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rtgwg                                                              R. Gu
Internet-Draft                                                     S. Hu
Intended status: Informational                              China Mobile
Expires: August 30, 2018                                   Michael. Wang
                                                                  Huawei
                                                             Fangwei. Hu
                                                         ZTE Corporation
                                                       February 26, 2018


     Deployment Model of Control Plane and User Plane Separated BNG
           draft-cuspdt-rtgwg-cu-separation-bng-deployment-01

Abstract

   This document introduces deployment model of BNG device with Control
   Plane and User Plane separation in order to give guidance of the
   deployment of CP and UP separated BNG devices in operators' network.

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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   time.  It is inappropriate to use Internet-Drafts as reference
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   This Internet-Draft will expire on August 30, 2018.

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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction and Overview . . . . . . . . . . . . . . . . . .   2
   2.  Concept and Terminology . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Deployment Model of BNG with CP and UP Separation . . . . . .   4
     3.1.  CP and UP of BNG deployment within only one district  . .   4
     3.2.  CP and UP of BNG deployment within different districts  .   6
   4.  The Process of BNG with CP and UP in Home Broadband Service .   7
   5.  High Availability Consideration . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction and Overview

   BNG is an Ethernet-centric IP edge router and acts as the aggregation
   point for the user traffic with some additional functions such as
   address management and Radius cooperating with Radius systems and
   subscriber management.  According to the rapid development of new
   services, such as 4K, IoT, etc. and the increasing numbers of
   distributed home broadband service users, high resource utilization,
   management of high-efficiency, and fast service provision are
   required.  Thus a new architecture of BNG with CP and UP separation
   which is also called Cloud BNG is proposed in [BBF-CloudCO][TR-384].

   The brandnew CP and UP separation architecture of BNG is constructed
   by Control Plane and User Plane, with concentrated CP responsible for
   control and management of UP's resrouces and subscribers' informaiton
   while distributed UP taking charge of policy implementation and
   traffic forwarding.  The obvious advantages of this new architecture
   can be listed as belows.

   Resource Utilization Improvement: Centralized Control Plane provides
   the capability of unified management of network resources and users
   information.  CP has an overview of all the resources and can
   distribute resources as specific user required, thus resources can be
   totally controlled and balanced.

   Management with High Effiency: Centralized CP provides unified
   management interface to the outside systems such as EMS, DHCP Server,
   Radius Server and etc.  In this situation, management can be much
   easier for centralized CP as it's the only device facing to the
   outside systems.



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   Dynamic and Flexibility: CP can be virtualized as a VNF with MANO
   management in NFV, while UP can be a virtual machine or physical
   device as demand.  Software-oriented CP can be designed with
   flexibility.  CP can handle all the situations dynamically such as
   few users accessing and large numbers of users accessing.

   Fast TTM: CP and UP can be deployed separately with CP deployed
   centrally and UP deployed in distribution closing to users.  Thus
   according to different situations such as session overload or
   extremely high throughput, CP and UP can be extended separately as
   well.  It can help shorten the time to marketing (TTM).

   As noted that the new architecture of BNG consists with CP and UP
   separation, CP and UP are deployed due to practical requirements.
   This document gives out CU separation BNG deployment model according
   to the actual deployment.

2.  Concept and Terminology

   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 [RFC2119].

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.  CP is a user control management component which
   support to manage UP's resources such as the user entry and user's
   QoS policy

   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.

   TTM: Time to Market.  It is the length of time it takes from a
   product or a service being conceived until its being available for
   sale.

   MANO: Management and Orchestration.  Functions are collectively
   provided by NFVO, VNFM and VIM.






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   VNF: Virtual Network Function.  Implementation of a Network Function
   that can be deployed on a Network Function Virtualization
   Infrastructure (NFVI).

