Architecture for Control Plane and User Plane Separated BNG
draft-cuspdt-rtgwg-cu-separation-bng-architecture-01
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| Authors | Shujun Hu , Fengwei Qin , Zhenqiang Li , Tee Mong Chua , Zitao Wang , Jun Song | ||
| Last updated | 2018-07-02 | ||
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draft-cuspdt-rtgwg-cu-separation-bng-architecture-01
rtgwg S. Hu
Internet-Draft F. Qin
Intended status: Informational Z. Li
Expires: January 3, 2019 China Mobile
T. Chua
Singapore Telecommunications Limited
Z. Wang
J. Song
Huawei
July 2, 2018
Architecture for Control Plane and User Plane Separated BNG
draft-cuspdt-rtgwg-cu-separation-bng-architecture-01
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
deployed separately at different network layer in actual network.
Status of This Memo
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This Internet-Draft will expire on January 3, 2019.
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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 . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
BNG device is defined as an Ethernet-centric IP edge router, and the
aggregation point for the user traffic. It performs Ethernet
aggregation and packets forwarding via IP/MPLS, and supports user
management, access protocols termination, QoS and policy management,
etc.
This document introduce an 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 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:
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
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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, cloud-based BNG with CU separation
conception is raised [TR-384]. The main idea of Control-Plane and
User-Plane separation method 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
also be introduced by 3GPP 5G architecture [3GPP.23.501].
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. 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
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.
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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
There are two parts of functions in traditional BNG: one is user
access management function, the other is router function. While in
cloud-based BNG, we find out that tearing these two functions apart
can make a difference. Actually the user management function can be
centralized deployed as a concentrated module or device which can be
called BNG-CP (Control Plane). The reserved functions such as router
function and forwarding engine can be deployed in the form of 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 |
| |
| +-------------+ +-----------+ +---------+ +----------+ |
| |Radius Server| |DHCP Server| | EMS | | MANO | |
| +-------------+ +-----------+ +---------+ +----------+ |
+------------------------------------------------------------------+
+------------------------------------------------------------------+
| CU-separated BNG system |
| +--------------------------------------------------------------+ |
| | +----------+ +----------+ +------++------++-----------+ | |
| | | Address | |Subscriber| |Radius||PPPoE/|| UP | | |
| | |management| |management| | ||IPoE ||management | | |
| | +----------+ +----------+ +------++------++-----------+ | |
| | CP | |
| +--------------------------------------------------------------+ |
| |
| |
| |
| +---------------------------+ +--------------------------+ |
| | +------------------+ | | +------------------+ | |
| | | Routing control | | | | Routing control | | |
| | +------------------+ | ... | +------------------+ | |
| | +------------------+ | | +------------------+ | |
| | |Forwarding engine | | | |Forwarding engine | | |
| | +------------------+ UP | | +------------------+ UP| |
| +---------------------------+ +--------------------------+ |
+------------------------------------------------------------------+
Architecture of CU Separated BNG
AS 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 VNFs and hosted in a 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, 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 the service.
Note that the User Plane SHOULD support both physical and virtual
network function. For example, BNG user plane L3 forwarding related
network functions can be disaggregated and distributed across the
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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 and RADIUS: cooperation with the RADIUS server and others
to implement AAA for access users.
(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, 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 |
| |
+----------------------------------+
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 be 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 are introduced in [draft-
cuspdt-rtgwg-cusp-requirements], and the carrying protocol are
presented in [draft-cuspdt-rtgwg-cu-separation-bng-protocol], the
information model of this interface are 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 seprated 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
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 centralized deployed which takes responsibility of a
user control management component managing UP's resources such as the
user entry and forwarding policy. And UP is distributed in the
bottom acting as a network edge and user policy implementation
component.
In order to fulfill a service, Neighboring policy and resource
management systems is deployed outside. In the neighboring system,
different service systems such as RADIUS 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 as following figure:
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+------------------------------------------------------------------+
| Neighboring policy and resource management systems |
| |
| +-------------+ +-----------+ +---------+ +----------+ |
| |Radius 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
None.
6. IANA Considerations
None.
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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>.
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", 2018.
[draft-cuspdt-rtgwg-cu-separation-bng-protocol]
Wang, Z., "Control-Plane and User-Plane separation BNG
control channel Protocol", 2018.
[draft-cuspdt-rtgwg-cu-separation-infor-model]
Wang, Z., "Information Model of Control-Plane and User-
Plane separation BNG", 2018.
[draft-cuspdt-rtgwg-cusp-requirements]
Hu, S., "Requirements for Control Plane and User Plane
Separated BNG Protocol", 2018.
[draft-hu-rtgwg-cu-separation-yang-model]
Hu, F., "YANG Data Model for Configuration Interface of
Control-Plane and User-Plane separation BNG", 2018.
[draft-huang-nov3-vxlan-gpe-extension-for-vbng]
Huang, L., "VXLAN GPE Extension for Packets Exchange
Between Control and User Plane of vBNG", 2017.
[TR-384] "Cloud Central Office Reference Architectural Framework",
BBF TR-384, 2018.
Authors' Addresses
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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
Zitao Wang
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: wangzitao@huawei.com
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Jun Song
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: song.jun@huawei.com
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