draft-ietf-dhc-dhcpv6-opt-prefix-delegation-02.txt   draft-ietf-dhc-dhcpv6-opt-prefix-delegation-03.txt 
DHC Working Group O. Troan DHC Working Group O. Troan
Internet-Draft R. Droms Internet-Draft R. Droms
Expires: August 11, 2003 Cisco Systems Expires: September 1, 2003 Cisco Systems
February 10, 2003 March 3, 2003
IPv6 Prefix Options for DHCPv6 IPv6 Prefix Options for DHCPv6
draft-ietf-dhc-dhcpv6-opt-prefix-delegation-02.txt draft-ietf-dhc-dhcpv6-opt-prefix-delegation-03.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 32 skipping to change at page 1, line 32
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http:// The list of current Internet-Drafts can be accessed at http://
www.ietf.org/ietf/1id-abstracts.txt. www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on August 11, 2003. This Internet-Draft will expire on September 1, 2003.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
The Prefix Delegation options provide a mechanism for automated The Prefix Delegation options provide a mechanism for automated
delegation of IPv6 prefixes using DHCP. This mechanism is intended delegation of IPv6 prefixes using DHCP. This mechanism is intended
for delegating long-lived prefix from a delegating router to a for delegating long-lived prefix from a delegating router to a
requesting router, across an administrative boundary, where the requesting router, across an administrative boundary, where the
delegating router does not require knowledge about the topology of delegating router does not require knowledge about the topology of
the links in the network to which the prefixes will be assigned. the links in the network to which the prefixes will be assigned.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. DHCPv6 specification dependency . . . . . . . . . . . . . . 3
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Model and Applicability . . . . . . . . . . . . . . . . . . 4 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Identity Association for Prefix Delegation . . . . . . . . . 6 5. Model and Applicability . . . . . . . . . . . . . . . . . . 4
6. Overview of DHCP with Prefix Delegation . . . . . . . . . . 7 5.1 Example network architecture . . . . . . . . . . . . . . . . 4
7. Interface Selection . . . . . . . . . . . . . . . . . . . . 7 6. Identity Association for Prefix Delegation . . . . . . . . . 6
8. Identity Association for Prefix Delegation Option . . . . . 8 7. Overview of DHCP with Prefix Delegation . . . . . . . . . . 7
9. IA_PD Prefix option . . . . . . . . . . . . . . . . . . . . 9 8. Interface Selection . . . . . . . . . . . . . . . . . . . . 7
10. Delegating Router Solicitation . . . . . . . . . . . . . . . 11 9. Identity Association for Prefix Delegation Option . . . . . 8
10.1 Requesting router behaviour . . . . . . . . . . . . . . . . 11 10. IA_PD Prefix option . . . . . . . . . . . . . . . . . . . . 10
10.2 Delegating router behaviour . . . . . . . . . . . . . . . . 11 11. Delegating Router Solicitation . . . . . . . . . . . . . . . 11
11. Requesting router initiated prefix delegation . . . . . . . 12 11.1 Requesting router behaviour . . . . . . . . . . . . . . . . 11
11.1 Requesting router behaviour . . . . . . . . . . . . . . . . 13 11.2 Delegating router behaviour . . . . . . . . . . . . . . . . 12
11.2 Delegating Router behaviour . . . . . . . . . . . . . . . . 14 12. Requesting router initiated prefix delegation . . . . . . . 13
12. Prefix Delegation reconfiguration . . . . . . . . . . . . . 15 12.1 Requesting router behaviour . . . . . . . . . . . . . . . . 13
12.1 Delegating Router behaviour . . . . . . . . . . . . . . . . 15 12.2 Delegating Router behaviour . . . . . . . . . . . . . . . . 14
12.2 Requesting Router behaviour . . . . . . . . . . . . . . . . 15 13. Prefix Delegation reconfiguration . . . . . . . . . . . . . 16
13. Relay agent behaviour . . . . . . . . . . . . . . . . . . . 15 13.1 Delegating Router behaviour . . . . . . . . . . . . . . . . 16
14. Security Considerations . . . . . . . . . . . . . . . . . . 15 13.2 Requesting Router behaviour . . . . . . . . . . . . . . . . 16
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16 14. Relay agent behaviour . . . . . . . . . . . . . . . . . . . 16
16. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 15. Security Considerations . . . . . . . . . . . . . . . . . . 16
17. Changes since revision-01 . . . . . . . . . . . . . . . . . 16 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . 17
Normative References . . . . . . . . . . . . . . . . . . . . 16 17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
Informative References . . . . . . . . . . . . . . . . . . . 17 18. Changes in draft-ietf-dhc-dhcpv6-opt-prefix-delegation-03 . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 17 Normative References . . . . . . . . . . . . . . . . . . . . 18
Full Copyright Statement . . . . . . . . . . . . . . . . . . 18 Informative References . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 18
Full Copyright Statement . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
This document describes new options for DHCP, which provide a This document describes new options for DHCP, which provide a
mechanism for the delegation of IPv6 prefixes. Through these mechanism for the delegation of IPv6 prefixes. Through these
options, a delegating router can delegate prefixes to authorised options, a delegating router can delegate prefixes to authorised
requesting routers. requesting routers.
The prefix delegation mechanism described in this document is The prefix delegation mechanism described in this document is
intended for simple delegation of prefixes from a delegating router intended for simple delegation of prefixes from a delegating router
skipping to change at page 3, line 29 skipping to change at page 3, line 29
For example, these options would be used by a service provider to For example, these options would be used by a service provider to
assign a prefix to a CPE device acting as a router between the assign a prefix to a CPE device acting as a router between the
subscriber's internal network and the service provider's core subscriber's internal network and the service provider's core
network. network.
