MIP6 Working Group H. Jang
Internet-Draft A. Yegin
Intended status: Standards Track Samsung
Expires: October 9, 2008 K. Chowdhury
Starent Networks
J. Choi
Samsung
April 7, 2008
DHCP Options for Home Information Discovery in MIPv6
draft-ietf-mip6-hiopt-12.txt
Status of this Memo
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This Internet-Draft will expire on October 9, 2008.
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Abstract
This draft defines a DHCP-based scheme to enable dynamic discovery of
Mobile IPv6 home network information. New DHCP options are defined
which allow a mobile node to request the home agent IP address, FQDN,
or home network prefix and obtain it via the DHCP response.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. DHCP options for HA Dynamic Discovery . . . . . . . . . . . . 5
3.1. Home Network Information Option . . . . . . . . . . . . . 5
3.1.1. Home Network Information Sub-options . . . . . . . . . 7
3.2. MIP6 Relay Agent Option . . . . . . . . . . . . . . . . . 10
3.2.1. MIP6 Relay Agent Sub-option . . . . . . . . . . . . . 11
4. Option Usage . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Mobile Node Behavior . . . . . . . . . . . . . . . . . . . 13
4.2. NAS/DHCP Relay Agent Behavior . . . . . . . . . . . . . . 15
4.3. DHCP Server Behavior . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 19
6. IANA Consideration . . . . . . . . . . . . . . . . . . . . . . 20
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1. Normative References . . . . . . . . . . . . . . . . . . . 22
8.2. Informative References . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . . . . 25
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1. Introduction
Before a mobile node can engage in Mobile IPv6 signaling with a home
agent, it should either know the IP address of the home agent via
pre-configuration, or dynamically discover it. The Mobile IPv6
specification [RFC3775] describes how home agents can be dynamically
discovered by mobile nodes that know the home network prefix. This
scheme does not work when prefix information is not already available
to the mobile node. One architecture to solve this problem is
described in [I-D.ietf-mip6-bootstrapping-integrated-dhc]. A part of
the solution is the capability to deliver home network prefix
information to the mobile node by means of the stateless DHCPv6
[RFC3736] [RFC3315]. Subsequently, the mobile node can engage in
dynamic home agent discovery using the prefix information. In
addition to delivering the prefix information, DHCP can also be used
to provide the IP addresses or FQDNs of the home agents that are
available to the mobile node. The solution involves defining a new
DHCP option to carry home network prefix, home agent IP address and
FQDN information.
As part of configuring the initial TCP/IP parameters, a mobile node
can find itself a suitable home agent. Such a home agent might
reside in the access network that the mobile node connects to, or in
a home network that the mobile node is associated with. A mobile
node can indicate its home network identity when roaming to a visited
network in order to obtain the MIP6 bootstrap parameters from the
home network. As an example, the visited network may determine the
home network of the mobile node based on the realm portion of the NAI
(Network Access Identifier) [RFC4282] used in access authentication.
The mobile node may or may not be connected to the "home" network
when it attempts to learn Mobile IPv6 home network information. This
allows operators to centrally deploy home agents while being able to
bootstrap mobile nodes that are already roaming. This scenario also
occurs when HMIPv6 [I-D.ietf-mipshop-4140bis] is used, where the
mobile node is required to discover the MAP (a special home agent)
that is located multiple hops away from the mobile node's attachment
point.
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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].
General mobility terminology can be found in [RFC3753]. The
following additional terms, as defined in [RFC4640], are used in this
document:
o Access Service Provider (ASP): A network operator that
provides direct IP packet forwarding to and from the
mobile node.
o Mobility Service Provider (MSP): A service provider
that provides Mobile IPv6 service. In order to obtain
such service, the mobile node must be authenticated and
authorized to use the Mobile IPv6 service.
o Mobility Service Authorizer (MSA): A service provider
that authorizes Mobile IPv6 service.
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3. DHCP options for HA Dynamic Discovery
This section introduces new DHCP options and their sub-options which
are used for dynamic discovery of the home agent IP address, FQDN, or
home prefix information in Mobile IPv6. The drafts
[I-D.ietf-mip6-radius] and
[I-D.ietf-mip6-bootstrapping-integrated-dhc] describe the complete
procedure for home agent assignment among the mobile node, NAS
(Network Access Server), DHCP and AAA entities for the bootstrapping
procedure in the integrated scenario.
