IPng Working Group A. Conta (Lucent)
INTERNET-DRAFT
July 1997
Transmission of IPv6 Packets over IPv6 and IPv4 Tunnels.
Specification
draft-conta-ipv6-trans-tunnel-00.txt
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working doc-
uments of the Internet Engineering Task Force (IETF), its Areas, and
its Working Groups. Note that other groups may also distribute work-
ing documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months. Internet-Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as a "working
draft" or "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 memo is unlimited.
Abstract
This memo describes the transmission of IPv6 packets over IPv6 and
IPv4 tunnels, and the IPv6 tunnel link local addresses.
1. Introduction
This document specifies the frame format for transmission of IPv6
packets and the method of forming IPv6 link-local addresses on IPv6
tunnels. It also specifies the content of the Source/Target Link-
layer Address option used in Inverse Neighbor Solicitation, and
Neighbor Advertisement messages when those messages are transmitted
over an IPv6 tunnel [IND_TUN].
Conta Expires in six months [Page 1]
INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997
The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED,
SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as
defined in RFC 2119.
2. Maximum Transmission Unit
The default MTU size for IPv6 or IPv4 tunnels is the MTU of the
underlying physical interface less the size of the tunnel headers
[TUNNEL].
The MTU can be reduced by manual configuration. An IPv6 or IPv4 tun-
nel MTU cannot be larger than its default size.
3. Frame format
IPv6 packets are transmitted in standard IPv6 packet format - IPv6
packets are payloads of IPv6 Tunnel packets.
The IPv6 tunnel header contains as Source and Destination the tunnel
entry-point and exit-point node addresses. The tunnel IPv6 header is
filled in conforming to [TUNNEL].
4. Stateless Autoconfiguration
This applies only for IPv6 tunnels.
The interface token [CONF] for an IPv6 tunnel pseudo-interface must
be unique on the virtual link represented by the tunnel, i.e., the
tunnel's end-point nodes must have distinct pseudo-interface tokens.
The default IPv6 tunnel pseudo-interface token is based on the under-
lying physical interface EUI-64 identifier [ETHER]. It is the result
of masking the forth and fifth octets of the EUI-64 identifier with
the fixed FFFC hexadecimal value.
For instance for an underlying physical interface EUI-64 identifier
36-56-78-FF-FE-9A-BC-DE.
the IPv6 tunnel pseudo-interface token is:
36-56-78-FF-FC-9A-BC-DE.
An IPv6 address prefix used for stateless autoconfiguration of an
IPv6 tunnel interface must have a length of 64 bits.
Conta Expires in six months [Page 2]
INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997
5. Link-Local Addresses
This applies only to IPv6.
The IPv6 link-local address [AARCH] for an IPv6 tunnel pseudo-
interface is formed by appending the pseudo-interface token, as
defined above, to the prefix FE80::/64.
10 bits 54 bits 64 bits
+----------+-----------------------+----------------------------+
|1111111010| (zeros) | Pseudo-Interface Token |
+----------+-----------------------+----------------------------+
6. Address Mapping - Unicast
The procedure for mapping IPv6 addresses to tunnel IPv6 or IPv4
addresses is described in [IND_TUN].
The Source/Target Virtual Link-layer Address option has the following
form when the (virtual) link layer is an IPv6 or IPv4 tunnel.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 | Type | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
4 | |
+ +
8 | |
+ IPv6 Address +
12 | |
+ +-------------------------------+
16 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
20 | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Conta Expires in six months [Page 3]
INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997
or
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 | IPv4 |
+- -+
4 | Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
6 | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option fields:
Type 1 for Source Link-layer address.
2 for Target Link-layer address.
Length 3 (in units of 8 octets) for IPv6 addresses
1 (in units of 8 octets) for IPv4 addresses
IPv6 Address
The 128 bit IPv6 address of the IPv6 tunnel pseudo-interface.
or
IPv4 Address
The 32 bit IPv4 address of the IPv4 tunnel pseudo-interface.
7. Security Considerations
The mechanisms defined in this document for generating IPv6 tunnel
address tokens are intended to provide virtual link uniqueness.
There is no security protection from duplication through forgery or
accident.
8. Acknowledgments
This draft is a result of a discussion with Steve Deering about the
applicability and benefits of Neighbor Discovery for IPv6 tunnels.
After more thinking and in combination with IPv6 Inverse Neighbor
Discovery things seemed to fall into place.
The IPv4 part is an idea that Dan Harrington suggested, and it was
very easy to add.
Conta Expires in six months [Page 4]
INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997
9. References
[RFC-1883] S. Deering, R. Hinden, "Internet Protocol Version 6 Speci-
fication"
[RFC-1885] A. Conta, and S. Deering "Internet Control Message Proto-
col for the Internet Protocol Version 6 (IPv6)"
[RFC-1970] T. Narten, E. Nordmark, W.Simpson "Neighbor Discovery for
IP Version 6 (IPv6)"
[IND_TUN] A. Conta "IPv6 ND Extensions for Inverse Neighbor Discov-
ery.
[TUNNEL] A. Conta, S. Deering "Generic IPv6 Encapsulation".
[ETHER] M. Crawford "Transmission of IPv6 packets over Ethernet"
Authors' Addresses
Alex Conta
Lucent Technologies Inc.
300 Baker Ave, Suite 100
Concord, MA 01742
+1-508-287-2842
email: aconta@lucent.com
Conta Expires in six months [Page 5]