rtgwg S. Hu Internet-Draft China Mobile Intended status: Informational V. Lopez Expires: April 25, 2019 Telefonica F. Qin Z. Li China Mobile T. Chua Singapore Telecommunications Limited Donald. Eastlake M. Wang J. Song Huawei October 22, 2018 Requirements for Control Plane and User Plane Separated BNG Protocol draft-cuspdt-rtgwg-cusp-requirements-03 Abstract This document introduces the Control Plane and User Plane separated BNG (Broadband Network Gateway) architecture and defines a set of associated terminology. It also specifies a set of protocol requirements for communication between the BNG-CP and the BNG-UPs in the Control Plane and User Plane Separated BNG. 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. Hu, et al. Expires April 25, 2019 [Page 1] Internet-Draft Requirements for CUSP October 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 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 2. Concept and Terminology . . . . . . . . . . . . . . . . . . . 3 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 3. CU Separated BNG Model . . . . . . . . . . . . . . . . . . . 3 3.1. Internal interfaces between the CP and UP . . . . . . . . 5 4. The usage of CU separation BNG protocol . . . . . . . . . . . 6 5. Control Plane and User Plane Separation Protocol Requirements 7 5.1. Transmit information tables . . . . . . . . . . . . . . . 7 5.2. Message Priority . . . . . . . . . . . . . . . . . . . . 7 5.3. Reliability . . . . . . . . . . . . . . . . . . . . . . . 7 5.4. Support for Secure Communication . . . . . . . . . . . . 8 5.5. Version negotiation . . . . . . . . . . . . . . . . . . . 8 5.6. Capability Exchange . . . . . . . . . . . . . . . . . . . 9 5.7. CP primary/backup capability . . . . . . . . . . . . . . 9 5.8. Event Notification . . . . . . . . . . . . . . . . . . . 9 5.9. Query Statistics . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction A Broadband Network Gateway (BNG) is an Ethernet-centric IP edge router and the aggregation point for user traffic. To provide centralized session management, flexible address allocation, high scalability for subscriber management capacity, and cost-efficient redundancy, the CU separated BNG is introduced [TR-384]. The CU separated Service Control Plane could be virtualized and centralized; Hu, et al. Expires April 25, 2019 [Page 2] Internet-Draft Requirements for CUSP October 2018 it is responsible for user access authentication and sending forwarding entries to user planes. The routing control and forwarding plane, i.e. BNG user plane (local), could be distributed across the infrastructure. This document introduces the Control Plane and User Plane separated BNG architecture and modeling. This document also defines the protocol requirements for Control Plane and User Plane Separated BNG (CUSP). 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) 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 UP's resources such as the user entry and user's QoS policy. CUSP: Control Plane and User Plane Separated BNG Protocol. 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. 3. CU Separated BNG Model Figure 1 shows the architecture of CU separated BNG Hu, et al. Expires April 25, 2019 [Page 3] Internet-Draft Requirements for CUSP October 2018 +------------------------------------------------------------------+ | 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| | | +---------------------------+ +--------------------------+ | +------------------------------------------------------------------+ Figure 1. Architecture of CU Separated BNG Briefly, a CU separated BNG is made up of a Control Plane (CP) and a set of User Planes (UPs) [TR-384], [I-D.cuspdt-rtgwg-cu-separation- bng-deployment]. The Control Plane is a user control management component which manages UP's resources such as the user entry and user's Quality of Service (QoS) policy, for example, the access bandwidth and priority management. This Control Plane could be virtualized and centralized. The functional modules inside the BNG Service Control Plane can be implemented as Virutl 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, update, and maintenance of channels between control planes and user planes [TR-384], [I- D.cuspdt-rtgwg-cu-separation-bng-deployment]. The User Plane (UP) is a network edge and user policy implementation component. It can support the forwarding plane functions on traditional BNG devices, Hu, et al. Expires April 25, 2019 [Page 4] Internet-Draft Requirements for CUSP October 2018 such as traffic forwarding, QoS, and traffic statistics collection, and it can also support the control plane functions on traditional BNG devices, such as routing, multicast, etc [TR-384], [I-D.cuspdt- rtgwg-cu-separation-bng-deployment]. 3.1. Internal interfaces between the CP and UP To support communication between the Control Plane and User Plane, several interfaces are involved. Figure 2 illustrates the three internal interfaces of CU Separated BNG. +----------------------------------+ | | | BNG-CP | | | +--+--------------+--------------+-+ | | | 1.Service | 2.Control | 3.Management| Interface | Interface | Interface | | | | +--+--------------+--------------+-+ | | | BNG-UP | | | +----------------------------------+ Figure 2. Interfaces between the BNG-CP and the BNG-UP 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. 