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Versions: 00 01 02                                                      
DNA WG                                                          JH. Choi
Internet-Draft                                               Samsung AIT
Expires: April 16, 2006                                    DongYun. Shin
                                                     Samsung Electronics
                                                               W. Haddad
                                                       Ericsson Research
                                                        October 13, 2005

                 Fast Router Discovery with L2 support

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 16, 2006.

Copyright Notice

   Copyright (C) The Internet Society (2005).


   For efficient DNA, a host should quickly receive an RA (Router
   Advertisement) upon a new link-layer connection.  This draft presents
   a quick RA acquisition scheme with the support of a link-layer
   entity, PoA (Point of Attachment).  Upon a new network attachment,
   the PoA may either trigger an AR (Access Router) to immediately send

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   an unicast RA, "RA Triggering" or send such an RA for itself, "RA
   Proxying".  We may put "RA Triggering" or "RA Proxying" functionality
   on a PoA to get the optimized result without IPv6 standard change.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Proposal Overview  . . . . . . . . . . . . . . . . . . . . . .  6
     3.1   RA Triggering  . . . . . . . . . . . . . . . . . . . . . .  6
     3.2   RA Proxying  . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  RA Triggering  . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  RA Proxying  . . . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1   RA Caching . . . . . . . . . . . . . . . . . . . . . . . .  9
       5.1.1   Manual Configuration . . . . . . . . . . . . . . . . .  9
       5.1.2   Scanning . . . . . . . . . . . . . . . . . . . . . . .  9
       5.1.3   MICS (Media Independent Comment Service) . . . . . . .  9
     5.2   RA Delivery  . . . . . . . . . . . . . . . . . . . . . . . 10
       5.2.1   802.11 . . . . . . . . . . . . . . . . . . . . . . . . 10
       5.2.2   802.16 . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   8.  Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 15
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1   Normative References . . . . . . . . . . . . . . . . . . . 16
     9.2   Informative References . . . . . . . . . . . . . . . . . . 16
       Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 17
       Intellectual Property and Copyright Statements . . . . . . . . 19

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1.  Introduction

   Upon establishing a new link-layer connection, a host should detect
   the identity of the currently attached link to ascertain the validity
   of the existing IP configuration.  If the host is attached to a
   different link, it also needs to acquire the IP configuration for the
   new link [4].

   An RA (Router Advertisement) message is necessary when the host has
   moved to a different link, so the number of messages needed for DNA
   can be minimized if the RA also can properly represent the link
   identity.  Moreover to quickly check for link change, the host has to
   receive the RA without delay.

   DNA solution should be able to 1) check for link change with a single
   RA message and 2) get the RA with minimum latency [5].  This draft
   presents only the second component, quick RA acquisition.  But the
   proposed method can work with any link identify detection scheme
   based on unsolicited RA, such as linkid prefix in [13] or CompleteRA
   in [12].

   There are several hindrances for sufficiently quick RA acquisition.
   First, Neighbor Discovery protocol [1] limits routers to a minimum
   interval of 3 seconds between sending multicast RA messages.  Second,
   it SHOULD delay the transmission for a random amount of time before a
   host sends an initial RS (Router Solicitation) message.  Third, a
   router MUST delay a response to a Router Solicitation by a random
   time too.

   In cellular environments, it may not be cost-effective to broadcast
   the RA over wireless link.  For DNA purpose, it's generally
   preferable to deliver the RA to the destination in unicast.

   PoA (Point of Attachment) is the link endpoint of the link, such as
   802.11 AP (Access Point) or 802.16 BS (Base Station).  We propose a
   scheme which uses the link-layer entity, PoA, in such a way that an
   RA is delivered to the host in unicast just after L2 connection is
   made without any random delay.

   When a host makes a new link-layer connection with a PoA, the PoA
   detects the new attachment.  So at this moment, the PoA may either
   trigger an AR (Access Router) to immediately send a suitable RA or
   send such an RA for itself.  For the latter case, the PoA needs to
   cache a suitable RA, such as 'RA optimized for DNA' defined in [5]

   For example, if AR and PoA are in the same box, whenever a new host
   is attached, PoA module can deliver Link Up event to AR module so
   that AR module can immediately fire an RA.  Or, if AR and PoA are

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   separated, PoA can cache a suitable RA and deliver it to a new host
   upon network attachment.

   In this draft, we design a scheme for a PoA to trigger an RA, "RA
   Triggering" and another one for a PoA to proxy an RA, "RA Proxying".
   In RA Proxying, we present a way to cache a necessary RA and send the
   RA in unicast without any delay.

