Internet DRAFT - draft-premec-mip4-ip6-proxy-mip4

draft-premec-mip4-ip6-proxy-mip4



MIP4                                                          D. Premec 
Internet Draft                                                 D. Damic 
Expires: December 2006                                   Siemens Mobile 
                                                          June 19, 2006 
                                    
 
                                      
        Mobility Management for IPv6 Hosts using Proxy Mobile IPv4 
                  draft-premec-mip4-ip6-proxy-mip4-00.txt 


Status of this Memo 

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   This Internet-Draft will expire on December 19, 2006. 

Abstract 

   The IPv6-based end-user device is commonly not able to utilize the 
   advantages introduced by the mobile IP protocols. However, this 
   specification describes how an end-user device supporting only IPv6 
   protocol stack may be provided with a mobility service by the mobile 
   IPv4-based access network. The unaltered end-user device relies on 
   the functionalities of the two network-side entities, the Home Agent 

 
 
 
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   and the new Proxy Mobile Node, acting on its behalf and providing the 
   IP layer mobility management. 

    

Conventions used in this document 

   Mobile station (MS) 

      Mobile station is an IPv6 host that can change its point of 
      attachment to the network. An MS does not implement the Mobile 
      IPv6 protocol nor is it a dual stack host. 

   Proxy Mobile Node (PMN) 

      Proxy mobile node is a function implemented by the access network. 
      Proxy mobile node performs mobile IPv4 signaling and traffic 
      tunneling on behalf of a MS. 

   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 [Bra1997]. 

Table of Contents 

    
   1. Introduction...................................................3 
      1.1. Motivation................................................3 
      1.2. Goals.....................................................3 
      1.3. Overview of the Solution..................................4 
      1.4. Advantages................................................4 
   2. Operation......................................................5 
      2.1. Initial Network Entry.....................................5 
      2.2. Movement to a new PMN.....................................9 
      2.3. Address Lifetime.........................................10 
   3. Home Agent Considerations.....................................11 
   4. Proxy Mobile Node Considerations..............................12 
   5. Mobile Station Considerations.................................13 
   6. Foreign Agent Considerations..................................13 
   7. Security Considerations.......................................14 
   8. IANA Considerations...........................................14 
   9. Acknowledgments...............................................14 
   10. References...................................................14 
      10.1. Normative References....................................14 
      10.2. Informative References..................................15 
   Author's Addresses...............................................16 
   Intellectual Property Statement..................................16 
 
 
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   Disclaimer of Validity...........................................17 
   Copyright Statement..............................................17 
   Acknowledgment...................................................17 
    
1. Introduction 

   This specification describes how an end-user device supporting only 
   IPv6 protocol stack may be provided with a mobility service by the 
   mobile IPv4-based access network. The mobility management is handled 
   completely by the network without any involvement of the end-user 
   device.  

1.1. Motivation 

   The operators of IPv4 networks are facing the problem of the shortage 
   of the IPv4 address space. One possibility to cope with this problem 
   is the introduction of NATs, but this approach is not ideal and has 
   its own set of issues. For example, some applications exchange the IP 
   addresses in the application layer payload. These addresses go 
   unnoticed by the NAT and are not rewritten, with the consequence that 
   the application fails. Such problems may be addressed by the 
   introduction of application layer gateways at the cost of additional 
   complexity. In this perspective, the deployment of IPv6, with its 
   huge address space, seems very appealing. 

   There is also a constant growth in the number of mobile devices 
   causing additional pressure on the already exhausted IPv4 address 
   space. These devices expect to be able to access the network from 
   anywhere, anytime and to provide the always-on experience. Those end-
   user devices also require some form of mobility management. However, 
   most commercial operating systems available today don't provide any 
   form of mobility support at the IP layer. 

   Mobile IPv4 [Per2002] as a mobility management protocol is slowly 
   gaining momentum and operators are implementing networks based on it 
   - there is already a significant infrastructure in the deployment 
   supporting the mobile IPv4.  

    

1.2. Goals 

   Goals of this specification are summarized below: 

   o  To provide a network based mobility solution for IPv6 hosts  

   o  IPv6 hosts doesn't implement whether IPv4 stack nor mobile IPv6 
 
 
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   o  Mobility management is based on mobile IPv4 

   o  Mobility management is handled completely within the network, 
      without the involvement of the hosts 

   o  IPv6 service for the hosts is provided exclusively by the home 
      network. Access network doesn't need to support IPv6 at all. 

