Mext Working Group                                              D. Oulai
Internet-Draft                                               S. Krishnan
Intended status: Standards Track                                Ericsson
Expires: September 4, 2009                                    H. Soliman
                                                    Elevate Technologies
                                                           March 3, 2009


                       DSMIPv6 Route Optimization
                    draft-oulai-mext-dsmip-ro-00.txt

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   This Internet-Draft will expire on September 4, 2009.

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

   Dual Stack MIPv6 (DSMIP) is a MIPv6 extension to support IPv4
   mobility for mobile hosts.  While route optimization is well defined
   for IPv6 traffic, this feature is not defined for IPv4.  However,
   Route Optimization has many advantages as reduced delays and lower
   load for the Home Agent.  This document proposes solutions for the
   different scenarios where IPv4 route optimization is performed.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions used in this document  . . . . . . . . . . . . . .  4
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Corresponding Node considerations  . . . . . . . . . . . . . .  6
   5.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Extensions to DSMIP  . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Data structures  . . . . . . . . . . . . . . . . . . . . .  9
     6.2.  IPv4 Route Optimization mode option  . . . . . . . . . . .  9
     6.3.  Route Optimization mode negotiation  . . . . . . . . . . .  9
     6.4.  Keygen tokens generation . . . . . . . . . . . . . . . . .  9
       6.4.1.  Home keygen token generation . . . . . . . . . . . . . 10
       6.4.2.  CareOf keygen token generation . . . . . . . . . . . . 10
   7.  Protocol operation . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Mobile Node with IPv4 Home address . . . . . . . . . . . . 11
       7.1.1.  Return Routability procedure . . . . . . . . . . . . . 11
       7.1.2.  Binding registration . . . . . . . . . . . . . . . . . 12
       7.1.3.  Packet processing  . . . . . . . . . . . . . . . . . . 13
     7.2.  Mobile Node with IPv4 CareOf address only  . . . . . . . . 14
       7.2.1.  Return Routability procedure . . . . . . . . . . . . . 14
       7.2.2.  Binding registration . . . . . . . . . . . . . . . . . 15
       7.2.3.  Packet processing  . . . . . . . . . . . . . . . . . . 15
       7.2.4.  NAT keepalives . . . . . . . . . . . . . . . . . . . . 16
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 18
   10. Normative References . . . . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20













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1.  Introduction

   Dual Stack MIPv6 (DSMIP) is a MIPv6 extension to support IPv4 traffic
   for mobile hosts [I-D.ietf-mext-nemo-v4traversal].  DSMIP is relevant
   for situations where applications MUST be run using IPv4 or when the
   MN is located in an IPv4 only network.  DSMIP introduces two new
   address options: the IPv4 Home Address and the IPv4 CareOf Address
   options.  With those options, a MN can send and receive IPv4 traffic
   although all the mobility signaling is MIPv6 based.  Therefore, there
   is no need to have a MIPv4 stack on the mobile.

   On the other hand, route optimization (RO) is a process that allows a
   MN to communicate directly with a CN without transiting by an anchor,
   the Home Agent.  There are several benefits from RO as shorter path
   delay, reduced bandwidth consumption and reduced load on the HA.
   However, RO is not defined for DSMIP.  The problem statement of DSMIP
   RO can be found in [PS REFERENCE].

   This document provides a solution for DSMIP RO.  We study two
   scenarios:

   1.  MN with a v4HoA
       This scenario implies that the MN has also a v6HoA as all DSMIP
       signaling is based on the v6HoA.  This scenario only considers
       v6CoA for the MN as the v4CoA case is tackled in the next
       scenario.

   2.  MN with a v4CoA only
       In this case, the MN is connected to an IPv4 only network.  The
       scenario considers v6HoA and v4HoA.

   We do not consider the situations where the MN has both v6CoA and
   v4CoA configured as [I-D.ietf-mext-nemo-v4traversal] clearly states
   that v6CoA SHOULD be preferred over the v4CoA.  Moreover, we reuse as
   much as possible MIPv6 RO mechanisms and add extensions when needed.
















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2.  Conventions used in this document

   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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3.  Terminology

   All the general mobility-related terms used in this document are to
   be interpreted as defined in the Mobile IPv6 [RFC3775] and DSMIP
   [I-D.ietf-mext-nemo-v4traversal] base specifications.