   IEEE 802.21 (Media Independent Handover) standard develops a
   specification [21] that provides link layer intelligence and other
   related network information to upper layers to optimize handovers
   between heterogeneous media.

   Utilizing the services defined in 802.21 MIH (Media Independent
   Handover) standard, we can put 'RA Triggering' or 'RA Proxying'
   functionality on a PoA to get the optimized result for quick RA
   acquisition without IPv6 standard change.

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2.  Terminology

      Access Router (AR)

      -  An Access Network Router residing on the edge of an Access
         Network and offers IP connectivity to hosts.

      Point of Attachment (PoA)

      -  The link endpoint on the link, such as 802.11 Access Point (AP)
         or 802.16 Base Station (BS), where a host may be connected.

      Link Up

      -  An event provided by the link layer that signifies a state
         change associated with the interface becoming capable of
         communicating data frames.

      Media Independent Handover Fuction (MIHF)

      -  The MIH Function provides asynchronous and synchronous services
         through well defined SAPs for lower layers and upper layers.
         The services provided include the Media Independent Event
         Service (MIES), the Media Independent Command Service (MICS),
         and the Media Independent Information Service (MIIS).

      Media Independent Handover (MIH) Protocol

      -  The Media Independent Handover protocol defines frame formats
         for exchanging messages between peer MIH Function entities.
         These messages are based on the primitives which are part of
         MIES, MICS and MIIS.  The MIHF Protocol allows peer MIH
         Function entities to interact with each other.

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3.  Proposal Overview

   When a host establishes a link-layer connection, in the process, a
   link-layer entity, PoA (Point of Attachment), can detect the new
   attachment and get the necessary information to deliver an unicast L2
   frame to the host, such as 802.11 MAC address or 802.16 CID
   (Connection Identifier) [19].

   The PoA may forward the information to an AR (Access Router) and
   trigger the AR to immediately send in unicast a suitable RA, such as
   'RA optimized for DNA' defined in [5].

   Or the PoA itself may cache such an RA beforehand and deliver the
   cached RA to the host in unicast as soon as the link-layer connection
   is established.

   In this draft, we refer the first scheme "RA Triggering" and the
   second "RA Proxying".

3.1  RA Triggering

   In case PoA and AR are in the same box, when a new host is attached,
   link-layer (PoA module) can deliver Link UP event notification [7] to
   IP layer (AR module) to generate a suitable RA and immediately send
   the RA (in an unicast L2 frame with the host's MAC address).

   In case PoA and AR are separated, upon a new network attachment, the
   PoA may deliver the AR the Link Up event notification with the
   information necessary to deliver an unicast RA.  Upon receiving this
   notification, the AR can send a suitable RA in unicast without delay.

   There are two ways for such a remote Link Up event notification.  We
   may use the MIES (Media Independent Event Service) defined in IEEE
   802.21 [21] or RS with TSLLAO (Tentative Source Link-Layer Address
   Option) [14].

3.2  RA Proxying

   RA Proxying consists of "RA Caching" and "RA Delivery".  RA Caching
   is to get a suitable RA and store it.  RA Delivery is to immediately
   send the cached RA to a new host in unicast

   There are several ways to cache the RA in a PoA.  We may manually
   cache the RA in the PoA or use the scanning scheme.  AR (Access
   Router)s periodically multicast a suitable RA, which goes through the
   PoA.  So the PoA may scan incoming L2 frames and cache a necessary
   RA.  The PoA can scan L2 frames either continuously or periodically
   to update the cached RA.  Or PoA and AR may use a special information

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   service, such as the MICS (Media Independent Command Service) defined
   in IEEE 802.21 [21] in such a way that the AR can forward the PoA the
   information necessary to generate a suitable RA and permit it to
   porxy the RA.

   For RA Delivery, PoA may put the cached RA into an unicast L2 frame
   with the host's MAC address (or CID for 802.16) and deliver it to the
   host in unicast immediately after link-layer connection is

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4.  RA Triggering

   In case PoA and AR are in the same box, when a new host is attached,
   Link Up event notification with the information necessary to deliver
   an unicast RA, such as the host's MAC address, can be propagated
   upwards from the link-layer (PoA module) to the IP layer (AR module)
   within a local stack.  Then IP layer (AR module) can immediately send
   a suitable RA in an unicast L2 frame with the new host's MAC address.

   In case PoA and AR are separated, we may use 802.21 MIES (Media
   Independent Event Service) [21] to enable a PoA to trigger a remote
   AR to fire an immediate RA in unicast.