   PNF: Physical Network Function

   DHCP: Dynamic Host Configuration Protocol

   PPPoE: Point to Point Protocol over Ethernet

   IPoE: Internet Protocol over Ethernet

3.  Deployment Model of BNG with CP and UP Separation

3.1.  CP and UP of BNG deployment within only one district

   +-------------------+
   |                   |
   |       Internet    |
   |                   |
   +---------^---------+
             |
         +---+---+
         |       |              +------------------------+
         |   CR  |              |                        |
         |       |              |            +--------+  |
         +---^---+              |     +------+ Radius |  |
             |                  |     |      +--------+  |
             |                  |  +--+---+              |
         +---+---+              |  |      |  +--------+  |
         |       +---SERVICE----+  |      +--+  DHCP  |  |
         | BNG-UP+---CONTROL----+  | BNG  |  +--------+  |
         |VNF/PNF+----MGNT------+  | -CP  |              |
         +---^---+              |  |  VNF |  +--------+  |
             |                  |  |      +--+   EMS  |  |
             |                  |  |      |  +--------+  |
         +---+---+              |  +--+---+              |
         |       |              |     |      +--------+  |
         |  OLT  |              |     +------+  MANO  |  |
         |       |              |            +--------+  |
         +---^---+              |   Management Network   |
             |                  +------------------------+
         +---+---+
         |  USER |
         +-------+

               Figure 1: Cloud BNG Deployed in One Disctict




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   Take one district as an example, here BNG-CP and BNG-UP are separated
   deployed.  As CP is computational intensive, virtualized CP acting as
   a VNF can meet the requirements of flexibility and fast calculation.
   UP is traffic intensive, which can be virtualized or stay physical
   depending on traffic.  The virtualized UP with low expense and high
   flexibility can be suitable in light traffic.  In hugh traffic,
   special hardware is needed with high traffic forwarding performance.

   In order to fulfill the function of BNG, BNG-CP needs to communicate
   with outside systems such as Radius and many others in the management
   network.  In addition, BNG-CP has different interfaces with BNG-UP.
   There are three kinds of interfaces between BNG-CP and BNG-UP
   according to its traffic catergories: Service Interface, Control
   Interface, and Management Interface.

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

          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 for the authentication.

   Control interface: The CP uses this interface to deliver service
   entries, and the UP uses this interface to report service events to
   the CP.

   Management interface: The CP uses this interface to deliver basic
   configurations to the UP.  This interface runs on NETCONF.

   Several related drafts describing these interfaces in details exist.
   VXLAN-GPE extention draft for C/U separated BNG is related with
   Servie Interface in [I-D.draft-huang-nov3-vxlan-gpe-extension-for-
   vbng].  The draft YANG data model for CU separated BNG focuses on
   Management Interface, seeing in [I-D.draft-hu-rtgwg-cu-separation-



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   yang-model].  Another two drafts [I-D.draft-cuspdt-rtgwg-cusp-
   requirements] and [I-D.draft-cuspdt-rtgwg-cu-separation-infor-model]
   are related with control interface with information model abstraction
   and suitable protocol discussion.

3.2.  CP and UP of BNG deployment within different districts

               +-------------------+
               |                   |
               |       Internet    |
               |                   |
               +---------^---------+
                         |               +------+ +----+ +---+ +----+
                     +---+---+           |Radius| |DHCP| |EMS| |MANO|
                     |       |           +---+--+ +--+-+ +-+-+ +-+--+
                     |       |               |       |     |     |
                 +---+   CR  +-----+     +---+-------+-----+-----+--+
                 |   |       |     |     |         BNG-CP           |
                 |   |       |     |     +---.--.------------.------+
                 |   +---^---+     +---------.--.--+         .
                 |   ....|....................  .  |         .
                 |   .   |           ............  |         .
                 |   .   +-------+   .             | .........
               +-+---.-+       +-+---.-+       +---+-.-+
               |       |       |       |       |       |
               | BNG-UP|       | BNG-UP|       | BNG-UP|
               |VNF/PNF|       |VNF/PNF|       |VNF/PNF|
               +---^---+       +---^---+       +---^---+
                   |               |               |
                   |               |               |
               +---+---+       +---+---+       +---+---+
               |  OLT  |       |  OLT  |       |  OLT  |
               +---+---+       +---+---+       +---+---+
             +-----|-----+         |         +-----|-----+
         +---+---+   +---+---+ +---+---+ +---+---+   +---+---+
         |USER A1|   |USER A2| |USER B1| |USER C1|   |USER C2|
         +-------+   +-------+ +-------+ +-------+   +-------+

