NETCONF                                                         G. Zheng
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                A. Clemm
Expires: March 27, May 15, 2018                                             Huawei
                                                      September 23,
                                                       November 11, 2017

         UDP based Publication Channel for Streaming Telemetry
                 draft-ietf-netconf-udp-pub-channel-00
                 draft-ietf-netconf-udp-pub-channel-01

Abstract

   This document describes a UDP-based publication channel for streaming
   telemetry use to collect data from devices.  A new shim header is
   proposed to facilitate the distributed data collection mechanism
   which directly pushes data from line cards to the collector.  Because
   of the lightweight UDP encapsulation, higher frequency and better
   transit performance can be achieved.

Requirements Language

   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].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on March 27, May 15, 2018.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Solution Overview . . . . . . . . . . . . . . . . . . . . . .   4
   4.  UDP Transport for Publication Channel . . . . . . . . . . . .   6   5
     4.1.  Data Format . .  Design Overview . . . . . . . . . . . . . . . . . . . . .   6   5
     4.2.  Options . . . . .  Data Format of the Message Header . . . . . . . . . . . .   6
     4.3.  Options . . . . . . . .   8
       4.2.1.  Reliability Option . . . . . . . . . . . . . . . . .   8
       4.2.2.  Authentication
       4.3.1.  Reliability Option  . . . . . . . . . . . . . . . .   9
     4.3. .   8
     4.4.  Data Encoding . . . . . . . . . . . . . . . . . . . . . .  10   9
   5.  IANA Considerations  Congestion Control  . . . . . . . . . . . . . . . . . . . . .  10   9
   6.  Operational  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11  10
     9.3.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  12  11
   Appendix A.  Change Log . . . . . . . . . . . . . . . . . . . . .  12  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12  11

1.  Introduction

   Streaming telemetry refers to sending a continuous stream of
   operational data from a device to a remote receiver.  This provides
   an ability to monitor a network from remote and to provide network
   analytics.  Devices generate telemetry data and push that data to a
   collector for further analysis.  By streaming the data, much better
   performance, finer-grained sampling, monitoring accuracy, and
   bandwidth utilization can be achieved than with polling-based
   alternatives.

   Sub-Notif [I-D.ietf-netconf-subscribed-notifications] and YANG-Push
   [I-D.ietf-netconf-yang-push] defines a mechanism that allows a
   collector to subscribe to updates of YANG-defined data that is
   maintained in a YANG [RFC7950] datastore.  The mechanism separates
   the management and control of subscriptions from the transport that
   is used to actually stream and deliver the data.  Two transports have
   been defined so far, NETCONF [RFC6241] and RESTCONF [RFC8040].

   While powerful in its features and general in its architecture, in
   its current form the mechanism needs to be extended to stream
   telemetry data at high velocity from devices that feature a
   distributed architecture.  Specifically, there are two aspects that
   need to be addressed:

   1.  The transports that have been defined so
   far, NETCONF and RESTCONF, are ultimately based on TCP (Transmission
   Control Protocol) and lack the efficiency needed to stream data
   continuously at high velocity.  A lighter-weight, more efficient
   transport, e.g. a transport based on UDP (User Datagram Protocol) is
   needed.

       *

   o  Firstly, data collector will suffer a lot of TCP connection connections from,
      for example, many line cards equipped on different devices.

       *

   o  Secondly, as no connection state needs to be maintained, UDP
      encapsulation can be easily implemented by hardware which will
      further improve the performance.

       *

   o  Thirdly, because of the lightweight UDP encapsulation, higher
      frequency and better transit performance can be achieved, which is
      important for streaming telemetry.

   2.  The current design involves

   This document specifies a single push server. higher-performance transport option for
   YANG-Push that leverages UDP.  Specifically, it facilitates the
   distributed data collection mechanism described in
   [I-D.zhou-netconf-multi-stream-originators].  In the case of data
   originating from multiple line cards, the design requires data to be
   internally forwarded from those line cards to the push server,
   presumably on a main board, which then combines the individual data
   items into a single consolidated stream.  This  The centralized data
   collection mechanism can result in a performance bottleneck,
   especially when large amounts of data are involved.  What is needed
   instead is the support for a distributed mechanism that allows to
   directly push multiple individual substreams, e.g. one from each line
   card, without needing to first pass them through an additional
   processing stage for internal consolidation, but still allowing those
   substreams to be managed and controlled via a single subscription.