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 configurations to the UP. This interface uses NETCONF. The CUSP (Control plane and User plane Separated BNG protocol) defines the control interface, and specifies the communication between the centralized control plane and user planes. This protocol should be designed to support establishing and maintaining a conversation between CP and UPs, and transporting the tables that are specified in [draft-cuspdt-rtgwg-cu-separation-infor-model]. Hu, et al. Expires April 25, 2019 [Page 5] Internet-Draft Requirements for CUSP October 2018 4. The usage of CU separation BNG protocol ----------------- //// \\\\ //// \\\\ // Cloud \\ | | | | | | | | | +-----------------+ | | | Control Plane | | \\ | | // \\\\ +------+----------+ //// \\\\ | //// ----+------------ | Control Interface (CUSP) +--------+----------+-------------+-----+ | | | | User's information IP address QoS: ....... May Include: | CIR; : User ID; | PIR; | User MAC; | CBS; | Access method(PPPoE, | PBS; | IPoE, etc) | ...... ..... | | | +-------------------V--------------+ | +-----------+ | ------- | /// \\\ +------+ +-------v---------+ +--------+ | | | OLT | | User Plane | | Core | | Internet | | +-------+ +-------+ Routing+-----+ | +------+ +-----------------+ +--------+ \\\ /// ------- Figure 3. CU Separation BNG protocol usage As shown in Figure 3, when users access the BNG network, the control plane solicits user information (such as user's ID, user's MAC, user's access methods, for example via PPPoE/IPoE), associates users with available bandwidth which is reported by User planes, and, based on the service's requirement, generates a set of tables, which may include user's information, UP's IP segment, and QoS, etc. Then the control plane can transmit these tables to the User planes. User Hu, et al. Expires April 25, 2019 [Page 6] Internet-Draft Requirements for CUSP October 2018 planes receive these tables, parse them, and then perform corresponding actions. 5. Control Plane and User Plane Separation Protocol Requirements This section specifies the requirements for the CU separation protocol. 5.1. Transmit information tables The Control Plane and User Plane Separation Protocol MUST allow the CP to send tables to each User Plane device. a) The current BNG service requires that the UP should support at least 2000 users being accessed every second. And every user requires at least 2000 bytes. To achieve high performance, the CU Separation protocol SHOULD be lightweight. b) CU separation protocol should support data encoded as either XML or binary. It allows user information data to be read, saved, and manipulated with tools specific to XML or binary. c) In order to provide centralized session management, high scalability for subscriber management capacity, and cost-efficient redundancy, batching ability should be provided. The CU Separation protocol should be able to group an ordered set of commands to a UP device. Each such group of commands SHOULD be sent to the UP in as few messages as practical. Furthermore, the protocol MUST support the ability to specify if a command group MUST have all-or-nothing semantics. d) The CU Separation protocol SHOULD be able to support at least hundreds of UP devices and tens of thousands of ports. For example, the protocol field sizes corresponding to UP or port numbers SHALL be large enough to support the minimum required numbers. This requirement does not relate to the performance of the system as the number of UPs or ports in the system grows. 5.2. Message Priority The CU Separation protocol MUST provide a means to express the protocol message priorities. 5.3. Reliability Heartbeat is a periodic signal generated by hardware or software to test for some aspects of normal operation or to synchronize other parts of network system. Hu, et al. Expires April 25, 2019 [Page 7] Internet-Draft Requirements for CUSP October 2018 In the CU separation BNG, a heartbeat is sent between CP and UPs at a regular interval on the order of seconds. If the CP/UP does not receive a heartbeat for a time--usually a few heartbeat intervals-- the CP/UP that should have sent the heartbeat is assumed to have failed. The CU separation protocol should support some kind of heartbeat monitoring mechanism. And this mechanism should have ability to distinguish whether the interruption is an actual failure. For example, in some scenarios (i.e. CP/UP update, etc), the connection between the UP and CP need to be interrupted. In this case, the interruption should not be reported. 5.4. Support for Secure Communication As mentioned above, CP may send some information tables to the UP which may be critical to the network function (e.g, User Information, IPv4/IPv6 information) and may reflect the business information (e.g, QoS, service level agreements, etc). Therefore, supporting the integrity of all CU Separation protocol messages and protecting against man-in-the-middle attacks MUST be supported. The CP Separation protocol should support security in a variety of scenarios. For example, the connections between the CP and UPs could be dedicated lines, VPNs within one domain, or could cross several domains, that is, cross third party networks. Thus it is likely that more than one security mechanism SHOULD be supported. TLS and IPsec are good candidates for such mechanisms. 