INTERNET-DRAFT S. Hu Intended status: Informational F. Qin Z. Li China Mobile T. Chua Singapore Telecommunications Ltd V. Lopez Telefonica D. Eastlake Z. Wang J. Song Huawei Expires: September 10, 2019 March 11, 2019 Architecture for Control Plane and User Plane Separated BNG draft-cuspdt-rtgwg-cu-separation-bng-architecture-04.txt Abstract This document defines an architecture for Broadband Network Gateway (BNG) devices with control plane (CP) and user plane (UP) separation. A BNG-CP is a user control management component while a 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. Distribution of this document is unlimited. Comments should be sent to the authors or the RGTWG working group mailing list: rtgwg@ietf.org. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Hu, et al [Page 1] INTERNET-DRAFT Architecture for CU Separated BNG Table of Contents 1. Introduction............................................3 1.1 Motivation.............................................3 2. Terminology.............................................4 3. CU Separated BNG Architecture...........................5 3.1 Internal Interfaces Between the CP and UP..............7 4. Usage of the CU Separation BNG..........................8 5. Security Considerations................................10 6. IANA Considerations....................................10 Normative References......................................11 Informative References....................................11 Authors' Addresses........................................12 Hu, et al [Page 2] INTERNET-DRAFT Architecture for CU Separated BNG 1. Introduction A Broadband Network Gateway (BNG) device is defined as an Ethernet- centric IP edge router, and the aggregation point for user traffic. It performs Ethernet aggregation and packet forwarding via IP/MPLS, and supports user management, access protocols termination, QoS, policy management, etc. This document describes an architecture for BNG devices with control plane (CP) and user plane (UP) separation. A BNG-CP is a user control management component while a 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 are deployed separately at different network layers in the network. 1.1 Motivation The rapid development of new services, such as 4K TV, 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 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, configuring each device in a network is very tedious 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 for fixed networks, the framework for 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 a 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 concept has also been introduced in the 3GPP 5G architecture [3GPP.23.501]. Hu, et al [Page 3] INTERNET-DRAFT Architecture for CU Separated BNG 2. 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. The following acronyms are used as specified below: AAA: Authentication Authorization Accounting. BNG: Broadband Network Gateway. A broadband remote access server (BRAS (Broadband Access Server), B-RAS or BBRAS) that 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 manages the UP's resources such as the user entry and user's QoS policy DHCP: Dynamic Host Configuration Protocol. EMS: Element Management System. IPoE: IP over Ethernet. MANO: Management and Orchestration. NFV: Network Function Virtualization. NFVI: NFV Infrastructure. PPPoE: Point-to-Point Protocol over Ethernet. 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. Hu, et al [Page 4] INTERNET-DRAFT Architecture for CU Separated BNG 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 that tearing these two functions apart can make a difference. The user management function can be centralized and deployed as a concentrated module or device, called the 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: +------------------------------------------------------------------+ | 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 Figure 1, 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. Hu, et al [Page 5] INTERNET-DRAFT Architecture for CU Separated BNG 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, 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 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 as following: The Control Plane should support: (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 via 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 support: (1) Control plane functions including routing, multicast, and MPLS. (2) Forwarding plane functions including traffic forwarding, QoS and traffic statistics collection. Hu, et al [Page 6] INTERNET-DRAFT Architecture for CU Separated BNG 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. +-----------------------------------+ | | | 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 Service Interface: The CP and UP use this interface to establish tunnels with each other and transmit PPPoE and IPoE packets over those tunnels. VXLAN is commonly used for such tunnels as discussed in [hu-nvo3-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 [cuspdt-rtgwg-cusp-requirements], and the carrying protocol is presented in [cuspdt-rtgwg-cu-separation-bng-protocol] which specifies the Simple Control and User Plane Separation protocol (S- CUSP). The information model of this interface is presented in [cuspdt-rtgwg-cu-separation-infor-model]. Management Interface: The CP uses this interface to deliver configurations to the UP. This interface uses NETCONF [cuspdt-rtgwg-cu-separation-yang-model]. Hu, et al [Page 7] INTERNET-DRAFT Architecture for CU Separated BNG 4. Usage of the CU Separation BNG In the CU separated BNG scenario, there are several processes when a home user accesses the Internet: (1) User dialup packets via PPPoE or IPoE from