   This document specifies a
   The proposed UDP publication channel natively supports the
   distributed data collection mechanism which
   can directly push data from line cards to a collector by using a UDP
   based publication channel.  Specifically, a higher-performance
   transport option for YANG-Push that leverages UDP is specified. mechanism.

   While this document will focus on the data publication channel, the
   subscription can be used in conjunction with the mechanism proposed
   in [I-D.ietf-netconf-yang-push] with necessary extensions.

   Although the distributed data streaming from device line cards is one
   typical scenario that the proposed UDP based publication channel can
   be useful, the proposal is general enough to fit more scenarios that
   require UDP transport for data collections, e.g. the IoT (Internet of
   Things) use case. extensions
   [I-D.zhou-netconf-multi-stream-originators].

2.  Terminology

   Streaming telemetry: refers to sending a continuous stream of
   operational data from a device to a remote receiver.  This provides
   an ability to monitor a network from remote and to provide network
   analytics.

   Component subscription: A subscription that defines the data from
   each individual entity which is managed and controlled by a single
   subscription server.

   Subscription agent: An agent that streams telemetry data per the
   terms of a component subscription.

3.  Solution Overview

   The typical distributed data collection solution is shown in figure Fig. 1.
   The subscription server located in Subscriber cannot see the main board receives Agents directly, so it will send the
   subscription requests or configurations.  It may be colocated, not
   necessary, with a NETCONF server which interacts with outside
   clients.
   Global Subscription information to the Master (e.g., main board).
   When receiving a subscription request, Global Subscription, the subscription
   server Subscription Server
   decomposes the subscription request into multiple component
   subscriptions, Component
   Subscriptions, each involving data from a separate internal telemetry
   source, for example a line card.  The component subscriptions Component Subscriptions are
   distributed within the device to the subscription agents Component Subscription Server located in
   line cards. Agents.
   Subsequently, each line card Agent generates its own stream of telemetry data,
   collecting and encapsulating the packets per the
   component subscription Component
   Subscription and streaming it them to the designated Collector.This
   distributed data
   collector.

   The publication channel supports collection mechanism may form multiple Publication
   Channels between the data originators and the Collector.  The
   Collector is able to assemble many pieces of data associated with one
   Global Subscription.

   The Publication Channel supports the reliable data streaming, for
   example for some alarm events.  The subscriber Collector has the option of
   deducing the packet loss and the disorder based on the information
   carried by the notification data.  And the subscriber Collector will decide the
   behavior to request retransmission.  The subscriber Collector can send the
   retransmission request to the subscriber server for further
   processing.

   Subscription server and subscription agents interact with each other
   in several ways:

   o  Subscription agents need to have a registration or announcement
      handshake with the subscription server, so the subscription server
      is aware of them and of lifecycle events (such as subscription
      agents appearing and disappearing).

   o  The subscription server relays the component subscriptions to the
      subscription agents.

   o  The subscription agents indicate status of component subscriptions
      to the subscription server.  The status of the overall "master"
      subscription is maintained by the subscription server.  The
      subscription server is also responsible for notifying the
      subscriber in case of any problems of component subscriptions.

   The rest of the draft describes the UDP based publication channel.

                retransmission +    + Global
                request        |    | subscription Subscription
                        +------------------------+
                        |      |    |  Main Board|  Master    |
                        |   +--v----v--------+   |
                        |   |  subscription  Subscription  |   |
                        |   |  server  Server        |   |
                        |   +--+----+-----+--+   |
                        |      |    |     |      |   internal
       Component        +------------------------+   subscription
       Subscription            |    |     |          distribution
               +---------------+    |     +--------------+
               |                    |                    |
     +------------------+  +------------------+  +------------------+
     |         |        |  |        |         |  |       |          |
     | +-------v------+ |  | +------v-------+ |  | +-----v--------+ |
     | | subscription Component    | |  | | subscription Component    | |  | | subscription Component    | |
     | | Subscription | |  | | Subscription | agent |  | | Subscription | | agent
     | | Server       | | agent  | | Server       | |  | | Server       | |
     | +--------------+ |  | +--------------+ |  | +--------------+ |
     |    Line Card       Agent 1    |  |    Line Card      Agent 2     |  |    Line Card        Agent n   |
     +---------+--------+  +--------+---------+  +----------+-------+
               |                    |                       |
               |                    | Publication Channel   |
               +--------------+     |     +-----------------+
                              |     |     |
                            +-v-----v-----v-+
                            |               |
                            |   Collector   |
                            |               |
                            +---------------+

