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Versions: 00 01 02 03                                                   
Internet Area                                                   M.Hui
Internet Draft                                                 H.Deng
Intended status: Informational                              China Mobile
Expires: August 27, 2009                               February 27, 2009



       Extension of DHCPv4 for policy routing of multiple interfaces
                                 terminal
                    draft-hui-mif-dhcpv4-routing-00.txt


Status of this Memo

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

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   This Internet-Draft will expire on August 27, 2009.

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   Copyright (c) 2009 IETF Trust and the persons identified as the
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Abstract

   Current multiple interfaces terminal causes the problem of selecting
   a proper interface for a specific application, and this is a new
   question which will change the previous internet model. This document
   proposes a solution which uses policy routing to map the IP flows to
   multiple interfaces.







































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Table of Contents


   1. Introduction................................................4
   2. Scenario....................................................5
   3. Solution....................................................6
      3.1. Routing policy.........................................6
      3.2. DHCP extension.........................................6
      3.3. Configuration procedure.................................8
   4. Security Considerations......................................9
   5. IANA Considerations........................................10
   6. References.................................................11
      6.1. Normative References...................................11
      6.2. Informative References.................................11
   Author's Addresses............................................12































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1. Introduction

   Currently, the terminal always has multiple interfaces to connect to
   different types of access networks. The challenge is how to assign
   different IP flows to each interface, and ensure all the interfaces
   can deliver the flow simultaneously.

   The operating systems only allow one default network connection now.
   If there are multiple connections of the host, all the flows will go
   to the default gateway based on RFC1122 description. One default
   gateway guarantees the host always has one entry to the network, but
   lead to the multiple connections be difficult. The most convenient
   way to make the host work under several networks at the same time is
   to add specific static route in the host route table, so that certain
   flow can use the assigned interface while others use the default one,
   but it is not easy for the ordinary users to handle it. We analyze
   this problem statement in another IETF draft 'draft-hui-ip-multiple-
   connections-ps-01'.

   In this document we will illustrate the specific scenario and give a
   probable solution by extending DHCPv4.

























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2. Scenario

   The usage of multiple interfaces is common. For example, the user has
   several applications run in his mobile terminal, and the terminal has
   multiple interfaces for different types of access technology such as
   WiFi and 3GPP LTE. It is important for the user to connect right
   access network for specific application. The problem is current
   internet model and protocol stack are not designed for multiple
   interface scenarios, for the mechanism of the mapping between
   application and multiple interfaces is lack.

   In this draft a solution of policy routing is proposed to map the
   application to specific interface based on policies defined by users
   or operators.
































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3. Solution

   In order to direct IP flows of the application to the right interface,
   DHCPv4 message can be extended to carry the routing policy, and the
   extension is added in the option field of the DHCP message.

3.1. Routing policy

   The routing policy can be applied in the host so that different IP
   flows can go to different interfaces depending on the policy. To
   maintain a simple host routing table, the policy can be allocated by
   the network side, i.e. the gateway. The policy is distributed to the
   host as soon as it attaches to the gateway, and the policy will be
   applied in the initial procedure of the host.

   The routing policy information should contain the proper interface
   allocation according to IP destination and service type. For doing
   this, IP flows can go to the appropriate network, and all connections
   can work simultaneously.

3.2. DHCP extension

   DHCP is a proper message to carry the host routing policy information,
   for DHCP take effect when host first attach to the network, and DHCP
   is a universal protocol used in the host IP deployment between
   network gateway and host.

   In the RFC2132, option 33 is defined as the static route option,
   which directs the IP flow to a router depending on the destination IP
   address. This is a kind of policy routing, but the destination IP
   address is not enough to indicate the relationship of IP flow and
   interface in nowadays complicated network deployment situation. More
   attributes are needed to determine a binding of application IP flow
   and interface.

