





Internet Engineering Task Force (IETF)                        Q. Wu, Ed.
Request for Comments: 6642                                        F. Xia
Category: Standards Track                                        R. Even
ISSN: 2070-1721                                                   Huawei
                                                               June 2012


  RTP Control Protocol (RTCP) Extension for a Third-Party Loss Report

Abstract

   In a large RTP session using the RTP Control Protocol (RTCP) feedback
   mechanism defined in RFC 4585, a feedback target may experience
   transient overload if some event causes a large number of receivers
   to send feedback at once.  This overload is usually avoided by
   ensuring that feedback reports are forwarded to all receivers,
   allowing them to avoid sending duplicate feedback reports.  However,
   there are cases where it is not recommended to forward feedback
   reports, and this may allow feedback implosion.  This memo discusses
   these cases and defines a new RTCP Third-Party Loss Report that can
   be used to inform receivers that the feedback target is aware of some
   loss event, allowing them to suppress feedback.  Associated Session
   Description Protocol (SDP) signaling is also defined.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6642.














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Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................3
      2.1. Requirements Notation ......................................3
      2.2. Glossary ...................................................4
   3. Example Use Cases ...............................................4
      3.1. Source-Specific Multicast (SSM) Use Case ...................4
      3.2. Unicast-Based Rapid Acquisition of Multicast Stream
           (RAMS) Use Case ............................................5
      3.3. RTP Transport Translator Use Case ..........................5
      3.4. Multipoint Control Unit (MCU) Use Case .....................6
      3.5. Mixer Use Case .............................................6
   4. Protocol Overview ...............................................6
   5. Format of RTCP Feedback Messages ................................7
      5.1. Transport-Layer Feedback: Third-Party Loss Report (TPLR) ...8
      5.2. Payload-Specific Feedback:  Third-Party Loss Report (TPLR) .8
   6. SDP Signaling ...................................................9
   7. Security Considerations ........................................10
   8. IANA Considerations ............................................11
   9. Acknowledgments ................................................11
   10. References ....................................................12
      10.1. Normative References .....................................12
      10.2. Informative References ...................................12












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1.  Introduction

   The RTP Control Protocol (RTCP) feedback messages [RFC4585] allow the
   receivers in an RTP session to report events and ask for action from
   the media source (or a delegated feedback target when using unicast
   RTCP feedback with Source-Specific Multicast (SSM) [RFC5760]).  There
   are cases where multiple receivers may initiate the same, or an
   equivalent, message towards the same media source or the same
   feedback target.  When the receiver count is large, this behavior may
   cause transient overload of the media source, the network, or both.
   This is known as a "feedback storm" or a "NACK storm".

   One scenario that can cause such feedback storms involves video Fast
   Update requests.  A storm of these feedback messages can occur in
   conversational multimedia scenarios like multipoint video switching
   conference [RFC4587], where many receivers may simultaneously lose
   synchronization with the video stream when the speaker is changed in
   the middle of a session.  Receivers that issue Fast Update requests
   (i.e., Full Intra Request (FIR) described in RFC 5104 [RFC5104]), can
   cause an implosion of FIR requests from receivers to the same media
   source since these requests must currently be made blind, without
   knowledge of requests made by other receivers.

   RTCP feedback storms may cause short-term overload and, in extreme
   cases, pose a possible risk of increasing network congestion on the
   control channel (e.g., RTCP feedback), the data channel, or both.  It
   is therefore desirable to provide a way of suppressing unneeded
   feedback.  This document specifies a new Third-Party Loss Report for
   this function.  It supplements the existing use of RTCP NACK packets
   and is also more precise in the uses where the network is active to
   suppress feedback.  It tells receivers explicitly that feedback for a
   particular packet or frame loss is not needed and can provide an
   early indication before the receiver reacts to the loss and invokes
   its packet loss repair machinery.  Section 3 provides some example
   use cases of when to send the Third-Party Loss Report message.

2.  Terminology

2.1.  Requirements Notation

   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 [RFC2119].