   MIES (Media Independent Event Service) refers to the events sent from
   the lower layers to the higher layers.  Events can also be sent from
   a local MIH entity to a peer MIH entity.  Events may carry useful
   information.  For example, Link Up event can carry a new host's MAC

   When a new host is attached to a PoA, the PoA may use Link Up event
   and MIH Protocol to notify a remote AR the new attachment with the
   information necessary to deliver an unicast RA, such as the host's
   MAC address.  Then the AR can immediately send a suitable RA in an
   unicast L2 frame with the new host's MAC address.

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5.  RA Proxying

   RA Proxying is used only when AR and PoA are separated.  If they are
   in the same box, we recommend to use RA Triggering instead.

5.1  RA Caching

   We present 3 different ways to store a suitable RA in PoA.

5.1.1  Manual Configuration

   In the simplest way, we can manually configure in PoA a suitable RA,
   such as RA with the linkid prefix in [13] or CompleteRA in [12].  In
   many cases, AR and PoA are under same administration and usually RA
   (Router Advertisement) message doesn't change so often.

5.1.2  Scanning

   A PoA may scan incoming L2 frame for a suitable RA and store it.

   First it scans L2 frame header to see whether it is a multicast
   frame.  If not, the PoA sends that frame down link and scans a next
   L2 frame.  If so, the PoA looks IP header to check whether it
   contains a suitable RA.  If incoming L2 frame doesn't contain a
   suitable RA, the PoA sends that frame down link and scans a next L2
   frame.  When the PoA finds a suitable RA, it stores it and sends a
   copy down link.

   A PoA can scan continuously, updating an old RA with a new RA.  Or if
   it costs too much for the PoA to scan every incoming L2 frame, we can
   control the scanning rate.  For example, we can set timer and execute
   scanning every T seconds.  Or we can make the PoA to be able to send
   RS (Router Solicitation) message.  Periodically the PoA sends an RS
   and an AR will reply a suitable RA and the PoA caches it.  It is
   noted that the PoA doesn't need to have IP address since it can use
   unspecified address as its source address.

   To help RA Caching, we may make it a rule that, whenever an AR
   changes its RA information, the AR advertises the new information
   several times, so that PoA can properly update its cached RA.

5.1.3  MICS (Media Independent Comment Service)

   We may use 802.21 MICS (Media Independent Comment Service) and MIH
   (Media Independent Handover) Protocol [21] to enable an AR to send a
   suitable RA to a PoA and delegate the PoA to proxy the RA.

   MICS (Media Independent Comment Service) refers to the commands sent

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   from the higher layers to the lower layers.  Commands can also be
   sent from a local MIH entity to a peer MIH entity.  These commands
   may carry the upper layer information to the lower layers on local
   device entity or at remote entity, and thus control the behavior of
   lower layers.  For example, a new AR may send its IP address to old
   PoA with a Remote MIH Command, "MIH Network Address Information".

   In a similar way, we may define a new Remote MIH Command, "MIH Router
   Advertisement Information" in 802.21 in such a way that 1) a PoA can
   use the command and MIP Protocol to request a suitable RA from an AR
   and permission to proxy the RA and 2) the AR can use the command and
   MIH Protocol to send a suitable RA to the PoA and delegate the PoA to
   deliver the RA to a new host upon network attachment

5.2  RA Delivery

   We present a way to immediately deliver an RA in unicast upon network
   attachement for 802.11 and 802.16 respectively.  The procedures
   describes in here can be extended to apply to other wireless
   technologies such as 3GPP and 3GPP.2.

5.2.1  802.11

   In 802.11 Wireless LAN technology, when a new host arrives at an
   AP(Access Point), it should associate with the AP.  The host sends an
   Association Request Message with its MAC address.  Then the AP sends
   an Association Response Message to grant association.

   As soon as association is made, the AP sends a cached RA to the host
   in an unicast 802.11 frame with the MAC address from the Association
   Request message.  The host receives the unicast RA just after
   association is made, which is the earliest possible time in current

5.2.2  802.16

   IEEE 802.16 spec [19] is rather different from Ethernet or 802.11 and
   it's still unclear how to run IPv6 over 802.16.  So we give a rough
   sketch of RA delivery over 802.16 and mention that further
   clarification is needed.

   The 802.16 MAC is connection-oriented.  All services, including
   inherently connectionless services, are mapped to a connection.