   RRP: Return Routability Procedure

   v4CN: IPv4 address of the CN

   v6CN: IPv6 address of the CN

   v4CoA: IPv4 CareOf Address of the MN

   v6CoA: IPv6 CareOf Address of the MN

   v4HoA: IPv4 Home Address of the MN

   v6HoA: IPv6 Home Address of the MN

   v4HoA-map: IPv4 HoA mapped IPv6 address






























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4.  Corresponding Node considerations

   To support this specification, a CN MUST be dual-stacked to
   understand some of the new options introduced here.  Note that this
   specification works also if the CN is in an IPv4 only network.
   Moreover, all CNs supporting this specification MUST listen the DSMIP
   UDP port to receive messages sent from v4CoAs as there could be
   NAT(s) between the MN and the CN.  On the other hand, if the HoA type
   or the CoA type used by the MN differs from the type of address
   configured by the CN, v4v6 transition mechanisms MUST be used to
   transfer the packets.  However, this is out of scope of this
   document.







































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5.  Overview

   To perform RO for DSMIP, we first need to guarantee that the v6HoA,
   v6CoA, v4HoA and v4CoA belong to the MN.  MIPv6 RRP provides
   reachability test for the v6HoA and v6CoA only.  Therefore, we define
   some steps for the IPv4 addresses reachability tests.  As DSMIP
   mandates v6HoA for the MN, the v4HoA reachability test MUST also
   ensure that the v4HoA and v6HoA belong to the same MN.  For this
   reason, the HoT message is encapsulated in a IPv4 header with v4HoA
   as destination address.  If the MN receives the Home Keygen Token, it
   means that it is reachable by the v4HoA.  Note that the v4HoA
   reachability test and the v6HoA are decoupled for security reasons,
   which means the CN has to send two different CoT messages for the
   reachability test.  See Section 7.1.1.1 for more details.

   The v4CoA reachability test is more complex.  Note that this test is
   performed only if the MN has only a v4CoA because DSMIP specification
   states that v6CoA SHOULD be prefered over v4CoA.  In this test, the
   CN MUST replace the v6CoA in the keygen token generation by a
   combination of the source address of the BU, the v4CoA and the UDP
   port as the MN can be in a private network.  This is need to ensure
   that the generated CareOf Keygen is unique for communication with
   that mobile node.  The CoT message is encapsulated in an IPv4 Header
   with v4CoA as destination address.  See Section 7.2.1.2 for more
   details.

   Another important aspect to perform DSMIP RO is the routing.  The UDP
   encapsulation is used the same way as in
   [I-D.ietf-mext-nemo-v4traversal] for private addresses.  As defining
   new IPv4 options is not recommended, we have three routing
   possibilities:

   1.  IPv6 tunnel
       The IPv4 packet is encapsulated as data in an IPv6 tunnel.  The
       tunnel header is represented by the IPv6 header as in MIPv6 RO.
       The normal MIPv6 RO process is performed then the IPv4 packet is
       processed by the IPv4 module.

   2.  IPv4 mapped address
       This approach only modifies the address in the HoA option and the
       Type 2 Routing Header.  The v6HoA is replaced with an IPv4 mapped
       IPv6 address.  Therefore, MIPv6 RO process is performed and after
       address swapping and IPSec operations, the endpoint MUST be able
       to forward the packet to the upper layer considering the IPv4
       HoA.

   3.  IPv4 tunnel
       This is use when the MN only has an v4CoA and IPv6 routing is not



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       possible.  Therefore, we perform an IP in IP tunnelling with the
       v4CoA as destination address for the outer header.  Note that
       IPv4-UDP encapsulation is performed when NAT is detected.

   A new option, IPv4 Route Optimization mode option, is defined in
   order to negotiate the routing mode (See Section 6.2).  This option
   is included in the CoTI/CoT messages.  If the CN responds with a
   different mode than the one requested by the MN, the MN MUST use the
   mode advertised by the CN or stop RO process.










































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6.  Extensions to DSMIP

6.1.  Data structures

   IPv4 HoA, IPv4 CoA and IPv4 RO mode fields MUST be added to the CN
   BCE as described in [RFC3775].  IPv4 RO mode and v4CN field MUST be
   added to the BULE as described in [RFC3775].