Many applications expect stable addresses. Even though this Many applications expect stable addresses. Even though this
mechanism makes automatic renumbering easier, it is expected that mechanism makes automatic renumbering easier, it is expected that
prefixes have a long lifespan. During renumbering it is expected prefixes have a long lifespan. During renumbering it is expected
that the old and the new prefix co-exist for some time. that the old and the new prefix co-exist for some time.
2. Terminology The design of this prefix delegation mechanism meets the requirements
for prefix delegation in Requirements for IPv6 prefix delegation [8].
2. DHCPv6 specification dependency
This document describes an extension to the DHCPv6 specification [6].
This document should be read in conjunction with the DHCPv6
specification for a complete specification of the Prefix Delegation
options and mechanism. Definitions for terms and acronyms not
specifically defined in this document are defined in the DHCPv6
specification [6].
3. Terminology
This document uses the terminology defined in RFC2460 [2] and the This document uses the terminology defined in RFC2460 [2] and the
DHCP specification [6]. In addition, this document uses the DHCP specification [6]. In addition, this document uses the
following terms: following terms:
requesting router The router that acts as a DHCP client and is requesting router The router that acts as a DHCP client and is
requesting prefix(es) to be assigned. requesting prefix(es) to be assigned.
delegating router The router that acts as a DHCP server, and is delegating router The router that acts as a DHCP server, and is
responding to the prefix request. responding to the prefix request.
Identity Association for Prefix Delegation (IA_PD) A collection of Identity Association for Prefix Delegation (IA_PD) A collection of
prefixes assigned to the requesting router. Each prefixes assigned to the requesting router. Each
IA_PD has an associated IAID. A requesting IA_PD has an associated IAID. A requesting
router may have more than one IA_PD assigned to router may have more than one IA_PD assigned to
it; for example, one for each of its interfaces. it; for example, one for each of its interfaces.
3. Requirements 4. Requirements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
document, are to be interpreted as described in RFC 2119 [1]. document, are to be interpreted as described in RFC 2119 [1].
4. Model and Applicability 5. Model and Applicability
The model of operation for prefix delegation is as follows. A The model of operation for prefix delegation is as follows. A
delegating router is provided DHCPv6 prefixes to be delegated to delegating router is provided IPv6 prefixes to be delegated to
requesting routers. Examples of ways in which the delegating router requesting routers. Examples of ways in which the delegating router
may be provided these prefixes are given in Section 11.2. A may be provided these prefixes are given in Section 12.2. A
requesting router requests prefix(es) from the delegating router, as requesting router requests prefix(es) from the delegating router, as
described in Section 11.1. The delegating router chooses prefix(es) described in Section 12.1. The delegating router chooses prefix(es)
for delegation, and returns the prefix(es) to the requesting router. for delegation, and responds with prefix(es) to the requesting
The requesting router is then responsible for the delegated router. The requesting router is then responsible for the delegated
prefix(es). For example, the requesting router might assign a subnet prefix(es). For example, the requesting router might assign a subnet
from a delegated prefix to one of its interfaces, and begin sending from a delegated prefix to one of its interfaces, and begin sending
router advertisements for the prefix on that link. router advertisements for the prefix on that link.
Each prefix has an associated valid and preferred lifetime, which Each prefix has an associated valid and preferred lifetime, which
constitutes an agreement about the length of time over which the constitutes an agreement about the length of time over which the
requesting router is allowed to use the prefix. A requesting router requesting router is allowed to use the prefix. A requesting router
can request an extension of the lifetimes on a delegated prefix and can request an extension of the lifetimes on a delegated prefix and
is required to terminate the use of a delegated prefix if the valid is required to terminate the use of a delegated prefix if the valid
lifetime of the prefix expires. lifetime of the prefix expires.
This prefix delegation mechanism would be appropriate for use by an This prefix delegation mechanism would be appropriate for use by an
ISP to delegate a prefix to a subscriber, where the delegated prefix ISP to delegate a prefix to a subscriber, where the delegated prefix
would possibly be subnetted and assigned to the links within the would possibly be subnetted and assigned to the links within the
subscriber's network. subscriber's network.
5.1 Example network architecture
Figure 1 illustrates a network architecture in which prefix Figure 1 illustrates a network architecture in which prefix
delegation would be used. delegation could be used.
+--------+ \ +--------+ \
| AAA | \ | AAA | \
| server | \ | server | \
+---+----+ | +---+----+ |
___|__________________ | ___|__________________ |
/ \ | / \ |
| ISP core network | | | ISP core network | |
\__________ ___________/ | \__________ ___________/ |
| | ISP | | ISP
skipping to change at page 6, line 5 skipping to change at page 6, line 5
the customer at the time of subscription to the ISP service. The the customer at the time of subscription to the ISP service. The
prefix delegation process begins when the requesting router requests prefix delegation process begins when the requesting router requests
configuration information through DHCP. The DHCP messages from the configuration information through DHCP. The DHCP messages from the
requesting router are received by the delegating router in the requesting router are received by the delegating router in the
aggregation device. When the delegating router receives the request, aggregation device. When the delegating router receives the request,
it consults the AAA server to authenticate and authorise the it consults the AAA server to authenticate and authorise the
requesting router. The AAA server returns the subscriber's requesting router. The AAA server returns the subscriber's
prefix(es) in a Framed-IPv6-Prefix attribute as described in RFC 3162 prefix(es) in a Framed-IPv6-Prefix attribute as described in RFC 3162
[7], and the delegating router returns them to the requesting router. [7], and the delegating router returns them to the requesting router.