   Connections are referenced with 16-bit connection identifiers (CIDs).
   Each 802.16 host has a standard 48-bit MAC address, but this serves
   mainly as an equipment identifier, since the primary addresses used
   during operation are the CIDs.

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   Upon entering the network, the host is assigned three management
   connections, the basic connection and the primary management
   connection and the secondary management connection.

   The secondary management connection is used for the transfer of
   standards-based management messages such as Dynamic Host
   Configuration Protocol (DHCP).  It is not decided yet but Neighbor
   Discovery messages, such as RS, RA, NS (Neighbor Solicitation) and NA
   (Neighbor Advertisement) may be delivered with this connection.

   To establish a link layer connection, an 802.16 host performs Ranging
   to acquire the correct timing offset and power adjustment.  The host
   sends the RNG-REQ message and the 802.16 BS (Base Station) replies
   RNG-RSP message to provide Basic and Primary Management CIDs for the

   Afterwards the host performs Registration, which is the process by
   which the host is allowed entry into the network and receives its
   Secondary Management CID.

   After Registration is completed, the 802.16 BS may send a cached RA
   to the host with the Secondary CID.  The RA will be delivered in
   unicast 802.16 frame and the host will receive it with minimum

   We point out that it's not decided yet that the Secondary CID is used
   for RA message transfer.  It's possible for RA to be delivered with a
   different CID.

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6.  IANA Considerations

   No new message formats or services are defined in this document.

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7.  Security Considerations

   Because DNA is based on Neighbor Discovery, its trust models and
   threats are similar to the ones presented in RFC 3756 [10].  Nodes
   connected over wireless interfaces may be particularly susceptible to
   jamming, monitoring and packet insertion attacks.

   The threats specific to DNA are that an attacker might fool a node to
   detect attachment to a different link when it is in fact still
   attached to the same link, and conversely, the attacker might fool a
   node to not detect attachment to a new link.

   In case PoA and AR are in the same box, there is no FRD specific
   security problem, because all procedures are executed within a local
   stack.  In case PoA and AR are separated, FRD can be performed in
   secure manner, if there is a secure path between PoA and AR.  For
   example, MIH (Media Independent Handover) services can be made
   available at L2 through secure port.

   Even when there is no secure path between PoA and AR, FRD doesn't
   introduce a new security vulnerability.  For the worst case, a host
   may reject the proxyed RA from PoA but will not make a false
   decision.  Currently any node in a link can cache an RA and
   retransmit it.  Use of [9] to secure Neighbor Discovery are important
   in achieving reliable detection of network attachment.  DNA schemes
   SHOULD incorporate the solutions developed in IETF SEND WG if
   available, where assessment indicates such procedures are required.

   In the presence of SEND, RA Caching may raise security concerns,
   since the PoA can be considered a man in the middle.  Especially it
   may be difficult for RA Caching with Scanning (Sec 5.1.2) to work
   with SEND.  If a router sends an RA with a SEND Timestamp option, it
   puts upper bound on how long the RA remains valid after the router
   advertises it.  So if a PoA caches the RA too long, it will become
   invalid and a host will discard it.

   We may resolve this issue by including a unique 64 bit number called
   an Ownership Proof (OP) in an RA.  The 64 bit number, OP, is the hash
   of a nonce and proves to a host that the RA was indeed generated by
   the router which is listed as the source of the RA.  The router must
   keep a table associating each OP to the nonce which was used to
   generate it.  When an RA carrying an OP option is received, a host
   may ignore the SEND Timestamp option if it falls outside the
   allowable window.

   With OP, DNA procedure is as below.  A PoA caches a suitable RA with
   an OP.  When a new host makes an attachment, the PoA immediately
   sends it the cached RA with an OP.  With this cached RA, the host may

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   perform DNA regardless of its SEND Timestamp and at the same time
   send an RS with the OP option.  Upon receiving the RS, the router may
   send an RA immediately because it is solicited in unicast.  When the
   router responds with a solicited RA it includes the nonce used to
   generate the OP.  Upon receiving the RA, the host may check if the
   hash of this nonce matches the OP received in the initial cached RA
   to verify it.  If not, the host stops the DNA procedure with the RA
   and restarts it with a new RA.

   DAN scheme should not result in excessive signaling.  A PoA performs
   FRD procedures to generate an RA message only when a new host is
   attached to itself.  Usually there is an upper bound for the number
   of hosts (wireless stations) that a PoA can support at a moment.  So
   the number of RA messages from FRD procedure is also limited by this
   upper bound.

