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rtgwg                                                              S. Hu
Internet-Draft                                                    F. Qin
Intended status: Informational                                     Z. Li
Expires: April 25, 2019                                     China Mobile
                                                                 T. Chua
                                    Singapore Telecommunications Limited
                                                        Donald. Eastlake
                                                                 Z. Wang
                                                                 J. Song
                                                                  Huawei
                                                        October 22, 2018


      Architecture for Control Plane and User Plane Separated BNG
          draft-cuspdt-rtgwg-cu-separation-bng-architecture-02

Abstract

   This document defines the new architecture of BNG devices with
   control plane (CP) and user plane (UP) separation.  BNG-CP is a user
   control management component while BNG-UP takes responsibility as the
   network edge and user policy implementation component.  Both BNG-CP
   and BNG-UP are core components for fixed broadband services and are
   deployed separately at different network layers.

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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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 25, 2019.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Concept and Terminology . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  CU separated BNG architecture . . . . . . . . . . . . . . . .   4
     3.1.  Internal interfaces between the CP and UP . . . . . . . .   6
   4.  The usage of CU separation BNG  . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   A BNG device is defined as an Ethernet-centric IP edge router, and
   the aggregation point for the user traffic.  It performs Ethernet
   aggregation and packet forwarding via IP/MPLS, and supports user
   management, access protocols termination, QoS and policy management,
   etc.

   This document introduce an architecture for BNG devices with control
   plane (CP) and user plane (UP) separation.  BNG-CP is a user control
   management component while BNG-UP takes responsibility as the network
   edge and user policy implementation components.  Both BNG-CP and BNG-
   UP are core components for fixed broadband services and deployed
   separately at different network layer in actual network.

1.1.  Motivation

   The rapid development of new services, such as 4K, IoT, etc, and
   increasing numbers of home broadband service users present some new
   challenges for BNGs such as:





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      Low resource utilization: The traditional BNG acts as both a
      gateway for user access authentication and accounting and an IP
      network's Layer 3 edge.  The mutually affecting nature of the
      tightly coupled control plane and forwarding plane makes it
      difficult to achieve the maximum performance of either plane.

      Complex management and maintenance: Due to the large numbers of
      traditional BNGs, a network must have each device configured one
      at a time when deploying global service policies.  As the network
      expands and new services are introduced, this deployment mode will
      cease to be feasible as it is unable to manage services
      effectively and rectify faults rapidly.

      Slow service provisioning: The coupling of control plane and
      forwarding plane, in addition to a distributed network control
      mechanism, means that any new technology has to rely heavily on
      the existing network devices.

   To address these challenges, a cloud-based BNG with CU separation
   conception is defined in [TR-384].  The main idea of Control-Plane
   and User-Plane separation is to extract and centralize the user
   management functions of multiple BNG devices, forming an unified and
   centralized control plane (CP).  And the traditional router's Control
   Plane and Forwarding Plane are both preserved on BNG devices in the
   form of a user plane (UP).  Note that the CU separation conception
   has also be introduced in the 3GPP 5G architecture [3GPP.23.501].

2.  Concept and Terminology

   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.

2.1.  Terminology

   BNG: Broadband Network Gateway.  A broadband remote access server
   (BRAS, B-RAS or BBRAS) routes traffic to and from broadband remote
   access devices such as digital subscriber line access multiplexers
   (DSLAM) on an Internet service provider's (ISP) network.  BRAS can
   also be referred to as a Broadband Network Gateway (BNG).

   CP: Control Plane.  The CP is a user control management component
   which supports to manage UP's resources such as the user entry and
   user's QoS policy





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   UP: User Plane.  UP is a network edge and user policy implementation
   component.  The traditional router's Control Plane and forwarding
   plane are both preserved on BNG devices in the form of a user plane.

   AAA: Authentication Authorization Accounting.

   DHCP: Dynamic Host Configuration Protocol.

   MANO: Management and Orchestration.

   NFV: Network Function Virtualization.

   PPPoE: Point to Point Protocol over Ethernet.

3.  CU separated BNG architecture

   The functions in a traditional BNG can be divided into two parts: one
   is the user access management function, the other is the router
   function.  In a cloud-based BNG, we find out that tearing these two
   functions apart can make a difference.  Actually the user management
   function can be centralized and deployed as a concentrated module or
   device which can be called BNG-CP (Control Plane).  The other
   functions, such as the router function and forwarding engine, can be
   deployed in the form of the BNG User Plane.  Thus the Cloud-based BNG
   architecture is made up of control plane and user plane.

