[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]
Versions: (draft-xia-dhc-host-gen-id) 00 01
02 03 04 05
Network Working Group S. Jiang
Internet-Draft F. Xia
Intended status: Standards Track B. Sarikaya
Expires: February 22, 2013 Huawei Technologies
August 21, 2012
Prefix Assignment in DHCPv6
draft-ietf-dhc-host-gen-id-03
Abstract
This document introduces a generic prefix announcement mechanism
using DHCPv6. In this new address configuration procedure, the
prefix is propagated from a DHCPv6 server to hosts through DHCPv6
message exchanging while the interface identifiers are independently
generated by the hosts. It enables both integral address assignment
and self-generated addresses in one single mechanism, DHCPv6. It
also enables stateless address configuration without RA attendance.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 22, 2013.
Copyright Notice
Copyright (c) 2012 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
Jiang, et al. Expires February 22, 2013 [Page 1]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
include Simplified BSD License text as described in Section 4.e of
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 . . . . 7
5.2. IA_PA Prefix Option . . . . . . . . . . . . . . . . . . . 8
6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8
7. IANA consideration . . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . . 9
10.2. Informative references . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11
Jiang, et al. Expires February 22, 2013 [Page 2]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
1. Introduction
A host IPv6 address is combined by a prefix and an interface
identifier. Currently, there are two mechanisms to configure a host
IPv6 address. [RFC3315] describes the operation of address
assignment by a DHCPv6 server. The operation assumes that the server
is responsible for the assignment of an integral address which
includes both prefix and interface identifier parts as described in
[RFC4291]. In the Stateless Address Autoconfiguration (SLACC,
[RFC4862]) model, the interface Identifier is generated by the host
itself while the prefix is configured through Router Advertisement
message defined in [RFC4861].
However, in a DHCPv6-managed network, assigning 128-bit address is
insufficient. Some hosts may want to use self-generated address,
which are combined by prefixes obtained from network configuration
and interface identifiers generated by hosts. The examples include
CGA [RFC3972], modified EUI-64 interface identifier [EUI-64],
temporary addresses for privacy [RFC4941] and etc.
In these scenarios, the address configuration precedure has to be
splitted in two motheds: integral address assignment through DHCPv6
and prefix announcement by RA advertisement. Some ISPs desire to
manage address configuration using one set of protocol, rather than
mixture of DHCPv6 and Neighbor Discovery.
There are also some network environments in that perfix annoucement
through RAs may not be the best choice. For example, hosts may
connect through tunnels, either layer 2 tunnels or layer 3 tunnels.
While a RA is only able to announce prefix on a single link, DHCPv6
configuration can be used to manage multiple links by setup DHCPv6
relay.
Up to now, there is no mechanism for the prefix announcement/
assignment in DHCPv6. [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-generated interface identifiers model, in which prefix(es) need
to be advertised or assigned to hosts.
This document introduces a generic prefix announcement mechanism
using DHCPv6. In this new address configuration procedure, the
prefix is propagated from a DHCPv6 server to hosts through DHCPv6
Jiang, et al. Expires February 22, 2013 [Page 3]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
message exchanging while the interface identifiers are independently
generated by the hosts. It is alternative of RA prefix assignment/
announcement. It enables both integral address assignment and self-
generated addresses in one single mechanism, DHCPv6. Note, in many
scenarios, neighbor discovery is still needed for routing and
reachability. In other scenarios, this mechanism enables stateless
address configuration while RA absents.
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
Jiang, et al. Expires February 22, 2013 [Page 4]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
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
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. This document targets to meet this
gap. 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.
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/Request |
|---------------------> |
| 2 Advertise/Reply |
| with IA_PA Option |
|<--------------------- |
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. A host MAY include a Option Request Option requesting
IA_PA in a Solicit or a IA_PA Option in a Request message to
request prefix assignment explicitly.
Jiang, et al. Expires February 22, 2013 [Page 5]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
2. The DHCPv6 server assigns one or more prefixes to the host in
Advertise messages or in the Reply messages responding to the
prefix requests from the hosts. When the prefix assignment in
advertise model, even if a host does not request, DHCPv6 server
can push it initiatively. 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
NoPrefixAvail (defined in [RFC3633])status-code is returned to
the host and the procedure is terminated. 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
[I-D.ietf-dhc-addr-registration]. However, the confirmation
procedure is out of scope.
When the host reaches T1 or T2 defined in Section 5.1, it SHOULD use
the same message exchanges, as described in section 18, "DHCP Client-
Initiated Configuration Exchange" of [RFC3315], to obtain or update
prefix(es) from a DHCPv6 server.
A DHCPv6 server MAY initiatively send a reconfiguration message to
the host, as described in section 19, "DHCP Server-Initiated
Configuration Exchange" of [RFC3315], to cause prefix(es) information
update.
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
Jiang, et al. Expires February 22, 2013 [Page 6]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
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:
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 .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Jiang, et al. Expires February 22, 2013 [Page 7]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
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.
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
Jiang, et al. Expires February 22, 2013 [Page 8]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
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] .
9. Acknowledgements
The authors would like to thanks Suresh Krishnan, Ted Lemon, Bing
Liu, Andre Kostur, Gaurav Halwasia, Bernie Volz 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.
Jiang, et al. Expires February 22, 2013 [Page 9]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
[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.
[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.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
10.2. Informative references
[RFC3314] Wasserman, M., "Recommendations for IPv6 in Third
Generation Partnership Project (3GPP) Standards",
RFC 3314, September 2002.
[RFC4968] Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
Based Networks", RFC 4968, August 2007.
[I-D.ietf-dhc-secure-dhcpv6]
Jiang, S. and S. Shen, "Secure DHCPv6 Using CGAs",
draft-ietf-dhc-secure-dhcpv6-06 (work in progress),
March 2012.
[I-D.ietf-dhc-addr-registration]
Jiang, S. and G. Chen, "A Generic IPv6 Addresses
Registration Solution Using DHCPv6",
draft-ietf-dhc-addr-registration-00 (work in progress),
May 2012.
Jiang, et al. Expires February 22, 2013 [Page 10]
Internet-Draft Prefix Assignment in DHCPv6 August 2012
[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
Jiang, et al. Expires February 22, 2013 [Page 11]
Html markup produced by rfcmarkup 1.129b, available from
https://tools.ietf.org/tools/rfcmarkup/