INTERNET-DRAFT S. Hu Intended status: Proposed Standard China Mobile D. Eastlake Z. Wang Huawei F. Qin Z. Li China Mobile J. Song Huawei T. Chua Singapore Telecommunications Ltd Expires: May 29, 2018 November 30, 2018 Control-Plane and User-Plane Separation BNG Control Channel Protocol draft-cuspdt-rtgwg-cu-separation-bng-protocol-03.txt Abstract This document specifies the CU Separation Broadband Network Gateway (BNG) control channel Protocol (CUSP) for communications between a Control Plane (CP) and a set of User Planes (UPs). CUSP is designed to be flexible and extensible so as to easily allow for the addition of further messages and objects, should further requirements be expressed in the future. Status of This Memo This Internet-Draft is submitted to IETF 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 CU Separation Protocol Table of Contents 1. Introduction............................................3 2. Concept and Terminology.................................4 2.1 Terminology............................................4 3. Protocol Overview.......................................5 3.1 Initialization Phase...................................5 3.2 Network Resource Report................................5 3.3 IPoE Session Establishment.............................6 3.4 PPPoE Session Establishment............................7 3.5 Setting the User's QoS Information.....................9 3.6 CUSP Session Statistics...............................10 4. CUSP Common Header.....................................11 5. Objective Message Formats..............................12 5.1 Objective TLV Format..................................12 6. Control Message Format.................................14 6.1 Control TLV Format....................................14 6.2 Hello Message.........................................15 6.3 Statistics Message....................................15 7. Event TLV Format.......................................17 7.1 Event TLV Format......................................17 7.2 USER_TRAFFIC_INFORMATION Message......................18 7.3 USER_DETECT_RESULT_INFORMATION Message................18 8. Resource Report TLV Format.............................20 8.1 Resource Report TLV Format............................20 9. Error Message Format..................................21 10. Security Considerations...............................22 11. IANA Considerations...................................22 11.1 Message Types........................................22 11.2 TLV Types Values.....................................22 11.3 ERRID Codes..........................................22 Normative References......................................23 Informative References....................................23 Authors' Addresses........................................24 Hu, et al [Page 2] INTERNET-DRAFT CU Separation Protocol 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 Control/User (CU) separated BNG is descried in [TR-384]. The CU separated Service Control Plane, which is responsible for user access authentication and setting forwarding entries in User Planes, can be virtualized and centralized. The routing control and forwarding plane, i.e. the BNG user plane (local), can be distributed across the infrastructure. This document specifies the CU Separation BNG control channel Protocol (CUSP) for communications between a BNG Control Plane (CP) and a set of User Planes (UPs). CUSP is designed to be flexible and extensible so as to easily allow for additional messages and objects, should further requirements be expressed in the future. Hu, et al [Page 3] INTERNET-DRAFT CU Separation Protocol 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. CP is a user control management component which supports the management of the UP's resources such as the user entry and forwarding policy. CU: Control / User. CUSP: Control and User Separate 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. Hu, et al [Page 4] INTERNET-DRAFT CU Separation Protocol 3. Protocol Overview 3.1 Initialization Phase UP CP | | | TCP Session Establishment | |<----------------------------->| | | | | | HELLO (version) | |------------------------------>| | | | | | HELLO (version) | |<----------------------------- | | | | | The initialization phase consists of two successive steps: 1) Establishment of a TCP connection (3-way handshake) between the CP and the UP using port tbd1. 