Prefix Assignment in DHCPv6
draft-ietf-dhc-host-gen-id-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (dhc WG) | |
|---|---|---|---|
| Authors | Sheng Jiang , Frank Xia , Behcet Sarikaya | ||
| Last updated | 2011-11-20 (Latest revision 2011-05-16) | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-dhc-host-gen-id-01
Network Working Group S. Jiang
Internet-Draft F. Xia
Intended status: Standards Track B. Sarikaya
Expires: May 24, 2012 Huawei Technologies
November 21, 2011
Prefix Assignment in DHCPv6
draft-ietf-dhc-host-gen-id-01.txt
Abstract
This document describes a procedure for configuring hosts' IPv6
address which the prefix is assigned from a DHCPv6 server through
DHCPv6 protocol while the interface identifiers are independently
generated by the hosts. The method is applicable to
Cryptographically Generated Addresses (CGA), and other IPv6 addresses
with host-generated interface identifiers.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 24, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Address Auto-configuration . . . . . . . . . . . . . . . . . . 4
4. DHCPv6 Operation . . . . . . . . . . . . . . . . . . . . . . . 5
5. DHCPv6 IA_PA Option . . . . . . . . . . . . . . . . . . . . . 6
5.1. Identity Association for Prefix Assignment Option . . . . 6
5.2. IA_PA Prefix Option . . . . . . . . . . . . . . . . . . . 7
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative references . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
[RFC3315] describes the operation of address assignment by a DHCPv6
server. A client uses a Solicit message to discover DHCPv6 servers
configured to assign addresses. A server sends an Advertise message
in response to announce the availability of the server to the client.
The client then uses a Request message to request addresses. The
server then returns addresses in a Reply message. The operation
assumes that the server is responsible for the assignment of an
integral address which includes prefix and interface identifier parts
as described in [RFC4291].
This document introduces a new DHCPv6 procedure to configure hosts'
IPv6 addresses. In this new procedure, the prefix is advertised from
a DHCPv6 server through DHCPv6 protocol while the interface
identifiers are independently generated by the hosts.
[RFC3633] defines Prefix Delegation options providing a mechanism for
automated delegation of IPv6 prefixes using the DHCPv6. This
mechanism is intended for delegating a long-lived prefix from a
delegating router to a requesting router. This mechanism "is not
bound to the assignment of IP addresses or other configuration
information to hosts" [RFC3633]. It delegates prefixes to a routable
device for itself use only. It does not support the host-genarated
interface identifiers model, in which prefix(es) need to be
advertised or assigned to hosts.
[RFC3972] describes a method for binding a public signature key to an
IPv6 address in the Secure Neighbor Discovery (SEND) protocol
[RFC3971]. The basic idea is to generate the interface identifier
(i.e., the rightmost 64 bits) of the IPv6 address by computing a
cryptographic hash of the public key. That is, the host decides its
interface identifier. As for the prefix part of the CGA, it is
probably got through Router Advertisement message defined in
[RFC4861], or through DHCPv6 operations defined in this document.
[I-D.ietf-csi-dhcpv6-cga-ps] describes potential issues in the
interaction between DHCPv6 and CGA. In that document , the usage of
DHCPv6 for assigning prefixes is proposed to facilitate separation of
prefix assignment and interface identifier generation.
There are also other host-generated IPv6 addresses, which are
combined by prefixes obtained from network configuration and
ingerface identifiers generated by hosts, such as modified EUI-64
interface identifier [EUI-64], temporary addresses for privacy
[RFC4941],etc. The DHCPv6 operations defined in this document also
supports such address methods.
The DHCPv6 operations defined in this document also supports the
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assigned prefix to be shared across multiple hosts.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
The terminology in this document is based on the definitions in
[RFC3315], in addition to the ones specified in this section
derivative prefix: A prefix is derived from another prefix. For
example, a /64 prefix is derived from a /48 prefix, that is, the
/64 prefix has the same leftmost 48 bits with the /48 prefix.
authorized prefix: A specific router is given a specific set of
subnet prefixes to advertise; other routers have an authorization
to advertise other subnet prefixes. In [RFC3971],Certification
Path Advertisement message is used to convey authorized prefixes.
3. Address Auto-configuration
Router Advertisements in [RFC4861] allow routers to inform hosts how
to perform Address Auto-configuration. For example, routers can
specify whether hosts should use DHCPv6 and/or stateless address
configuration. In Router Advertisement message, M and O bits are
used for indication of address auto-configuration mode.