                    Fig. 1 Distributed Data Collection

4.  UDP Transport for Publication Channel

   In [I-D.voit-netconf-notification-messages],

4.1.  Design Overview

   As specified in YANG-Push, the transport
   independent message header telemetry data is proposed for encapsulated in the
   NETCONF/RESTCONF notification use. message, which is then encapsulated and
   carried in the transport protocols, e.g.  TLS, HTTP2.  The following shim header refers
   figure shows the overview of the UDP publication message structure.

   o  Next to the UDP encapsulation, the DTLS layer is to provide
      reusable security and implements authentication functions over UDP.

   o  The Message Header contains information that can facilitate the
      message header
   definition.

4.1. transmission before de-serializing the notification
      message.

   o  Notification Message is the encoded content that the publication
      channel transports.  The common encoding method includes GPB [1],
      CBOR [RFC7049], JSON, and XML.
      [I-D.ietf-netconf-notification-messages] describes the structure
      of the Notification Message for both single notification and
      multiple bundled notifications.

                                 +--------------+
                                 | Notification |
                                 | Message      |
                                 +--------------+

                                 +--------------+
                                 |   Message    |
                                 |   Header     |
                                 +--------------+

                                 +--------------+
                                 |     DTLS     |
                                 +--------------+

                                 +--------------+
                                 |      UDP     |
                                 +--------------+

                  Fig. 2 UDP Publication Message Overview

4.2.  Data Format of the Message Header

   The Message Header contains information that can facilitate the
   message transmission before de-serializing the notification message.
   The data format of the UDP based based publication transport is shown as follows.

      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
     +---------------------------------------------------------------+
     ~                      UDP Header                               ~
     +-------+---------------+-------+-------------------------------+
     | Vers. |    Flag       | Rsvd  ET   |      Length                   |
     +-------+---------------+-------+-------------------------------+
     |                      Notification-Time                        |
     +---------------------------------------------------------------+
     |                      Message-Generator-ID                     |
     +---------------------------------------------------------------+
     ~                      Options                                  ~
     +---------------------------------------------------------------+
     ~                      Message Content                          ~
     +---------------------------------------------------------------+

   Right after the UDP header, a simple inform header is attached to
   carry the necessary information with regard to
     +---------------------------------------------------------------+
     ~                      Options                                  ~
     +---------------------------------------------------------------+

                       Fig. 3 Message Header Format

   The Message Header contains the streaming mode. following field:

   o  The Vers. field  Vers.: represents the PDU (Protocol Data Unit) encoding version.
      The initial version value is 0.

   o  The Flag  Flag: is a bitmap indicating what features this packet has and the
      corresponding options attached.  Each bit associates to one
      feature and one option data.  When the bit is set to 1, the
      associated feature is enabled and the option data is attached.
      The sequence of the presence of the options follows the bit order
      of the bitmap.  In this document, 2 flags are the flag is specified as
      follows:

      *  bit 0, the reliability flag;

      *  bit 1, the authentication flag;

      *  other bits are reserved.

   o  The Length field  ET: is a 4 bits identifier to indicate the encoding type used for
      the Notification Message. 16 types of encoding can be expressed:

      *  0: GPB;

      *  1: CBOR;

      *  2: JSON;

      *  3: XML;

      *  others are reserved.

   o  Length: is the total length of the message, measured in octets,
      including message header.

   o  The Message-Generator-ID  Message-Generator-ID: is a 32-bit identifier of the process which
      created the message notification.  This allows disambiguation of
      an information source, such as the identification of different
      line cards sending the notification messages.

   o  The Notification-Time,  Notification-Time: is the time at which the message leaves the
      exporter, expressed in seconds since the UNIX epoch of 1 January
      1970 at 00:00 UTC, encoded as an unsigned 32-bit integer.

   o  The Options  Options: is a variable-length field.  The details of the Options
      will be described in the respective sections below.

   After the inform header is the real content which is encoded.  The
   actual encoding is based on the subscription, e.g., in binary with
   GPB [1] or CBOR [RFC7049].

4.2.

4.3.  Options

   The order of packing the data fields in the Options field follows the
   bit order of the Flag field.

4.2.1.

