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RFC 8328

Policy-Based Management Framework for the Simplified Use of Policy Abstractions (SUPA)

Pages: 15
Informational

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Independent Submission                                            W. Liu
Request for Comments: 8328                           Huawei Technologies
Category: Informational                                           C. Xie
ISSN: 2070-1721                                            China Telecom
                                                            J. Strassner
                                                          G. Karagiannis
                                                     Huawei Technologies
                                                                M. Klyus
 
                                                                   J. Bi
                                                     Tsinghua University
                                                                Y. Cheng
                                                            China Unicom
                                                                D. Zhang
                                                     Huawei Technologies
                                                              March 2018


                 Policy-Based Management Framework for
            the Simplified Use of Policy Abstractions (SUPA)

Abstract

The Simplified Use of Policy Abstractions (SUPA) policy-based management framework defines base YANG data models to encode policy. These models point to device-, technology-, and service-specific YANG data models developed elsewhere. Policy rules within an operator's environment can be used to express high-level, possibly network-wide, policies to a network management function (within a controller, an orchestrator, or a network element). The network management function can then control the configuration and/or monitoring of network elements and services. This document describes the SUPA basic framework, its elements, and interfaces.
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Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates for any level of Internet Standard;
   see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8328.

Copyright Notice

   Copyright (c) 2018 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
   (https://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.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2.2. Abbreviations and Definitions . . . . . . . . . . . . . . 4 3. Framework for Generic Policy-Based Management . . . . . . . . 5 3.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Operation . . . . . . . . . . . . . . . . . . . . . . . . 10 3.3. The GPIM and the EPRIM . . . . . . . . . . . . . . . . . 10 3.4. Creation of Generic YANG Modules . . . . . . . . . . . . 10 4. Security Considerations . . . . . . . . . . . . . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 6.1. Normative References . . . . . . . . . . . . . . . . . . 12 6.2. Informative References . . . . . . . . . . . . . . . . . 12 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 14 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction

Traffic flows over increasingly complex enterprise and service provider networks are becoming more and more important. Meanwhile, the rapid growth of this variety makes the task of network operations and management applications deploying new services much more difficult. Moreover, network operators want to deploy new services quickly and efficiently. Two possible mechanisms for dealing with this growing difficulty are 1) the use of software abstractions to simplify the design and configuration of monitoring and control operations and 2) the use of programmatic control over the configuration and operation of such networks. Policy-based management can be used to combine these two mechanisms into an extensible framework. There is a set of policy rules within an operator's environment that defines how services are designed, delivered, and operated. The SUPA (Simplified Use of Policy Abstractions) data model represents a high-level, possibly network-wide policy, which can be input to a network management function (within a controller, an orchestrator, or a network element). The network management function can then control the configuration and/or monitoring of network elements and services according to such policies. SUPA defines a Generic Policy Information Model (GPIM) [SUPA-INFO] for use in network operations and management applications. The GPIM defines concepts and terminology needed by policy management independent of the form and content of the policy rule. The Event- Condition-Action (ECA) Policy Rule Information Model (EPRIM) [SUPA-INFO] extends the GPIM by defining how to build policy rules according to the ECA paradigm. Both the GPIM and the EPRIM are targeted at controlling the configuration and monitoring of network elements throughout the service development and deployment life cycle. The GPIM and the EPRIM can both be translated into corresponding YANG [RFC6020] [RFC7950] modules that define policy concepts, terminology, and rules in a generic and interoperable manner; additional YANG modules may also be derived from the GPIM and/or EPRIM to manage specific functions. The key benefit of policy management is that it enables different network elements and services to be instructed to behave the same way, even if they are programmed differently. Management applications will benefit from using policy rules that enable scalable and consistent programmatic control over the configuration and monitoring of network elements and services.
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   Some typical and useful instances for authors to understand the
   applicability of SUPA, such as SNMP blocking upon load of link
   reaching a threshold and virtual matching migration upon the changing
   of user location, are described in [SUPA-APP].