6.2.  IPv4 Route Optimization mode option

   This option is created to negotiate the IPv4 RO mode.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |   Length      |      Mode     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type   -  TBD

   Length -   3

   Mode   -   0 : All modes supported
              1 : IPv6 encapsulation
              2 : IPv4 mapped IPv6 addresses
              3 : IPv4 encapsulation
              4 : IPv4-UDP encapsulation


                    IPv4 Route Optimization mode Option

6.3.  Route Optimization mode negotiation

   The MN MUST include an IPv4 RO mode option in the CoTI message.  The
   choice of the IPv4 RO mode included in the CoTI message can be driven
   by policies and is out of the scope of this specification.  If the CN
   detects NAT(s) presence, it MUST respond in the CoT message with
   value 4 (IPv4-UDP) as RO mode.  If the CN supports the mode requested
   by the MN and there is no NAT(s) in between, the CN SHOULD
   acknowledge the mode chosen by the MN.  If the CN responds with a
   different mode, the MN MUST use the RO mode chosen by the CN.
   Otherwise, if the CN indicates 0 (All modes supported), the MN uses
   the mode initially selected in the CoTI message.

6.4.  Keygen tokens generation

   This section describes the Home and CareOf Keygen generation when
   v4HoA or v4CoA is involved in the RRP.  The token generation process
   MUST include the IPv4 addresses as the CN is stateless during the
   RRP.



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6.4.1.  Home keygen token generation

   The CN uses the same formula as used in [RFC3775], which is:

   home keygen token :=
   First (64, HMAC_SHA1 (Kcn, (home address | nonce | 0)))

   In case a v4HoA is involved, the home address is replaced by a
   combined home address described below:

   Combined HoA:= (v6HoA | v4HoA)

6.4.2.  CareOf keygen token generation

   In case the MN is using a v4CoA, the CareOf keygen token generation
   is more complex as there could be NAT(s) between the MN and the CN.
   As the MN could be in a private network, the CoA value used for
   calculation MUST be unique.  The CN uses the same formula as used in
   [RFC3775], which is:

   careOf keygen token :=
   First (64, HMAC_SHA1 (Kcn, (careOf address | nonce | 1)))

   In case a v4CoA is involved, the careOf address is replaced by a
   combined careOf address described below:

   Combined CoA:=
   (v4CoA | Source UDP port | Source IPv4 address of the CoTI message)

   This insures that the value used for careOf token calculation is
   unique even if there are NATs in between.




















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7.  Protocol operation

   In this document, we assume that MN and CN are dual stacked.  The
   solutions proposed depend of the addresses configured on the MN and
   the CN.  We assume that the MN knows at which address to reach the CN
   by using DNS for example.

7.1.  Mobile Node with IPv4 Home address

   If the MN has v6CoA and v4CoA configured at the same time,
   [I-D.ietf-mext-nemo-v4traversal] suggests to use the v6CoA.  The case
   where the MN is configured with v4CoA only is tackled in Section 7.2.

7.1.1.  Return Routability procedure

   The RRP procedure is presented in Figure 1.


   Mobile node                 Home agent           Correspondent node
        |                                                     |
        |  Home Test Init (HoTI)   |                          |
        |------------------------->|------------------------->|
        |                          |                          |
        |  Care-of Test Init (CoTI)                           |
        |---------------------------------------------------->|
        |                          |                          |
        |                          |  v4HoA Home Test (HoT)   |
        |<-------------------------|<-------------------------|
        |                          |                          |
        |                            v4CoA  Care-of Test (CoT)|
        |<----------------------------------------------------|
        |                                                     |



        Figure 1: Return Routability procedure for v4HoA and v4CoA

7.1.1.1.  Home address reachability test

   The MN includes a v4HoA option in the HoTI.  If a CN receives a HoTI
   message without any HoA option, it MUST process it as a request for
   v6HoA reachability test.  In this case, the Home keygen token and the
   HoT message are generated as described in [RFC3775].  If the HoTI
   message contains a v4HoA option only, the CN MUST process the message
   as a v4HoA reachability test.  After generating the Home Keygen token
   based on the v6HoA and the v4HoA, the CN responds with a HoT message.

   If a v4HoA reachability test is, the CN MUST encapsulate the HOT



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   message in an IPv4 header.  The HoT message is descried below:

   External header:
      Src = v4CN
      Dest = v4HoA
   Internal header:
      Src = v6CN
      Dest = v6HoA
   HoT message
      IPv4 HoA Option = v4HoA
      Other options

                  HoT message for v4HoA reachability test

   The MN MUST set the Hop Limit to 1 for the inner IPv6 header.
   Therefore, the IPv4 tunnel endpoint MUST be also the destination for
   the HoT message.  If the MN receives the HoT message at v4HoA
   address, it will internally transfer the packet to its IPv6 process
   as there is an v6inv4 encapsulation.  The MN will also noticed that
   he is the IPv6 endpoint of the HoT message and will process it.  If
   the MN is not the IPv6 endpoint, the HoT message will be dropped
   because either there is no way of forwarding IPv6 packets or either
   the MN will decrement the Hop limit to 0.  By this way, we can simply
   check that v4HoA and v6HoA belong to the same MN.

