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HIP Working Group                                                 T. Sun
Internet-Draft                                                   H. Deng
Intended status: Informational                                    D. Liu
Expires: January 11, 2011                                   China Mobile
                                                           July 10, 2010


Route Configuration by DHCPv6 Option for Hosts with Multiple Interfaces
                  draft-sun-mif-route-config-dhcp6-02

Abstract

   Currently, more and more hosts have multiple interfaces such as GPRS,
   WiFi etc.  One key issue is how to make the applications on the host
   access the network accordingly through the proper interfaces.  The
   approach presented in this document is to extend DHCPv6 option to
   configure route tables of the hosts.  In this way, the hosts can
   select a appropriate route.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 11, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Solution of Multiple Interface Usage . . . . . . . . . . . . .  4
   3.  DHCPv6 Option Extensions . . . . . . . . . . . . . . . . . . .  6
     3.1.  Host and Server Behavior . . . . . . . . . . . . . . . . .  6
     3.2.  Route Information Option . . . . . . . . . . . . . . . . .  6
     3.3.  Some Considerations of the DHCPv6 Option . . . . . . . . .  7
       3.3.1.  Conflict of Route Rules  . . . . . . . . . . . . . . .  7
       3.3.2.  Application Situations . . . . . . . . . . . . . . . .  7
       3.3.3.  Not Limited to DHCP Servers  . . . . . . . . . . . . .  7
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12






























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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
   cellular network, one or multiple VPNs or tunnels.  In view of more
   and more versatile applications, users may expect a host to utilize
   several interfaces simultaneously.

   An application uses certain interface through select the
   corresponding source IP address. if the applicaiton does not specifiy
   it, the transport layer must ask the IP layer.  According to
   [RFC1122] all the packets whose destination IP addresses are not
   specified in the route table will be sent to the default gateway for
   forwarding.  Accordingly, the IP address corresponding to the default
   gateway will be chosen as the source IP address.

   To avoid all packets passing through the same interface corresponding
   to the default gateway, the approach proposed in this document
   configures certain routes in route tables of the host.  The
   configuration information is obtained through DHCP messages which
   extend the DHCPv6 option.

   An optional extension to Router Advertisement messages is described
   in [RFC4191] for communicating default router preferences and more-
   specific routes from routers to hosts.  To address multi-homed
   problems in a flexible way, [I-D.hui-mif-dhcpv4-routing-02] extends
   DHCPv4 through introducing TOS and specific routes into DHCP options.
   This document considers the situations for IPv6 cases.  Similar
   approach was presented in [I-D.dec-dhcpv6-route-option-03] , however,
   TOS and metrics information have not been involved.





















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2.  Solution of Multiple Interface Usage

   The procedures for a host to configure the routing information and
   select the interface are depicted in Figure 1.  The routing
   configuration procedures are shown as steps a1) to a3).

   a1)  An interface sends Information-requirement when the connection
        is established or when an existing connection receives
        reconfiguration message from the server.

   a2)  The server sends routing information through DHCPv6 option as to
        be defined in Section 3.2.

   a3)  The routing information received from the interface is used to
        update 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).

   b1)  An application calls sockets to build IP packets.

   b2)  The socket selects source address based on the routing table.

   b3)  The socket sends packets to the corresponding interface.

   b4)  The interface will forward the packets to the next hop (the
        corresponding gateway).



               +----+    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



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   the strong ES model as defined in [RFC1122].


















































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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 Section 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.

     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).




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

   Preference N: An integer to indicate the priority of applying the Nth
   route rule.  The Preference identified the priority of a rule. if
   there are conflications, e.g., two rules have the same "Dest.  Add.
   Pref." but different "Next Hop IPv6 Address", the rule with high
   preference SHOULD be applied by the host.

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

3.3.  Some Considerations of the DHCPv6 Option

3.3.1.  Conflict of Route Rules

   The host can use such information obatined from the DHCP message to
   build a "connection manager" on the host or to update the "Policy
   Table" defined in [RFC3484].  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



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   conveyed by certain node in the network instead of a DHCP server.
   Such a node, for example in mobile network, may be the "ANDSF (Access
   Network Discovery and Selection function)" defined in TS 23.402.
















































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4.  IANA Considerations

   The option code of OPTION_ROUTE_INFO will be defined by IANA.
















































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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.

   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              December 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.

   [RFC3484]  Draves, R., "Default Address Selection for Internet
              Protocol version 6 (IPv6)", RFC 3484, February 2003.

   [RFC4191]  Draves, R. and D. Thaler, "Default Router Preferences and
              More-Specific Routes", RFC 4191, November 2005.

6.2.  Informative References

   [I-D.blanchet-mif-problem-statement]
              Blanchet, M. and P. Seite, "Multiple Interfaces Problem
              Statement", May 2010, <draft-ietf-mif-problem-statement
              (work in progress)>.

   [I-D.dec-dhcpv6-route-option-03]
              Dec, W. and R. Johnson, "DHCPv6 Route Option", March 2010,
              <draft-dec-dhcpv6-route-option-03(work in progress)>.

   [I-D.hui-mif-dhcpv4-routing-02]
              Hui, M. and H. Deng, "Extension of DHCPv4 for policy
              routing of multiple interfaces terminal", March 2010,
              <draft-hui-mif-dhcpv4-routing-02(work in progress)>.















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Authors' Addresses

   Tao Sun
   China Mobile
   Unit2, 28 Xuanwumenxi Ave,Xuanwu District
   Beijing 100053
   China

   Email: suntao@chinamobile.com


   Hui Deng
   China Mobile
   Unit2, 28 Xuanwumenxi Ave,Xuanwu District
   Beijing 100053
   China

   Email: denghui@chinamobile.com


   Dapeng Liu
   China Mobile
   Unit2, 28 Xuanwumenxi Ave,Xuanwu District
   Beijing 100053
   China

   Email: liudapeng@chinamobile.com
























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