   To carry the host routing information, the extension of the DHCP
   option is showed as follow:









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    Code    Len   Destination 1          Mask 1
    +-----+-----+-----+-----+-----+-----+-----+
    |  x  |  n  |  d1 |  d2 |  d3 |  d4 |  m1 |
    +-----+-----+-----+-----+-----+-----+-----+
                       TOS1    Router1
    +-----+-----+-----+-----+-----+-----+-----+
    |  m2 |  m3 |  m4 |  t1 |  r1 |  r2 |  r3 |
    +-----+-----+-----+-----+-----+-----+-----+
          Metric1     Destination 2     Mask2
    +-----+-----+-----+-----+-----+-----+-----+
    |  r4 |  e1 |  d1 |  d2 |  d3 |  d4 |  m1 |
    +-----+-----+-----+-----+-----+-----+-----+
                       TOS2  Router2
    +-----+-----+-----+-----+-----+-----+-----+
    |  m2 |  m3 |  m4 |  t1 |  r1 |  r2 |  r3 |
    +-----+-----+-----+-----+-----+-----+-----+
          Metric2
    +-----+-----+-----+
    |  r4 |  e1 | ...
    +-----+-----+-----+



                      Figure 1 DHCP extension format.

   Code is an 8 bits number represents the specific DHCP option, which
   needs to be assigned by IANA.

   Len represents the length of the option form the byte after the Len
   field, and it takes 8 bit.

   Destination is the Destination IP address of the datagram, occupying
   4 byte. Mask field represents the subnet mask of the destination.

   TOS is 8 bit length which follows the definition in RFC1349, and it
   represents the requirement of specific IP flow, such as bandwidth and
   delay.

   Router is the IP address of the network gateway which takes 32 bit
   length. Either the router interface address or the corresponding host
   interface address is suitable.

   Metric is the measurement of the routing performance, it represent
   different types of value to measure the route, such as hops. The
   length of metric is 8 bit. The metric in host routing table means the
   bandwidth of the access network and the route has lower metric
   represents better performance. It will be useful when the route


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   policies get from different interfaces conflict, if more than one
   route items have same destination and TOS but with different router
   address, the one has lower metric will be used.

3.3. Configuration procedure

   The DHCP routing policy is carried in the DHCP message, when host
   requires IP configuration as soon as it first attaches the network,
   DHCP server will send the routing policy together with the IP
   configuration to the host.

   Then the routing policy carried on the DHCP message is obtained by
   the host, and applied as the static routing entries in the host
   routing table.

   When it comes to the source address selection of the datagram, the
   host operating system will look up the routing table according to the
   destination IP address first, if it finds an available routing, the
   interface of this routing will be used to send out the datagram, and
   the IP address of this interface is selected to be the source address
   of the datagram. The detail of the source address selection is
   described in RFC1122 and RFC3484.

   So that the static routing entry can constrain specific IP flow to
   certain interface. Depending on the destination and TOS, the IP flow
   can find a proper router as the next hop, and goes out through the
   corresponding interface. Thus different IP flows can use multiple
   connections properly and simultaneously.




















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4. Security Considerations

   This document doesn't propose any new protocol.











































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5. IANA Considerations

   This document requires a new number for DHCP option code x described
   in section 3.2.










































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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.

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

   [RFC2132] S. Alexander, Silicon Graphics, Inc., and R. Droms, " DHCP
             Options and BOOTP Vendor Extensions ", RFC 2132, March 1997.

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

   [RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site-
             Multihoming Architectures", RFC 3582, August 2003.

   [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
             in IPv6", RFC 3775, June 2004.

   [RFC4177] Huston, G., "Architectural Approaches to Multi-homing for
             IPv6", RFC 4177, September 2005.

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

6.2. Informative References

   [MONAMI6] Ernst, T., "Motivations and Scenarios for Using Multiple
             Interfaces and global Addresses", May 2008, <draft-ietf-
             monami6-multihoming-motivation-scenario-03(work in
             progress)>.












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Author's Addresses

   Min Hui
   China Mobile
   53A,Xibianmennei Ave.,
   Xuanwu District,
   Beijing 100053
   China
   Email: huimin.cmcc@gmail.com


   Hui Deng
   China Mobile
   53A,Xibianmennei Ave.,
   Xuanwu District,
   Beijing 100053
   China
   Email: denghui02@gmail.com




























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