April, 2004
X31-20040419-xxx
3GPP2 TSG-X
Wireless Packet Data Networking
Title: Dynamic Home Subnet Prefix or the Home Agent discovery for Mobile IPv6
Source:
Kuntal Chowdhury
(972) 685-7788
chowdury@nortelnetworks.com
Abstract:
This contribution proposes a method for dynamically assigning a Home Subnet Prefix and/or a
Home Agent list to a Mobile IPv6 capable mobile. This eliminates the need for statically
provisioning the Home Subnet Prefix and/or the default list of Home Agents in the handsets. The
Home Subnet Prefix and/or the Home Agent can also be allocated based on the Mobile’s current
location from where it is attempting to access IPv6 network. The decision in the Home AAA to
assign the mobile a Home Subnet prefix and/or can be based on the user’s subscription profile
with Mobile IPv6.
Recommendation:
Review and adopt in X.P0011-D.
Notice
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This document has been prepared by Nortel Networks to assist the development of specifications
by 3GPP2. It is proposed to the Committee as a basis for discussion and is not to be construed
as a binding proposal on Nortel Networks. Nortel Networks specifically reserves the right to
amend or modify the material contained herein and to any intellectual property of Nortel Networks
other than provided in the copyright statement above
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2.
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Introduction
The Mobile IPv6 specification draft-ietf-mobileip-ipv6-24.txt allows the mobile node to dynamically
discover the Home Agents in the mobile’s Home link. This however will require static provisioning
of the prefix of the home subnet in the mobile. This will have two drawbacks:
a. Will create administrative burden for the network operator. This will also require out-ofband ways to update this information stored in the mobile with updated home-link prefix
information in case of network re-configuration.
b. This will prevent opportunistic and local assignment of Home Agents in the network
especially in the case of roaming. Even though home agent services are available in the
local network or in the immediate vicinity of the local access network, the mobile have to
register with the statically provisioned home link that may thousands of miles away.
In order to circumvent these issues associated with dynamic home agent discovery in Mobile
IPv6, we propose a method that can be applied with minimum change in existing operator’s
network.
Dynamic Home Prefix and/or Home Agent list Assignment
Before Mobile Station performs Mobile IPv6 Binding Update for Home Registration, the MS must
establish a PPP link with the PDSN. The PPP link setup procedure is same as that of Simple IPv6
access. At the LCP phase, the MS performs PAP/CHAP to authenticate the user with Home AAA
server. Upon successful authentication, the HAAA sends back Access-Accept to the PDSN. The
Home AAA may also include several attributes or VSAs in the Access-Accept that may be used
by the PDSN to apply specific services for the user. These attributes/VSAs are included based on
the user’s profile in the HAAA. If the user is allowed to run Mobile IPv6, the user’s profile must
indicate that. When the HAAA detects that the user is allowed to perform Mobile IPv6 registration,
then the HAAA determines most appropriate home link prefix for the user. These selection criteria
can be based on several factors such as but not limited to:
a. Location of the user (indicated by the NAS-IPv6 address)
b. Location of the user’s default Home-Link (may be static in the profile).
c. Status of the default Home-Link.
The HAAA returns a VSA that contains a list of Home-Link prefixes that the MS should attempt to
register when the MS initiates Mobile IPv6 home registration. The list contains Home-Link
prefixes in the order of preference, starting from the most preferred to least preferred. Upon
receiving the VSA with the list of Home-Link prefixes, the PDSN stores the information (end of
LCP phase). After the mobile completes the IPv6CP (NCP) phase, the PDSN transmits the
Assigned Home-Link information to the MS in two possible ways as described in the subsequent
sections.
Additionally, the HAAA can also assign the Home Agent(s) that should anchor the MIP6 session.
This will eliminate the need for the MS to discover Home Agents on the selected/assigned Home
Link.
2.1
MIP6 specific ICMPv6
The MS attempts to autoconfigure it’s globally routable IPv6 address either by sending a Router
Solicitation to the PDSN or the PDSN sends a proactive Router Advertisement to the MS as soon
as the NCP (IPv6CP) phase completes. The PDSN inserts the list of Home-Link prefixes and/or
the list of Home Agents addresses that it received from the HAAA in a MIP6 specific ICMPv6
message. The proposed message format is as shown below:
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Home-Link prefix option contains the assigned IPv6 prefixes of the Home-Link of the MS. When
advertising more than one Home-Link prefixes in the order of preference, as many Home-Link
prefix options as Home-Link prefixes are included in an ICMPv6 message.
0
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Type
|
Code
|
Checksum
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
+
+
.
.
.
List of IPv6 Address prefix of the Home-Links
.
.
.
+
+
|
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. Home-Link Prefix Option Format
Type
8-bit identifier of the option type (TBD: IANA)
Code:
0
Checksum
The ICMP checksum.
List of IPv6 Address prefix of the Home-Links: The IPv6 prefixes of the Home-Link. This field is
extracted from the VSA received from the HAAA.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Type
|
Code
|
Checksum
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
+
+
.
.
.
List of IPv6 Addresses of the Home-Agents
.
.
.
+
+
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. Home-Agent Option Format
Type
8-bit identifier of the option type (TBD: IANA)
Code:
0
Checksum
The ICMP checksum.
List of IPv6 Addresses of the Home-Agents: The IPv6 Addresses of the Home-Agents. This field
is extracted from the VSA received from the HAAA.
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2.2
PPP vendor specific packet
The PDSN extracts the values (Home-Link prefixes) from the VSA received from the Home AAA
and sends to the MS in PPP vendor specific packet. The packet format of the PPP packet is as
follows:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Code
| Identifier
|
Length
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Magic-Number
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
OUI
|
Kind
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
+
+
.