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8.  Acknowledgment

   We gratefully acknowledge the generous assistance we received from
   Xiaoyu Liu, YounHee Han and James Kempf for notifying us the
   usability of 802.21 standard and clarifying the MIH Spec to us.  We
   show our special gratitude to HeeJin Jang, Subba Reddy and Surekha
   Biruduraju for implementing and testing FRD scheme to provide
   enlightening insights.  The authors wish to express our appreciation
   to Syam Madanapalli and Wable Ranjitsingh for valuable feedback.
   Thanks to Suresh Krishnan, Greg Daley, Brett Pentland, Nick Moore and
   YongGeun Hong for their contributions to this draft.

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9.  References

9.1  Normative References

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

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

   [3]  Hinden, R. and S. Deering, "Internet Protocol Version 6 (IPv6)
        Addressing Architecture", RFC 3513, April 2003.

   [4]  Choi, JH. and G. Daley, "Goals of Detecting Network Attachment
        in IPv6", RFC 4135, August 2005.

9.2  Informative References

   [5]   Choi, J. and E. Nordmark, "DNA solution framework",
         draft-ietf-dna-soln-frame-00 (work in progress), April 2005.

   [6]   Nordmark, E. and J. Choi, "DNA with unmodified routers: Prefix
         list based approach", draft-ietf-dna-cpl-01 (work in progress),
         July 2005.

   [7]   Yegin, A., "Link-layer Event Notifications for Detecting
         Network Attachments", draft-ietf-dna-link-information-02 (work
         in progress), July 2005.

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

   [9]   Arkko, J., Kempf, J., Sommerfeld, B., Zill, B., and P.
         Nikander, "SEcure Neighbor Discovery (SEND)",
         draft-ietf-send-ndopt-06 (work in progress), July 2004.

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

   [11]  Pentland, B., "An Overview of Approaches to Detecting Network
         Attachment in IPv6", draft-dnadt-dna-discussion-00 (work in
         progress), February 2005.

   [12]  Narayanan, S., "Detecting Network Attachment in IPv6 Networks
         (DNAv6)", draft-pentland-dna-protocol-01 (work in progress),
         July 2005.

   [13]  Madanapalli, S. and J. Choi, "DNA Solution: Link Identifier

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         based approach", draft-jinchoi-dna-protocol2-01 (work in
         progress), July 2005.

   [14]  Daley, G., "Tentative Source Link-Layer Address Options for
         IPv6 Neighbour Discovery", draft-daley-ipv6-tsllao-02 (work in
         progress), July 2005.

   [15]  Aboba, B., "Detecting Network Attachment (DNA) in IPv4",
         draft-ietf-dhc-dna-ipv4-16 (work in progress), September 2005.

   [16]  Nordmark, E., "MIPv6: from hindsight to foresight?",
         draft-nordmark-mobileip-mipv6-hindsight-00 (work in progress),
         November 2001.

   [17]  Kempf, J., Khalil, M., and B. Pentland, "IPv6 Fast Router
         Advertisement", draft-mkhalil-ipv6-fastra-05 (work in
         progress), July 2004.

   [18]  Daley, G. and J. Choi, "Movement Detection Optimization in
         Mobile IPv6", draft-daley-mobileip-movedetect-01 (work in
         progress), May 2003.

   [19]  IEEE 802.16-2001, "IEEE Standard for Local and Metropolitan
         Area Networks - Part 16: Air Interface for Fixed Broadband
         Wireless Access Systems," Apr. 8, 2002.

   [20]  IEEE 802.16 TGe Working Document (Draft Standard), "Amendment
         for Physical and Medium Access Control Layers for Combined
         Fixed and Mobile Operation in Licensed Bands",
         IEEE 802.16e/D8, May 2005.

   [21]  IEEE 802.21 Working Document (Draft Standard),
         "IEEE P802.21/D00.01: Draft IEEE Standard for Local and
         Metropolitan Area Networks: Media Independent Handover
         Services," July, 2005

Authors' Addresses

   JinHyeock Choi
   Samsung AIT
   Communication Lab
   P.O.Box 111 Suwon 440-600

   Phone: +82 31 280 9233
   Email: jinchoe@samsung.com

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   DongYun Shin
   Samsung Electronics
   Device Solution Group
   P.O.Box 111 Suwon 440-600

   Phone: +82 2 2191 4868
   Email: yun7521@samsung.com

   Wassim Haddad
   Ericsson Research
   8400 Decarie Blvd.
   Town of Mount Royal, QC

   Phone: +1 514 345 7900 #2334
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