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2.2.  Glossary

   TPLR  - Third-Party Loss Report

   TLLEI - Transport-Layer Third-Party Loss Early Indication

   PSLEI - Payload-Specific Third-Party Loss Early Indication

   PT    - Payload Type

   FMT   - Feedback Message Type

   FCI   - Feedback Control Information [RFC4585]

   AVPF  - Audio-Visual Profile with RTCP-based feedback [RFC4585]

   SSRC  - Synchronization Source

   BRS   - Burst/Retransmission Source [RFC6285]

   FIR   - Full Intra Request [RFC5104]

   PLI   - Picture Loss Indication [RFC4585]

   SSM   - Source-Specific Multicast [RFC5760]

   RAMS  - Unicast-based Rapid Acquisition of Multicast Stream [RFC6285]

   MCU   - Multipoint Control Unit [RFC5117]

3.  Example Use Cases

   The operation of feedback suppression is similar for all types of RTP
   sessions and topologies [RFC5117]; however, the exact messages used
   and the scenarios in which suppression is employed differ for various
   use cases.  The following sections outline some of the intended use
   cases for using the Third-Party Loss Report for feedback suppression
   and give an overview of each.

3.1.  Source-Specific Multicast (SSM) Use Case

   In SSM RTP sessions as described in "RTP Control Protocol (RTCP)
   Extensions for Single-Source Multicast Sessions with Unicast
   Feedback" [RFC5760], one or more media sources send RTP packets to a
   distribution source.  The distribution source relays the RTP packets
   to the receivers using a source-specific multicast group.





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   As outlined in RFC 5760 [RFC5760], there are two Unicast Feedback
   models that may be used for reporting: the Simple Feedback Model and
   the Distribution Source Feedback Summary Model.  In the Simple
   Feedback Model, there's no need for the distribution source to create
   the RTCP TPLRs; instead, RTCP NACKs are reflected by the distribution
   source to the other receivers.  However, in the Distribution Source
   Feedback Summary Model, the distribution source will not redistribute
   the NACK for some reason (e.g., to prevent revealing the identity or
   existence of a system sending NACK) and may send an RTCP TPLR message
   to the systems that were unable to receive the NACK and won't receive
   the NACK via other means.  The RTCP TPLR can be generated at the
   distribution source when downstream loss is reported (e.g.,
   downstream loss report is received), which indicates to the receivers
   that they should not transmit feedback messages for the same loss
   event for a certain time.  Therefore, the distribution source in the
   Distribution Source Feedback Summary Model can be reasonably certain
   that it will help the situation (i.e., the distribution source is
   unable receive the NACK) by sending this RTCP TPLR message to all the
   relevant receivers impacted by the packet loss.

3.2.  Unicast-Based Rapid Acquisition of Multicast Stream (RAMS) Use
      Case

   The typical RAMS architecture [RFC6285] may have several Burst/
   Retransmission Sources (BRSs) behind the multicast source placed at
   the same level.  These BRSs will receive the primary multicast RTP
   stream from the media source and cache the most recent packets after
   joining the multicast session.  If packet loss happens at the
   upstream of all the BRSs or the downstream of BRSs, one or all of the
   BRSs may send an RTCP NACK or RTCP TPLR message to the distribution
   source, where the SSRC in this RTCP NACK or RTCP TPLR message is the
   BRS that is sending the message.  The distribution source forwards/
   reflects this message down on the primary SSM.  The details on how
   the distribution source deals with this message are specified in
   [RETRANS-FOR-SSM].

3.3.  RTP Transport Translator Use Case

   A Transport Translator (Topo-Trn-Translator), as defined in RFC 5117
   [RFC5117], is typically forwarding the RTP and RTCP traffic between
   RTP clients, for example, converting from multicast to unicast for
   domains that do not support multicast.  The translator may suffer a
   loss of important video packets.  In this case, the translator may
   forward an RTCP TPLR message received from upstream in the same way
   it forwards other RTCP traffic.  If the translator acting as the
   monitor [MONARCH] is aware of packet loss, it may use the SSRC of the
   monitor as the SSRC of the packet sender to create a NACK message and
   send it to the receivers that are not aware of packet loss.



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3.4.  Multipoint Control Unit (MCU) Use Case

   When the speaker is changed in a voice-activated multipoint video
   switching conference [RFC4587], an RTP mixer can be used to select
   the available input streams and forward them to each participant.  If
   the MCU is doing a blind switch without waiting for a synchronization
   point on the new stream, it can send a FIR to the new video source.
   In this case, the MCU should send a FIR suppression message to the
   new receivers.  For example, when the RTP mixer starts to receive FIR
   from some participants, it can suppress the remaining session
   participants from sending FIR by sending out an RTCP TPLR message.