.
.
List of IPv6 Address prefix of the Home-Links
.
.
.
+
+
|
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. Home-Link Prefix PPP packet Format
Code
0 for Vendor Specific
Identifier The Identifier field MUST be changed for each Vendor Specific packet sent.
Length
>= 12
Magic-Number
The Magic-Number field is four octets and aids in detecting links that are in the
looped-back condition. Until the Magic-Number Configuration Option has been successfully
negotiated, the Magic-Number MUST be transmitted as zero. See the Magic-Number
Configuration Option for further explanation.
OUI
Three octets. The vendor's Organizationally Unique Identifier. 0xCF0002 for 3GPP2.
Kind
One octet. Indicates a sub-type for the OUI. Indicates Home Link prefix list.
List of IPv6 Address prefix of the Home-Links: The IPv6 prefixes of the Home-Link. This field is
extracted from the VSA received from the HAAA.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Code
| Identifier
|
Length
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
Magic-Number
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
OUI
|
Kind
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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|
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+
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List of IPv6 Addresses of the Home-Agents
.
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+
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4. Home-Link Prefix PPP packet Format
Code
0 for Vendor Specific
Identifier The Identifier field MUST be changed for each Vendor Specific packet sent.
Length
>= 12
Magic-Number
The Magic-Number field is four octets and aids in detecting links that are in the
looped-back condition. Until the Magic-Number Configuration Option has been successfully
negotiated, the Magic-Number MUST be transmitted as zero. See the Magic-Number
Configuration Option for further explanation.
OUI
Three octets. The vendor's Organizationally Unique Identifier. 0xCF0002 for 3GPP2.
Kind
One octet. Indicates a sub-type for the OUI. Indicates HA address list.
List of IPv6 Addresses of the Home-Agents: The IPv6 Addresses of the Home-Agents. This field
is extracted from the VSA received from the HAAA.
3.
Dynamic Home Agent Discovery after Dynamic Home Prefix Assignment
After the MS discovers the assigned Home-Link prefixes (in the case when the HAAA distributed
the prefix of the possible home links only) from the PDSN, the MS performs dynamic Home Agent
discovery as outlined in draft-ietf-mobileip-ipv6-24.txt. The order of Home Agent discovery will be
based on the order of the Home-Link prefixes appearing in the RA message or the PPP vendor
specific message. The first/top of the entry has the highest preference. See call flows in section 5.
4.
The format of the attribute/VSA
The HAAA server formats the attribute/VSA that carries the list of assigned Home-Link prefixes in
the following fashion. The order of the Home-Link prefixes in the attribute/VSA represents the
relative preference of the Home-Link.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type
| Length
| Reserved
|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
|
+
+
.
.
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List of IPv6 Address prefix of the Home-Links
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. Home-Link Prefix list attribute/VSA format
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type
| Length
| Reserved
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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List of IPv6 Addresses of the Home-Agents
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6. Home-Agent list attribute/VSA format
5.
Call flows
MN
Home
AAA
PDSN
LCP CHAP/PAP
a
b
Access-Request
MIPv6
allowed
Access-Accept
(HL-prefix/HA List)
Store HLprefix/HA List
NCP/IPv6CP
ICMPv6 (MIP6)
(HL-prefix/HA List options)
HA
c
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f
g
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Figure 7. Home-Link Prefix/HA list discovery using RA (ICMPv6) options
a) MN performs PAP/CHAP as part of PPP setup.
b) PDSN sends an Access-Request to the HAAA.
c) The HAAA authenticates and authorizes the user. At this step the HAAA checks the
user’s profile and determines that the user is allowed to run mobile IPv6. The HAAA
checks the location from where the mobile user is attempting to access the network. This
can be done by using the PDSN’s NAS-IPv6 address as the input. Based on this
knowledge and other operator defined criteria, the HAAA creates a preferred list of
Home-Links for the user.
d) The HAAA sends back Access-Accept with the HL-prefix-list as an attribute/VSA among
other necessary attributes/VSAs.
e) The PDSN stores the received values of HL-prefix-list in the local cache.
f) The NCP/IPv6CP phase completes with PDSN and the MN negotiating IIDs for link local
and global address autoconfiguration.
g) The PDSN sends MIP6 message (ICMPv6 options) that includes the HL-prefix options
and/or the Home Agent list option.
MN
Home
AAA
PDSN
LCP CHAP/PAP
HA
a
b
Access-Request
MIPv6
allowed
Access-Accept
(HL-prefix/HA List)
Store HLprefix/HA List
PPP vendor specific packet
(HL-prefix/HA List)
24
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c
d
e
f
Figure 8. Home-Link Prefix/HA list discovery using PPP vendor specific packet
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a) MN performs PAP/CHAP as part of PPP setup.
b) PDSN sends an Access-Request to the HAAA.
c) The HAAA authenticates and authorizes the user. At this step the HAAA checks the
user’s profile and determines that the user is allowed to run mobile IPv6. The HAAA
checks the location from where the mobile user is attempting to access the network. This
can be done by using the PDSN’s NAS-IPv6 address as the input. Based on this
knowledge and other operator defined criteria, the HAAA creates a preferred list of
Home-Links for the user.
d) The HAAA sends back Access-Accept with the HL-prefix-list as an attribute/VSA among
other necessary attributes/VSAs.
e) The PDSN stores the received values of HL-prefix-list in the local cache. This is step is
optional for the PDSN because the PDSN can send the received HL-prefix list to the MN
in the LCP phase.
f) The PDSN sends the HL-prefix list and/or the HA list to the MN in the PPP vendor
specific packet as part of the LCP phase or part of the NCP phase.
8