A NAS is assumed to be co-located with a DHCP relay agent or a DHCP
server in this solution. In the network where a NAS is not co-
located with a DHCP relay nor a server, the server may not be
provided with the home network information from the NAS, and thereby
it may assign to mobile node the home information which has been
preconfigured by the administrator or which is acquired through the
mechanism that is not described in this document.
3.1. Home Network Information Option
This option is proposed to allow exchange of the home network
information between the mobile node (DHCP client) and the DHCP
server. It is used to indicate the target home network requested by
the mobile node to the DHCP server in the Information-request
message. In the Reply message, it conveys the home network
information assigned by the DHCP server to the mobile node.
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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_MIP6_HNINF | Option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Id-type | |
+-+-+-+-+-+-+-+-+ +
. Sub-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code
OPTION_MIP6_HNINF (TBD)
Option-len
1 + length of Sub-options in units of octets.
Id-type
The type of Home Network Identifier:
0 Visited domain (local ASP)
1 Target MSP
2 No preference
Sub-options
A series of Home Network Information sub-options.
The Id-type in the request specifies the location of the home network
requested by the mobile node as below:
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o The Id-type 0 indicates the mobile node is interested in
learning the home network information that pertains to the
currently visited network. This type can be used to
discover local home agents in the local ASP. In this case,
the Option-len is set to 1.
o The Id-type 1 indicates the mobile node is interested in
learning the home network information that pertains to the
given realm. This type can be used to discover home agents
that are hosted by a user's home domain or by any target
domain. The option MUST carry a Home Network Information
sub-option whose Sub-opt-code is 1, which specifies the
requested target MSP. The target MSP can be a mobile node's
home MSP or any MSP which has a trusted roaming relationship
with the mobile node's MSA.
o If the mobile node has no preference, the Id-type is set
to 2 and the Option-len field is set to 1. In this case,
the assignment of the home network information is within
the server's own discretion. For the detailed description,
refer to Section 4.
The Id-type in the reply indicates the location of the home network
information provided by the DHCP server which is carried in the
following Home Network Information sub-options.
3.1.1. Home Network Information Sub-options
This sub-option is a container of each of home network parameter in
the Home Network Information option.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-opt-code | Sub-opt-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Home Network Parameter .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-opt-code
A 16-bit unsigned integer for the type of the following
Home Network Parameter field. Possible values are:
0 Reserved
1 Home network identifier
2 IPv6 home network prefix
3 IPv6 home agent address
4 A pair of IPv6 and IPv4 addresses of
dual-stacked home agent
5 Home agent FQDN
6 ~ (2^16-1) Reserved
Sub-opt-len
The length of the Home Network Parameter field in units
of octets.
Home Network Parameter
The provided home network information according to the
Sub-opt-code. This is encoded as specified as below.
While the Sub-opt-code 1 is available both in the requesting and
returned Home Network Information options, the Sub-opt-codes 2, 3, 4
and 5 are available only in the returned one.
When the Sub-opt-code is set to 1 in the request, the Home Network
Parameter field MUST contain the identifier to specify the home
network requested by the mobile node. This field MUST be set in the
form of a FQDN [RFC1035], encoded as specified in Section 8 of
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[RFC3315]. This sub-option in the request SHOULD be copied into the
Home Network Information option returned in the reply.
When the Sub-opt-code is set to 2, the Home Network Parameter field
includes the IPv6 home network prefix, its lifetime and length
information as below.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preferred Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix-len | |
+-+-+-+-+-+-+-+-+ |
| |
| IPv6 Home Network Prefix |
| (16 octets) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+ .
. Home Network Prefix Options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Preferred Lifetime
32-bit unsigned integer. The length of time in seconds
(relative to the time the packet is sent) that addresses
generated from the prefix via stateless address
auto-configuration remain preferred [RFC4862]. A value of
0xffffffff represents infinity.
Valid Lifetime
32-bit unsigned integer. The length of time in seconds
(relative to the time the packet is sent) that addresses
generated from the prefix via stateless address
auto-configuration remain in the valid state [RFC4862].
A value of 0xffffffff represents infinity. When the valid
lifetime expires, the address becomes invalid. The valid
lifetime must be greater than or equal to the preferred
lifetime.
Prefix-len
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The number of leading bits in the following IPv6 Home
Network Prefix that are valid.
IPv6 Home Network Prefix
An IPv6 home network prefix.
Home Network Prefix Options
DHCPv6 options associated with the IPv6 home network
prefix.
When the Sub-opt-code is set to 3, the Home Network Parameter field
MUST contain the 128-bit IPv6 address of the home agent.
