One document matched: draft-hui-ip-multiple-connections-00.txt


Internet Area                                                     M.Hui 
Internet Draft                                                   H.Deng 
Intended status: Informational                              China Mobile 
Expires: April 27, 2009                                 October 27, 2008 
                                    
 
                                      
         Scenario and Solution: Simple IP Multi-homing of the Host 
                 draft-hui-ip-multiple-connections-00.txt 


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Copyright Notice 

   Copyright (C) The IETF Trust (2008). 

Abstract 

   Current host routing mechanism doesn't allow simple IP multi-homing 
   for the default gateway consideration. This document proposes a 
   solution to make multiple connections can work simultaneously.  

Conventions used in this document 

   In examples, "C:" and "S:" indicate lines sent by the client and 
   server respectively. 

   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 RFC-2119 
       . 

Table of Contents 

    
   1. Introduction...................................................3 
   2. Scenario.......................................................3 
   3. Solution.......................................................3 
      3.1. Routing policy............................................3 
      3.2. DHCP extension............................................4 
      3.3. Configuration procedure...................................5 
   4. Security Considerations........................................5 
   5. IANA Considerations............................................5 
   6. References.....................................................5 
      6.1. Normative References......................................5 
      6.2. Informative References....................................6 
   Author's Addresses................................................6 
   Intellectual Property Statement...................................6 
   Disclaimer of Validity............................................7 
    
    



 
 
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1. Introduction 

   Simple IP Multi-homing means the host connects to more than one 
   physical network through different network interfaces, and assigns 
   different network flows to each interface, and ensure all the 
   interfaces can deliver the flow simultaneously.  

   Current host operating systems allow one default connection at once. 
   If there are multiple connections of the host, all the flows will go 
   to the default gateway, although you can find several ''0.0.0.0'' routs 
   in the host route table. One default gateway guarantees the host 
   always has one exit to the network, but cause the multiple 
   connections be impossible. 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. 

2. Scenario  

   Simple IP Multi-homing is a necessary part of daily life. For example, 
   Mike must connect with the VPN by Ethernet interface when he is at 
   work, at the same time he wants to watch the stock market, which is 
   forbidden in the VPN, so he needs another connection to the GPRS 
   network simultaneously. 

   The problem is Mike can not use two connections at the same time for 
   his different service requirement, because all the IP flows go to the 
   same interface which related to the default gateway in the host 
   routing table. That is the point need to be solved in simple IP 
   multi-homing. 

3. Solution  

   The default gateway problem can be solved by applying routing policy 
   in the host. 

3.1. Routing policy 

   The routing policy can applied in the host so that different IP flows 
   can go to different interfaces depending on the polices. 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. 


 
 
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   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. 

   To carry the host routing information, DHCP should make an extension 
   in the DHCP option field. The format is showed as follow: 

    Code    Len         Destination 1    Mask 1 
    +-----+-----+-----+-----+-----+-----+-----+ 
    |  x  |  n  |  d1 |  d2 |  d3 |  d4 |  m1 | 
    +-----+-----+-----+-----+-----+-----+-----+ 
   TOS1    Router1               Destination 2 
   +-----+-----+-----+-----+-----+-----+-----+ 
   |  t1 |  r1 |  r2 |  r3 |  r4 |  d1 |  d2 | 
   +-----+-----+-----+-----+-----+-----+-----+ 
               Mask 2  TOS2    Router2         
   +-----+-----+-----+-----+-----+-----+-----+ 
   |  d3 |  d4 |  m2 |  t2 |  r1 |  r2 |  r3 | 
   +-----+-----+-----+-----+-----+-----+-----+ 
     
   +-----+----- 
   |  r4 |  ... 
   +-----+----- 
                      Figure 1 DHCP extension format. 

   Code is a 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. 

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

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

   Router is the next hop IP address. Either the router interface 
   address or the corresponding host interface address is suitable.  
 
 
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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, which 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. 

4. Security Considerations 

   This document doesn't propose any new protocol. 

5. IANA Considerations 

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

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.  

   [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.  


 
 
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   [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)>. 

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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