the BNG-UP are sent to the BNG-CP through the BNG-UP's Service Interface. (2) BNG-CP processes the dialup packet. Confirming the user's authorization with the outside neighboring systems in the management network, the BNG-CP makes the decision to permit or deny the user access. (3) After that, the BNG-CP tells the UP to do perform authorized forwarding actions with appropriate QoS policies. (4) If the user is certificated and permitted, the UP forwards the traffic into the Internet with appropriate QoS policies such as limited bandwidth, etc. Otherwise, the user is denied to access the Internet. In actual deployments, a CU separated BNG device is composed of a CP and one or more UPs. The CP is usually centrally deployed and takes responsibility as a user control management component managing UP's resources such as the user entry and forwarding policy. The UPs are distributed and act as a network edge and user policy implementation component. In order to fulfill a service, neighboring policy and resource management systems are deployed outside the BNG. In the neighboring systems, different service systems such as RADIUS/DIAMETER server, DHCP server and EMS are included. If a BNG-CP is virtualized as a NFV, the NFVI management system MANO is also included here. A BNG-CP has connections with the outside neighboring systems to transmit management traffic. The deployment scenario is shown in the following figure: Hu, et al [Page 8] INTERNET-DRAFT Architecture for CU Separated BNG +------------------------------------------------------------------+ | Neighboring policy and resource management systems | | | | +-------------+ +-----------+ +---------+ +----------+ | | | AAA Server| |DHCP Server| | EMS | | MANO | | | +-------------+ +-----------+ +---------+ +----------+ | +------------------------+-----------------------------------------+ | | +-----------------+-----------------+ | | | BNG-CP | | | +-+-----------+------------+--------+ Service| Control| Management| ||| Interface| Interface| Interface| ||| (VXLAN)| (CUSP)| (NETCONF)| ||| | | | ||| +-+-----------+------------+-+ +---------------------------+ | | | | | BNG-UP | | BNG-UP... | | | | | +-------+--------------------+ +---------------+-----------+ | | | | +-------------+-------------+ +--------------+------------+ | | | | | Access Network | | Access Network | | | | | +-+-----------+-----------+-+ +-+---------+----------+----+ | | | | | | | | | | | | +--+---+ +----+-+ +---+--+ +----+-+ +----+-+ +--+---+ |User11| |User12| ... |User1N| |User21| |User22| ... |User2N| +------+ +------+ +------+ +------+ +------+ +------+ Figure 3. Deployment Example Hu, et al [Page 9] INTERNET-DRAFT Architecture for CU Separated BNG 5. Security Considerations The Service, Control, and Management Interfaces between the CP and UP might be across the general Internet or other hostile environment. Thus, appropriate protections MUST be implemented to provide integrity, authenticity, and secrecy of traffic over those interfaces. For example, the implementation of IPSEC, DTLS, or TLS as appropriate. However, such security protocols need not always be used and lesser security precautions might be appropriate because, in some cases, the communication between the CP and UP might be in a more benign environment. 6. IANA Considerations This document requires no IANA actions. Hu, et al [Page 10] INTERNET-DRAFT Architecture for CU Separated BNG 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, . Informative References [_3GPP.23.501] "System Architecture for the 5G System", 3GPP GPP TS 23.501 15.0.0, 2018. [cuspdt-rtgwg-cu-separation-bng-deployment] Gu, R., "Deployment Model of Control Plane and User Plane Separated BNG", draft- cuspdt-rtgwg-cu-separation-bng-deployment, work in progress, 2018. [cuspdt-rtgwg-cu-separation-bng-protocol] Wang, Z., "Control-Plane and User-Plane separation BNG control channel Protocol", draft-cuspdt-rtgwg-cu-separation-bng-protocol, work in progress, 2018. [cuspdt-rtgwg-cu-separation-infor-model] Wang, Z., "Information Model of Control-Plane and User- Plane separation BNG", draft- cuspdt-rtgwg-cu-separation-infor-model, work in progress, 2018. [cuspdt-rtgwg-cusp-requirements] Hu, S., "Requirements for Control Plane and User Plane Separated BNG Protocol", draft-cuspdt- rtgwg-cusp-requirements, work in progress, 2018. [cuspdt-rtgwg-cu-separation-yang-model] Hu, F., "YANG Data Model for Configuration Interface of Control-Plane and User-Plane separation BNG", draft-cuspdt-rtgwg-cu-separation-yang- model, work in progress, 2018. [hu-nov3-vxlan-gpe-extension-for-vbng] Huang, L., "VXLAN GPE Extension for Packets Exchange Between Control and User Plane of vBNG", draft-hu-nvo3-vxlan-gpe-extension-for-vbrg, work in progress, 2017. [TR-384] Broadband Forum, "Cloud Central Office Reference Architectural Framework", BBF TR-384, 2018. Hu, et al [Page 11] INTERNET-DRAFT Architecture for CU Separated BNG 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 Victor Lopez Telefonica Spain Email: victor.lopezalvarez@telefonica.com Hu, et al [Page 12] INTERNET-DRAFT Architecture for CU Separated BNG Donald Eastlake, 3rd Huawei Technologies 1424 Pro Shop Court Davenport, FL 33896 USA Phone: +1-508-333-2270 Email: d3e3e3@gmail.com Zitao Wang Huawei Technologies 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: wangzitao@huawei.com Jun Song Huawei Technologies 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: song.jun@huawei.com Hu, et al [Page 13] INTERNET-DRAFT Architecture for CU Separated BNG Copyright, Disclaimer, and Additional IPR Provisions Copyright (c) 2019 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 Provisions Relating to IETF Documents (http://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. Hu, et al [Page 14]