7.1.1.2.  CareOf address reachability test

   The MN includes a v4HoA option and an IPv4 RO mode option in the CoTI
   message and the CN responds with a CoT message after generating the
   CareOf Keygen token based on the v6CoA.  Moreover, tokens and Kbm
   generation are based on the v6CoA address.  See Section 6.3 and
   Section 6.4 for details.

7.1.2.  Binding registration

   When the Kbm is created, the MN sends a BU to the CN.  If the BU is
   sent to trigger RO for traffic using v6HoA only, the BU is
   constructed as defined in [RFC3775].  In the case the MN requires
   v4HoA RO only, it includes the v4HoA option and the parameter built
   based on the Kbm generated for the v4HoA.  If v6HoA and v4HoA RO are
   required, the MN MUST include both HoA options and both parameters.
   The MN also inserts an IPv4 Route Optimization mode option containing
   the value chosen after the CoTI/CoT messages exchange.  See
   Section 6.3.  The BU MUST not be encapsulated as IPv6 connectivity
   exists between MN and CN.
   When receiving the BU message, the CN recomputes the Home and CareOf
   Keygens then the binding management key.  Note that distinct BCE will
   be created for v4HoA and v6HoA.  Then, the CN MUST send a BAck.  The



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   CN MUST also include the IPv4 RO mode option in the BAck.  Not
   receiving this option in the BAck means that the CN does not support
   IPv4 RO.

7.1.3.  Packet processing

   With IPv6 based routing, two options are possible:

   1.  Normal MIPv6 RO with encapsulated IPv4 packets
       In this case, the MN and the CN process the packet as in the
       MIPv6 RO using HoA option and Type 2 Routing Header in the IPv6
       external header.  The IPv6 header encapsulates an IPv4 packet.
       When leaving the MN, the addresses are:

   External header:
      Src = v6CoA
      Dest = v6CN
      HoA option = v6HoA
   Internal header:
      Src = v4HoA
      Dest = v4CN

       After receiving this packet, the CN performs regular MIPv6 RO
       process before decapsulating and processing the IPv4 packet.  For
       security reasons, when detecting that there is an IPv4 packet
       encapsulated in a IPv6 packet that passes the RO process, the MN
       MUST check if the IPv4 source and destination addresses
       correspond respectively to the v4HoA and v4CN addresses
       registered in the related BCE.  If not, the packet MUST be
       discarded.  When leaving the CN, the addresses are:

   External header:
      Src = v6CN
      Dest = v6CoA
      Type 2 Routing Header = v6HoA
   Internal header:
      Src = v4CN
      Dest = v4HoA

       When receiving this packet, the MN performs regular MIPv6 RO
       process before decapsulating and processing the IPv4 packet.  For
       security reasons, when detecting that there is an IPv4 packet
       encapsulated in a IPv6 packet that passes the RO process, the MN
       MUST check if the IPv4 source and destination addresses
       correspond respectively to the v4CN and v4HoA addresses
       registered in the related BCE.  If not, the packet MUST be
       discarded.




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   2.  Normal MIPv6 RO with IPv4 mapped IPv6 addresses
       This solution assumes that MN and CN understand IPv4 mapped
       addresses.  An IPv4 mapped address, labeled v4HoA-map address, is
       formed with the v4HoA.  When sending a packet, the MN configures
       the addresses as below:

   IPv6 header:
      Src = v6CoA
      Dest = v6CN
      HoA option = v4HoA-map

       After receiving this packet, the CN performs regular MIPv6 RO
       process.  Then, the CN detects the v4HoA-map and forwards the
       packet to the next layer considering v4HoA as source address.
       When leaving the CN, the addresses are:

   IPv6 header:
      Src = v6CN
      Dest = v6CoA
      Type 2 Routing Header = v4HoA-map

       After performing regular MIPv6 RO process, the MN forwards the
       packet to the next layer considering IPv4 addresses.

7.2.  Mobile Node with IPv4 CareOf address only

7.2.1.  Return Routability procedure

   In this case, it is impossible to use directly the MIPv6 RO process
   as there is no v6CoA.

7.2.1.1.  Home address reachability test

   If a v4HoA is configured, the MN SHOULD perform Home address
   reachability test in the RRP the same way as described in
   Section 7.1.1.1.  Otherwise, process described in [RFC3775] is
   applied.