3.5.  Mixer Use Case

   A mixer, in accordance with RFC 5117 [RFC5117], aggregates multiple
   RTP streams from other session participants and generates a new RTP
   stream sent to the session participants.  In some cases, the delivery
   of video frames delivery may get damaged, for example, due to packet
   loss or delayed delivery, between the media source and the mixer.  In
   such cases, the mixer needs to check if the packet loss will result
   in PLI or FIR transmissions from most of the group by analyzing the
   received video.  If so, the mixer may initiate FIR or PLI towards the
   media source on behalf of all the session participants and send out
   an RTCP TPLR message to the session participants that may or are
   expected to send a PLI or FIR.  Alternatively, when the mixer starts
   to receive FIR or PLI from some participants and would like to
   suppress the remaining session participants from sending FIR or PLI,
   it can just forward the FIR/PLI from one session participant to
   others.

4.  Protocol Overview

   This document extends the RTCP feedback messages defined in the RTP/
   AVPF [RFC4585] by defining an RTCP Third-Party Loss Report (TPLR)
   message.  The RTCP TPLR message can be used by the intermediaries to
   inform the receiver that the sender of the RTCP TPLR has received
   reports that the indicated packets were lost and ask the receiver not
   to send feedback to it regarding these packets.  Intermediaries are
   variously referred to as distribution sources, Burst/Retransmission
   Sources, MCUs, RTP translators, or RTP mixers, depending on the
   precise use case described Section 3.

   RTCP TPLR follows a similar message type format as RTCP NACK or Full
   Intra Request Command.  However, RTCP TPLR is defined as an
   indication that the sender of the feedback has received reports that
   the indicated packets were lost, while NACK [RFC4585] just indicates
   that the sender of the NACK observed that these packets were lost.
   The RTCP TPLR message is generated by an intermediary that may not



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   have seen the actual packet loss.  It is sent following the same
   timing rule as sending NACK, defined in RFC 4585 [RFC4585].  The RTCP
   TPLR message may be sent in a regular full compound RTCP packet or in
   an early RTCP packet, as per the RTP/AVPF rules.  Intermediaries in
   the network that receive an RTCP TPLR MUST NOT send their own
   additional Third-Party Loss Report messages for the same packet
   sequence numbers.  They SHOULD simply forward the RTCP TPLR message
   received from upstream to the receiver(s).  Additionally, they may
   generate their own RTCP TPLR that reports a set of the losses they
   see, which are different from ones reported in the RTCP TPLR they
   received.  The RTCP TPLR does not have retransmission request
   [RFC4588] semantics.

   When a receiver gets an RTCP TPLR message, it MUST follow the rules
   for NACK suppression in RFC 4585 [RFC4585] and refrain from sending a
   feedback request (e.g., NACK or FIR) for the missing packets reported
   in the message, which is dealt with in the same way as receiving a
   NACK.

   To increase the robustness to the loss of a TPLR, the RTCP TPLR may
   be retransmitted.  If the additional TPLR arrives at the receiver,
   the receiver SHOULD deal with the additional TPLR in the same way as
   receiving the first TPLR for the same packet, and no additional
   behavior for receiver is required.

   A receiver may have sent a feedback message according to the RTP/AVPF
   scheduling algorithm of RFC 4585 [RFC4585] before receiving an RTCP
   TPLR message, but further feedback messages for those sequence
   numbers SHOULD be suppressed after receiving the RTCP TPLR.  Nodes
   that do not understand the RTCP TPLR message will ignore it and might
   therefore still send feedback according to the AVPF scheduling
   algorithm of RFC 4585 [RFC4585].  The media source or intermediate
   nodes cannot be certain that the use of an RTCP TPLR message actually
   reduces the amount of feedback they receive.

5.  Format of RTCP Feedback Messages

   This document introduces two new RTCP feedback messages for Third-
   Party Loss Report.  Applications that are employing one or more loss-
   repair methods MAY use the RTCP TPLR together with their existing
   loss-repair methods either for every packet they expect to receive or
   for an application-specific subset of the RTP packets in a session.

   The following two sections each define an RTCP TPLR message.  Both
   messages are feedback messages as defined in Section 6.1 of RFC 4585
   [RFC4585] and use the header format defined there.  Each section
   defines how to populate the PT, FMT, length, SSRC of packet sender,
   SSRC of media source, and FCI fields in that header.



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5.1.  Transport-Layer Feedback: Third-Party Loss Report (TPLR)

   This TPLR message is identified by RTCP packet type values PT=RTPFB
   and FMT=7.

   Within the common packet header for feedback messages (as defined in
   Section 6.1 of RFC 4585 [RFC4585]), the "SSRC of packet sender" field
   indicates the source of the request, and the "SSRC of media source"
   field denotes the media sender of the flow for which the indicated
   losses are being suppressed.

