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draft-ietf-ion-ipv6-atm-00.txt
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Internet-Draft Grenville Armitage
Lucent Technologies
Peter Schulter
BrightTiger Technologies
Markus Jork, Geraldine Harter
Digital
October 11th, 1997
IPv6 over ATM Networks
<draft-ietf-ion-ipv6-atm-00.txt>
Status of this Memo
This document was submitted to the IETF Internetworking over NBMA
(ION) WG. Publication of this document does not imply acceptance by
the ION WG of any ideas expressed within. Comments should be
submitted to the ion@nexen.com mailing list.
Distribution of this memo is unlimited.
This memo 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. 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
"lid-abstracts.txt" listing contained in the Internet-Drafts shadow
directories on ds.internic.net (US East Coast), nic.nordu.net
(Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific
Rim).
Abstract
This document is a companion to the ION working group's architecture
document 'IPv6 over Non Broadcast Multiple Access (NBMA) networks'.
It provides specific details on how to apply the IPv6 over NBMA
architecture to ATM networks. This architecture allows conventional
host-side operation of the IPv6 Neighbor Discovery protocol, while
also supporting the establishment of 'shortcut' ATM forwarding paths
(when using SVCs). Operation over administratively configured Point
to Point PVCs is also supported.
Revision History
September 1997, split draft-ietf-ion-tn-01.txt apart to isolate
the ATM specific details from the NBMA-generic architecture.
Armitage, et al. Expires April 11th, 1998 [Page 1]
Internet Draft draft-ietf-ion-ipv6-atm-00.txt October 11th, 1997
New name of this document: draft-ietf-ion-ipv6-atm-00.txt,
containing the ATM-specific details. (General architecture
document now: draft-ietf-ion-ipv6-00.txt.)
1. Introduction.
This document is an ATM-specific companion document to the ION
working group's "IPv6 over Non Broadcast Multiple Access (NBMA)
networks" specification [1]. Terminology and architectural
descriptions will not be repeated here.
The use of ATM to provide point to point PVC service, or flexible
point to point and point to multipoint SVC service, is covered by
this document.
A minimally conforming IPv6/ATM driver SHALL support the PVC mode of
operation. An IPv6/ATM driver that supports the full SVC mode SHALL
also support PVC mode of operation.
2. Specification Terminology
The following terminology is used in the items of specification in
this document:
o MUST, SHALL, or MANDATORY -- the item is an absolute
requirement of the specification.
o SHOULD or RECOMMENDED -- the item should generally be followed
for all but exceptional circumstances.
o MAY or OPTIONAL -- the item is truly optional and may be
followed or ignored according to the needs of the implementor.
They are to be interpreted as described in RFC 2119 [16].
3. ATM specific codepoints and parameters.
3.1 Packet encapsulation for PVC environments
Following the model in RFC 1483 [2], AAL5 SHALL be the default
Adaptation Layer service, and (LLC/SNAP) encapsulation SHALL be
default encapsulation used by unicast and multicast packets across
pt-pt PVC links. As defined in [1], the default IPv6 packet
encapsulation SHALL be:
[0xAA-AA-03][0x00-00-00][0x86-DD][IPv6 packet]
(LLC) (OUI) (PID)
3.1.1 Optional null encapsulation
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IPv6/ATM drivers MAY also support null encapsulation as a
configurable option. When null encapsulation is enabled, the IPv6
packet is passed directly to the AAL5 layer. Both ends of the PVC
MUST be configured to use null encapsulation. The PVC will not be
available for use by protocols other than IPv6.
3.1.2 PPP encapsulation
The concatentation of IPv6 over PPP with PPP over AAL5 PVCs is not
covered by this specification.
3.2 Packet encapsulation for SVC environments
Following the model in RFC 1483 [2], AAL5 SHALL be the default
Adaptation Layer service, and (LLC/SNAP) encapsulation SHALL be the
default encapsulation used by unicast and multicast packets across
SVC links.
3.2.1 Unicast packet encapsulation
As defined in [1], the default IPv6 unicast packet encapsulation
SHALL be:
[0xAA-AA-03][0x00-00-00][0x86-DD][IPv6 packet]
(LLC) (OUI) (PID)
3.2.2 Multicast packet encapsulation
As defined in [1], the default IPv6 multicast packet encapsulation
SHALL be:
[0xAA-AA-03][0x00-00-5E][0x00-01][pkt$cmi][0x86DD][IPv6 packet]
(LLC) (OUI) (PID) (mars encaps)
The IPv6/ATM driver's Cluster Member ID SHALL be copied into
the 2 octet pkt$cmi field prior to transmission.
3.2.3 Optional null encapsulation
IPv6/ATM drivers MAY also support null encapsulation as a
configurable option. Null encapsulation SHALL only be used for
passing IPv6 packets from one IPv6/ATM driver to another. Null
encapsulation SHALL NOT be used on the pt-pt SVC between the IPv6/ATM
driver and its local MARS.
If null encapsulation is enabled, the IPv6 packet is passed directly
to the AAL5 layer. Both ends of the SVC MUST agree to use null
encapsulation during the call SETUP phase. The SVC will not be
available for use by protocols other than IPv6.