7.2.1.2.  CareOf address reachability test

   For the v4CoA reachability test, the MN sends a CoTI message
   described below:









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   External header:
      Src = v4CoA
      Dest = v4CN
   UDP header
   Internal header:
      Src = v6HoA
      Dest = v6CN
   CoTI message
      IPv4 CoA Option = v4CoA
      IPv4 RO mode option = 3 or 4

   The CoTI message MUST include an IPv4 CoA option and be UDP
   encapsulated as described in [I-D.ietf-mext-nemo-v4traversal].  An
   IPv4 RO mode option MUST be present with a value equal to 3 (IPv4
   encapsulation) or 4 (IPv4-UDP encapsulation).  After receiving the
   CoTI message, due to the presence of an IPv4 CoA option, the CN
   understand that this is a v4CoA reachability test.  The CN calculates
   the CoA Keygen Token as described in Section 6.4.2.  Then, the CN
   generates a CoT message and send it encapsulated to the MN.  The
   format of the CoT message is described below:

   External header:
      Src = v4CN
      Dest = v4CoA
   UDP header (optional)
   Internal header:
      Src = v6CN
      Dest = v6HoA
   CoT message
      IPv4 CoA Option = v4CoA
      IPv4 RO mode option = 0 or 3 or 4

   For security reason, the Hop limit of the IPv6 header MUST be set to
   1.  Therefore, v4CoA and v6HoA MUST belong to the MN.  After
   receiving the tokens, the MN is able to generate the Kbm.

7.2.2.  Binding registration

   The procedure here is the same as the one described in Section 7.1.2
   except that the BU and BA messages MUST be encapsulated using the
   chosen RO mode.

7.2.3.  Packet processing

   In this scenario, we can not use HoA option or Type 2 Routing header
   as they are not defined for IPv4.  Also, source routing is not a good
   approach as many firewalls will block packets with source routing
   option.  Moreover, defining new options for IPv4 is not recommended



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   as IPv4 is already widespread.  The approach chosen here is to use an
   IP-in-IP encapsulation.  When leaving the MN, the addresses are:

   External header:
      Src = v4CoA
      Dest = v4CN
   Internal header:
      Src = v4HoA
      Dest = v4CN

   For security reasons, the CN MUST check if the sources of the outer
   and inner header match in a BCE.  If not, the packet MUST be
   discarded.  When leaving the CN, the addresses are:

   External header:
      Src = v4CN
      Dest = v4CoA
   Internal header:
      Src = v4CN
      Dest = v4HoA

   For security reasons, the MN MUST check if the destination of the
   outer and inner header match in a BULE.  If not, the packet MUST be
   discarded.

7.2.4.  NAT keepalives

   When a CN detects NAT(s) in the path, it MUST include a NAT detection
   option in the CoTI message and the NAT keepalives are performed using
   the BU and BA messages as described in
   [I-D.ietf-mext-nemo-v4traversal].




















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8.  Security Considerations

   There are no new messages added here and all messages exchanges are
   secured using the same mechanisms described in
   [I-D.ietf-mext-nemo-v4traversal] and [RFC3775].  This specification
   requires to perform IPv4 HoA and CoA reachability tests.  For this
   purpose, the v4HoA and v4CoA are included in the token generation
   process.











































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9.  IANA Considerations

   This specification requires a type for the IPv4 RO mode option
   included in the mobility header.















































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10.  Normative References

   [I-D.ietf-mext-nemo-v4traversal]
              Soliman, H., "Mobile IPv6 Support for Dual Stack Hosts and
              Routers", draft-ietf-mext-nemo-v4traversal-09 (work in
              progress), February 2009.

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

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

   [RFC4449]  Perkins, C., "Securing Mobile IPv6 Route Optimization
              Using a Static Shared Key", RFC 4449, June 2006.

   [RFC4866]  Arkko, J., Vogt, C., and W. Haddad, "Enhanced Route
              Optimization for Mobile IPv6", RFC 4866, May 2007.

































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Authors' Addresses

   Desire Oulai
   Ericsson
   8400 Blvd Decarie
   Town of Mount Royal, Quebec
   Canada

   Email: desire.oulai@ericsson.com


   Suresh Krishnan
   Ericsson
   8400 Blvd Decarie
   Town of Mount Royal, Quebec
   Canada

   Email: Suresh.Krishnan@ericsson.com


   Hesham Soliman
   Elevate Technologies

   Email: hesham@elevatemobile.com



























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