   The FCI field MUST contain one or more entries of Transport-Layer
   Third-Party Loss Early Indication (TLLEI).  Each entry applies to the
   same media source identified by the SSRC contained in the "SSRC of
   media source" field of the Feedback header.  The length field in the
   TLLEI feedback message MUST be set to N+2, where N is the number of
   FCI entries.

   The FCI field for TLLEI uses a similar message type format to that
   defined in the Section 6.2.1 of RFC 4585 [RFC4585].  The format is
   shown in Figure 1.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            PID                |             BLP               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 1: Syntax of an FCI Entry in the TLLEI Feedback Message

   Packet ID (PID): 16 bits

      The PID field is used to specify a lost packet.  The PID field
      refers to the RTP sequence number of the lost packet.

   bitmask of lost packets (BLP): 16 bits

      The BLP allows for reporting losses of any of the 16 RTP packets
      immediately following the RTP packet indicated by the PID.  The
      BLP's definition is identical to that given in Section 6.2.1 of
      [RFC4585].

5.2.  Payload-Specific Feedback:  Third-Party Loss Report (TPLR)

   This TPLR message is identified by RTCP packet type values PT=PSFB
   and FMT=8, which are used to suppress FIR [RFC5104] and PLI
   [RFC4585].




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   Within the common packet header for feedback messages (as defined in
   Section 6.1 of RFC 4585 [RFC4585]), the "SSRC of packet sender" field
   indicates the source of the request, and the "SSRC of media source"
   is not used and SHALL be set to 0.  The SSRCs of the media senders to
   which this message apply are in the corresponding FCI entries.

   The FCI field for a Payload-Specific Third-Party Loss Early
   Indication (PSLEI) consists one or more FCI entries.  Each entry
   applies to a different media source, identified by its SSRC, the
   content of which is depicted in Figure 2.  The length field in the
   PSLEI feedback message MUST be set to N+2, where N is the number of
   FCI entries.

   The format is shown in Figure 2.

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                              SSRC                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

      Figure 2: Syntax of an FCI Entry in the PSLEI Feedback Message

   Synchronization source (SSRC): 32 bits

      The SSRC value of the media source that is already aware, or in
      the process of being made aware, that some receiver lost
      synchronization with the media stream and for which the PSLEI
      receiver's own response to any such error is suppressed.

6.  SDP Signaling

   The Session Description Protocol (SDP) [RFC4566] attribute, rtcp-fb,
   is defined in Section 4 of RFC 4585 [RFC4585] and may be used to
   negotiate the capability to handle specific AVPF commands and
   indications.  The ABNF for rtcp-fb is described in Section 4.2 of RFC
   4585 [RFC4585].  In this section, we extend the rtcp-fb attribute to
   include the commands and indications that are described for Third-
   Party Loss Reports in the present document.

   In the ABNF [RFC5234] for rtcp-fb-val defined in RFC 4585 [RFC4585],
   the feedback type "nack", without parameters, indicates use of the
   Generic NACK feedback format as defined in Section 6.2.1 of RFC 4585
   [RFC4585].  In this document, we define two parameters that indicate
   the third-party loss supported for use with "nack", namely:

   o  "tllei" denotes support of Transport-Layer Third-Party Loss Early
      Indication.



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   o  "pslei" denotes support of Payload-Specific Third-Party Loss Early
      Indication.

   The ABNF for these two parameters for use with "nack" is defined here
   (please refer to Section 4.2 of RFC4585 [RFC4585] for complete ABNF
   syntax).

           rtcp-fb-val        =/ "nack" rtcp-fb-nack-param
           rtcp-fb-nack-param = SP "tllei"
                                   ;Transport-Layer Third-Party
                                   ; Loss Early Indication
                               / SP "pslei"
                                   ;Payload-Specific Third-Party
                                   ; Loss Early Indication
                               / SP token [SP byte-string]
                                   ; for future commands/indications
           token =     <as defined in Section 9 of [RFC4566]>
           byte-string = <as defined in Section 9 of [RFC4566]>

7.  Security Considerations

   The security considerations documented in [RFC4585] are also
   applicable for the TPLR messages defined in this document.

   More specifically, spoofed or maliciously created TPLR feedback
   messages cause missing RTP packets to not be repaired in a timely
   fashion and add risk of (undesired) feedback suppression at RTCP
   receivers that accept such TPLR messages.  Any packet loss detected
   by a receiver that also receives a TPLR message for the same missing
   packet(s) will negatively impact the application that relies on the
   (timely) RTP retransmission capabilities.

