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

        Route Configuration by DHCPv6 Option for Hosts with Multiple

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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 key issue here is to select
   appropriate route according to RFC 1122. The approach presented in
   this document is extending DHCPv6 option to configure route tables of
   the hosts.

Table of Contents

   1. Introduction................................................2
   2. Solution of Multiple Interface Usage.........................3
   3. DHCPv6 Option Extensions.....................................4
      3.1. Host and Server Behavior................................4
      3.2. Route Information Option................................4
      3.3. Some Considerations of the DHCPv6 Option................6
         3.3.1. Conflict of Route Rules............................6
         3.3.2. Application Situations.............................6
         3.3.3. Not Limited to DHCP Servers........................6
   4. IANA Considerations.........................................6
   5. Security Considerations......................................6
   6. References..................................................7
      6.1. Normative References....................................7
      6.2. 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

   To avoid all packets passing through the same interface corresponding
   to the default gateway, the approach in this document configures
   certain routes in route tables of hosts. The configuration
   information is sent through extending DHCPv6 option.

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   In [RFC 4191], multiple default routers and specific routes are used
   to handle multi-homed scenarios. 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. Similar approach was presented in [I-D-
   dec-dhcpv6-route-option-00] where TOS and metrics information have
   not been involved.

2. Solution of Multiple Interface Usage

   The procedures of configuring routing information and selecting
   interface are depicted in Figure 1.

   The routing 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 routing information through DHCPv6 option as
      to be defined in Section 3.2.

   o a3) The routing information received from the interface is used to
      configure the routing 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 selects source address based on the routing 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|<------|Route Table|
   +-----------+     +------+  b2   +-----------+

     Figure 1 The procedures of updating a routing 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
   "Route Information" defined in 3.2.

   The server constructs a Reply message to provide route information 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. Route Information Option

   The DHCPv6 option is extended to contain multiple pieces of route
   information. Each piece of route information contains TOS, metric,
   destination IP address and the next hop IP address. The ROUTE_INFO
   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_ROUTE_INFO  |    option-len |   Preference 1          |
   +  TOS 1  | Metric 1  | Dest. Add. Pref. Len|  Dest. Add. Pref. |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                   .
   .                                                               .
   +        Next Hop IPv6 Address                                  .
   .                                                               .
   .                                                               .
   .                                                               .
   + Preference N  |  TOS N  | Metric N  |  Dest. Add. Pref. Len   |
   +  Dest. Add. Pref.                                             .
   +        Next Hop IPv6 Address                                  .
   .                                                               .

                  Figure 2 The Route Information Option.

   option-code OPTION_ROUTE_INFO (should be defined by IANA).

   option-len length of the route rule field in octets.

   Preference N An integer to indicate the priority of applying the Nth
             route rule.

   TOS N  The Nth TOS (Type-of-Service, 8 bits).

   Metric N The Nth route metric ranging from 1 to 9999.

   Dest. Add. Prefix Len Length of the IPv6 destination address prefix,
             an 8-bit unsigned integer ranging from 0 to 128.

   Dest. Add. Prefix The IPv6 destination address prefix

   Next Hop IPv6 Address A 128-bit IPv6 address that will be used as the
             next hop when forwarding packets.

   In the above, the "Preference" of one route rule comes before the
   "metric." Namely, if there are conflict routes for one destination,

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   the one with highest preference value should be used. For example,
   the network administrator uses one route in a connection for security
   or reliability considerations, even though the metric of the route is

3.3. Some Considerations of the DHCPv6 Option

3.3.1. Conflict of Route Rules

   For the situations where a route option conflicts with one previous
   route rules, 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.

4. IANA Considerations

   The option code of ROUTE RULE 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

   [I-D.dec-dhcpv6-route-option-00] Dec, W., and Johnson, R, "DHCPv6
             Route Option," draft-dec-dhcpv6-route-option-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.

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Authors' Addresses

   Tao Sun
   China Moible
   53A,Xibianmennei Ave.,
   Xuanwu District,
   Beijing 100053
   Email: suntao@chinamobile.com

   Hui Deng
   China Moible
   53A,Xibianmennei Ave.,
   Xuanwu District,
   Beijing 100053
   Email: denghui@chinamobile.com

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