2. Terminology

2.1. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

2.2. Abbreviations and Definitions

SUPA: The Simplified Use of Policy Abstractions is a policy-based management framework that defines a data model to be used to represent high-level, possibly network-wide policies. This data model can be input to a network management function (within a controller, an orchestrator, or a network element). YANG: An acronym for "Yet Another Next Generation". YANG is a data modeling language used to model configuration and state data manipulated by the Network Configuration Protocol (NETCONF), NETCONF remote procedure calls, and NETCONF notifications [RFC6020] ECA: Event-Condition-Action is a shortcut for referring to the structure of active rules in event-driven architecture and active database systems. EMS: An Element Management System is software used to monitor and control network elements (devices) in telecommunications. NMS: A Network Management System is a set of hardware and/or software tools that allow an IT professional to supervise the individual components of a network within a larger network management framework. OSS: An Operations/Operational Support System is a computer system used by telecommunications service providers to manage their networks (e.g., telephone networks). BSS: A Business Support System is used to support various end-to-end telecommunication services.
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   GPIM: A Generic Policy Information Model defines concepts and
   terminology needed by policy management independent of the form and
   content of the policy rule.

   EPRIM: An ECA Policy Rule Information Model extends the GPIM by
   defining how to build policy rules according to the ECA paradigm.

   GPDM: Generic Policy Data Models [SUPA-DATA] are created from the
   GPIM.  These YANG data model policies are used to control the
   configuration of network elements that model the service(s) to be
   managed.  The relationship between the information model (IM) and
   data model (DM) can be founded in [RFC3444].

   Declarative Policy: Policies that specify the goals to be achieved
   but not how to achieve those goals (also called "intent-based"
   policies).  Please note that declarative policies are out of scope
   for the initial phase of SUPA.

3. Framework for Generic Policy-Based Management

This section briefly describes the design and operation of the SUPA policy-based management framework.

3.1. Overview

Figure 1 shows a simplified functional architecture of how SUPA is used to define policies for creating snippets of network element configurations. SUPA uses the GPIM to define a consensual vocabulary that different actors can use to interact with network elements and services. The EPRIM defines a generic structure for imperative policies. The GPIM, and/or the combination of the GPIM and the EPRIM, is converted to generic YANG modules. In one possible approach (shown with asterisks in Figure 1), SUPA Generic Policy and SUPA ECA Policy YANG modules together with the Resource and Service YANG data models specified in the IETF (which define the specific elements that will be controlled by policies) are used by the Service Interface Logic. This Service Interface Logic creates appropriate input mechanisms for the operator to define policies (e.g., a web form or a script) for creating and managing the network configuration. The operator interacts with the interface, and the policies input by operators are then translated into configuration snippets. Note that the Resource and Service YANG data models may not exist. In this case, the SUPA generic policy YANG modules serve as an extensible basis to develop new YANG data models for the Service Interface Logic. This transfers the work specified by the Resource
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   and Service YANG data models specified in the IETF into the Service
   Interface Logic.

                        +---------------------+
    +----------+       \|        SUPA         |
    |   IETF   |---+----+  Information Models |
    +----------+   |   /|    GPIM and EPRIM   |
                   |    +---------+-----------+
       Assignments |              | Defines Policy Concepts
       and Managed |             \|/
         Content   |    +---------+-----------+
                   |   \|    SUPA Generic     |
                   +----+    & ECA Policy     |
                       /|    YANG modules     |
                        +---------+-----------+
                                  *  Possible Approach
    +-----------------------------*-----------------------------+
    |  Management System          *                             |
    |                            \*/                            |
    |            Fills  +---------+---------+  +-------------+  |
    | +--------+ Forms \| Service Interface |/ |Resource and |/ | +----+
    | |Operator|--------+       Logic       +--|Service YANG |----|IETF|
    | +--------+ Runs  /| (locally defined  |\ | data models |\ | +----+
    |           scripts |forms, scripts,...)|  +-------------+  |
    |                   +---------+---------+                   |
    |                            \|/                            |
    |                     +-------+--------+                    |
    |                     |  Local Devices |                    |
    |                     | and Management |                    |
    |                     |     Systems    |                    |
    |                     +----------------+                    |
    +-----------------------------------------------------------+

                         Figure 1: SUPA Framework

   Figure 1 shows the SUPA Framework at a high level of abstraction.
   The operator actor can interact with SUPA in other ways not shown in
   Figure 1.  In addition, other actors (e.g., an application developer)
   that can interact with SUPA are not shown for simplicity.

   The EPRIM defines an ECA policy as an example of imperative policies.
   An ECA policy rule is activated when its event clause is true; the
   condition clause is then evaluated and, if true, signals the
   execution of one or more actions in the action clause.  This type of
   policy explicitly defines the current and desired states of the
   system being managed.  Imperative policy rules require additional
   management functions, which are explained in Section 3.2.
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   Figure 2 shows how the SUPA Policy Model is used to create policy
   data models step-by-step and how the policy rules are used to
   communicate among various network management functions located on
   different layers.