The requesting router assigns longer prefixes from the delegated The requesting router subnets the delegated prefix and assigns the
prefix for assignment to links in the subscriber's network. In a longer prefixes to links in the subscriber's network. In a typical
typical scenario based on the network shown in Figure 1, the scenario based on the network shown in Figure 1, the requesting
requesting router subnets a single delegated /48 prefix into /64 router subnets a single delegated /48 prefix into /64 prefixes and
prefixes and assigns one /64 prefix to each of the links in the assigns one /64 prefix to each of the links in the subscriber
subscriber network. network.
The prefix delegation options can be used in conjunction with other The prefix delegation options can be used in conjunction with other
DHCP options carrying other configuration information to the DHCP options carrying other configuration information to the
requesting router. The requesting router may, in turn, then provide requesting router. The requesting router may, in turn, then provide
DHCP service to hosts attached to the internal network. For example, DHCP service to hosts attached to the internal network. For example,
the requesting router may obtain the addresses of DNS and NTP servers the requesting router may obtain the addresses of DNS and NTP servers
from the ISP delegating router, and then pass that configuration from the ISP delegating router, and then pass that configuration
information on to the subscriber hosts through a DHCP server in the information on to the subscriber hosts through a DHCP server in the
requesting router. requesting router.
5. Identity Association for Prefix Delegation 6. Identity Association for Prefix Delegation
An IA_PD is a construct through which a delegating router and a An IA_PD is a construct through which a delegating router and a
requesting router can identify, group and manage a set of related requesting router can identify, group and manage a set of related
IPv6 prefixes. Each IA_PD consists of an IAID and associated IPv6 prefixes. Each IA_PD consists of an IAID and associated
configuration information. An IA_PD for prefixes is the equivalent configuration information. An IA_PD for prefixes is the equivalent
of an IA (described in DHCPv6 specification [6]) for addresses. of an IA (described in DHCPv6 specification [6]) for addresses.
An IA_PD is different from an IA, in that it does not need to be An IA_PD is different from an IA, in that it does not need to be
associated with exactly one interface. One IA_PD can be associated associated with exactly one interface. One IA_PD can be associated
with the requesting router, with a set of interfaces or with exactly with the requesting router, with a set of interfaces or with exactly
one interface. A requesting router must create at least one distinct one interface. A requesting router must create at least one distinct
IA_PD. It may associate a distinct IA_PD with each of its downstream IA_PD. It may associate a distinct IA_PD with each of its downstream
network interfaces and use that IA_PD to obtain a prefix for that network interfaces and use that IA_PD to obtain a prefix for that
interface from the delegating router. interface from the delegating router.
The IAID uniquely identifies the IA_PD and must be chosen to be The IAID uniquely identifies the IA_PD and must be chosen to be
unique among the IA_PD IDs on the requesting router. The IAID is unique among the IA_PD IAIDs on the requesting router. The IAID is
chosen by the requesting router. For any given use of an IA_PD by chosen by the requesting router. For any given use of an IA_PD by
the requesting router, the IAID for that IA_PD MUST be consistent the requesting router, the IAID for that IA_PD MUST be consistent
across restarts of the requesting router. The requesting router may across restarts of the requesting router. The requesting router may
maintain consistency either by storing the IAID in non-volatile maintain consistency either by storing the IAID in non-volatile
storage or by using an algorithm that will consistently produce the storage or by using an algorithm that will consistently produce the
same IAID as long as the configuration of the requesting router has same IAID as long as the configuration of the requesting router has
not changed. If the requesting router uses only one IAID, it can use not changed. If the requesting router uses only one IAID, it can use
a well-known value, e.g zero. a well-known value, e.g zero.
The configuration information in an IA_PD consists of one or more The configuration information in an IA_PD consists of one or more
IPv6 prefixes along with the times T1 and T2 for the IA_PD. See IPv6 prefixes along with the times T1 and T2 for the IA_PD. See
section Section 8 for the representation of an IA_PD in a DHCP section Section 9 for the representation of an IA_PD in a DHCP
message. message.
6. Overview of DHCP with Prefix Delegation 7. Overview of DHCP with Prefix Delegation
Prefix delegation with DHCP is independent of address assignment with Prefix delegation with DHCP is independent of address assignment with
DHCP. A requesting router can use DHCP for just prefix delegation or DHCP. A requesting router can use DHCP for just prefix delegation or
for prefix delegation along with address assignment and other for prefix delegation along with address assignment and other
configuration information. configuration information.
A requesting router first creates an IA_PD and assigns it an IAID. A requesting router first creates an IA_PD and assigns it an IAID.
The requesting router then transmits a Solicit message containing an The requesting router then transmits a Solicit message containing an
IA_PD option describing the IA_PD. Delegating routers that can IA_PD option describing the IA_PD. Delegating routers that can
delegate prefixes to the IA_PD respond to the requesting router with delegate prefixes to the IA_PD respond to the requesting router with
skipping to change at page 7, line 37 skipping to change at page 7, line 37
options in a Reply message. The requesting router records the options in a Reply message. The requesting router records the
lifetimes for the delegated prefix(es) and uses the prefix(es) as lifetimes for the delegated prefix(es) and uses the prefix(es) as
described in the previous section. described in the previous section.
Before the valid lifetime on each delegated prefix expires, the Before the valid lifetime on each delegated prefix expires, the
requesting router includes the prefix in an IA_PD option sent in a requesting router includes the prefix in an IA_PD option sent in a
Renew message to the delegating router. The delegating router Renew message to the delegating router. The delegating router
responds by returning the prefix with updated lifetimes to the responds by returning the prefix with updated lifetimes to the
requesting router. requesting router.