    

1.3. Overview of the Solution 

   When the access network detects an attachment of a new IPv6 device, 
   the PMN (Proxy Mobile Node) will register the device with the HA 
   using its own IPv4 care-of address. The IPv6 traffic of the MS will 
   consequently be tunneled between the PMN and the HA in the IPv4 
   tunnel. Tunnel end points are PMN itself and the HA.   

    

                               IPv6 
         MS---IPv6----PMN------over-----------HA---IPv6 network 
                               IPv4 

                        Figure 1 Deployment example 

    

   The PMN is not processing IPv6 packets in any way besides tunneling 
   them between the HA and the MS. Thus, from the perspective of the MS, 
   the complete access network looks like a bridge, i.e. it appears to 
   be a single link layer connecting the MS with its HA. The MS can not 
   tell that it is not attached to its home link - in other words, it 
   believes to be attached directly to the HA. 

   When the MS moves to the new PMN, the new PMN will register its care-
   of address with the HA, thus redirecting the MS traffic to itself.   

    

1.4. Advantages 

   Advantages of the proposed solution are combination of advantages 
   listed in [Tsi2006] and [Leu2006]. They are briefly summarized below: 

   o  Mobility support for unmodified IPv6 hosts  

 
 
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   o  Leverage the existing mobile IPv4 network infrastructure, allowing 
      the MIPv4-based access network to provide mobility service to IPv6 
      hosts 

   o  Mobility management is handled completely within the network, 
      without the involvement of the hosts 

   o  Reduced radio link consumption: no MIP signaling over the air and 
      no tunnel overhead over the air 

   o  Network uses just a single mobility protocol to support both IPv4 
      and IPv6 hosts (protection of investment and reduction of 
      operating costs) 

    

2. Operation 

   We assume a mobile IPv4-based access network. This access network is 
   connected to the router on the home network acting as a MIPv4 HA. The 
   HA is a dual stack node and is also acting as a default router on its 
   IPv6 link. 

   We introduce a new entity which is executing mobile IPv4 procedures 
   on behalf of the mobile node. We call this new entity a Proxy Mobile 
   Node (PMN). The PMN resides in the access network and is located on 
   the traffic path to the MS.  

   The PMN is assumed to have direct link layer connectivity (from the 
   perspective of the IP layer) with the MS. When the MS attaches to the 
   network, in the course of link establishment it will be 
   authenticated. During the authentication process, the access network 
   will learn the NAI of the MS, and the NAI must be made available to 
   the PMN. All these actions happen at the link layer, before any IP 
   layer connectivity.  

    

2.1. Initial Network Entry 

   After the authentication and after the link layer connectivity is 
   successfully established, the MS, being an IPv6 host, will send a 
   Neighbor solicitation message on a newly established link to 
   configure its link local address. The following figure illustrates 
   the procedure in more detail: 

    
 
 
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        MS              PMN                    HA       home 
                                                        link  
        |  link up       |                      |         | 
    1)  <---------------->                      |         | 
        |                |                      |         | 
        |  NS(LLA)       |                      |         | 
    2)  +--------------->|                      |         | 
        |                |                      |         | 
        |                |                      |         | 
    3)  |               *** acq. CoA            |         | 
        |                |                      |         | 
        |                |  RegReq              |         | 
    4)  |                +---------------------->         | 
        |                |                      |         | 
        |                |  RegResp             |         | 
    5)  |                <----------------------|         | 
        |                |                      |         | 
        |                | IP4[RA(home prefix)] |         | 
    6)  |                <----------------------|         | 
        |                |                      |         | 
    7)  | RA(home prefix)|                      |         | 
        <----------------+                      |         | 
        |                |                      |         | 
    8)  |                |  IP4[NS(LLA)]        |         | 
        |                +---------------------->         | 
        |                |                      |  proxy  | 
    9)  |                |                     ***  DAD   | 
        |                |                      |         | 
        |                |                      |         | 
        |                |                      |         | 
        |                |                      |         | 
        |                |                      |         | 
        |                |                      |         | 
         

                      Figure 2 Initial network entry 

   1. In this step the link is established and the MS is authenticated. 
      The PMN SHALL learn the NAI of the MS in this step. 