   The GPIM is used to construct policies.  The GPIM defines generic
   policy concepts as well as two types of policies: ECA policy rules
   and declarative policy statements.

   A set of Generic Policy Data Models (GPDM) are then created from the
   GPIM.  These YANG data model policies are then used to control the
   configuration of network elements that model the service(s) to be
   managed.

   Resource and Service YANG Data Models: Models of the service as well
   as physical and virtual network topology including the resource
   attributes (e.g., data rate or latency of links) and operational
   parameters needed to support service deployment over the network
   topology.

                              |  SUPA Policy Model
                              |
                              |  +----------------------------------+
                              |  | Generic Policy Information Model |
                              |  +----------------------------------+
                              |        D                 D
                              |        D   +-------------v-------------+
 +----------------------+     |        D   |   ECA Policy Rule         |
 | OSS/BSS/Orchestrator <--+  |        D   |   Information Model       |
 +----------^-----------+  |  |        D   +---------------------------+
            C              |  |        D                          D
            C              |  |  +----+D+------------------------+D+---+
            C              +-----+     D  SUPA Policy Data Model  D    |
 +----------v-----------+     |  | ----v-----------------------+  D    |
 |  EMS/NMS/Controller  <--------+ | Generic Policy Data Model |  D    |
 +----------^-----------+     |  | ----------------------------+  D    |
            C              +-----+              D                 D    |
            C              |  |  |    +---------v-----------------v--+ |
 +----------v-----------+  |  |  |    |  ECA Policy Rule Data Model  | |
 |  Network Element     <--+  |  |    +------------------------------+ |
 +----------------------+     |  +-------------------------------------+
                              |
                              |
Legend:
The double-headed arrow with Cs = "communication"
The arrow with Ds = "derived from"

                   Figure 2: SUPA Policy Model Framework
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   SUPA Policy Model:  This model represents one or more policy modules
      that contain the following entities:

      Generic Policy Information Model:  A model for defining policy
         rules that are independent of data repository, data definition,
         query, implementation language, and protocol.  This model is
         abstract and is used for design; it MUST be turned into a data
         model for implementation.

      Generic Policy Data Model:  A model of policy rules that are
         dependent on data repository, data definition, query,
         implementation language, and protocol.

      ECA Policy Rule Information Model (EPRIM):  This model represents
         a policy rule as a statement that consists of an event clause,
         a condition clause, and an action clause.  This type of policy
         rule explicitly defines the current and desired states of the
         system being managed.  This model is abstract and is used for
         design; it MUST be turned into a data model for implementation.

      ECA Policy Rule Data Model:  A model of policy rules, derived from
         EPRIM, where each policy rule consists of an event clause, a
         condition clause, and an action clause.

      EMS/NMS/Controller:  This represents one or more entities that are
         able to control the operation and management of a network
         infrastructure (e.g., a network topology that consists of
         network elements).

      Network Element (NE):  An element that can interact with the local
         or remote EMS/NMS/Controller in order to exchange information,
         such as configuration information, policy-enforcement
         capabilities, and network status.

   Relationships among Policy, Service, and Resource models are
   illustrated in Figure 3.
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         +---------------+                   +----------------+
         |    Policy     |         (1)       |    Service     |
         |               |*******************|                |
         |   ( SUPA )    |*******************| ( L3SM, ... )  |
         +---------------+                   +----------------+
                **                                  /*\
                  **                                *
                    **                            *
                 (2)  **                        *   (3)
                        **                    *
                          **                *
                            **            *
                        +-------------------+
                        |    Resource       |
                        |                   |
                        | (Inventory, ... ) |
                        +-------------------+

     Figure 3: Relationship among Policy, Service, and Resource Models

   In Figure 3:

   (1)  The policy manages and can adjust service behavior as necessary
        (1:1..n).  In addition, data from resources and services are
        used to select and/or modify policies during runtime.

   (2)  The policy manages and can adjust resource behavior as necessary
        (1:1..n).

   (3)  Resource hosts service; changing resources may change service
        behavior as necessary.