   A solution to prevent such attack with maliciously sent TPLR messages
   is to apply an authentication and integrity protection framework for
   the feedback messages.  This can be accomplished using the RTP
   profile that combines Secure RTP [RFC3711] and AVPF into SAVPF
   [RFC5124].

   Note that intermediaries that are not visible at the RTP layer that
   wish to send the Third-Party Loss Reports on behalf of the media
   source can only do so if they spoof the SSRC of the media source.
   This is difficult if SRTP is in use.  If the intermediary is visible
   at the RTP layer, this is not an issue, provided the intermediary is
   part of the security context for the session.







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8.  IANA Considerations

   Per this document, IANA has added two values to the '"ack" and "nack"
   Attribute Values' sub-registry [RFC4585] of the 'Session Description
   Protocol (SDP) Parameters' registry.

   The value registration for the attribute value "nack":

      Value name:     tllei
      Long name:      Transport-Layer Third-Party Loss Early Indication
      Usable with:    nack
      Reference:      RFC 6642

      Value name:     pslei
      Long name:      Payload-Specific Third-Party Loss Early Indication
      Usable with:    nack
      Reference:      RFC 6642

   The following value has been registered as one FMT value in the "FMT
   Values for RTPFB Payload Types" registry
   (http://www.iana.org/assignments/rtp-parameters).

     RTPFB range
     Name           Long Name                         Value  Reference
     -------------- --------------------------------- -----  ---------
     TLLEI          Transport-Layer Third-Party         7    [RFC6642]
                    Loss Early Indication

   The following value has been registered as one FMT value in the "FMT
   Values for PSFB Payload Types" registry
   (http://www.iana.org/assignments/rtp-parameters).

     PSFB range
     Name            Long Name                        Value  Reference
     -------------- --------------------------------- -----  ---------
     PSLEI          Payload-Specific Third-Party        8    [RFC6642]
                    Loss Early Indication

9.  Acknowledgments

   The authors would like to thank David R. Oran, Magnus Westerlund,
   Colin Perkins, Ali C. Begen, Tom Van Caenegem, Francis Dupont,
   Ingemar Johansson, Bill Ver Steeg, Jonathan Lennox, and WeeSan Lee
   for their valuable comments and suggestions on this document.







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10.  References

10.1.  Normative References

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

   [RFC4585]  Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey,
              "Extended RTP Profile for Real-time Transport Control
              Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585,
              July 2006.

   [RFC4588]  Rey, J., Leon, D., Miyazaki, A., Varsa, V., and R.
              Hakenberg, "RTP Retransmission Payload Format", RFC 4588,
              July 2006.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

   [RFC5104]  Wenger, S., Chandra, U., Westerlund, M., and B. Burman,
              "Codec Control Messages in the RTP Audio-Visual Profile
              with Feedback (AVPF)", RFC 5104, February 2008.

   [RFC3711]  Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
              Norrman, "The Secure Real-time Transport Protocol (SRTP)",
              RFC 3711, March 2004.

   [RFC5124]  Ott, J. and E. Carrara, "Extended Secure RTP Profile for
              Real-time Transport Control Protocol (RTCP)-Based Feedback
              (RTP/SAVPF)", RFC 5124, February 2008.

10.2.  Informative References

   [RFC6285]  Ver Steeg, B., Begen, A., Van Caenegem, T., and Z. Vax,
              "Unicast-Based Rapid Acquisition of Multicast RTP
              Sessions", RFC 6285, June 2011.

   [MONARCH]  Wu, Q., Hunt, G., and P. Arden, "Monitoring Architectures
              for RTP", Work in Progress, May 2012.

   [RETRANS-FOR-SSM]
              Van Caenegem, T., Ver Steeg, B., and A. Begen,
              "Retransmission for Source-Specific Multicast (SSM)
              Sessions", Work in Progress, May 2011.




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   [RFC5117]  Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117,
              January 2008.

   [RFC4587]  Even, R., "RTP Payload Format for H.261 Video Streams",
              RFC 4587, August 2006.

   [RFC5760]  Ott, J., Chesterfield, J., and E. Schooler, "RTP Control
              Protocol (RTCP) Extensions for Single-Source Multicast
              Sessions with Unicast Feedback", RFC 5760, February 2010.

Authors' Addresses

   Qin Wu (editor)
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   EMail: sunseawq@huawei.com


   Frank Xia
   Huawei
   1700 Alma Dr., Suite 500
   Plano, TX 75075
   USA

   Phone: +1 972-509-5599
   EMail: xiayangsong@huawei.com


   Roni Even
   Huawei
   14 David Hamelech
   Tel Aviv 64953
   Israel

   EMail: even.roni@huawei.com













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