When the Sub-opt-code is set to 4, it MUST contain both of IPv6 and
IPv4 addresses of the dual-stacked home agent which can serve for
both Mobile IPv6 and Mobile IPv4. A 128-bit IPv6 address is followed
by a 32-bit IPv4 address in this field.
When the Sub-opt-code is set to 5, it MUST contain the FQDN of the
home agent as described in Section 8 of [RFC3315].
Multiple sub-options may exist in a Home Network Information option
to carry more than one home information.
3.2. MIP6 Relay Agent Option
This option carries the home network information for the mobile node
(the NAS may know this, for instance, through AAA by using
[I-D.ietf-mip6-radius]) from the DHCP relay agent to the DHCP server.
The DHCP relay agent sends this option to the DHCP server in the
Relay-forward message.
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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_MIP6_RELAY | Option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Sub-options .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option-code
OPTION_MIP6_RELAY (TBD)
Option-len
The length of Sub-options in units of octets.
Sub-options
A series of MIP6 Relay Agent sub-options.
3.2.1. MIP6 Relay Agent Sub-option
This sub-option is a container of each of home network parameter
included in the MIP6 Relay option.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-opt-code | Sub-opt-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Home Network Parameter .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Sub-opt-code
A 16-bit unsigned integer for the type of the following
Home Network Parameter field. Possible values are:
0 Reserved
1 IPv6 home network prefix
2 IPv6 home agent address
3 A pair of IPv6 and IPv4 addresses of
dual-stacked home agent
4 Home agent FQDN
5 ~ (2^16-1) Reserved
Sub-opt-len
The length of the Home Network Parameter field in units
of octets.
Home Network Parameter
A home network prefix, home agent IP address or home agent
FQDN to be provided to the DHCP server according to the
Sub-opt-code.
The Sub-opt-len and the Home Network Parameter fields in the sub-
option for the home network prefix, home agent address, dual-stacked
home agent addresses, and home agent FQDN are set in the same manner
as those of the Home Network Information sub-option specified in
Section 3.1.1.
Multiple sub-options may exist in a MIP6 Relay Agent option to carry
more than one home information.
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4. Option Usage
The requesting and sending of the proposed DHCP options follow the
rules for DHCPv6 options in [RFC3315].
4.1. Mobile Node Behavior
A mobile node does not need to perform the home information discovery
procedure after every change in attachment. It may try to perform
the home network information discovery when it lacks home network
information for MIPv6 or needs to change the home agent for some
reasons, for example, to recover from the single point of failure of
the existing home agent or to use the local home agent located in the
network where the mobile node is currently attached. Note that
despite the home information discovery procedure the mobile node may
decide to keep the old home agent still in use afterwards, in order
to avoid losing the current sessions.
For acquiring the home network information, a mobile node MUST send
an Information-request message including the Home Network Information
option according to the stateless DHCPv6 [RFC3736][RFC3315]. The
mobile node MUST also include the Option code for the Home Network
Information option in the Option Request option in the request.
During the process of requesting the bootstrapping information, the
mobile node MUST clarify its preference about the requested home
network with the Id-type in the Home Network Information option. If
it does not care about the location of the home network where the
home agent is to be assigned, it MUST clarify that fact by setting
the Id-type to 2. The Id-type 2 means that the mobile node has no
preferred home network and is willing to use any information provided
by the DHCP server. Once it decides where the home agent is to be
assigned, the specific information to be assigned depends mainly on
the server's policy or the server's knowledge.
When the mobile node sets the Id-type to 1 in the request, it MUST
include the Home Network Information sub-option with Sub-opt-code 1
which carries the FQDN of the target network such as "example.com".
Note that a single Home Network Information option can carry at most
one Home Network Information sub-option with Id-type 1 in the
request.
The mobile node MUST NOT include the Home Network Information option
whose Id-type is other than 0, 1, and 2 as defined as Section 3.1. A
value of 1 is only available for the Sub-opt-code in the request.
The mobile node can request more than one home information by using
multiple Home Network Information options in the request. For
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instance, if the mobile node wants to retrieve home network
information from both the visited network (ASP) and the target MSP
with a single transaction, it can request the information by using
two Home Network Information options with Id-type 0 and Id-type 1.
It can also request the home information for more than one target
MSPs at the same time by including multiple Home Network Information
options with Id-type 1. However, there MUST NOT be more than one
Home Network Information option with Id-type 0 nor more than one Home
Network Information option with Id-type 2 in the request.
