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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 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]