One document matched: draft-sun-mif-address-policy-dhcp6-00.txt
<Working Group Name> T. Sun
Internet Draft H. Deng
Intended status: Informational X. Duan
Expires: September 2009 China Mobile
March 5, 2009
Address Selection Policy Configuration by DHCPv6 Option
draft-sun-mif-address-policy-dhcp6-00.txt
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Abstract
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Internet-Draft Address Policy Configured by DHCPv6 March 2009
For hosts with multiple interfaces, the problem is how to make it run
several applications simultaneously on variant interfaces such as
GPRS, Wifi etc. To achieve this, one way is to select appropriate IP
address so that the packets can be sent to the corresponding
interface for forwarding. RFC 3484 defines a ''policy table'' for
default IP address selection. This document extends the DHCPv6 option
message so that the policy table can be dynamically updated.
Table of Contents
1. Introduction................................................2
2. Solutions...................................................4
2.1. Route Table Updation....................................4
2.2. The Option of DHCPv6.......................
2.3. Some Considerations of the DHCPv6 Option................5
2.3.1. Conflict of Route Rules............................5
2.3.2. Application Situations.............................6
2.3.3. Not Limited to DHCP Servers........................6
3. IANA Considerations.........................................6
4. Conclusions....................................
5. References..................................................6
5.1. Normative References....................................6
5.2. Informative References..................................7
1. Introduction
A host such as a laptop or a smart-phone may have multiple interfaces
for connections, e.g., a wired Ethernet LAN, a 802.11 LAN, a 3G cell
network, one or multiple VPNs or tunnels. In view of more and more
versatile applications, users may expect a host to utilize several
interfaces at the same time.
If the source IP address is selected and bind by an application, then
the application can use certain interface in this way. However,
source IP addresses are generally added by sockets in IP layer.
According to [RFC 1122], all the packets whose destination IP
addresses is not specified in the route table will be send to a
default gateway for forwarding. Accordingly, the IP address
corresponding to the default gateway is chosen as the source IP
address.
To avoid all packets passing through the same interface corresponding
to the default gateway, the approach in this document configures the
IP address ''policy table'' defined in [RFC 3484]
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To address multi-homed problems in a flexible way, [I-D-hui-mif-
dhcpv4-routing-00] extends DHCPv4 through introducing TOS and
specific routes into DHCP options. This document considers IPv6
situations. The approach presented in [I-D. sun-mif-route-config-
dhcp6-00] is an approach which extends DHCP option for sending route
information. The route table and the address selection policy table
can be used jointly to let multiple interfaces work simultaneously.
2. Solution of Multiple Interface Usage
The procedures of configuring policy table of address selection are
depicted in Figure 1.
The policy table configure procedures are shown as steps a1 to a3.
o a1) An interface sends Information-requirement when the connection
is established or when an existing connection receives
reconfiguration message from the server.
o a2) The server sends policy rults through DHCPv6 option as to be
defined in Section 3.2.
o a3) The policy rules received from the interface is used to
configure the policy table of the host.
The procedures that an application employs an interface for network
access are depicted in Figure 1 as steps b1 to b4.
o b1) An application calls sockets to build IP packets.
o b2) The socket determines the destination and selects source
address based on the policy table.
o b3) The socket sends packets to the corresponding interface.
o b4) The interface will forward the packets to the next hop (the
corresponding gateway).
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+----+ a1 +---------+ b4 +-------+
|DHCP|<--------- |Interface|--------->|Network|
+----+ --------> +---------+ +-------+
a2 | |
| |
b3 | |
^ | a3
| ----->----+
| |
+-----------+ b1 +------+ +-----------+
|Application|---->|Socket|<------|PolicyTable|
+-----------+ +------+ b2 +-----------+
Figure 1 The procedures of updating a policy table and select an
interface for an application.
Notice that the approach proposed in this document is feasible under
the strong ES model as defined in RFC1122.