On receiving the Reply message including the Home Network Information
option, the mobile node SHOULD check whether the option is valid. It
MUST ignore the option whose Id-type is other than 0, 1, and 2. It
MUST also ignore the Home Network Information sub-option in the reply
whose Sub-opt-code is other than 1, 2, 3, 4, and 5 as described in
Section 3.1.1.
When the mobile node obtains the Home Network Information option with
Id-type 1, it SHOULD check whether the returned option includes the
home network identifier in its sub-option. If it is not provided in
the sub-option, the Home Network Information option MUST be ignored
and skipped. The home network identifiers provide a way to match the
Home Network Information options in the request and the reply when
the mobile node has sent the request with multiple Home Network
Information options with the same Id-type 1 but with different home
network identifiers.
The Reply message can carry multiple Home Network Information
options. A single Home Network Information option also can contain
multiple Home Network Information sub-options. When provided with
more than one Home Network Information options having the different
id-types or multiple sub-options for the same id-type, the mobile
node is required to have a selection mechanism to determine which one
to use for establishing a Mobile IPv6 session. For example, if the
mobile node acquires both IPv6 address and FQDN of the home agent, it
may try to use the address information of the home agent first.
However, the selection mechanism is outside the scope of this
document.
If the mobile node attempts to retrieve information in its current
network but fails, it SHOULD employ previously retrieved information.
If no information has been retrieved previously and there is no
configuration that enables the mobile node to find and use a home
agent, the mobile node SHOULD log an error and, depending on
configured policy, revert to network access without a mobility
protocol.
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4.2. NAS/DHCP Relay Agent Behavior
As described in Section 3, a NAS is assumed to be co-located with a
DHCP relay or a DHCP server. The NAS communicates with the mobile
node during the network access authentication and typically also
interacts with backend AAA systems. It is expected that the NAS is
or becomes aware of the mobility related information for the mobile
node at this time using mechanisms such as Diameter or RADIUS
attributes [I-D.ietf-mip6-radius]. The NAS passes the information to
the co-located DHCP relay agent or the server. The following
describes the behavior of the DHCP relay agent when the NAS functions
as a DHCP relay.
When receiving a DHCP message from the mobile node, the DHCP relay
agent forwards the message to the DHCP server or another DHCP relay
as per [RFC3315]. If the relay determines that the NAS has passed
home network information for this mobile node and has available home
information for it, it SHOULD include the home network information in
the MIP6 Relay Agent option, and attach this option in the Relay-
forward message. The relay SHOULD include each of home information
in a MIP6 Relay Agent sub-option, and include all sub-options in a
single MIP6 Relay Agent option. It MUST NOT include the MIP6 Relay
agent sub-option whose Sub-opt-code is other than 1, 2, 3, and 4 as
described in Section 3.2.1.
In case the DHCP relay does not maintain any home network information
for the requesting mobile node, it simply forwards the received
message to the DHCP server according to the [RFC3315].
Upon receiving a Relay-reply message from the DHCPv6 server, the
relay SHALL follow the guidelines defined in [RFC3315]. It extracts
a Reply message from the Relay Message option in the Relay-reply
message and relays it to the mobile node.
4.3. DHCP Server Behavior
When the server receives a Relay-forward message, it may include the
MIP6 Relay Agent option in case there was home information available
for the mobile node at the relay. The home network information
received from the relay SHOULD be kept in the server so that the
server can provide the information when it is requested by the mobile
node. The server may carry this in the reply when the mobile node
requested the home network information with a Id-type of 1.
The server MUST ignore the MIP6 Relay Agent option whose Sub-opt-code
is other than 1, 2, 3, and 4 as described in Section 3.2.1.
When a DHCP server receives an Information-request message or it in
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the Relay-forward message, it SHOULD check whether the Information-
request includes the Home Network Information option. If the mobile
node included a Home Network Information option and a Home Network
Information option is requested by the Option Request option in the
Information-request, the server MUST include a Home Network
Information option in the Reply message.
The server MUST ignore the Home Network Information option in the
request whose Id-type is other than 0, 1, and 2 as described in
Section 3.1. It MUST also ignore the Home Network Information sub-
option in the request whose Sub-opt-code is not 1.