4.3.1.  Reliability Option

   The UDP based publication transport described in this document
   provides two streaming modes, the reliable mode an the unreliable
   mode, for different SLA (Service Level Agreement) and telemetry
   requirements.

   In the unreliable streaming mode, the line card pushes the
   encapsulated data to the data collector without any sequence
   information.  So the subscriber does not know whether the data is
   correctly received or not.  Hence no retransmission happens.

   The reliable streaming mode provides sequence information in the UDP
   packet, based on which the subscriber can deduce the packet loss and
   disorder.  Then the subscriber can decide whether to request the
   retransmission of the lost packets.

   In most case, the unreliable streaming mode is preferred.  Because
   the reliable streaming mode will cost more network bandwidth and
   precious device resource.  Different from the unreliable streaming
   mode, the line card cannot remove the sent reliable notifications
   immediately, but to keep them in the memory for a while.  Reliable
   notifications may be pushed multiple times, which will increase the
   traffic.  When choosing the reliable streaming mode or the unreliable
   streaming mode, the operate need to consider the reliable requirement
   together with the resource usage.

   When the reliability flag bit is set to 1 in the Flag field, the
   following option data will be attached
      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
     +---------------------------------------------------------------+
     |            Notification ID                                    |
     +---------------------------------------------------------------+
     |            Previous Notification ID                           |
     +---------------------------------------------------------------+

   The notification ID is generated continuously by the message
   generator.  Different subscribers share the same notification ID
   sequence.  Current ID and previous ID will be added in the packets.

   For example, there are two subscriber A and B,

   o  Notification IDs for the generator are : [1, 2, 3, 4, 5, 6, 7, 8,
      9], in which Subscriber A subscribes [1,2,3,6,7] and Subscriber B
      subscribes [1,2,4,5,7,8,9].

   o  Subscriber A will receive : [0,1][1,2][2,3][3,6][6,7].

   o  Subscriber B will receive : [0,1][1,2][2,4][4,5][5,7][7,8].

4.2.2.  Authentication Option

   When the authentication flag bit is set to 1 in the Flag field, a 24
   octets data field will be included in the Options.  The message is
   signed, and the signature is filled in the 24 octets Authentication

                     Fig. 4 Reliability Option field.  So that a receiver can verify the authenticity of the
   message.

   HMAC [RFC2104] defines a mechanism for message authentication using
   cryptographic hash functions.  Any message digest algorithm can be
   used, but the cryptographic strength of HMAC depends on the
   properties of the underlying hash function.  As suggested by
   [RFC6151], new protocol designs should not employ HMAC-MD5 [RFC2202].
   Alternatives to HMAC-MD5 include HMAC-SHA256 [RFC4231] and AES-CMAC
   [RFC4493].

   Implementations permit multiple acceptable algorithms, while the
   HMAC-SHA256 algorithm is mandatory in this document. Format

   The resulting
   message digest (output of HMAC) is truncated to 24 octets, which is
   the 192 leftmost bits of the HMAC computation, to fit the size of the
   Authentication Option field.  It notification ID is recommended in [RFC2104] that generated continuously by the
   truncated output length should be not less than half message
   generator.  Different subscribers share the length of same notification ID
   sequence.  Current ID and previous ID will be added in the hash output to match packets.

   For example, there are two subscriber A and B,

   o  Notification IDs for the birthday attack bound.

4.3. generator are : [1, 2, 3, 4, 5, 6, 7, 8,
      9], in which Subscriber A subscribes [1,2,3,6,7] and Subscriber B
      subscribes [1,2,4,5,7,8,9].

   o  Subscriber A will receive : [0,1][1,2][2,3][3,6][6,7].

   o  Subscriber B will receive : [0,1][1,2][2,4][4,5][5,7][7,8].

4.4.  Data Encoding

   Subscribed data can be encoded in GPB, CBOR, XML or JSON format.  It
   is conceivable that additional encodings may be supported as options
   in the future.  This can be accomplished by augmenting the
   subscription data model with additional identity statements used to
   refer to requested encodings.

   Implementation may support different encoding method per
   subscription.  When bundled notifications is supported between the
   publisher and the receiver, only subscribed notifications with the
   same encoding can be bundled as one message.