   2. The MS sends the Neighbor solicitation to configure its link local 
      address. 





 
 
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   3. When the Neighbor solicitation arrives at PMN, the PMN MAY detect 
      that this is an IPv6 packet. This MAY trigger the PMN to register 
      with the HA. First, the PMN MUST acquire the IPv4 address which it 
      will use as a care-of address for the MS. How exactly the PMN 
      acquires the IPv4 care-of address is not defined in this 
      specification, but typically the PMN may request the address from 
      the DHCPv4 server, or it can maintain its own address pool.  

   4. The PMN SHALL generate the MIPv4 Registration request using the 
      CoA obtained in step 3 and NAI [Cal2002a] learned during the 
      authentication. Further, the Registration request SHALL contain an 
      IPv6 tunneling mode extension requesting the IPv6 operation mode, 
      as defined in [Tsi2006]. The Registration request MAY also contain 
      an IPv6 prefix extension [Tsi2006].  

   5. The HA SHALL create the binding between the MS, identified by its 
      NAI, and the CoA received in the Registration request. The HA 
      SHALL include the IPv6 code extension [Tsi2006] as a confirmation 
      that it supports tunneling of IPv6 traffic over MIPv4 tunnel. The 
      code filed in the extension SHALL be set to 1 indicating that the 
      traffic will be tunneled to the IPv4 CoA. When the PMN receives 
      the Registration reply, it creates a binding between the newly 
      established tunnel and the L2 link associated with the MS. 

   6. Immediately after sending the Registration reply, the HA SHOULD 
      send the Router advertisement over the newly established MIPv4 
      tunnel. The Router advertisement is encapsulated and sent to the 
      PMN. The inner header destination address is set to all-nodes-on-
      the-link address and the Router advertisement message contains the 
      home link prefix in the prefix information option. The Router 
      advertisement also controls which kind of address configuration 
      the MS may use: stateless or stateful.  

   7. The PMN SHALL decapsulate and deliver any packets it receives via 
      the MIPv4 tunnel directly to the MS. In this step we see the 
      delivery of the Router advertisement sent by the HA. 

   8. After the MIPv4 tunnel is established, the PMN SHALL start 
      delivering the uplink traffic to the HA. Here the Neighbor 
      solicitation from step 2, which was delayed until the MIPv4 tunnel 
      was set up, is tunneled to the HA. 






 
 
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   9. The arrival of a Neighbor solicitation message verifying the 
      tentative address SHALL trigger the HA to perform proxy DAD on 
      behalf of the MS [Joh2004]. Having successfully performed proxy 
      DAD, the HA SHALL deliver any traffic on the home link destined to 
      this address via the MIPv4 tunnel to the current location of the 
      MS. Every time the MS configures an additional IPv6 address, the 
      HA SHALL perform proxy DAD for this additional address and bind it 
      to the MIPv4 tunnel associated with the MS. 

   If the PMN is aware that the MS is an IPv6-only host, then the PMN 
   MAY initiate the setup of the MIPv4 tunnel immediately after the link 
   layer connection is successfully established. In other words, the 
   step 1 in the figure above may be followed by the step 3. This has 
   the advantage that the MIPv4 tunnel is setup in advance, before any 
   IPv6 traffic arrives at the PMN. The benefit is that the delay caused 
   by the tunnel setup is minimized. This is especially important 
   because the tunnel setup delay may influence the DAD process. 

   It is apparent from the discussion above that the IPv6 traffic is 
   tunneled between the PMN and the HA. Thus the whole access network 
   appears to the MS as a single link connected directly to its HA. The 
   MS is effectively deceived into believing that it is attached to its 
   home link. 

   The MS MAY use either stateful or stateless methods to configure its 
   home address. This specification doesn't mandate or prefer one method 
   over another and is compatible with both methods. Important point is 
   that whenever the MS configures an additional address, the HA SHALL 
   perform the proxy DAD for it and add it to its binding cache. 

    
















 
 
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2.2. Movement to a new PMN 

   The following figure describes the sequence of events when the MS 
   moves to a new link which is associated with the new PMN.  