2) Establishment of a CUSP session over the TCP connection. Once the TCP connection is established, the CP and the UP initialize the CUSP session during which the version negotiation is performed. The version information is carried within Hello messages (see Section 6.2). If the CUSP session establishment phase fails because the CP or UP disagree on the version parameters or one of the CP or UP does not answer after the expiration of the establishment timer, the TCP connection is immediately closed. 3.2 Network Resource Report The CP configures the BNG's access interface via NETCONF, and UPs report the attributes of their interfaces and slots. Hu, et al [Page 5] INTERNET-DRAFT CU Separation Protocol UP CP | | | slot attributes report | | via CUSP | |----------------------------->| | | | port attributes report | | via CUSP | |----------------------------->| | | | Configure BNG access | | interface via NETCONF | |<---------------------------->| | | | | Details of the Resource Report Message can be found in Sections 8. 3.3 IPoE Session Establishment UP CP | | | UP reports its resources | |----via CUSP------------------->| | | | Configure BNG access | |<---interface via NETCONF-------| | | | CP sends ACCESS_IF_INFO | |<---to UPs via CUSP-------------| | | | User dialup via VXLAN | |<------------------------------>| | | | CP sends USER_BASEC_INFO | |<---to UPs via CUSP-------------| | | | CP sends USER_IPV4_INFO | |<---to UPs via CUSP-------------| | | | CP sends ROUTEV4 INFO | |<---to UPs via CUSP-------------| | | | UP reports the USER_DETECT_RESULT_INFO |----to CP via CUSP------------->| | | | UP reports the USER_TRAFFIC_INFO |----to CP via CUSP------------->| Hu, et al [Page 6] INTERNET-DRAFT CU Separation Protocol | | Once a CUSP session has been established, if an IPoE session is required, the UPs report attributes of the interfaces and slots to be used for the IPoE session via CUSP, and the CP initiate a NETCONF session to configure the requested access interface of BNG. Once the above process has been accomplished, the CP sends to the UP the ACCESS_IF_INFO (Access Interface Information) message that contains a variety of objects that specify the set of constrains and attributes for the BNG access interface. For example, ifname = 0001 [RFC2863], BNG service enable, IPv4 connection trigger enable, neighbor detection enable, etc. Then the user dials up via VXLAN, the CP sends to the UP the USER_BASIC_INFOR message USER_IPV4_INFOR, and USER_ROUTEV4_INFO that contains a variety of objects that specify the attributes for the user's basic information, user's ipv4 information, and routing information. Upon receiving the above messages from a CP, the UPs reports the user detection results and user's traffic status via the USER_DETECT_RESULT_INFO message and USER_TRAFFIC_INFO, message. 3.4 PPPoE Session Establishment Hu, et al [Page 7] INTERNET-DRAFT CU Separation Protocol UP CP | | | UP reports the resources | |----via CUSP------------------->| | | | Configure BNG access | |<-------interface via NETCONF-->| | | | CP sends ACCESS_IF_INFO | |<---to UPs via CUSP-------------| | | | User dialup via VXLAN | |<------------------------------>| | | | CP sends USER_BASEC_INFO | |<---to UPs via CUSP-------------| | | | CP sends USER_IPV4_INFO | |<---to UPs via CUSP-------------| | | | CP sends ROUTEV4 INFO | |<---to UPs via CUSP-------------| | | | CP sends USER_PPP_INFO | |<---to UPs via CUSP-------------| | | | UP reports the USER_DETECT_RESULT_INFO |----to CP via CUSP------------->| | | | UP reports the USER_TRAFFIC_INFO |----to CP via CUSP------------->| | | Once a CUSP session has been established, if an PPPoE session is required, the UPs report attributes of the corresponding interfaces and slots to be used for the PPPoE session via CUSP, and the CP initiate a NETCONF session to configure requested access interface of the BNG. Once the above process has been accomplished, the CP sends to the UP the ACCESS_IF_INFO (Access Interface Information) message that contains a variety of objects that specify the set of constrains and attributes for the BNG access interface. For example, ifname = 0001 [RFC2863], BNG service enable, IPv4 connection trigger enable, neighbor detection enable, etc. Then the user dials up via VXLAN, the CP sends to the UP the USER_BASIC_INFOR message, the USER_PPP_INFO message, USER_IPV4_INFOR message, and USER_ROUTEV4_INFO message that contains a variety of objects that specify the attributes of the user's basic information, Hu, et al [Page 8] INTERNET-DRAFT CU Separation Protocol user's PPP information, user's ipv4 information, and routing information. Upon