5.  IANA Considerations

   TBD

6.  Operational Considerations  Congestion Control

   While efficient, UDP has no build-in congestion-avoidance congestion control mechanism.
   It is not recommended to use the UDP based publication channel over
   congestion-sensitive network paths.  The deployments require the
   communications from exporters to collectors are always congestion
   controllable, i.e., the transport is over dedicated links or the
   streaming rate can be limited.

6.  IANA Considerations

   TBD

7.  Security Considerations

   The security of the UDP based publication channel depends on the
   subscription channel.  Typically, both NETCONF and RESTCONF support
   the secure configuration of the private key for the publication
   channel.  So that the message data can be encrypted by using
   symmetric key algorithms.

   TBD

8.  Acknowledgements

   The authors of this documents would like to thank Eric Voit, Tim
   Jenkins, and Huiyang Yang for the initial comments.

9.  References

9.1.  Normative References

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/info/rfc2104>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2202]  Cheng, P. and R. Glenn, "Test Cases for HMAC-MD5 and HMAC-
              SHA-1", RFC 2202, DOI 10.17487/RFC2202, September 1997,
              <https://www.rfc-editor.org/info/rfc2202>.

   [RFC4231]  Nystrom, M., "Identifiers and Test Vectors for HMAC-SHA-
              224, HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512",
              RFC 4231, DOI 10.17487/RFC4231, December 2005,
              <https://www.rfc-editor.org/info/rfc4231>.

   [RFC4493]  Song, JH., Poovendran, R., Lee, J., and T. Iwata, "The
              AES-CMAC Algorithm", RFC 4493, DOI 10.17487/RFC4493, June
              2006, <https://www.rfc-editor.org/info/rfc4493>.

   [RFC6151]  Turner, S. and L. Chen, "Updated Security Considerations
              for the MD5 Message-Digest and the HMAC-MD5 Algorithms",
              RFC 6151, DOI 10.17487/RFC6151, March 2011,
              <https://www.rfc-editor.org/info/rfc6151>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

9.2.  Informative References

   [I-D.ietf-netconf-notification-messages]
              Voit, E., Bierman, A., Clemm, A., and T. Jenkins,
              "Notification Message Headers and Bundles", draft-ietf-
              netconf-notification-messages-02 (work in progress),
              October 2017.

   [I-D.ietf-netconf-subscribed-notifications]
              Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
              A. Tripathy, "Custom Subscription to Event Notifications",
              draft-ietf-netconf-subscribed-notifications-04 Streams",
              draft-ietf-netconf-subscribed-notifications-07 (work in
              progress), September October 2017.

   [I-D.ietf-netconf-yang-push]
              Clemm, A., Voit, E., Prieto, A., Tripathy, A., Nilsen-
              Nygaard, E., Bierman, A., and B. Lengyel, "Subscribing to
              YANG datastore push updates", draft-ietf-netconf-yang-
              push-09 "YANG Datastore
              Subscription", draft-ietf-netconf-yang-push-11 (work in
              progress), September October 2017.

   [I-D.voit-netconf-notification-messages]

   [I-D.zhou-netconf-multi-stream-originators]
              Zhou, T., Zheng, G., Voit, E., Bierman, A., Clemm, A., and T. Jenkins,
              "Notification Message Headers and Bundles", draft-voit-
              netconf-notification-messages-01 A. Bierman,
              "Subscription to Multiple Stream Originators", draft-zhou-
              netconf-multi-stream-originators-00 (work in progress), July
              October 2017.

9.3.  URIs

   [1] https://developers.google.com/protocol-buffers/

Appendix A.  Change Log

   (To be removed by RFC editor prior to publication)

   A.1. draft-ietf-zheng-udp-pub-channel-00 to v00

   o  Modified the telemetry header format.

   o  Add a section on the Authentication Option.

   o  Cleaned up the text and removed unnecessary TBDs.

   A.2. v01

   o  Removed the detailed description on distributed data collection
      mechanism from this document.  Mainly focused on the description
      of a UDP based publication channel for telemetry use.

   o  Modified the telemetry header format.

Authors' Addresses
   Guangying Zheng
   Huawei
   101 Yu-Hua-Tai Software Road
   Nanjing, Jiangsu
   China

   Email: zhengguangying@huawei.com

   Tianran Zhou
   Huawei
   156 Beiqing Rd., Haidian District
   Beijing
   China

   Email: zhoutianran@huawei.com

   Alexander Clemm
   Huawei
   2330 Central Expressway
   Santa Clara, California
   USA

   Email: alexander.clemm@huawei.com