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Versions: 00 01 02 03                                                   
MIF Working Group                                                 T. Sun
Internet-Draft                                                   H. Deng
Intended status: Standards Track                                  D. Liu
Expires: January 28, 2011                                   China Mobile
                                                           July 27, 2010


Route Configuration by DHCPv6 Option for Hosts with Multiple Interfaces
                  draft-sun-mif-route-config-dhcp6-03

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 define new 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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 28, 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   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.  Requirements Notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Background . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Scenario Descriptions  . . . . . . . . . . . . . . . . . .  4
   3.  Route Information Option Format  . . . . . . . . . . . . . . .  6
   4.  Route Information Option Format Usage  . . . . . . . . . . . .  8
     4.1.  DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . .  8
     4.2.  DHCPv6 Server Behavior . . . . . . . . . . . . . . . . . .  8
   5.  Implementation Considerations  . . . . . . . . . . . . . . . .  9
     5.1.  Conflict of Route Rules  . . . . . . . . . . . . . . . . .  9
     5.2.  Not Limited to DHCPv6 Servers  . . . . . . . . . . . . . .  9
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13




























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1.  Requirements Notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].














































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2.  Introduction

2.1.  Background

   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.  Issues in such scenarios are
   summarized in [I-D.blanchet-mif-problem-statement] .

   An application uses certain interface through select the
   corresponding source IP address. if the application does not specify
   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 defining a new DHCPv6
   option based on [RFC3315].

   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-03] through
   introducing TOS and specific routes into DHCPv4 options.  This
   document considers the situations for IPv6 cases.

2.2.  Scenario Descriptions

   The scenario addressed by the approach proposed in this document is
   illustrated in Figure 1.  In the figure, the MIF host have three
   interfaces connected to the access network Ethernet, WiFi and 3G
   respectively.













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                                +---------+
                                |   3G    |
                                +---------+
                                     |
                                  I3 |
                                     ^
                                     |
            +-----------+   I1   +--------+   I2   +-----------+
            | Ethernet  |<------>|MIF Host|<------>|   WiFi    |
            +-----------+        +--------+        +-----------+


                      Figure 1: The MIF host scenario

   The procedures that an application employs an interface for network
   access are depicted in Figure 2 as steps a1) to a4).

   a1)  An application calls sockets to build IP packets.

   a2)  The socket selects source address based on the routing table.

   a3)  The socket sends packets to the corresponding interface.

   a4)  The interface will forward the packets to the next hop (the
        corresponding gateway).



                               +---------+   b4     +-------+
                               |Interface|--------->|Network|
                               +---------+          +-------+
                                     |
                                  b3 |
                                     ^
                                     |
               +-----------+ b1  +------+       +-----------+
               |Application|---->|Socket|<------|Route Table|
               +-----------+     +------+  b2   +-----------+


    Figure 2: 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].






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3.  Route Information Option Format

   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 3.

      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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Pref. 1   |     TOS 1     |       Metric 1                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-
     | Dest.Pref.Len |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                                                               |
     |                        Dest.Pref.                             |
     |                                                               |
     |               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                        Next Hop Pref.                         |
     |                                                               |
     |                                                               |
     |               -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+ |
     |               |                                               .
     +-+-+-+-+-+-+-+-+                                               .
     .                                                               .
     .                                                               .
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Pref. N   |     TOS N     |       Metric N                |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-
     | Dest.Pref.Len |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                                                               |
     |                        Dest.Pref.                             |
     |                                                               |
     |               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                        Next Hop Pref.                         |
     |                                                               |
     |                                                               |
     |               -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+ |
     |               |
     +-+-+-+-+-+-+-+-+




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                  Figure 3: The Route Information Option

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

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

   Pref.N: An integer to indicate the priority of applying the Nth route
   rule.  The Preference identified the priority of a rule. if there are
   conflictions, 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, an 16-bit unsigned integer ranging
   from 1 to 9999.

   Dest.Pref.Len: Length of the IPv6 destination subnet prefix, an 8-bit
   unsigned integer ranging from 0 to 128.

   Dest.Pref.: The IPv6 destination address prefix

   Next Hop Pref.: A 128-bit IPv6 prefix 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.




















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4.  Route Information Option Format Usage

4.1.  DHCPv6 Client Behavior

   The MIF host(DHCPv6 client) supports Route Information extension,
   SHOULD send Option Request Option that includes OPTION_ROUTE_INFO to
   indicate that Route Information Option is requested.  The Route
   Information option MUST NOT appear in any messages other than the
   following ones : Solicit, Request, Renew, Rebind, Information-
   Request.

   If the MIF host receives no route information, it MAY try another
   server or retransmit the ORO message.  In this situation, the host
   MUST limit the rate of the retransmition.

4.2.  DHCPv6 Server Behavior

   The DHCPv6 server MUST NOT send Route Option in messages other than
   ADVERTISE or REPLY.

   The maximum number of routing information in one DHCPv6 message
   depend on the maximum DHCPv6 message size defined in [RFC3315].





























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5.  Implementation Considerations

5.1.  Conflict of Route Rules

   The host can use such information obtained from the DHCPv6 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.

5.2.  Not Limited to DHCPv6 Servers

   The solution presented in this document is with the context of DHCPv6
   message.  It should be pointed out that similar message may not be
   conveyed by certain node in the network instead of a DHCPv6 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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6.  IANA Considerations

   The option code of OPTION_ROUTE_INFO will be defined by IANA.
















































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7.  Security Considerations

   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.

   DHCP authentication option [RFC3118] MAY be used for security.






































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8.  References

8.1.  Normative References

   [RFC1122]  Braden, R., "Requirements for Internet Hosts -
              Communication Layers", STD 3, RFC 1122, October 1989.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3118]  Droms, R. and W. Arbaugh, "Authentication for DHCP
              Messages", RFC 3118, June 2001.

   [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.

8.2.  Informative References

   [I-D.blanchet-mif-problem-statement]
              Blanchet, M. and P. Seite, "Multiple Interfaces Problem
              Statement", July 2010,
              <draft-ietf-mif-problem-statement-05 (work in progress)>.

   [I-D.hui-mif-dhcpv4-routing-03]
              Hui, M. and H. Deng, "Extension of DHCPv4 for policy
              routing of multiple interfaces terminal", March 2010,
              <draft-hui-mif-dhcpv4-routing-03(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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