   Policies are used to control the management of resources and
   services, while data from resources and services are used to select
   and/or modify policies during runtime.  More importantly, policies
   can be used to manage how resources are allocated and assigned to
   services.  This enables a single policy to manage one or multiple
   services and resources as well as their dependencies.  The use of
   (1:1..n) in point (1) and (2) above show that one policy rule is able
   to manage and can adjust one or multiple services/resources.  Lines
   (1) and (2) (connecting policy to resource and policy to service) are
   the same, and line (3) (connecting resource to service) is different
   as it's navigable only from resource to service.
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3.2. Operation

SUPA can be used to define various types of policies, including policies that affect services and/or the configuration of individual network elements or groups of network elements. SUPA can be used by a centralized and/or distributed set of entities for creating, managing, interacting with, and retiring policy rules. The SUPA scope is limited to policy information and data models. SUPA does not define network resource data models or network service data models; both are out of scope. Instead, SUPA makes use of network resource data models defined by other working groups or Standards Development Organizations (SDOs). Declarative policies are out of scope for the initial phase of SUPA.

3.3. The GPIM and the EPRIM

The GPIM provides a shared vocabulary for representing concepts that are common to different types of policies, but which are independent of language, protocol, repository, and level of abstraction. Hence, the GPIM defines concepts and vocabulary needed by policy management systems independent of the form and content of the policy. The EPRIM is a more specific model that refines the GPIM to specify policy rules in an ECA form. This enables different policies at different levels of abstraction to form a continuum, where more abstract policies can be translated into more concrete policies and vice versa. For example, the information model can be extended by generalizing concepts from an existing data model into the GPIM; the GPIM extensions can then be used by other data models.

3.4. Creation of Generic YANG Modules

An information model is abstract. As such, it cannot be directly instantiated (i.e., objects cannot be created directly from it). Therefore, both the GPIM and the combination of the GPIM and the EPRIM are translated into generic YANG modules. SUPA will provide guidelines for translating the GPIM (or the combination of the GPIM and the EPRIM) into concrete YANG data models that define how to manage and communicate policies between systems. Multiple imperative policy YANG data models may be instantiated from the GPIM (or the combination of the GPIM and the EPRIM). In particular, SUPA will specify a set of YANG data models that will consist of a base policy model for representing policy management concepts independent of the type or structure of a policy; it will
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   also specify an extension for defining policy rules according to the
   ECA paradigm.  (Note: This means that policies can be defined using
   the GPIM directly, or using the combination of the GPIM and the
   EPRIM.  If you use only the GPIM, you get a technology- and vendor-
   independent information model that you are free to map to the data
   model of your choice; note that the structure of a policy is NOT
   defined.  If you use the GPIM and the EPRIM, you get a technology-
   and vendor-independent information model that defines policies as an
   ECA policy rule (i.e., imperative).)

   The process of developing the GPIM, the EPRIM, and the derived/
   translated YANG data models is realized following the sequence shown
   below.  After completing this process and, if the implementation of
   the YANG data models requires it, the GPIM and EPRIM and the derived/
   translated YANG data models are updated and synchronized.

      (1)=>(2)=>(3)=>(4)=>(3')=>(2')=>(1')

      Where:
      (1)=GPIM
      (2)=EPRIM
      (3)=YANG data models
      (4)=Implementation
      (3')=update of YANG data models
      (2')=update of EPRIM
      (1')=update of GPIM

   The YANG module derived from the GPIM contains concepts and
   terminology for the common operation and administration of policy-
   based systems as well as an extensible structure for policy rules of
   different paradigms.  The YANG module derived from the EPRIM extends
   the generic nature of the GPIM by representing policies using an ECA
   structure.

   The above sequence allows for the addition of new model elements, as
   well as the editing of existing ones, in the GPIM and EPRIM.  In
   practice, the implementation sequence may be much simpler.
   Specifically, it is unlikely that the GPIM will need to be changed.
   In addition, changes to the EPRIM will likely be focused on fine-
   tuning the behavior offered by a specific set of model elements.
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4. Security Considerations

This informational document presents the framework and workflow of SUPA as well as an explanation on the relationship of policy, service and resources. This document does not introduce any new security issues, and the framework has no security impact on the Internet. The same considerations are relevant as those for the base NETCONF protocol (see Section 9 in [RFC6241]).

5. IANA Considerations

This document has no IANA actions.