It MUST construct the Home Network Information option(s) according to
the following logic, and include it or them in the Reply. The
Information-request message includes:
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o A. Home Network Information option with Id-type 0
The DHCP server MUST include each of configured local home
information in the Home Network Information sub-option, and
include all sub-options in a single Home Network Information
option. It MUST set the Id-type to 0 in the Home Network
Information option to be returned.
o B. Home Network Information option with Id-type 1
The Home Network Information option which carries more than
one target MSP or which does not carry any target MSP MUST be
ignored. If the DHCP server has the corresponding information
for the target MSP, it MUST include each of information in the
Home Network Information sub-option, and include all sub-options
in a single Home Network Information option. It MUST set the
Id-type to 1 in the Home Network Information option to be
returned, and copy the sub-option of the request which includes
the target MSP into the Home Network Information option to be
returned.
o C. Home Network Information option with Id-type 2
In this case, the assignment of home information relies
on the server's local policy, and the DHCP server is required
to have its own policy so that it can reply with the proper
information in the Home Network Information option. The policy
can be determined based on several factors such as home agent
availability and the authorization information of the mobile
node. However, the specific policy setting is not in the scope
of this document. The DHCP sever MUST include each of home
information in the Home Network Information sub-option, and
include all sub-options in one or more than one Home Network
Information option(s) with Id-type 0 or 1 in the reply.
The server MUST NOT include the Home Network Information option in
the reply whose Id-type is other than 0, 1, and 2. It also MUST NOT
include the Home Network Information sub-option in the reply whose
Sub-opt-code is other than 1, 2, 3, 4, and 5 as described in Section
3.1.1.
The Reply message can carry multiple Home Network Information
options. The provided multiple options SHOULD be listed in order of
preference. multiple sub-options also SHOULD be listed in order of
preference within a single option. Note that there MUST NOT be more
than one Home Network Information option with Id-type 0 nor more than
one Home Network Information option with Id-type 2 in the reply. The
value of Id-type 2 is valid in the reply only when the server
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received the option with Id-type 2 but has no data to returned to the
mobile node.
In case the server cannot find any home information for Id-type 0 or
2, it MUST return the Home Network Information option with the Id-
type set to the requested Id-type and the Option-len set to 1. In
case of Id-type 1 in the request, it MUST return the Home Network
Information option by setting the Id-type to 1 and the Option-len to
1 + the length of the Home Network Information sub-option including
target MSP.
There is no requirement that the server return this option and its
data in a Relay message as other Relay Agent option
[RFC4580][RFC4649].
The DHCP server should provide all of the matching home information
in Home Network Information option(s) based on its policy. It may
return the partially matched results. For example, when received the
Home Network Information option which specifies "xxx.example.com" as
the target network, it may return "example.com" to the mobile node.
In this case, "xxx.example.com" is returned in the sub-option with
Sub-opt-code 1, and "example.com" in the sub-option with Sub-opt-code
5. Note that the detailed rule for returning partially matched ones
follows the server's own policy and outside the scope of this
document.
There can be several ways that the DHCP server knows the requested
home network information. For instance, as described in [I-D.ietf-
mip6-radius], a NAS can learn the information via RADIUS during
network access authentication, and the DHCP relay co-located with the
NAS can transfer it to the DHCP server by using the proposed DHCP
option in this document. Or the home information may have been
configured statically in the DHCP server by the administrator.
However, the mechanism by which the DHCP server is provisioned with
the home network information or obtains it dynamically is outside the
scope of this document.
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5. Security Considerations
Secure delivery of home agent and home network information from a
DHCP server to the mobile node (DHCP client) relies on the same
security as DHCP. The particular option defined in this draft does
not have additional impact on DHCP security.
Aside from the DHCP client to server interaction, an operator must
also ensure secure delivery of mobile IP information to the DHCP
server. This is outside the scope of DHCP and the newly defined
option.
The mechanisms in this specification could be used by attackers to
learn the addresses of home agents in the home network, or to feed
incorrect information to mobile nodes.
The ability to learn addresses of nodes may be useful to attackers
because brute-force scanning of the address space is not practical
with IPv6. Thus, they could benefit from any means which make
mapping the networks easier. For example, if a security threat
targeted at routers or even home agents is discovered, having a
simple mechanism to easily find out possible targets may prove to be
an additional security risk.
Apart from discovering the address(es) of home agents, attackers will
not be able to learn much from this information, and mobile nodes
cannot be tricked into using wrong home agents, as the actual
communication with the home agents employs mutual authentication.
The mechanisms from this specification may also leak interesting
information about network topology and prefixes to attackers, and
where there is no security to protect DHCP, even modify this
information. Again, the mobile nodes and home agents employ end-to-
end security when they communicate with each other. The authentic
source of all information is that communication, not the information
from DHCP.
