Internet DRAFT - draft-palet-v6ops-6in4-vs-6over4
draft-palet-v6ops-6in4-vs-6over4
Internet Engineering Task Force J. Palet
Internet-Draft Consulintel
Expires: May 20, 2006 November 16, 2005
6in4 versus 6over4 terminology
draft-palet-v6ops-6in4-vs-6over4-01.txt
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document clarifies the existing terminology confusion among
references to IPv6/IPv4 encapsulations and IPv4/IPv6 transition
mechanisms.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of 'in' and 'over' . . . . . . . . . . . . . . . . . 4
3. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 8
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1. Introduction
A number of IETF documents have used in an "interchangeable" way
several expressions such as:
o 6in4
o 6-in-4
o IPv6-in-IPv4
o IPv6 in IPv4
o 6over4
o 6-over-4
o IPv6-over-IPv4
o IPv6 over IPv4
o 4in6
o 4-in-6
o IPv4-in-IPv6
o IPv4 in IPv6
o 4over6
o 4-over-6
o IPv4-over-IPv6
o IPv4 over IPv6
Note that this list is not exhaustive and many other similar
expressions may be also in use. For example, in some situations
other encapsulating layers are used (i.e., 6/UDP/4), and similar
expressions are being used as well.
As a consequence, documents from vendors, product manuals,
publications, papers, books, tutorials, training material and many
others, use also those expressions.
However not all those documents, including the IETF ones, are
actually referring to the same IPv6/IPv4 encapsulations or IPv4/IPv6
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transition mechanisms.
The result of this terminology confusion is a number of errors among
vendors, operators, engineers and end-users when designing and
documenting products, or when setting up transition mechanisms, being
the cause of unnecessary operational costs, specially for beginners
which try to setup IPv6 for their first occasions.
2. Definition of 'in' and 'over'
IP in IP Tunneling was defined by [1]. Afterwards [2], obsoleted by
[3], defines the basic IPv4/IPv6 transition mechanisms, including the
encapsulation of IPv6 packets in IPv4 ones (by means of protocol 41);
this document is being updated as "ietf-v6ops-mech-v2".
Similarly, [4], defines the encapsulation of IPv4 packets in IPv6
ones.
A first conclusion can be extracted from this documents (even if some
of them actually use, some times, "over"): Those encapsulation
mechanisms are the ones that should use the "in" terminology. Note
that they are just encapsulation mechanisms, which often are used by
several transition mechanisms.
Furthermore, [5] specify a transition mechanism, which uses 6in4
(encapsulation of IPv6 packets in IPv4 ones), creating a virtual IPv6
link over an IPv4 multicast infrastructure. This transition
mechanism is named as "6over4". This name was chosen because the
mechanism (use of IPv4 multicast for Neighbor Discovery) is exactly
analogous to the mechanism for IPv6 over Ethernet (use of Ethernet
multicast for Neighbor Discovery).
Clearly, "6in4" and "6over4" are quite different things, actually
6over4 is a transition mechanism which uses 6in4 as the procedure for
encapsulating IPv6 packets in IPv4 multicast infrastructures.
The fact that they are different things and specially the requirement
for a (IPv4) multicast infrastructure for 6over4, makes necessary to
clarify the difference and avoid confusions among both.
Engineers operating networks and their customers (for example when
setting up tunnels), often do not read all the IETF documents, so
they could easily misunderstand if a tunnel is "6over4" or "6in4"
(specially when vendor documents use both terms to actually name
"6in4", possibly because the misusage of those terms in [2], [3]),
and this creates some extra troubleshooting time and confusion.
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3. Conclusions
In order to avoid this kind of confusion, it should be understood the
difference between 6over4 and 6in4 (and any other equivalent
terminologies). Future documents should take this in consideration.
It is recommended as well that new documents which describe other
encapsulations and protocols, such as IPv4 in IPv6, IPv6 in UDP/IPv4,
IPv6 in IPv6, etc., for consistency reasons, use "in" instead of
"over".
It is also recommended that existing documents are amended ASAP to
avoid the existing confusion.
4. Security Considerations
This document does not have any protocol-related security
considerations.
5. IANA Considerations
This document does not have any specific IANA considerations.
6. Acknowledgements
The author would like to acknowledge the inputs of Brian Carpenter.
7. References
7.1. Normative References
[1] Simpson, W., "IP in IP Tunneling", RFC 1853, October 1995.
[2] Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6
Hosts and Routers", RFC 1933, April 1996.
[3] Gilligan, R. and E. Nordmark, "Transition Mechanisms for IPv6
Hosts and Routers", RFC 2893, August 2000.
[4] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6
Specification", RFC 2473, December 1998.
[5] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4
Domains without Explicit Tunnels", RFC 2529, March 1999.
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7.2. Informative References
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Author's Address
Jordi Palet Martinez
Consulintel
San Jose Artesano, 1
Alcobendas - Madrid
E-28108 - Spain
Phone: +34 91 151 81 99
Fax: +34 91 151 81 98
Email: jordi.palet@consulintel.es
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