone: +1 415 617 3304 Phone: +1 415 812 4839
Email: mogul@pa.dec.com
Expiration Fax: +1 415 812 4471
EMail: deering@parc.xerox.com
November 23, 1996 Jeffrey Mogul
Digital Equipment Corporation Western Research Laboratory
250 University Avenue
Palo Alto, CA 94301
Phone: +1 415 617 3304
EMail: mogul@pa.dec.com
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