6. References

6.1. Normative References

[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>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2. Informative References

[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between Information Models and Data Models", RFC 3444, DOI 10.17487/RFC3444, January 2003, <https://www.rfc-editor.org/info/rfc3444>. [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, <https://www.rfc-editor.org/info/rfc6020>. [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>. [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>.
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   [SUPA-APP] Cheng, Y., Liu, D., Fu, B., Zhang, D., and N. Vadrevu,
              "Applicability of SUPA", Work in Progress,
              draft-cheng-supa-applicability-01, March 2017.

   [SUPA-DATA]
              Halpern, J., Strassner, J., and S. Van der Meer, "Generic
              Policy Data Model for Simplified Use of Policy
              Abstractions (SUPA)", Work in Progress, draft-ietf-supa-
              generic-policy-data-model-04, June 2017.

   [SUPA-FRAME]
              Zhou, C., Contreras, L., Sun, Q., and P. Yegani, "The
              Framework of Simplified Use of Policy Abstractions
              (SUPA)", Work in Progress, draft-zhou-supa-framework-02,
              May 2015.

   [SUPA-INFO]
              Strassner, J., Halpern, J., and S. Meer, "Generic Policy
              Information Model for Simplified Use of Policy
              Abstractions (SUPA)", Work in Progress, draft-ietf-supa-
              generic-policy-info-model-03, May 2017.

   [SUPA-STATE]
              Karagiannis, G., Strassner, J., Sun, Q., Contreras, L.,
              Yegani, P., and J. Bi, "Problem Statement for Simplified
              Use of Policy Abstractions (SUPA)", Work in Progress,
              draft-karagiannis-supa-problem-statement-07, June 2015.

   [SUPA-VALUE]
              Klyus, M., Strassner, J., Liu, W., Karagiannis, G., and J.
              Bi, "SUPA Value Proposition", Work in Progress,
              draft-klyus-supa-value-proposition-00, March 2016.
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Acknowledgements

This document has benefited from reviews, suggestions, comments, and proposed text provided by the following members, listed in alphabetical order: Andy Bierman, Marc Blanchet, Mohamed Boucadair, Scott O. Bradner, Scott Cadzow, Zhen Cao, Vikram Choudhary, Benoit Claise, Spencer Dawkins, Mehmet Ersue, Ian Farrer, Fernando Gont, Joel Halpern, Jonathan Hansford, Jing Huang, Xing Li, Marco Liebsch, Diego R. Lopez, Johannes Merkle, Marie-Jose Montpetit, Kostas Pentikousis, Simon Perreault, Hosnieh Rafiee, Raghav Rao, Jose Saldana, Jon Saperia, Tom Taylor, Jean Francois Tremblay, Tina Tsou, Eric Voit, Gunter Wang, Yangyang Wang, Bert Wijnen, and Tianran Zhou. Part of the initial draft of this document was picked up from previous documents: [SUPA-VALUE], [SUPA-STATE], and [SUPA-FRAME]. We appreciatively acknowledge the authors, contributors, and acknowledged parties of those documents.

Contributors

The following people contributed to the creation of this document, listed in alphabetical order: Luis M. Contreras, Telefonica I+D Dan Romascanu, Avaya Juergen Schoenwaelder, Jacobs University, Germany Qiong Sun, China Telecom Parviz Yegani, Huawei Technologies Cathy Zhou, Huawei Technologies

Authors' Addresses

Will (Shucheng) Liu Huawei Technologies Bantian, Longgang District Shenzhen 518129 China Email: liushucheng@huawei.com Chongfeng Xie China Telecom China Telecom Information Technology Innovation Park Beijing 102209 China Email: xiechf.bri@chinatelecom.cn
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   John Strassner
   Huawei Technologies
   2330 Central Expressway
   Santa Clara, CA  95138
   United States of America

   Email: john.sc.strassner@huawei.com


   Georgios Karagiannis
   Huawei Technologies
   Hansaallee 205
   Dusseldorf  40549
   Germany

   Email: Georgios.Karagiannis@huawei.com


   Maxim Klyus

   Email: xmaruto@gmail.com


   Jun Bi
   Tsinghua University
   Network Research Center, Tsinghua University
   Beijing  100084
   China

   Email: junbi@tsinghua.edu.cn


   Ying Cheng
   China Unicom
   No.21 Financial Street, XiCheng District
   Beijing  100033
   China

   Email: chengying10@chinaunicom.cn


   Dacheng Zhang
   Huawei Technologies
   Beijing
   China

   Email: dacheng.zhang@huawei.com