   The following figure describes the architecture of CU separated BNG:
























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    +------------------------------------------------------------------+
    |        Neighboring policy and resource management systems        |
    |                                                                  |
    |   +-------------+   +-----------+   +---------+   +----------+   |
    |   |AAA    Server|   |DHCP Server|   |   EMS   |   |   MANO   |   |
    |   +-------------+   +-----------+   +---------+   +----------+   |
    +------------------------------------------------------------------+

    +------------------------------------------------------------------+
    |                       CU-separated BNG system                    |
    | +--------------------------------------------------------------+ |
    | |   +----------+  +----------+ +------++------++-----------+   | |
    | |   | Address  |  |Subscriber| |AAA   ||PPPoE/||    UP     |   | |
    | |   |management|  |management| |      ||IPoE  ||management |   | |
    | |   +----------+  +----------+ +------++------++-----------+   | |
    | |                              CP                              | |
    | +--------------------------------------------------------------+ |
    |                                                                  |
    |                                                                  |
    |                                                                  |
    | +---------------------------+      +--------------------------+  |
    | |  +------------------+     |      |  +------------------+    |  |
    | |  | Routing control  |     |      |  | Routing control  |    |  |
    | |  +------------------+     | ...  |  +------------------+    |  |
    | |  +------------------+     |      |  +------------------+    |  |
    | |  |Forwarding engine |     |      |  |Forwarding engine |    |  |
    | |  +------------------+  UP |      |  +------------------+  UP|  |
    | +---------------------------+      +--------------------------+  |
    +------------------------------------------------------------------+
                    Figure 1. Architecture of CU Separated BNG


   As in the above figure, the BNG Control Plane could be virtualized
   and centralized, which provides significant benefits such as
   centralized session management, flexible address allocation, high
   scalability for subscriber management capacity, and cost-efficient
   redundancy, etc.  The functional components inside the BNG Service
   Control Plane can be implemented as Virtual Network Functions (VNFs)
   and hosted in a Network Function Virtualization Infrastructure
   (NFVI).

   The User Plane Management module in the BNG control plane centrally
   manages the distributed BNG User Planes (e.g. load balancing), as
   well as the setup, deletion, and maintenance of channels between
   Control Planes and User Planes.  Other modules in the BNG control
   plane, such as address management, AAA, and etc., are responsible for
   the connection with outside subsystems in order to fulfill those
   services.  Note that the User Plane SHOULD support both physical and



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   virtual network functions.  For example, BNG user plane L3 forwarding
   related network functions can be disaggregated and distributed across
   the physical infrastructure.  And the other control plane and
   management plane functions in the CU Separation BNG can be moved into
   the NFVI for virtualization [TR-384].

   The details of CU separated BNG's function components are described
   as following:

   The Control Plane should supports:

      (1)Address management: unified address pool management.

      (2)AAA: This component performs Authentication, Authorization and
      Accounting, together with Radius, DIAMETER.  The BNG communicates
      with the AAA server to check whether the subscriber who sent an
      Access-Request has network access authority.  Once the subscriber
      goes online, this component together with the Service Control
      component implement accounting, data capacity limitation, and QoS
      enforcement policies.

      (3)Subscriber management: user entry management and forwarding
      policy management.

      (4)PPPoE/IPoE: process user dialup packets of PPPoE/IPoE.

      (5)UP management: management of UP interface status, and the
      setup, deletion, and maintenance of channels between CP and UP.

   The User Plane should supports:

      (1)Control plane functions including routing, multicast, and MPLS.

      (2)Forwarding plane functions including traffic forwarding, QoS
      and traffic statistics collection.

3.1.  Internal interfaces between the CP and UP

   To support the communication between the Control Plane and User
   Plane, several interfaces are involved.  Figure 2 illustrates the
   internal interfaces of CU Separated BNG.










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                +----------------------------------+
                |                                  |
                |               BNG-CP             |
                |                                  |
                +--+--------------+--------------+-+
                   |              |              |
         1.Service |   2.Control  |  3.Management|
         Interface |   Interface  |   Interface  |
                   |              |              |
                +--+--------------+--------------+-+
                |                                  |
                |               BNG-UP             |
                |                                  |
                +----------------------------------+

       Figure 2. Internal interfaces between the CP and UP of the BNG device

   Service interface: The CP and UP use this interface to establish
   VXLAN tunnels with each other and transmit PPPoE and IPoE packets
   over the VXLAN tunnels which are present in [draft-huang-nov3-vxlan-
   gpe-extension-for-vbng].

   Control interface: The CP uses this interface to deliver service
   entries, and the UP uses this interface to report service events to
   the CP.  The requirements of this interface is introduced in [draft-
   cuspdt-rtgwg-cusp-requirements], and the carrying protocol is
   presented in [draft-cuspdt-rtgwg-cu-separation-bng-protocol], the
   information model of this interface is presented in [draft-cuspdt-
   rtgwg-cu-separation-infor-model].

   Management interface: The CP uses this interface to deliver
   configurations to the UP.  This interface runs NETCONF [draft-hu-
   rtgwg-cu-separation-yang-model].

4.  The usage of CU separation BNG

   In the CU separated BNG scenario, there are several processes when a
   home user accesses the Internet:

      (1)User dialup packets of PPPoE or IPoE from BNG-UP which will be
      send to BNG-CP from BNG-UP's Service Interface.

      (2)BNG-CP processes the dialup packet.  Confirming with the
      outside neighboring systems in the management network, BNG-CP
      makes the decision to permit or deny of the dial through
      certification.





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      (3)After that, BNG-CP tells UP to do the responding forwarding
      actions with related policies.