7. Interface Selection 8. Interface Selection
Delegated prefixes are not associated with a particular interface in Delegated prefixes are not associated with a particular interface in
the same way as addresses are for address assignment, and the rules the same way as addresses are for address assignment, and the rules
described in the section "Client Source Address and Interface described in the section "Client Source Address and Interface
Selection" of the DHCP specification [6] do not apply. Selection" of the DHCP specification [6] do not apply.
When a requesting router sends a DHCP message, it SHOULD be sent on When a requesting router sends a DHCP message, it SHOULD be sent on
the interface associated with the upstream router (ISP network). The the interface associated with the upstream router (ISP network). The
upstream interface is typically determined by configuration. This upstream interface is typically determined by configuration. This
rule applies even in the case where a separate IA_PD is used for each rule applies even in the case where a separate IA_PD is used for each
downstream interface. downstream interface.
When a requesting router sends a DHCP message directly to a When a requesting router sends a DHCP message directly to a
delegating router using unicast (after receiving the Server Unicast delegating router using unicast (after receiving the Server Unicast
option from that delegating router), the source address SHOULD be an option from that delegating router), the source address SHOULD be an
address from the upstream interface and which is suitable for use by address from the upstream interface and which is suitable for use by
the delegating router in responding to the requesting router. the delegating router in responding to the requesting router.
8. Identity Association for Prefix Delegation Option 9. Identity Association for Prefix Delegation Option
The IA_PD option is used to carry a prefix delegation identity The IA_PD option is used to carry a prefix delegation identity
association, the parameters associated with the IA_PD and the association, the parameters associated with the IA_PD and the
prefixes associated with it. prefixes associated with it.
The format of the IA_PD option is: The format of the IA_PD option is:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 8, line 39 skipping to change at page 8, line 39
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_IA_PD (TBD) option-code: OPTION_IA_PD (TBD)
option-length: 12 + length of IA_PD-options field. option-length: 12 + length of IA_PD-options field.
IAID The unique identifier for this IA_PD; the IAID must IAID The unique identifier for this IA_PD; the IAID must
be unique among the identifiers for all of this be unique among the identifiers for all of this
requesting router's IA_PDs. requesting router's IA_PDs.
T1 The time at which the requesting router contacts T1 The time at which the requesting router should
the delegating router from which the prefixes in contact the delegating router from which the
the IA_PD were obtained to extend the lifetimes of prefixes in the IA_PD were obtained to extend the
the prefixes delegated to the IA_PD; T1 is a time lifetimes of the prefixes delegated to the IA_PD;
duration relative to the current time expressed in T1 is a time duration relative to the current time
units of seconds.
T2 The time at which the requesting router contacts
any available delegating router to extend the
lifetimes of the prefixes assigned to the IA_PD; T2
is a time duration relative to the current time
expressed in units of seconds. expressed in units of seconds.
T2 The time at which the requesting router should
contact any available delegating router to extend
the lifetimes of the prefixes assigned to the
IA_PD; T2 is a time duration relative to the
current time expressed in units of seconds.
IA_PD-options Options associated with this IA_PD. IA_PD-options Options associated with this IA_PD.
The IA_PD-options field encapsulates those options that are specific The IA_PD-options field encapsulates those options that are specific
to this IA_PD. For example, all of the IA_PD Prefix Options carrying to this IA_PD. For example, all of the IA_PD Prefix Options carrying
the prefixes associated with this IA_PD are in the IA_PD-options the prefixes associated with this IA_PD are in the IA_PD-options
field. field.
An IA_PD option may only appear in the options area of a DHCP An IA_PD option may only appear in the options area of a DHCP
message. A DHCP message may contain multiple IA_PD options. message. A DHCP message may contain multiple IA_PD options.
The status of any operations involving this IA_PD is indicated in a The status of any operations involving this IA_PD is indicated in a
Status Code option in the IA_PD-options field. Status Code option in the IA_PD-options field.
Note that an IA_PD has no explicit "lifetime" or "lease length" of Note that an IA_PD has no explicit "lifetime" or "lease length" of
its own. When the valid lifetimes of all of the prefixes in a IA_PD its own. When the valid lifetimes of all of the prefixes in a IA_PD
have expired, the IA_PD can be considered as having expired. T1 and have expired, the IA_PD can be considered as having expired. T1 and
T2 are included to give delegating routers explicit control over when T2 are included to give delegating routers explicit control over when
a requesting router recontacts the delegating router about a specific a requesting router should contact the delegating router about a
IA_PD. specific IA_PD.
In a message sent by a requesting router to a delegating router, In a message sent by a requesting router to a delegating router,
values in the T1 and T2 fields indicate the requesting router's values in the T1 and T2 fields indicate the requesting router's
preference for those parameters. The requesting router sets T1 and preference for those parameters. The requesting router sets T1 and
T2 to 0 if it has no preference for those values. In a message sent T2 to zero if it has no preference for those values. In a message
by a delegating router to a requesting router, the requesting router sent by a delegating router to a requesting router, the requesting
MUST use the values in the T1 and T2 fields for the T1 and T2 router MUST use the values in the T1 and T2 fields for the T1 and T2
parameters. The values in the T1 and T2 fields are the number of parameters. The values in the T1 and T2 fields are the number of
seconds until T1 and T2. seconds until T1 and T2.