If null encapsulation is enabled on data SVCs between routers,
inter-router NHRP traffic SHALL utilize a separate, parallel SVC.
Use of null encapsulation is not encouraged when IPv6/ATM is used
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with MARS/NHRP/ND as described in [1].
3.3 MARS control messages
The encapsulation of MARS control messages (between MARS and MARS
Clients) remains the same as shown in RFC 2022 [3]:
[0xAA-AA-03][0x00-00-5E][0x00-03][MARS control message]
(LLC) (OUI) (PID)
The key control field values are:
The mar$afn field remains 0x0F (ATM addresses)
The mar$pro field SHALL be 0x86DD (IPv6)
The mar$op.version field remains 0x00 (MARS)
The mar$spln and mar$tpln fields (where relevant) are either 0 (for
null or non-existent information) or 16 (for the full IPv6 protocol
address)
No changes to the way ATM addresses are stored in [3].
3.4 NHRP control messages
The encapsulation of NHRP control messages remains the same as shown
in RFC xxxx [4]:
[0xAA-AA-03][0x00-00-5E][0x00-03][NHRP control message]
(LLC) (OUI) (PID)
The key control field values are:
The ar$afn field remains 0x0F (ATM addresses)
The ar$pro field SHALL be 0x86DD (IPv6)
The ar$op.version field remains 0x01 (NHRP)
The ar$spln and ar$tpln fields (where relevant) are either 0 (for
null or non-existent information) or 16 (for the full IPv6 protocol
address)
No changes to the way ATM addresses are stored in [3].
3.5 Neigbor Discovery control messages
Section 5.2 of [1] describes the ND Link-layer address option. For
IPv6/ATM drivers, the subfields SHALL be encoded in the following
manner:
[NTL] defines the type and length of the ATM number immediately
following the [STL] field. The format is as follows:
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7 6 5 4 3 2 1 0
+-+-+-+-+-+-+-+-+
|0|x| length |
+-+-+-+-+-+-+-+-+
The most significant bit is reserved and MUST be set to zero. The
second most significant bit (x) is a flag indicating whether the
ATM number is in:
ATM Forum AESA format (x = 0).
Native E.164 format (x = 1).
The bottom 6 bits represent an unsigned integer value indicating
the length of the associated ATM address field in octets.
The [STL] format is the same as the [NTL] field. Defines the length
of the subaddress field, if it exists. If it does not exist this
entire octet field MUST be zero. If the subaddress exists it will be
in AESA format, so flag x SHALL be zero.
[NBMA Number] is a variable length field containing the ATM address
of the Link layer target. It is always present.
[NBMA Subaddress] is a variable length field containing the ATM
subaddress of the Link layer target. It may or may not be present.
When it is not, the option ends after the [NBMA Number] (or any
additional padding for 8 byte alignment).
The octet ordering of the [NBMA Number] and [NBMA Subaddress] fields
SHALL be the same as that used in MARS and NHRP control messages.
4. Interface Tokens
For both PVC and SVC modes of operation, one of the following methods
SHALL be used to generate Interface Tokens as required by section 5.1
of [1].
4.1 Interface Tokens Based on MAC or ESI values
When the underlying ATM interface is identified by an ATM End System
Address (AESA, formerly known as an NSAPA), the interface token MAY
be formed from the ESI and SEL values in the AESA as follows:
[0x00][ESI][SEL]
[0x00] is a one octet field which is always set to 0.
Note that the bit corresponding to the EUI-64 Global/Local bit
[5] is always reset indicating that this address is not a
globally unique IPv6 interface token.
[ESI] is a six octet field.
This field always contains the six octet ESI value for the
AESA used to address the specific instance of the IPv6/ATM
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interface.
[SEL] is a one octet field.
This field always contains the SEL value from the AESA used to
address the specific instance of the IPv6/ATM interface.
4.2 Interface Tokens Based on EUI-64 Values
Where the underlying ATM NIC driver has access to a set of one or
more 64 bit EUI-64 values unique to the ATM NIC (e.g. EUI-64
addresses configured into the NIC's ROM), the IPv6/ATM interface
SHOULD use one of these values to create a unique interface token.
after inverting the Global/Local identifier bit. (Any relationship
between these values and the ESI(s) registered with the local ATM
switch by the ATM driver are outside the scope of this document.)
When EUI-64 values are used for IPv6 interface tokens the only
modification allowed to the octet string read from the NIC is
inversion of the Global/Local identifier bit.
4.3 Interface Tokens Based on Native E.164 Addresses
When an interface uses Native E.164 addresses then the E.164 values
MAY be used to generate an interface token as follows:
[D14][D13D12][D11D10][D9D8][D9D6][D5D4][D3D2][D1D0]
[D14] A single octet containing the semi-octet representing the most
significant E.164 digit shifted left four bits to the most
significant four bits of the octet. The lower four bits MUST be set
to 0. Note that the EUI-64 Global/Local indicator is set to 0
indicating that this is not a globally unique IPv6 interface token.