3. DHCPv6 Option Extensions
3.1. Host and Server Behavior
The host must include ''Option Request'' option to let the server know
the option the host interested. The request option code is set as the
''Address Policy'' defined in 3.2.
The server constructs a Reply message to provide IP address policy
rules to the host. Also, a server may send a Reconfigure Message to
a host. The host may initiate a request when receiving the
Reconfigure message for the host.
3.2. Address Policy Option
The DHCPv6 option is extended to contain multiple pieces of default
address selection policy rules. Each piece of rules contains address,
preference and label which are properties defined in [RFC3484]. The
ADDRESS_POLICY option is depicted in Figure 2.
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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_ADDRESS_POLICY | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ Add. Prefix Len 1 | Address Prefix 1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ Preference 1 | Label 1 +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ Add. Prefix Len N | Address Prefix N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ Preference N | Label N +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2 The Address Policy Option.
option-code OPTION_ ADDRESS_POLICY (should be defined by IANA).
option-len length of the route rule field in octets
Address Prefix Len Length of a IPv6 destination address prefix, an 8-
bit unsigned integer ranging from 0 to 128.
Address Prefix The address prefix
Preference A number identifies the priority of one type of IP address.
Label A number that used to mark the correspondence between source
and destination address.
3.3. Some Considerations of the DHCPv6 Option
3.3.1. Conflict of A Policy Table
For the situations where the rule in the policy table conflicts with
one previous policy table, the latter one will override the previous
rule.
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3.3.2. Application Situations
There are two situations when DHCPv6 is applied, i.e., with or
without stateless autoconfiguration. For the stateless case, since
the address has been configured based on the link-local/site-local
address, the DHCPv6 is used to obtain options.
3.3.3. Not Limited to DHCP Servers
The solution presented in this document is with the context of DHCP
message. It should be pointed out that similar message may not be
conveyed by certain node in the network instead of a DHCP server.
Router solicitation and advertisement are also potential approach to
convey the
4. IANA Considerations
The option code of ADDRESS_POLICY will be defined by IANA.
5. Security Considerations
The security issues in this document are similar with those that have
been met when using DHCPv6 options.
The interface selection is affected by the routing and address
selection rules sent from servers. Therefore, incorrect information
received by hosts will cause improper interface selection leading to
bad user experiences. Attacks such as deny of services (DoS) or man-
in-the-middle may redirect host's solicitation, change the
information or flood the host with invalidate messages. Approaches to
guarantee the communication securities between hosts and servers
should be applied based on the network access types of the interfaces.
6. References
6.1. Normative References
[RFC1122] Braden, R., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122, October 1989.
[RFC3484] R. Draves, "Default Address Selection for Internet Protocol
version 6 (IPv6)", RFC3484, February 2003.
[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.
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[RFC4191] Draves, R. and D. Thaler, "Default Router Preferences and
More-Specific Routes", RFC 4191, November 2005.
6.2. Informative References
[RFC2461] Narten, T., Nordmark, E., and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461,
December 1998.
[I-D. blanchet-mif-problem-statement] Blanchet, M., "Multiple
Interfaces Problem Statement", draft-blanchet-mif-problem-
statement-00 (work in progress), December 2008.
[I-D.hui-mif-dhcpv4-routing-00] Hui, M., and Deng, H. ''Extension of
DHCPv4 for policy routing of multiple interfaces terminal,''
draft-hui-mif-dhcpv4-routing-00(work in progress), February
2009
[I-D. sun-mif-route-config-dhcp6-00] Sun, T., and Deng, H., ''DHCPv6
Route Option,'' draft-sun-mif-route-config-dhcp6-00(work in
progress), March 2009
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Authors' Addresses
Tao Sun
China Moible
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: suntao@chinamobile.com
Hui Deng
China Moible
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: denghui@chinamobile.com
Xiaodong Duan
China Moible
53A,Xibianmennei Ave.,
Xuanwu District,
Beijing 100053
China
Email: duanxiaodong@chinamobile.com
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