The delegating router selects the T1 and T2 times to allow the The delegating router selects the T1 and T2 times to allow the
requesting router to extend the lifetimes of any prefixes in the requesting router to extend the lifetimes of any prefixes in the
IA_PD before the lifetimes expire, even if the delegating router is IA_PD before the lifetimes expire, even if the delegating router is
unavailable for some short period of time. Recommended values for T1 unavailable for some short period of time. Recommended values for T1
and T2 are .5 and .8 times the shortest preferred lifetime of the and T2 are .5 and .8 times the shortest preferred lifetime of the
prefixes in the IA_PD, respectively. If the time at which the prefixes in the IA_PD that the delegating router is willing to
prefixes in an IA_PD are to be renewed is to be left to the extend, respectively. If the time at which the prefixes in an IA_PD
discretion of the requesting router, the delegating router sets T1 are to be renewed is to be left to the discretion of the requesting
and T2 to 0. router, the delegating router sets T1 and T2 to 0.
9. IA_PD Prefix option If a delegating router receives an IA_PD with T1 greater than T2, and
both T1 and T2 are greater than 0, the delegating router ignores the
invalid values of T1 and T2 and processes the IA_PD as though the
delegating router had set T1 and T2 to 0.
If a requesting router receives an IA_PD with T1 greater than T2, and
both T1 and T2 are greater than 0, the client discards the IA_PD
option and processes the remainder of the message as though the
delegating router had not included the IA_PD option.
10. IA_PD Prefix option
The IA_PD Prefix option is used to specify IPv6 address prefixes The IA_PD Prefix option is used to specify IPv6 address prefixes
associated with an IA_PD. The IA_PD Prefix option must be associated with an IA_PD. The IA_PD Prefix option must be
encapsulated in the IA_PD-options field of an IA_PD option. encapsulated in the IA_PD-options field of an IA_PD option.
The format of the IA_PD Prefix option is: The format of the IA_PD Prefix option is:
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 11, line 13 skipping to change at page 11, line 19
of zero to indicate no preference. A requesting router may set the of zero to indicate no preference. A requesting router may set the
IPv6 prefix field to zero and a given value in the prefix-length IPv6 prefix field to zero and a given value in the prefix-length
field to indicate a preference for the size of the prefix to be field to indicate a preference for the size of the prefix to be
delegated. delegated.
In a message sent by a delegating router the preferred and valid In a message sent by a delegating router the preferred and valid
lifetimes should be set to the values of AdvPreferredLifetime and lifetimes should be set to the values of AdvPreferredLifetime and
AdvValidLifetime as specified in section "Router Configuration AdvValidLifetime as specified in section "Router Configuration
Variables" of RFC2461 [3], unless administratively configured. Variables" of RFC2461 [3], unless administratively configured.
A requesting router discards any prefixes for which the preferred
lifetime is greater than the valid lifetime. A delegating router
ignores the lifetimes set by the requesting router if the preferred
lifetime is greater than the valid lifetime and ignores the values
for T1 and T2 set by the requesting router if those values are
greater than the preferred lifetime.
The values in the preferred and valid lifetimes are the number of The values in the preferred and valid lifetimes are the number of
seconds remaining for each lifetime. seconds remaining for each lifetime.
An IA_PD Prefix option may appear only in an IA_PD option. More than An IA_PD Prefix option may appear only in an IA_PD option. More than
one IA_PD Prefix Option can appear in a single IA_PD option. one IA_PD Prefix Option can appear in a single IA_PD option.
The status of any operations involving this IA_PD Prefix option is The status of any operations involving this IA_PD Prefix option is
indicated in a Status Code option in the IAprefix-options field. indicated in a Status Code option in the IAprefix-options field.
10. Delegating Router Solicitation 11. Delegating Router Solicitation
The requesting router locates and selects a delegating router in the The requesting router locates and selects a delegating router in the
same way as described in section "DHCP Server Solicitation" of the same way as described in section "DHCP Server Solicitation" of the
DHCP specification [6]. The details of the solicitation process are DHCP specification [6]. The details of the solicitation process are
described in this section. described in this section.
10.1 Requesting router behaviour 11.1 Requesting router behaviour
The requesting router creates and transmits a Solicit message as The requesting router creates and transmits a Solicit message as
described in sections "Creation of Solicit Messages" and described in sections "Creation of Solicit Messages" and
"Transmission of Solicit Messages" of the DHCP specification [6]. "Transmission of Solicit Messages" of the DHCP specification [6].
The requesting router creates an IA_PD and assigns it an IAID. The The requesting router creates an IA_PD and assigns it an IAID. The
requesting router MUST include the IA_PD option in the Solicit requesting router MUST include the IA_PD option in the Solicit
message. message.
The requesting router processes any received Advertise messages as The requesting router processes any received Advertise messages as
described in section "Receipt of Advertise Messages" in the DHCP described in section "Receipt of Advertise Messages" in the DHCP
specification [6]. The requesting router MAY choose to consider the specification [6]. The requesting router MAY choose to consider the
presence of advertised prefixes in its decision about which presence of advertised prefixes in its decision about which
delegating router to respond to. delegating router to respond to.
The requesting router MUST ignore any Advertise message that includes The requesting router MUST ignore any Advertise message that includes
a Status Code option containing the value NoPrefixAvail, with the a Status Code option containing the value NoPrefixAvail, with the
exception that the requesting router MAY display the associated exception that the requesting router MAY display the associated
status message to the user. status message to the user.