Whatever address auto-configuration mode a host uses, the following
two parts are necessary for the host to formulate it's IPv6 address:
o A prefix. In [RFC3971], Certification Path Solicitation and
Certification Path Advertisement messages are designed for
verifying routers being authorized to act as routers.
Certification Path Advertisement message can also be used to
verify that routers are authorized to advertise a certain set of
subnet prefixes. In the stateless auto-configuration address
mode, the prefixes in Router Advertisement message should be a
subset of authorized prefixes, or derivative prefixes from
authorized prefixes. In the stateful auto-configuration address
mode, prefix assignment from a DHCPv6 server is not currently
support.
o An interface identifier. Modified EUI-64 interface identifier
[EUI-64] is a widely-used host generated interface identifier. It
generates interface identifier from the host MAC address. The
interface identifier of [RFC3972] is generated by computing a
cryptographic hash of a public key of a host. The host is
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responsible for interface identifier generation.
In the ND-managed environment, RA is used to assign the prefix.
So far, there is no mechanism to support the scenario that prefixes
are managed by a DHCPv6 server. The DHCPv6 operation defined in this
document enables the DHCPv6 server to assign a prefix, rather than a
integral address, to the host, so that the host can obtain an IPv6
address by combining the prefix with its own generated interface
identifier. It actually enables the auto address configuration
through DHCPv6.
This document targets to meet this gap.
4. DHCPv6 Operation
Figure 1 shows the operation of separating prefix assignment and
interface identifier generation in the DHCPv6.
+------------+ +-------------+
|Host(Client)| |DHCPv6 Server|
+------------+ +-------------+
| 1 Solicit |
|---------------------> |
| 2 Advertise |
|<--------------------- |
3 Combination of Prefix |
and Interface Identifier |
| |
Figure 1: DHCPv6 Operation
1. A host uses a Solicit message to discover DHCPv6 servers that
have been configured to assign prefixes for the host. Identity
Association for Prefix Delegation Option (IA_PD) is defined in
[RFC3633] for prefix delegation between a requesting router and
delegating router. Referring to the definition, a new Identity
Association for Prefix Assignment (IA-PA) option is defined in
Section 5.1 to enable the prefix assignment from a DHCPv6 server
to a host.
2. The DHCPv6 server assigns one or more prefixes to the host in
Advertise messages or in the Reply messages to the prefix
requests from the hosts. The assigned prefixes SHOULD be a
subset of the authorized prefixes or derivative prefixes of the
authorized prefixes. Identity Association for Prefix Assignment
Option in Section 5.1 is used for conveying the assigned
prefixes. If there is not a proper prefix available, a status-
code is returned to the host and the procedure is terminated.
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When receiving multiple prefixes, the host may use pre-configured
hints for prefix assignment preference. The hints are authorized
prefixes advertised by an authorized router through Certification
Path Advertisement defined in [RFC3971].
3. The host generates an interface identifier and formulates a
combined IPv6 address by concatenating the assigned prefix and
the self-generated interface identifier. There are many ways to
generate interface identifier. [RFC3972] defines a method to
generate the interface identifier by computing a cryptographic
hash of a public key of the host. Modified EUI-64 interface
identifier [EUI-64] is generated based on the host MAC address.
After the host generates an IPv6 address using the above procedure,
the host may send a Request message to the DHCPv6 server in order to
confirm the usage of the new address. The confirmation procedure may
be completed together with the address registration procedure.
However, the confirmation procedure is out of scope.
5. DHCPv6 IA_PA Option
In this section, one new option is defined, Identity Association for
Prefix Assignment Option . The format of this new DHCPv6 IA_PA
Option has been deliberately designed to be the same with IA_PD
option[RFC3633]. The IA_PD Prefix and IA Address sub-options from
IA_PD option are also reused. However, the two options are different
on the semantics and usage models.
The prefixed assigned through this DHCPv6 IA_PA option could be
shared accross multiple hosts.
5.1. Identity Association for Prefix Assignment Option
The IA_PA option is used to carry a prefix assignment identity
association, the parameters associated with the IA_PA and the
prefixes associated with it.
The format of the IA_PA option is:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_IA_PA | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IAID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| T1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| T2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. IA_PA-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_IA_PA (TBA1)
option-length: 12 + length of IA_PA-options field.
IAID: The unique identifier for this IA_PA; the IAID must
be unique among the identifiers for all of this
host's IA_PAs.