             Figure 2: Cloud BNG Deployed in Several Discticts

   If scubscribers are distributed in serveral districts, CP is deployed
   centrally with UP deployed in different districts closing to
   subscribers.  Thus the deployment model can be a few complex.  Take
   three districts A B C for example.  Here three UPs are placed which
   share one CP.  CP is usually deployed in Core Date Center such as in
   the province datacenter with UP in edge Date Centers such as
   datacenter in cities.  In the Data Centers design, we have core data
   centers and edge data centers according to their location and



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   responsibility.  Core datacenters are often planned in province for
   the control and management, while edge datacenters in cities or towns
   for easy service access.

   In this scenario, centralized CP faces to the subsystems outside and
   communicate with all these UPs for the control and management.

   Under the CP's control, the corresponding traffic is forwarded by UP
   to the Internet.

4.  The Process of BNG with CP and UP in Home Broadband Service

   Take a user Bob accessing to the Internet by Home Broadband Service
   as an example.  The process includs the service traffic from user to
   the internet and signaling traffic between BNG-UP and BNG-CP.  Below
   is the whole process.

   (1)User Bob dialups with packets of PPPoE or IPoE from BNG-UP which
   will send to BNG-CP with its information.  This belongs to signaling
   traffic.

   (2)BNG-CP processes the dialup packets.  Confirming with the outside
   neighboring systems in the management network, BNG-CP makes the
   decision to permit or deny of the dial through certification.  In
   this step, BNG-CP manages resources and generates tables with
   information such as User Infor, IP Infor, QoS Info and etc.  This
   belongs to signaling traffic.

   (3)BNG-CP sends tables to the corresponding UP or choose one UP in
   corresponding UPs.  This belongs to signaling traffic.

   (4)BNG-UP receives the tables, matches rules and performs
   corresponding actions.

   (5)If Bob is certificated and permitted, the UP forwards the traffic
   into the Internet with related policies such as limited bandwidth,
   etc.  Otherwise, Bob is denied to access the Internet.  This belongs
   to service traffic.

   From Step 2 to Step 4, the information model defined in [I-D.draft-
   cuspdt-rtgwg-cu-separation-infor-model] can be used.

5.  High Availability Consideration

   As the BNG-CP takes the responsibility of control and management such
   as communicating with outside systems, generating flow tables and
   managing UP's resources, high availability of the key component
   should be considered.  Some technology is adopted to ensure the



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   reliability, such as N+N or N+K active standby BNG-CP.  N+N active
   standby means 1:1 backup for example, while N+K active standby means
   N:1 backup for example.  When active CP fails, standby CP should take
   the role of active according to some mechanism.  Actually in the
   deployment, resources should be reserved for the backup BNG-CP VNF.

6.  Security Considerations

   None.

7.  IANA Considerations

   None.

8.  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>.

Authors' Addresses

   Rong Gu
   China Mobile
   32 Xuanwumen West Ave, Xicheng District
   Beijing, Beijing  100053
   China

   Email: gurong_cmcc@outlook.com


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

   Email: shujun_hu@outlook.com


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

   Email: wangzitao@huawei.com



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   Fangwei Hu
   ZTE Corporation
   No.889 Bibo Rd
   Shanghai  201203
   China

   Phone: +86 21 68896273
   Email: hu.fangwei@zte.com.cn











































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