      (4)If the user is certificated and permitted, the UP forwards the
      traffic into the Internet with related policies such as limited
      bandwidth, etc.  Otherwise, the user is denied to access the
      Internet.

   In the actual deployment, a CU separated BNG device is composed of CP
   and UPs.  CP is centraly deployed and takes responsibility as a user
   control management component managing UP's resources such as the user
   entry and forwarding policy.  And UP is distributed in the bottom of
   the figure acting as a network edge and user policy implementation
   component.

   In order to fulfill a service, Neighboring policy and resource
   management systems are deployed outside.  In the neighboring system,
   different service systems such as RADIUS/DIAMETER. server, DHCP
   server and EMS are included.  Besides if BNG-CP is virtualized as a
   NFV.  The NFV infrastructure management system MANO is also included
   here.  BNG-CP has connections with the outside neighboring systems to
   transmit management traffic.

   The deployment scenarios are described in the following figure:



























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+------------------------------------------------------------------+
|        Neighboring policy and resource management systems        |
|                                                                  |
|   +-------------+   +-----------+   +---------+   +----------+   |
|   |   AAA Server|   |DHCP Server|   |   EMS   |   |   MANO   |   |
|   +-------------+   +-----------+   +---------+   +----------+   |
+--------------------------------+---------------------------------+
                                 |
                                 |
                                 |
               +-----------------+-----------------+
               |                                   |
               |              BNG-CP               |
               |                                   |
               +---------------+------------+------+
        Service|      Control|  Management|      |||
    Interface|    Interface|    Interface|          |||
(VXLAN-GPE)|  (CUSP,etc.)|    (Netconf)|               |||
        |              |            |                     |||
      +--------------+------------+         +---------------------------+
      |                           |         |                           |
      |           BNG-UP          |         |           BNG-UP          |
      |                           |         |                           |
      +-------------+-------------+         +--------------+------------+
                    |                                      |
                    |                                      |
      +-------------+-------------+         +--------------+------------+
      |                           |         |                           |
      |        Access Network     |         |        Access Network     |
      |                           |         |                           |
      +-+-----------+-----------+-+         +-+--------+-----------+----+
        |           |           |             |        |           |
        |           |           |             |        |           |
        |           |           |             |        |           |
  +-----++     +----+-+     +---+--+     +----+-+   +----+-+      +--+---+
  |User11|     |User12| ... |User1N|     |User21|   |User22|  ... |User2N|
  +------+     +------+     +------+     +------+   +------+      +------+


5.  Security Considerations

   TBD.

6.  IANA Considerations

   This document requires no IANA actions.





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7.  References

7.1.  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>.

7.2.  Informative References

   [_3GPP.23.501]
              "System Architecture for the 5G System", 3GPP GPP TS
              23.501 15.0.0, 2018.

   [draft-cuspdt-rtgwg-cu-separation-bng-deployment]
              Gu, R., "Deployment Model of Control Plane and User Plane
              Separated BNG", work in progress, 2018.

   [draft-cuspdt-rtgwg-cu-separation-bng-protocol]
              Wang, Z., "Control-Plane and User-Plane separation BNG
              control channel Protocol", work in progress, 2018.

   [draft-cuspdt-rtgwg-cu-separation-infor-model]
              Wang, Z., "Information Model of Control-Plane and User-
              Plane separation BNG", work in progress, 2018.

   [draft-cuspdt-rtgwg-cusp-requirements]
              Hu, S., "Requirements for Control Plane and User Plane
              Separated BNG Protocol", work in progress, 2018.

   [draft-hu-rtgwg-cu-separation-yang-model]
              Hu, F., "YANG Data Model for Configuration Interface of
              Control-Plane and User-Plane separation BNG", work in
              progress, 2018.

   [draft-huang-nov3-vxlan-gpe-extension-for-vbng]
              Huang, L., "VXLAN GPE Extension for Packets Exchange
              Between Control and User Plane of vBNG", work in progress,
              2017.

   [TR-384]   Broadband Forum, "Cloud Central Office Reference
              Architectural Framework", BBF TR-384, 2018.




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Authors' Addresses

   Shujun Hu
   China Mobile
   32 Xuanwumen West Ave, Xicheng District
   Beijing, Beijing  100053
   China

   Email: hushujun@chinamobile.com


   Fengwei Qin
   China Mobile
   32 Xuanwumen West Ave, Xicheng District
   Beijing, Beijing  100053
   China

   Email: qinfengwei@chinamobile.com


   Zhenqiang Li
   China Mobile
   32 Xuanwumen West Ave, Xicheng District
   Beijing, Beijing  100053
   China

   Email: lizhenqiang@chinamobile.com


   Tee Mong Chua
   Singapore Telecommunications Limited
   31 Exeter Road, #05-04 Comcentre Podium Block
   Singapore City  239732
   Singapore

   Email: teemong@singtel.com


   Donald Eastlake, 3rd
   Huawei
   1424 Pro Shop Court
   Davenport, FL  33896
   USA

   Email: d3e3e3@gmail.com






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   Zitao Wang
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: wangzitao@huawei.com


   Jun Song
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: song.jun@huawei.com



































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