5.5. Version negotiation The CU separated BNG may consist of different vendors' devices implementing different versions of protocol. Threfore, the CU separation protocol MUST provide some mechanisms to perform the version negotiation. Version negotiation is the process that the CU separated BNG's Control-Plane uses to evaluate the protocol versions supported by both the control-plane and the user-plane devices. Then a suitable protocol version is selected for communication in CUSP. The process is a "negotiation" because it requires identifying the most recent protocol version that is supported by both the control-plane and the user-plane devices or determining that they have no version in common. Hu, et al. Expires April 25, 2019 [Page 8] Internet-Draft Requirements for CUSP October 2018 5.6. Capability Exchange The UP Capability Report displays the device's profile, service capability, and other assigned capabilities within the CU separated BNG. The CU separation protocol should MUST provide some mechanism to exchange the UP device's capabilities. 5.7. CP primary/backup capability A backup CP for failure recovery is required for the CU separated BNG network. And the CUSP should provide some mechanism to implement the backup CP: a) In some scenarios, there may be two CP devices both declaring the primary CP. Thus the CUSP should support or associate with some mechanisms to determine which CP is the primary device. b) In the scenario of the primary CP down, the CUSP should support switching between primary and backup CP. 5.8. Event Notification The CUSP protocol SHOULD be able to asynchronously notify the CP of events on the UP such as failures and changes in available resources and capabilities. Some scenarios that may initiate event notifications are listed below. a) Sending response message: As mentioned above, the control plane solicits users' information, associates them with available bandwidth, and generates a set of tables based on the service's requirement. Then the control plane transmits these tables to the conresponding User plane. The UP should respond with an event notification to inform the CP that the tables are received. b) User trace: The user trace mechanism can support the Control Plane tracing and monitoring the network status for users (for example the real-time bandwidth, etc), to help debug the user's application. Therefore, the UPs SHOULD be able to notify the CP with the User trace message. c) Sending statistics parameters: In CU separation BNG, the User- plane will report the traffic statistics parameters to the Control-plane, such as the ingress packets, ingress bytes, egress packets, egress bytes, etc. These parameters can help measure the BNG network performance. Available network resources can be allocated basing on the statistics parameters by the BNG-CP. Therefore, the UPs SHOULD be able to notify the CP with statistics parameters. Hu, et al. Expires April 25, 2019 [Page 9] Internet-Draft Requirements for CUSP October 2018 d) Report the result of User Detect: "User Detect" message will be send periodically to detect user dial-up and disconnect. The UPs SHOULD be able to notify the CP with the result of User Detect. 5.9. Query Statistics The CUSP protocol MUST provide a means for the CP to be able to query statistics (performance monitoring) from the UP. 6. Security Considerations As this is an Informational requirements document, detailed technical Security Considerations are not included. However, Section 5.4 covers general security requirements and Section 5.7 covers backup requirements relevant to some denial of service scenarios. 7. IANA Considerations This document requires no IANA actions. 8. References 8.1. Normative References [I-D.cuspdt-rtgwg-cu-separation-bng-deployment] Gu, R., Hu, S., and Z. Wang, "Deployment Model of Control Plane and User Plane Separation BNG", draft-cuspdt-rtgwg- cu-separation-bng-deployment-00 (work in progress), October 2017. [I-D.cuspdt-rtgwg-cu-separation-infor-model] Wang, Z., Gu, R., Lopezalvarez, V., and S. Hu, "Information Model of Control-Plane and User-Plane separation BNG", draft-cuspdt-rtgwg-cu-separation-infor- model-00 (work in progress), February 2018. [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, . Hu, et al. Expires April 25, 2019 [Page 10] Internet-Draft Requirements for CUSP October 2018 8.2. Informative References [TR-384] Broadband Forum, ""Cloud Central Office Reference Architectural Framework",", BBF TR-384, January. 2018. Authors' Addresses Shujun Hu China Mobile 32 Xuanwumen West Ave, Xicheng District Beijing, Beijing 100053 China Email: shujun_hu@outlook.com Victor Lopez Telefonica Sur 3 building, 3rd floor, Ronda de la Comunicacion s/n Madrid 28050 Spain Email: victor.lopezalvarez@telefonica.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 Hu, et al. Expires April 25, 2019 [Page 11] Internet-Draft Requirements for CUSP October 2018 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 Michael 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]