        MS          nPMN             oPMN            HA       home    
                                                              link     
        |  link up    |  context tx.   |             |         |    
    1)  <------------>|<-------------->|             |         |    
        |             |                |             |         |    
        |             |                |             |         |    
    2)  |            *** acq. CoA      |             |         |    
        |             |                |             |         |    
        |             |  RegReq        |             |         |    
    3)  |             +------------------------------>         |    
        |             |                |             |         |    
        |             |  RegResp       |             |         |    
    4)  |             <------------------------------|         |    
        |             |                |             |         |    
        |             |                | RegRev      |         |    
    5)  |             |                <-------------+         |    
        |             |                |             |         |    
        |             |                | RegRevAck   |         |    
    6)  |             |                +------------->         |    
        |             |                |             |         |    
        |             |                |             |         |    
        |             |                |             |         |    
         

                      Figure 3 Movement to a new PMN 

 

   1. In this step the MS changed its point of attachment to the 
      network. The new link layer connection with the new PMN (nPMN) is 
      established. It is assumed that during the link layer handover the 
      old PMN (oPMN) transfers the MS related context to the new PMN. 
      The context SHALL include at least the NAI and the current 
      sequence number used in MIPv4 Registration request messages. It 
      MAY also include any packets still buffered/arriving at the oPMN. 
      The protocol for exchanging context between PMNs is out of scope 
      of this specification 

   2. - 4. These steps are the same as steps 3-5 in the section 2.1.  



 
 
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   5. When the HA receives a Registration request for a MS for which it 
      already has a binding cache entry, the HA SHOULD send the 
      Registration Revoke message to the previous mobility agent, i.e. 
      to the oPMN. This will expedite the release of resources at the 
      oPMN. The oPMN can safely remove all its resource associated with 
      the PMN since it now knows that it will not receive any further 
      traffic from the HA for this MS. The HA will perform steps 4. and 
      5. simultaneously. 

   6. The oPMN acknowledges to the HA the release of the MS related 
      resources. 

   From the message flow above, it is obvious that the MS itself is not 
   involved in the handover at all. In fact, from the perspective of the 
   MS nothing changed, the illusion that it is connected to its home 
   link is still being maintained by the network despite the fact that 
   the MS actually changed its point of attachment. 

     

2.3. Address Lifetime 

   Lifetime of the IPv6 address assigned to the MS and the binding 
   lifetime held in the HA's MIPv4 context are not directly related to 
   each other. PMN SHALL refresh the mobility binding before it expires. 
   If the mobility binding ever expires, for whatever reason, both PMN 
   and the HA SHALL release all resources related to that mobility 
   binding. In case when the binding lifetime expires at the HA, the HA 
   MAY send the Registration Revocation to the PMN, to insure that the 
   PMN will also release its resources and that the state in both the HA 
   and the PMN is in sync. 

   The MS is expected to take care of the lifetime of its IPv6 address. 
   The HA SHALL be aware of the lifetimes of the IPv6 addresses assigned 
   to the MS. If the MS is allowed to autoconfigure [Tho1998] its IPv6 
   address, then the MIPv4 binding lifetime SHALL be limited by the HA 
   to be no more than the (remaining) lifetime of the prefix used for 
   IPv6 address autoconfiguration. The HA MAY act as the DHCPv6 relay 
   agent in order to learn the lifetimes of IPv6 addresses assigned by 
   means of DHCPv6. If the IPv6 address of the MS ever expires, the HA 
   SHALL stop defending it on the home link and SHALL remove it from its 
   binding cache entry. 





 
 
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3. Home Agent Considerations 

   The home agent MUST support Mobile IPv4 protocol [Per2002] and the 
   following extensions defined in [Tsi2006]: IPv6 tunneling mode 
   extension, IPv6 code extension and IPv6 prefix extension. 

   Home agent is a dual stack router supporting also IPv6. The home 
   agent MUST be configured with at least one 64-bit prefix which will 
   serve as the home link prefix. On the interface(es) advertising the 
   home link prefix, the HA provides the services of a default IPv6 
   router on the link. It also has the role of an IPv6 home agent 
   [Joh2004]: it MUST defend home address of the MS while it is away 
   from home, it MUST intercept its traffic and it MUST tunnel it via 
   the MIPv4 tunnel to the current location of the MS. When the HA 
   tunnels the packet to the PMN, the destination address of the outer 
   header is the registered IPv4 care-of address and the source address 
   is the HA's IPv4 address. The inner packet is the unmodified IPv6 
   datagram as captured on the home link.  

   The HA MUST provide the Mobile IPv4 service [Per2002] on at least one 
   interface which is connected to the IPv4 network. 