10.2 Delegating router behaviour 11.2 Delegating router behaviour
The delegating router processes Solicit messages from requesting The delegating router processes Solicit messages from requesting
routers in the same way as described in section "Receipt of Solicit routers in the same way as described in section "Receipt of Solicit
messages" of the DHCP specification [6]. If the message contains an messages" of the DHCP specification [6]. If the message contains an
IA_PD option and the delegating router is configured to delegate IA_PD option and the delegating router is configured to delegate
prefix(es) to the requesting router, the delegating router selects prefix(es) to the requesting router, the delegating router selects
the prefix(es) to be delegated to the requesting router. The the prefix(es) to be delegated to the requesting router. The
mechanism through which the delegating router selects prefix(es) for mechanism through which the delegating router selects prefix(es) for
delegation is not specified in this document. Examples of ways in delegation is not specified in this document. Examples of ways in
which the delegating router might select prefix(es) for a requesting which the delegating router might select prefix(es) for a requesting
router include: static assignment based on subscription to an ISP; router include: static assignment based on subscription to an ISP;
dynamic assignment from a pool of available prefixes; selection based dynamic assignment from a pool of available prefixes; selection based
on an external authority such as a RADIUS server using the Framed- on an external authority such as a RADIUS server using the Framed-
IPv6-Prefix option as described in RFC 3162 [7]. IPv6-Prefix option as described in RFC 3162 [7].
If the delegating router cannot delegate any prefixes to an IA_PD in If the delegating router cannot delegate any prefixes to an IA_PD in
the message from the requesting router, the delegating router MUST the message from the requesting router, the delegating router MUST
include the IA_PD in the Reply message with no prefixes in the IA_PD include the IA_PD in the Advertise message with no prefixes in the
and a Status Code option in the IA_PD containing status code IA_PD and a Status Code option in the IA_PD containing status code
NoPrefixAvail. NoPrefixAvail.
If the requesting router includes an IA_PD Prefix option in the IA_PD If the requesting router includes an IA_PD Prefix option in the IA_PD
option in its Solicit message, the delegating router MAY choose to option in its Solicit message, the delegating router MAY choose to
use the information in that option to select the prefix(es) or prefix use the information in that option to select the prefix(es) or prefix
size to be delegated to the requesting router. size to be delegated to the requesting router.
The delegating router sends an Advertise message to the requesting The delegating router sends an Advertise message to the requesting
router in the same way as described in section "Creation and router in the same way as described in section "Creation and
transmission of Advertise messages" in the DHCP specification [6]. transmission of Advertise messages" in the DHCP specification [6].
skipping to change at page 12, line 43 skipping to change at page 13, line 8
router. router.
If the delegating router will not assign any prefixes to any IA_PDs If the delegating router will not assign any prefixes to any IA_PDs
in a subsequent Request from the requesting router, the delegating in a subsequent Request from the requesting router, the delegating
router MUST send an Advertise message to the requesting router that router MUST send an Advertise message to the requesting router that
includes a Status Code option with code NoPrefixAvail and a status includes a Status Code option with code NoPrefixAvail and a status
message for the user, a Server Identifier option with the delegating message for the user, a Server Identifier option with the delegating
router's DUID and a Client Identifier option with the requesting router's DUID and a Client Identifier option with the requesting
router's DUID. router's DUID.
11. Requesting router initiated prefix delegation 12. Requesting router initiated prefix delegation
A requesting router uses the same message exchanges as described in A requesting router uses the same message exchanges as described in
section "DHCP Client-Initiated Configuration Exchange" of the DHCP section "DHCP Client-Initiated Configuration Exchange" of the DHCP
specification [6] to obtain or update prefix(es) from a delegating specification [6] to obtain or update prefix(es) from a delegating
router. The requesting router and the delegating router use the router. The requesting router and the delegating router use the
IA_PD Prefix option to exchange information about prefix(es) in much IA_PD Prefix option to exchange information about prefix(es) in much
the same way IA Address options are used for assigned addresses. the same way IA Address options are used for assigned addresses.
11.1 Requesting router behaviour 12.1 Requesting router behaviour
The requesting router uses a Request message to populate IA_PDs with The requesting router uses a Request message to populate IA_PDs with
prefixes. The requesting router includes one or more IA_PD options prefixes. The requesting router includes one or more IA_PD options
in the Request message. The delegating router then returns the in the Request message. The delegating router then returns the
prefixes for the IA_PDs to the requesting router in IA_PD options in prefixes for the IA_PDs to the requesting router in IA_PD options in
a Reply message. a Reply message.
The requesting router includes IA_PD options in any Renew, or Rebind The requesting router includes IA_PD options in any Renew, or Rebind
messages sent by the requesting router. The IA_PD option include all messages sent by the requesting router. The IA_PD option include all
of the prefixes the requesting router currently has associated with of the prefixes the requesting router currently has associated with
skipping to change at page 13, line 39 skipping to change at page 13, line 51
If such verification is needed the requesting router MUST initiate a If such verification is needed the requesting router MUST initiate a
Rebind/Reply message exchange as described in the section "Creation Rebind/Reply message exchange as described in the section "Creation
and Transmission of Rebind Messages" of the DHCP specification [6], and Transmission of Rebind Messages" of the DHCP specification [6],
with the exception that the retransmission parameters should be set with the exception that the retransmission parameters should be set
as for the Confirm message, described in the section "Creation and as for the Confirm message, described in the section "Creation and
Transmission of Confirm Messages" of the DHCP specification [6]. The Transmission of Confirm Messages" of the DHCP specification [6]. The
requesting router includes any IA_PDs, along with prefixes associated requesting router includes any IA_PDs, along with prefixes associated
with those IA_PDs in its Rebind message. with those IA_PDs in its Rebind message.
Each prefix has valid and preferred lifetimes whose duration is Each prefix has valid and preferred lifetimes whose durations are
specified in the IA_PD Prefix option for that prefix. The requesting specified in the IA_PD Prefix option for that prefix. The requesting
router uses Renew and Rebind messages to request the extension of the router uses Renew and Rebind messages to request the extension of the
lifetimes of a delegated prefix. lifetimes of a delegated prefix.