T1: The time at which the host should
contact the DHCPv6 server from which the
prefixes in the IA_PA were obtained to extend the
lifetimes of the prefixes assigned to the IA_PA;
T1 is a time duration relative to the current time
expressed in units of seconds.
T2: The time at which the host should
contact any available DHCPv6 server to extend
the lifetimes of the prefixes assigned to the
IA_PA; T2 is a time duration relative to the
current time expressed in units of seconds.
IA_PA-options: Options associated with this IA_PA.
The details of the fields are similar to the IA_PD option description
in [RFC3633]. The difference is here a DHCPv6 server and a host
involved, while a delegating router and requesting router involved in
[RFC3633].
5.2. IA_PA Prefix Option
OPTION_IAPREFIX (26) "IA_PD Prefix Option" defined in Section 10 of
[RFC3633] is reused.
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Originally, the option is used for conveying prefix information
between a delegating router and a requesting router. Here the IA_PD
Prefix option is used to specify IPv6 address prefixes associated
with an IA_PA in Section 5.1. The IA_PD Prefix option must be
encapsulated in the IA_PA-options field of an IA_PA option.
6. Applicability
In point-to-point link model, DHCPv6 operation with host-generated
interface identifier, described in this document, may be used.
[RFC4968] provides different IPv6 link models that are suitable for
802.16 based networks and a point-to-point link model is recommended.
Also, 3GPP and 3GPP2 have earlier adopted the point-to-point link
model based on the recommendations in [RFC3314]. In this model, one
prefix can only be assigned to one interface of a host (mobile
station) and different hosts (mobile stations) can't share a prefix.
The unique prefix can be used to identify the host. It is not
necessary for a DHCPv6 server to generate an interface identifier for
the host. The host may generate its interface identifier as
described in [RFC4941]. An interface identifier could even be
generated via random number generation.
Modified EUI-64 interface identifier [EUI-64] is also typically
generated by hosts. [RFC4941] has defined temporary addresses for
privacy purposes. The temporary addresses is also generated by hosts
using random algorithm. The DHCPv6 operations defined in this
document also supports such address methods.
7. IANA consideration
This document defines a new DHCPv6 [RFC3315] option, which must be
assigned Option Type values within the option numbering space for
DHCPv6 messages:
The OPTION_IA_PA Option (TBA1), described in Section 5.1.
8. Security Considerations
Security considerations in DHCPv6 are described in [RFC3315].
To guard against attacks through prefix assignment, a host and a
DHCPv6 server SHOULD use DHCPv6 authentication as described in
Section 21, "Authentication of DHCP messages" of [RFC3315] or Secure
DHCPv6 [I-D.ietf-dhc-secure-dhcpv6] .
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9. Acknowledgements
The authors would like to thanks Suresh Krishnan, Ted Lemon and other
members of DHC WG for their valuable comments.
10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
Neighbor Discovery (SEND)", RFC 3971, March 2005.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, March 2005.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
[RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic
Host Configuration Protocol (DHCP) version 6", RFC 3633,
December 2003.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
10.2. Informative references
[RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
Based Networks", RFC 4968, August 2007.
[RFC3314] Wasserman, M., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards",
RFC 3314, September 2002.
[I-D.ietf-csi-dhcpv6-cga-ps]
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Jiang, S., Shen, S., and T. Chown, "DHCPv6 and CGA
Interaction: Problem Statement",
draft-ietf-csi-dhcpv6-cga-ps-07 (work in progress),
May 2011.
[I-D.ietf-dhc-secure-dhcpv6]
Jiang, S. and S. Shen, "Secure DHCPv6 Using CGAs",
draft-ietf-dhc-secure-dhcpv6-03 (work in progress),
June 2011.
[EUI-64] "Guidelines for 64-bit Global Identifier (EUI-64)
Registration Authority", http://standards.ieee.org/
regauth/oui/tutorials/EUI64.html", March 1997.
Authors' Addresses
Sheng Jiang
Huawei Technologies
Q14, Huawei Campus, No.156, BeiQing Road
Hai-Dian District, Beijing 100095
P.R. China
Email: jiangsheng@huawei.com
Frank Xia
Huawei Technologies
1700 Alma Dr. Suite 500
Plano, TX 75075
Email: xiayangsong@huawei.com
Behcet Sarikaya
Huawei Technologies
1700 Alma Dr. Suite 500
Plano, TX 75075
Email: sarikaya@ieee.org
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