Internet-Draft K. Yamamoto (NAIST)
K. Cho (Sony CSL)
Expires in six months Y. Inoue (Fujitsu)
H. Esaki (Toshiba)
Y. Atarashi (Hitachi)
A. Hagiwara (Bay Networks)
February, 1998
IPv6 over Point-to-Point ATM Link
<draft-yamamoto-ipv6-over-p2p-atm-01.txt>
Status of this Memo
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Abstract
This memo defines a communication mechanism to exchange both IPv6
unicast and multicast packets over an ATM network used as a
point-to-point link.
1. Introduction
ATM has become one of the most popular link-layer technologies in
the Internet. Typical usage of ATM is categorized as follows:
(1) Broadcast network such as LAN emulation(LANE)
(2) Non-Broadcast Multiple Access(NBMA) networks
(3) Point-to-point networks
This memo discusses a communication mechanism for an IPv6[IPV6] over
a point-to-point ATM link(3). One of applications of ATM is a fat
pipe typically found in backbone networks.
This memo defines IEEE 802.2 logical link control(LLC) headers for
IPv6 over a point-to-point ATM link. The default of MTU size of
point-to-point ATM and a mechanism to generate an interface
identifier are also specified.
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2. Scope of This Memo
Throughout this memo, the term "point-to-point ATM link" means that
one virtual circuit(VC) is established between two nodes and the VC
can be accessible through one logical network interface. This link
is abstracted as a serial link to the IPv6 layer. It is not our
intention to recommend that ATM be used exclusively for
point-to-point networks.
In this memo, ATM Adaptation Layer 5(AAL5)[ATM-ENCAP] is assumed to
carry IPv6 packets over ATM. Both IPv6 unicast and multicast
packets are delivered only to the opposite end of the point-to-point
ATM link.
Please note that point-to-point ATM link here is not a special case
of NBMA(2). While NBMA requires a special mechanism for multicast,
a point-to-point ATM link here does not require it.
There is strong demand to implement an IPv6 network over a
point-to-point ATM link without such a special mechanism. So, it is
highly desired to define LLC headers of IPv6 over a point-to-point
ATM link for inter-operability.
3. Standard Keywords
This memo occasionally uses terms which are in capital letters.
When the terms "MUST", "SHOULD", "MUST NOT", "SHOULD NOT", and "MAY"
appear capitalized, they are being used to indicate particular
requirements, whose definitions are found in [KEYWORDS].
4. IPv6 packet encapsulation
LLC encapsulation is adopted to exchange IPv6 packets over a
point-to-point ATM link in this memo. Null encapsulation is not
adapted since it is very likely that both IPv6 and IPv4 are used on
a point-to-point ATM link at the same time.
0x86DD is assigned for the EtherType of IPv6[IPV6-ETHER], so this
memo chooses 0x86DD as the Protocol Identifier(PID) according to
[ATM-ENCAP]. The encapsulation for both IPv6 unicast and multicast
on a point-to-point ATM link is defined as follows:
+-------------------------------+
| LLC 0xAA-AA-03 |
+-------------------------------+
| OUI 0x00-00-00 |
+-------------------------------+
| PID 0x86-DD |
+-------------------------------+
| . |
| IPv6 packet |
| . |
+-------------------------------+
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Internet Draft IPv6 over ATM February 1998
5. MTU size
The default MTU size for IPv6 over point-to-point ATM SHOULD be 9180
octets according to [AAL5-MTU]. Values other than the default MAY
be used.
An automatic negotiation mechanism for the MTU is not defined in
this memo. It is not usually necessary on ATM point-to-point links
as long as the same MTU value is correctly configured at each end
of nodes.
However, it is useful to provide a configuration mechanism of MTU in
certain cases. For example, suppose that a host and a router are
connected with a point-to-point ATM link and the router is also
attached to a LAN whose MTU is smaller than 9180. To prevent
overhead of Path MTU Discovery triggered by the host, an
administrator may wish to configure the MTU of the ATM interface to
the smaller one in the router. This value will be announced to the
host via Router Advertisements(RA) through the point-to-point ATM
link then the host will adjust its MTU for the link.
6. Interface Identifier
An interface for a point-to-point ATM link MUST have a 64 bit
interface token for IPv6. It MUST be unique within the link. That
is, for the point-to-point ATM link, it MUST be different from the
peer's token.
The interface token SHOULD be generated according to the following
steps:
(A) If the ATM interface has an EUI 64 bit MAC address, generate an
interface identifier with it according to "Links or Nodes with
EUI-64 Identifiers" in Appendix A of [AARCH].
(B) If the ATM interface has an IEEE 802 48 bit MAC address,
generate an interface identifier with it according to "Links or
Nodes with IEEE 802 48 bit MAC's" in Appendix A of [AARCH].
Note: A node may have multiple virtual interfaces on a single
physical ATM interface. Though such a node may generate the same
interface identifier for the virtual interfaces, it is not a problem
since interface identifiers are not necessarily unique on the node.
(C) If an EUI 64 bit MAC address is available anywhere on the node,
generate an interface identifier with it according to "Links or
Nodes with EUI-64 Identifiers" in Appendix A of [AARCH].
(D) If an IEEE 802 48 bit MAC address is available anywhere on the
node, generate an interface identifier with it according to
"Links or Nodes with IEEE 802 48 bit MAC's" in Appendix A of
[AARCH].
(E) If an IEEE global identifier is not available, a different
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Internet Draft IPv6 over ATM February 1998
source of uniqueness should be used. For example, a suggested
source of uniqueness is machine serial numbers. If such a source
is available, generate an interface identifier with it according
to "Links with Non-Global Identifiers" in Appendix A of [AARCH].