The requesting router uses a Release message to return a delegated The requesting router uses a Release message to return a delegated
prefix to a delegating router. The prefixes to be released MUST be prefix to a delegating router. The prefixes to be released MUST be
included in the IA_PDs. included in the IA_PDs.
The Confirm and Decline message types are not used with Prefix The Confirm and Decline message types are not used with Prefix
Delegation. Delegation.
skipping to change at page 14, line 28 skipping to change at page 14, line 41
3FFE:FFFF:1:2::/64 for assignment to the other link. 3FFE:FFFF:1:2::/64 for assignment to the other link.
If the requesting router assigns a delegated prefix to a link to If the requesting router assigns a delegated prefix to a link to
which the router is attached, and begins to send router which the router is attached, and begins to send router
advertisements for the prefix on the link, the requesting router MUST advertisements for the prefix on the link, the requesting router MUST
set the valid lifetime in those advertisements to be no later than set the valid lifetime in those advertisements to be no later than
the valid lifetime specified in the IA_PD Prefix option. A the valid lifetime specified in the IA_PD Prefix option. A
requesting router MAY use the preferred lifetime specified in the requesting router MAY use the preferred lifetime specified in the
IA_PD Prefix option. IA_PD Prefix option.
11.2 Delegating Router behaviour Handling of Status Codes options in received Reply messages is
described in "Receipt of Reply Messages" of the DHCP specification
[6]. The NoPrefixAvail Status Code is handled in the same manner as
the NoAddrsAvail Status Code.
12.2 Delegating Router behaviour
When a delegating router receives a Request message from a requesting When a delegating router receives a Request message from a requesting
router that contains an IA_PD option, and the delegating router is router that contains an IA_PD option, and the delegating router is
authorised to delegate prefix(es) to the requesting router, the authorised to delegate prefix(es) to the requesting router, the
delegating router selects the prefix(es) to be delegated to the delegating router selects the prefix(es) to be delegated to the
requesting router. The mechanism through which the delegating router requesting router. The mechanism through which the delegating router
selects prefix(es) for delegation is not specified in this document. selects prefix(es) for delegation is not specified in this document.
Section 10.2 gives examples of ways in which a delegating router Section 11.2 gives examples of ways in which a delegating router
might select the prefix(es) to be delegated to a requesting router. might select the prefix(es) to be delegated to a requesting router.
A delegating router examines the prefix(es) identified in IA_PD A delegating router examines the prefix(es) identified in IA_PD
Prefix options (in an IA_PD option) in Renew and Rebind messages and Prefix options (in an IA_PD option) in Renew and Rebind messages and
responds according to the current status of the prefix(es). The responds according to the current status of the prefix(es). The
delegating router returns IA_PD Prefix options (within an IA_PD delegating router returns IA_PD Prefix options (within an IA_PD
option) with updated lifetimes for each valid prefix in the message option) with updated lifetimes for each valid prefix in the message
from the requesting router. If the delegating router cannot find a from the requesting router. If the delegating router finds that any
binding for the requesting router's IA_PD the delegating router of the prefixes are not in the requesting router's binding entry, the
returns the IA_PD containing no prefixes with a Status Code option delegating router returns the prefix to the requesting router with
set to NoBinding in the Reply message. If the delegating router lifetimes of 0.
finds that any of the prefixes are not in the requesting router's
binding entry, the delegating router returns the prefix to the Behaviour in the case where the delegating router cannot find a
requesting router with lifetimes of 0. binding for the requesting router's IA_PD:
Renew message If the delegating router cannot find a binding
for the requesting router's IA_PD the delegating
router returns the IA_PD containing no prefixes
with a Status Code option set to NoBinding in the
Reply message.
Rebind message If the delegating router cannot find a binding
for the requesting router's IA_PD and the
delegating router determines that the prefixes in
the IA_PD are not appropriate for the link to
which the requesting router's interface is
attached according to the delegating routers
explicit configuration, the delegating router MAY
send a Reply message to the requesting router
containing the IA_PD with the lifetimes of the
prefixes in the IA_PD set to zero. This Reply
constitutes an explicit notification to the
requesting router that the prefixes in the IA_PD
are no longer valid. If the delegating router is
unable to determine if the prefix is not
appropriate for the link, the Rebind message is
discarded.
A delegating router may mark any prefix(es) in IA_PD Prefix options A delegating router may mark any prefix(es) in IA_PD Prefix options
in a Release message from a requesting router as "available", in a Release message from a requesting router as "available",
dependent on the mechanism used to acquire the prefix, e.g in the dependent on the mechanism used to acquire the prefix, e.g in the
case of a dynamic pool. case of a dynamic pool.
The delegating router MUST include an IA_PD Prefix option or options The delegating router MUST include an IA_PD Prefix option or options
(in an IA_PD option) in Reply messages sent to a requesting router. (in an IA_PD option) in Reply messages sent to a requesting router.
12. Prefix Delegation reconfiguration 13. Prefix Delegation reconfiguration
This section describes prefix delegation in Reconfigure message This section describes prefix delegation in Reconfigure message
exchanges. exchanges.
12.1 Delegating Router behaviour 13.1 Delegating Router behaviour
The delegating router initiates a configuration message exchange with The delegating router initiates a configuration message exchange with
a requesting router, as described in the section "DHCP Server- a requesting router, as described in the section "DHCP Server-
Initiated Configuration Exchange" of the DHCP specification [6]. The Initiated Configuration Exchange" of the DHCP specification [6]. The
delegating router specifies the IA_PD option in the Option Request delegating router specifies the IA_PD option in the Option Request
option to cause the requesting router to include an IA_PD option to option to cause the requesting router to include an IA_PD option to
obtain new information about delegated prefix(es). obtain new information about delegated prefix(es).
