Architecture for Control Plane and User Plane Separated BNG
draft-cuspdt-rtgwg-cu-separation-bng-architecture-02
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
|
|
|---|---|---|---|
| Authors | Shujun Hu , Fengwei Qin , Zhenqiang Li , Tee Mong Chua , Donald E. Eastlake 3rd , Zitao Wang , Jun Song | ||
| Last updated | 2018-10-22 | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-cuspdt-rtgwg-cu-separation-bng-architecture-02
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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.
Hu, et al. Expires April 25, 2019 [Page 1]
Internet-Draft Architecture for CU Separated BNG October 2018
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. Code Components extracted from this document must
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:
Hu, et al. Expires April 25, 2019 [Page 2]
Internet-Draft Architecture for CU Separated BNG October 2018
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
Hu, et al. Expires April 25, 2019 [Page 3]
Internet-Draft Architecture for CU Separated BNG October 2018
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:
Hu, et al. Expires April 25, 2019 [Page 4]
Internet-Draft Architecture for CU Separated BNG October 2018
+------------------------------------------------------------------+
| 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
Hu, et al. Expires April 25, 2019 [Page 5]
Internet-Draft Architecture for CU Separated BNG October 2018
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.
Hu, et al. Expires April 25, 2019 [Page 6]
Internet-Draft Architecture for CU Separated BNG October 2018
+----------------------------------+
| |
| 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.
Hu, et al. Expires April 25, 2019 [Page 7]
Internet-Draft Architecture for CU Separated BNG October 2018
(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:
Hu, et al. Expires April 25, 2019 [Page 8]
Internet-Draft Architecture for CU Separated BNG October 2018
+------------------------------------------------------------------+
| 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.
Hu, et al. Expires April 25, 2019 [Page 9]
Internet-Draft Architecture for CU Separated BNG October 2018
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.
Hu, et al. Expires April 25, 2019 [Page 10]
Internet-Draft Architecture for CU Separated BNG October 2018
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
Hu, et al. Expires April 25, 2019 [Page 11]
Internet-Draft Architecture for CU Separated BNG October 2018
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
Hu, et al. Expires April 25, 2019 [Page 12]