(F) If a good source of uniqueness cannot be found, generate an
interface identifier with a random number according to "Links
with Non-Global Identifiers" in Appendix A of [AARCH].
7. Neighbor Discovery
As of this writing, NDP[IPV6-ND] over point-to-point links is being
discussed in IPng working group. If an RFC on this topic will
appear in the future, NDP over point-to-point ATM links is required
to implement according to the RFC.
Until such an RFC becomes available, this memo specifies the
following requirements. If a node receives a Neighbor Solicitation
message from its peer through the point-to-point ATM link, the node
MUST send a Neighbor Advertisement message in response. A node MUST
NOT discard a Neighbor Solicitation message nor a Neighbor
Advertisement message even if a link layer address option is not
included in the message or if a link layer address option with an
unknown format to the node is included in the message. This is
because link layer address resolution is not necessary on
point-to-point ATM links. Moreover, in all cases, any link layer
address options SHOULD be ignored since they do not provide any
useful information.
8. Relationship with PPP
This memo is one of the current simple solutions. PPP[PPP] is a
more advanced solution with more features and subsequently needs
more resources. Currently, the only feature provided by PPP which
is not covered by this memo is Maximum Receive Unit (MRU)
negotiation. Duplicated Token Discovery is possible by Duplicated
Address Detection defined in [IPV6-AUTO].
This memo provides an enough mechanism for current several
well-managed and relatively static ATM environments. IPv6 over PPP
over a point-to-point ATM link combined with [PPP] and [PPPATM] may
be used in the future if less-managed and more dynamic IPv6 on ATM
circumstances are needed or if more useful configuration options are
defined for it.
9. Security Consideration
It is believed that this memo does not introduce new security
problems to IPv6.
Acknowledgements
The authors thank Katsushi KOBAYASHI, Noritoshi DEMIZU, and Tetsuya
JINMEI for their feedback for early versions of this draft.
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References
[AAL5-MTU] R. Atkinson, "Default IP MTU for use over ATM AAL5", RFC
1626, 1994.
[AARCH] R. Hinden and S. Deering "IP Version 6 Addressing
Architecture", Internet-Draft,
<draft-ietf-ipngwg-addr-arch-v2-06.txt>, 1997.
[ATM-ENCAP] J. Heinanen, "Multiprotocol Encapsulation over ATM
Adaptation Layer 5", RFC1483, 1993.
[EUI64] "64-Bit Global Identifier Format Tutorial",
http://standards.ieee.org/db/oui/tutorials/EUI64.html.
[IPV6] S. Deering and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 1883, 1996.
[IPV6-AUTO] S. Thomson and T. Narten, "IPv6 Stateless Address
Autoconfiguration", Internet-Draft,
<draft-ietf-ipngwg-addrconf-v2-01.txt>, 1997
[IPV6-ETHER] M. Crawford, "Transmission of IPv6 Packets over
Ethernet Networks", Internet-Draft,
<draft-ietf-ipngwg-trans-ethernet-04.txt>, 1997.
[IPV6-ND] T. Narten, E. Nordmark, and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", Internet-Draft,
<draft-ietf-ipngwg-discovery-v2-01.txt>, 1997.
[KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[PPP] D. Haskin and E. Allen, "IP Version 6 over PPP",
Internet-Draft, <draft-ietf-ipngwg-ipv6-over-ppp-05.txt>, 1997.
[PPPATM] G. Gross, M. Kaycee, A. Lin, A. Mails, and J. Stephens,
"PPP Over AAL5", Internet-Draft,
<draft-ietf-pppext-aal5-04.txt>, 1997.
Author's Address
Kazuhiko YAMAMOTO
Graduate School of Information Science
Nara Institute of Science and Technology(NAIST)
8916-5 Takayama, Ikoma 630-01 JAPAN
Phone: +81-743-72-5111
FAX: +81-743-72-5329
EMail: Kazu@Mew.org
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Internet Draft IPv6 over ATM February 1998
Kenjiro CHO
Sony Computer Science Laboratory Inc.
3-14-13 Higashi-Gotanda, Shinagawa-ku 141 JAPAN
Phone: +81-3-5448-4380
FAX: +81-3-5448-4273
EMail: kjc@csl.sony.co.jp
Yoshinobu INOUE
Fujitsu Limited
4-1-1 Kamikodanaka, Nakahara-ku, Kawasaki 211-88 JAPAN
Phone: +81-44-754-3263
FAX: +81-44-754-3864
EMail: shin@nd.net.fujitsu.co.jp
Hiroshi ESAKI
Computer and Network Product Division, Toshiba Corporation
Suite 19A, 1-1-1 Shibaura, Minato-ku 105-01 JAPAN
Phone: +81-3-3457-2563
FAX: +81-3-5444-9331
EMail: hiroshi@isl.rdc.toshiba.co.jp
Yoshifumi ATARASHI
Office Systems Division, Hitachi, Ltd.
810 Shimoimaizumi, Ebina-shi 243-04 JAPAN
Phone: +81-462-35-2111
FAX: +81-462-35-8325
EMail: atarashi@ebina.hitachi.co.jp
Atsushi HAGIWARA
Bay Networks K.K.
28th Shiroyama JT Mori bldg.
4-3-1, Torano-mon, Minato-ku 105 JAPAN
Phone: +81-3-5402-7001
FAX: +81-3-5402-0179
EMail: ahagiwar@baynetworks.co.jp
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