However, attacks against the information carried in DHCP may lead to
denial-of-service if mobile nodes are unable to connect to any home
agent, or choose a home agent that is not the most preferred one.
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6. IANA Consideration
This document defines new DHCPv6 options, and IANA is requested to
assign the following new DHCPv6 Option Codes/Sub-option Codes in the
registry maintained in
http://www.iana.org/assignments/dhcpv6-parameters:
o OPTION_MIP6_HNINF for the Home Network Information option
o OPTION_MIP6_RELAY for the MIP6 Relay Agent option
The Sub-option Code for the Home Network Information option:
o Reserved 0
o Home network identifier 1
o IPv6 Home network prefix 2
o IPv6 Home agent address 3
o A pair of IPv6 and IPv4 addresses 4
of dual-stacked home agent
o Home agent FQDN 5
o Reserved 6 ~ (2^16-1)
The Sub-option Codes for the MIP6 Relay Agent option:
o Reserved 0
o IPv6 Home network prefix 1
o IPv6 Home agent address 2
o A pair of IPv6 and IPv4 addresses 3
of dual-stacked home agent
o Home agent FQDN 4
o Reserved 5 ~ (2^16-1)
These Sub-option Codes should be placed in a new name space "DHCPv6
Mobile IPv6 Sub-option Codes" under the same registry. Future values
can be allocated via Standards Action or IESG Approval.
In addition, a new name space "Home Network Information Option Id-
type Values" should be created, again in the same registry. Values
0, 1, and 2 are assigned by this document as specified in Section
3.1. Future values can be allocated via Standards Action or IESG
Approval.
New values for this name space can be allocated using Standards
Action according to [RFC2434].
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7. Acknowledgments
The authors would like to thank Kilian Weniger, Domagoj Premec,
Basavaraj Patil, Vijay Devarapalli, Gerardo Giaretta, Bernie Volz,
David W. Hankins, Behcet Sarikaya, Vidya Narayanan, Francis Dupont,
Sam Weiler, Jari Arkko and Miguel A. Diaz for their valuable
feedback.
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8. References
8.1. Normative References
[I-D.ietf-mip6-bootstrapping-integrated-dhc]
Chowdhury, K. and A. Yegin, "MIP6-bootstrapping for the
Integrated Scenario",
draft-ietf-mip6-bootstrapping-integrated-dhc-05 (work in
progress), July 2007.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[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.
[RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol
(DHCP) Service for IPv6", RFC 3736, April 2004.
[RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
in IPv6", RFC 3775, June 2004.
[RFC4282] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The
Network Access Identifier", RFC 4282, December 2005.
[RFC4580] Volz, B., "Dynamic Host Configuration Protocol for IPv6
(DHCPv6) Relay Agent Subscriber-ID Option", RFC 4580,
June 2006.
[RFC4649] Volz, B., "Dynamic Host Configuration Protocol for IPv6
(DHCPv6) Relay Agent Remote-ID Option", RFC 4649,
August 2006.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
8.2. Informative References
[I-D.ietf-mip6-radius]
Chowdhury, K., "RADIUS Mobile IPv6 Support",
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Internet-Draft DHCPv6 for Home Info Discovery in MIPv6 April 2008
draft-ietf-mip6-radius-04 (work in progress),
February 2008.
[I-D.ietf-mipshop-4140bis]
Castelluccia, C., "Hierarchical Mobile IPv6 Mobility
Management (HMIPv6)", draft-ietf-mipshop-4140bis-01 (work
in progress), November 2007.
[RFC3753] Manner, J. and M. Kojo, "Mobility Related Terminology",
RFC 3753, June 2004.
[RFC4640] Patel, A. and G. Giaretta, "Problem Statement for
bootstrapping Mobile IPv6 (MIPv6)", RFC 4640,
September 2006.
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Authors' Addresses
Heejin Jang
Samsung Advanced Institute of Technology
P.O. Box 111
Suwon 440-600
Korea
Email: heejin.jang@samsung.com
Alper E. Yegin
Samsung Electronics
Istanbul
Turkey
Email: a.yegin@partner.samsung.com
Kuntal Chowdhury
Starent Networks
30 International Place
Tewksbury, MA 01876
US
Email: kchowdhury@starentnetworks.com
JinHyeock Choi
Samsung Advanced Institute of Technology
P.O. Box 111
Suwon 440-600
Korea
Email: jinchoe@samsung.com
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Full Copyright Statement
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