   When the MS configures an additional IPv6 address, in order to verify 
   its uniqueness it starts the DAD process by sending a Neighbor 
   solicitation message to the solicited node multicast group. When the 
   HA receives such a packet via the MIPv4 tunnel, it MUST not deliver 
   it to the home link. Instead, the HA MUST perform proxy DAD on the 
   home link for the address being verified. If the DAD is successful, 
   the HA SHALL add the verified address to the binding cache entry for 
   the MS and SHALL treat the newly configured IPv6 address as an 
   additional home address of the MS. If the DAD process fails, the HA 
   SHALL relay the received Neighbor advertisement to the MS via the 
   MIPv4 tunnel.  

   If the MS is allowed to autoconfigure its home address, then the HA 
   SHALL perform the proxy DAD for the home address of the MS 
   immediately after the DAD process for the link local address of the 
   MS is successfully over. The home address to be defended is 
   formulated by the HA using the home link prefix and the interface 
   identifier part of the LLA. This is because the IPv6 host is not 
   required to verify additionally configured addresses if they are 
   based on the same interface identifier used by the one of the already 
   verified addresses. 

   The HA MAY, at its own discretion, disallow the MS from configuring 
   and using a particular IPv6 address. When the HA receives the 
   Neighbor solicitation message verifying the tentative address, it MAY 
 
 
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   reply to the MS with a Neighbor advertisement packet pretending that 
   the address being verified is already in use on the home link. This 
   will effectively block the MS from using the tentative address.  

   When the HA receives the packet via the MIPv4 tunnel, it MAY check 
   that the source IPv6 address of the inner packet is a legitimate 
   address that the MS is allowed to use. If this is not the case, the 
   HA SHALL discard the packet and SHALL terminate the mobility session 
   by sending the Registration revocation to the PMN. 

   The HA SHALL clear the on-link determination bit in prefix 
   information, thus preventing the MS to attempt the direct 
   communication with the correspondent nodes having the same prefix. 

   The HA SHALL be aware of the address lifetime of the home address 
   assigned to the MS. If the address lifetime expires, the HA SHALL 
   remove the expired address from its binding cache entry. 

    

4. Proxy Mobile Node Considerations 

   When the PMN detects an IPv6-only MS on the link, the PMN SHALL 
   register the MS with the HA by sending the MIPv4 Registration request 
   message. The Registration request message shall contain the NAI of 
   the MS and the IPv6 tunneling mode extension as defined in 
   [Cal2002b].  

   If there is no IPv6 code extension [Tsi2006] in the Registration 
   response message or if the code value in the IPv6 code extension 
   doesn't equal 1, the PMN SHALL not provide the MS with mobility 
   service.  

   The PMN SHALL decapsulate the packets received from the HA and SHALL 
   deliver the inner IPv6 packets to the MS. The PMN SHALL generate the 
   appropriate link layer header and prepend it to the IPv6 packets 
   delivered to the MS. 

   The PMN SHALL encapsulate the IPv6 packets received from the MS and 
   SHALL send them to the HA via the established MIPv4 tunnel. The 
   source address of the outer header is the registered IPv4 care-of 
   address and the destination address is the HA's IPv4 address. The 
   inner packet is the unmodified IPv6 datagram as received from the MS. 

   For the MS traffic, the PMN is acting as a link layer bridge. In 
   particular, the PMN SHALL never decrease the hop limit field in the 
   IPv6 header nor will it change any other field in the IPv6 header. 
 
 
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   The PMN SHALL intercept Router advertisements sent by the HA and 
   inspect them before relaying them to the MS. If the Router 
   advertisement contains the source link layer address option, the PMN 
   SHALL use the advertised link layer address as the source address 
   when constructing the link layer header, provided that the underlying 
   link layer technology makes use of such an address. The intercepted 
   source LLA MAY be transferred during the handover to the new PMN as 
   part of the MS context, and the new PMN SHOULD use the transferred 
   link layer address when constructing the link layer header.  

   The PMN SHALL protect all MIPv4 signaling messages with the MN-HA 
   authentication extension. 

    

5. Mobile Station Considerations 

   Mobile station is a plain IPv6 host, and it does not have a Mobile IP 
   stack. There are no additional requirements on the mobile station.  

    

6. Foreign Agent Considerations 

   Solution described in this document supports the use of unmodified 
   foreign agents. To the FA, the PMN will appear as regular mobile 
   node. However, the use of FA will add an additional layer of 
   encapsulation. 

