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<Working Group Name>                                              T. Sun
Internet Draft                                                   H. Deng
Intended status: Informational                                   X. Duan
Expires: September 2009                                     China Mobile
                                                         March 10,
2009


          Address Selection Policy Configuration by DHCPv6 Option
                 draft-sun-mif-address-policy-dhcp6-01.txt


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Abstract




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   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................6
         2.3.1. Conflict of Route Rules............................6
         2.3.2. Application Situations.............................6
         2.3.3. Not Limited to DHCP Servers........................6
   3. IANA Considerations.........................................6
   4. Conclusions....................................
   5. References..................................................7
      5.1. Normative References....................................7
      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  |   IF-Based 1          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +  Add. Prefix Len 1  |     Address Prefix 1                    .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                             .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +       Preference 1  |      Label  1                           +
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   .                                                               .
   .                                                               .
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   +   IF-Based N  |  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.

   IF-Based N  A flag used to indicate whether the Nth rule is
             ''interface Based'' (=1) or ''host based'' (=0).

   Address   Prefix Len Length of an 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 Nth rule correspondence
             between source and destination address.

   The ''IF-Based'' flag is used to indicate whether the rule applies only
   to the interface that received the DHCP reply message or the rule is
   ''host based'' and applies to all the interfaces. This flag is
   introduced for merging route policies that received from multiple
   interfaces.



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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.

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.







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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.

   [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.yang-mif-req] Yang, P., Seite, P., Williams, C., and J. Qin,
             "Requirements on multiple Interface (MIF) of simple IP",
             draft-yang-mif-req-00 (work in progress), March 2009.

   [draft-fujisaki-dhc-addr-select-opt-07] Matsumoto, A., Niinobe, S.,
             Hiromi, R., and Kanayama, K., ''Distributing Address
             Selection Policy using DHCPv6,'' draft-fujisaki-dhc-addr-
             select-opt-07 (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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