[D13D12] A single octet containing the semi-octet representing the
second most significant E.164 digit [D13] shifted left four places to
the most significant bits of the octet, and the third most
significant semi-octet in the four least significant bits of the
octet.
[D11D10] - [D1D0] Octets each containing two E.164 digits, one in the
most significant four bits, and one in the least significant four
bits as indicated.
4.5 Multiple Logical Links on a Single Interface
A logical ATM interface might be associated with a different SEL
field of a common AESA prefix, or a set of entirely separate ESIs
might have been registered with the local ATM switch to create a
range of unique AESAs.
The minimum information required to uniquely identify each logical
ATM interface is (within the context of the local switch port) their
ESI+SEL combination.
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For the vhost case described in section 5.1.2 of [1], vhost SHALL
select a different interface token from the range of 64 bit values
available to the ATM NIC (as described in 4.1). Each vhost SHALL
implement IPv6/ATM interfaces in such a way that no two or more
vhosts end up advertising the same interface token onto the same LL.
(Conformance with this requirement may be achieved by choosing
different SEL values, ESI values, or both.)
5. UNI 3.0/3.1 signaling issues (SVC mode).
When an IPv6 node places a call to another IPv6 node, it SHOULD
follow the procedures in [6] and [7] for signalling UNI 3.0/3.1 SVCs
[9] and negotiating MTU. The default MTU size on a LL is 9188 bytes
as specified in [7].
Note that while the procedures in [7] still apply to IPv6 over ATM,
IPv6 Path MTU Discovery [8] is used by nodes and routers rather than
IPv4 MTU discovery. Additionally, while IPv6 nodes are not required
to implement Path MTU Discovery, IPv6/ATM nodes SHOULD implement it.
Also, since IPv6 nodes will negotiate an appropriate MTU for each VC,
Path MTU should never be triggered since neither node should ever
receive a Packet Too Big message to trigger Path MTU Discovery. When
nodes are communicating via one or more routers Path MTU Discovery
will be used just as it is for legacy networks.
6. Conclusion and Open Issues.
This document is an ATM-specific companion document to the ION
working group's "IPv6 over Non Broadcast Multiple Access (NBMA)
networks" specification [1]. It specifies codepoints for the
administratively configured PVC, and dynamically established SVC,
modes of operation.
There are no major open issues. Comments to the ION mailing list are
solicited (ion@nexen.com).
7. Security Consideration
While this proposal does not introduce any new security mechanisms
all current IPv6 security mechanisms will work without modification
for ATM. This includes both authentication and encryption for both
Neighbor Discovery protocols as well as the exchange of IPv6 data
packets.
Acknowledgments
The original IPv6/ATM work by G. Armitage occurred while employed at
Bellcore. Elements of section 4 were borrowed from Matt Crawford's
draft on IPv6 over Ethernet.
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Internet Draft draft-ietf-ion-ipv6-atm-00.txt October 11th, 1997
Author's addresses
Grenville Armitage
Bell Laboratories, Lucent Technologies
101 Crawfords Corner Road
Holmdel, NJ 07733
USA
Email: gja@lucent.com
Peter Schulter
BrightTiger Technologies
125 Nagog Park
Acton, MA 01720
Email: paschulter@acm.org
Markus Jork
European Applied Research Center
Digital Equipment Corporation
CEC Karlsruhe
Vincenz-Priessnitz-Str. 1
D-76131 Karlsruhe
Germany
email: jork@kar.dec.com
Geraldine Harter
Digital UNIX Networking
Digital Equipment Corporation
110 Spit Brook Road
Nashua, NH 03062
Email: harter@zk3.dec.com
References.
[1] G. Armitage, P.Schulter, M. Jork, G. Harter, "IPv6 over Non-
Broadcast Multiple Access (NBMA) networks", INTERNET DRAFT, draft-
ietf-ion-ipv6-00.txt, October 1997
[2] J. Heinanen, "Multiprotocol Encapsulation over ATM Adaption Layer
5", RFC 1483, USC/Information Science Institute, July 1993.
[3] G.J. Armitage, "Support for Multicast over UNI 3.1 based ATM
Networks", RFC 2022, Bellcore, November 1996.
[4] J. Luciani, et al, "NBMA Next Hop Resolution Protocol (NHRP)",
INTERNET DRAFT, draft-ietf-rolc-nhrp-11.txt, March 1997.
[5] "64-Bit Global Identifier Format Tutorial",
http://standards.ieee.org/db/oui/tutorials/EUI64.html.
[6] M. Perez, et al, "ATM Signalling Support for IP over ATM", RFC
1755, February 1995
[7] R. Atkinson, "Default IP MTU for use over ATM AAL5", RFC 1626,
May 1994
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Internet Draft draft-ietf-ion-ipv6-atm-00.txt October 11th, 1997
[8] J. McCann, et al, "Path MTU Discovery for IP version 6", RFC
1981, August 1996
[9] ATM Forum, "ATM User Network Interface (UNI) Specification
Version 3.1", ISBN 0-13-393828-X, Prentice Hall, Englewood Cliffs,
NJ, June 1995.
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