   If the PMN chooses to register with the FA, the PMN will provide its 
   IPv4 address as a care-of address and SHALL request the dynamic 
   assignment of its home address by setting the home address field in 
   Registration request to all zeros. The home address will be assigned 
   by the HA in the Registration response message. The home address may 
   be allocated from private address space and the FA may also implement 
   the support for overlapping address spaces as described in [Leu2006]. 

   When the PMN has an uplink packet to send, it will first encapsulate 
   it using the assigned IPv4 home address as the source address and the 
   HA's IPv4 address as the destination address. Then it will deliver 
   the encapsulated packet to the FA using either direct or encapsulated 
   delivery style [Mon2001]. Before sending the packet to the HA, the FA 
   will encapsulate the packet once again, using its CoA as a source 
   address and HoA address as a destination address.  

    

 
 
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   Advantage of using the non-collocated CoA mode is that the number of 
   publicly routable IPv4 addresses is minimized: only one is needed per 
   FA instead of one per PMN. The disadvantage is that the FA will add 
   another layer of encapsulation when tunneling back to the HA. This 
   adds additional processing overhead and diminishes the MTU size. 

    

7. Security Considerations 

   The security considerations mentioned in [Leu2006] also apply to this 
   specification. 

   According to this specification, IPv6 Neighbor discovery messages are 
   tunneled between the MS and the HA. A number of security concerns and 
   threats related to neighbor discovery protocol are listed in the 
   security considerations section of [Nar1998] and in the [Nik2004]. A 
   misbehaving MS can launch exactly the same attacks as the malicious 
   IPv6 host physically attached to its home link (wire), but not more. 
   In the view of the author, this specification does not introduce any 
   new threats related to ND. 

    

8. IANA Considerations 

   There are no IANA issues in this document. 

    

9. Acknowledgments 

   This specification is based on the discussions and work in the WiMAX 
   Forum as well as the drafts [Cal2002b], [Leu2006] and [Tsi2006]. 

    

10. References 

10.1. Normative References 

   [Ark2005] Arkko, J., Kempf, J., Zill, B., Nikander, P. "Secure 
             Neighbor Discovery (SEND)", RFC 3971, March 2005. 

   [Bra1997] Bradner, S., "Key words for use in RFCs to Indicate 
             Requirement Levels", BCP 14, RFC 2119, March 1997. 

 
 
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   [Cal2002a]Calhoun, P. and C. Perkins, "Mobile IP Network Access 
             Identifier Extension for IPv4", RFC 2794, March 2000. 

   [Joh2004] Johnson, D., Perkins, C., Arkko, J., "Mobility Support in 
             IPv6", RFC 3775, June 2004 

   [Mon2001] Montenegro, G., "Reverse Tunneling for Mobile IP, revised", 
             RFC 3024, January 2001. 

   [Nar1998] Narten, T., Nordmark, E. and W. Simpson, "Neighbor 
             Discovery for IP Version 6 (IPv6)", RFC 2461, December 
             1998. 

   [Nik2004] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor 
             Discovery (ND) Trust Models and Threats", RFC 3756, May 
             2004. 

   [Per2002] Perkins, C., "IP Mobility Support for IPv4", RFC 3344, 
             August 2002. 

   [Tho1998] S. Thomson, T. Narten, "IPv6 Stateless Address 
             Autoconfiguration", RFC 2462, December 1998 

10.2. Informative References 

   [Cal2002b]Calhoun, P., Engelstad P., Hiller, T., and McCann P., "IPv6 
             over Mobile IPv4", draft-mccann-mobileip-ipv6mipv4-03.txt, 
             October 2002. 

   [Leu2006] Leung, K., Dommety, G., Yegani, P., "Mobility Management 
             using Proxy Mobile IPv4", draft-leung-mip4-proxy-mode-
             00.txt, February 2006. 

   [Tsi2006] Tsirtsis, G., Soliman, H. and Park, V., "Dual Stack Mobile 
             IPv4", draft-tsirtsis-v4v6-mipv4-01.txt, April 2006. 












 
 
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Author's Addresses 

   Domagoj Premec 
   Siemens Mobile 
   Heinzelova 70a 
   10010 Zagreb 
   Croatia 
       
   Phone: +385.1.610 5293 
   Email: domagoj.premec@siemens.com 
    

   Damjan Damic 
   Siemens Mobile 
   Heinzelova 70a 
   10010 Zagreb 
   Croatia 
       
   Phone: +385.1.633 1337 
   Email: damjan.damic@siemens.com 
    

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