12.2 Requesting Router behaviour 13.2 Requesting Router behaviour
The requesting router responds to a Reconfigure message received from The requesting router responds to a Reconfigure message received from
a delegating router as described in the DHCP specification [6]. The a delegating router as described in the DHCP specification [6]. The
requesting router MUST include the IA_PD Prefix option(s) (in an requesting router MUST include the IA_PD Prefix option(s) (in an
IA_PD option) for prefix(es) that have been delegated to the IA_PD option) for prefix(es) that have been delegated to the
requesting router by the delegating router from which the Reconfigure requesting router by the delegating router from which the Reconfigure
message was received. message was received.
13. Relay agent behaviour 14. Relay agent behaviour
A relay agent forwards messages containing Prefix Delegation options A relay agent forwards messages containing Prefix Delegation options
in the same way as described in section "Relay Behaviour" of the DHCP in the same way as described in section "Relay Behaviour" of the DHCP
specification [6]. specification [6].
If a delegating router communicates with a requesting router through If a delegating router communicates with a requesting router through
a relay agent, the delegating router may need a protocol or other a relay agent, the delegating router may need a protocol or other
out-of-band communication to add routing information for delegated out-of-band communication to add routing information for delegated
prefixes into the provider edge router. prefixes into the provider edge router.
14. Security Considerations 15. Security Considerations
Security considerations in DHCP are described in the section Security considerations in DHCP are described in the section
"Security Considerations" of the DHCP specification [6]. "Security Considerations" of the DHCP specification [6].
A rogue delegating router can issue bogus prefixes to a requesting A rogue delegating router can issue bogus prefixes to a requesting
router. This may cause denial of service due to unreachability. router. This may cause denial of service due to unreachability.
An intruder requesting router may be able to mount a denial of An intruder requesting router may be able to mount a denial of
service attack by repeated requests for delegated prefixes that service attack by repeated requests for delegated prefixes that
exhaust the delegating router's available prefixes. exhaust the delegating router's available prefixes.
skipping to change at page 16, line 21 skipping to change at page 17, line 13
routers and delegating routers SHOULD use DHCP authentication as routers and delegating routers SHOULD use DHCP authentication as
described in section "Authentication of DHCP messages" in the DHCP described in section "Authentication of DHCP messages" in the DHCP
specification [6]. For point to point links, where one trusts that specification [6]. For point to point links, where one trusts that
there is no man in the middle, or one trusts layer two there is no man in the middle, or one trusts layer two
authentication, DHCP authentication or IPsec may not be necessary. authentication, DHCP authentication or IPsec may not be necessary.
Because a requesting router and delegating routers must each have at Because a requesting router and delegating routers must each have at
least one assigned IPv6 address, the routers may be able to use IPsec least one assigned IPv6 address, the routers may be able to use IPsec
for authentication of DHCPv6 messages. The details of using IPsec for authentication of DHCPv6 messages. The details of using IPsec
for DHCPv6 are under development. for DHCPv6 are under development.
15. IANA Considerations 16. IANA Considerations
IANA is requested to assign option codes to these options from the IANA is requested to assign option codes to:
option-code space as defined in section "DHCPv6 Options" of the
DHCPv6 specification [6].
IANA is requested to assign a status code to the NoPrefixAvail status OPTION_IA_PD
code from the status-code space as defined in section "Status Codes"
of the DHCPv6 specification [6].
16. Acknowledgements OPTION_IAPREFIX
from the option-code space as defined in section "DHCPv6 Options" of
the DHCPv6 specification [6].
IANA is requested to assign a status code:
NoPrefixAvail Delegating router has no prefixes available to
assign to the IAPD(s)
from the status-code space as defined in section "Status Codes" of
the DHCPv6 specification [6].
17. Acknowledgements
Thanks for the input and review by (in alphabetical order) Steve Thanks for the input and review by (in alphabetical order) Steve
Deering, Dave Forster, Brian Haberman, Tatuya Jinmei, Shin Miyakawa, Deering, Dave Forster, Brian Haberman, Tatuya Jinmei, Shin Miyakawa,
Pekka Savola, Bernie Volz, Trevor Warwick and Toshi Yamasaki. Pekka Savola, Bernie Volz, Trevor Warwick and Toshi Yamasaki.
17. Changes since revision-01 18. Changes in draft-ietf-dhc-dhcpv6-opt-prefix-delegation-03
o Clarified the usage of how Preferred/Valid lifetimes should be o Clarified that this draft is an extension of the DHCPv6
used in Router Advertisements. specification and that complete specification and terminology can
be found in the DHCPv6 specification.
o Clarified the use of NoPrefixAvail in the case were the delegating o Updated relevant sections to be consistent with draft-ietf-dhc-
router cannot delegate any prefixes. dhcpv6-interop-00.txt. This includes T1/T2 times, preferred and
valid lifetimes and Rebind/Renew usage.
o Use Rebind/Reply message exchange for binding confirmation rather o Clarified the usage of the NoPrefixAvail Status Code
than Renew/Reply.
o Clarified delegating router behaviour when no binding is found for
Renew/Rebind.
o Various editorial changes
Normative References Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) [2] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 2460, December 1998. Specification", RFC 2460, December 1998.
[3] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for [3] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for
 End of changes. 

This html diff was produced by rfcdiff 1.23, available from http://www.levkowetz.com/ietf/tools/rfcdiff/