receiving the above messages from a CP, the UPs reports the user detection results and user's traffic status via USER_DETECT_RESULT_INFO message and USER_TRAFFIC_INFO, etc. 3.5 Setting the User's QoS Information UP CP | | | UP reports the resources | |----via CUSP------------------->| | | | Configure BNG Access interface |<-----via NETCONF---------------| | | | Configure QOS template | |<-----via NETCONF---------------| | | | User dials up via VXLAN | |<---CP sends objective TLV/Event| | report, etc. | | | | CP sends USER_QOS_INFO | |<---to UPs via CUSP-------------| | | Once a CUSP session has been established, if a user's Quality of Service (QoS) needs to be set dynamically, then the UPs report attributes of the relevant interfaces and slots via CUSP, and the CP initiate a NETCONF session to configure the requested access interfaces of the BNG and User's configuration template. Then the user dials up via VXLAN, the CP sends the USER_BASIC_INFOR message, USER_IPV4_INFOR message, and USER_ROUTEV4_INFO message to the UP, the UPs reports the user detection results and user's traffic status. Once above process has been accomplished, the CP sends the USER_QOS_AUTH_INFO message to the UPs; this message contains a variety of objects that specify the set of constrains and attributes for the user's required QoS. (The format of these QoS attributes should be parallel to the QoS configuration templates.) Hu, et al [Page 9] INTERNET-DRAFT CU Separation Protocol 3.6 CUSP Session Statistics UP CP | | | | |<-----statistic_REQUEST ------------| | | |------statistic_REQUEST (ACK)------>| | | |------statistic_BEGIN-------------->| | | |<-----statistic_BEGIN (ACK)---------| | | |------statistic_DATA--------------->| | | |------statistic_END---------------->| | | |<-----statistic_END (ACK)-----------| | | | | If the CUSP session goes down, the CU separation BNG is required to save the users' information. And if the CUSP session restarts, the CP may request that the UP send the previous session's statistics to synchronize user information. The above figure shows this process, and the details of the session statistic message can be found in Sections 6.3. Hu, et al [Page 10] INTERNET-DRAFT CU Separation Protocol 4. CUSP Common Header A CUSP message consists of a common header followed by a variable- length body made of a set of objects. Receiving a CUSP message with a missing mandatory object MUST trigger an Error message (see Section 5.6). Conversely, if an object is optional, the object may or may not be present. Common header: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message-Type |F| Resv | Message-Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transaction id | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ CUSP Message Common Header Message-Type (8 bits): The following message types are defined in this document: Value Meaning ----- ------------------ 1 Update objective 2 Hello 3 statistics Request 4 statistics Begin 5 statistics Data 6 statistics End 7 Source Report 8 Event Report 9 Error F (1 bit): Setting the F bit to one enables the control message ACK mode and setting the F bit to zero disables that mode. Resv (7 bits): Reserved bits. They MUST be set to zero on transmission and MUST be ignored on receipt. Message-Length (16 bits): Total length of the CUSP message including the common header, expressed in bytes as an unsigned integer. Transaction ID (32 bits): This field is used to identify requests. It is echoed back in the corresponding ACK / response / Error message. Hu, et al [Page 11] INTERNET-DRAFT CU Separation Protocol 5. Objective Message Formats CUSP objects have a common format. They begin with a CUSP common header (see Section 4). This is followed by object-specific fields defined for each different object. The object may also include one or more type-length-value (TLV) encoded data sets. Each TLV has the same structure as described in Section 5.1. 5.1 Objective TLV Format A CUSP object may include a set of one or more optional TLVs. All CUSP objective TLVs have the following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | TLV-Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 2 bytes TLV-Length: 2 bytes Value: variable A CUSP objective TLV is comprised of 2 bytes for the type, 2 bytes specifying the TLV-Length, and a value field. The Type and TLV-Length fields are unsigned integers. The first 4 bits of Type field indicate the operation of this TLV, currently, there are two types: 0 - update the objectives; 1 - delete the object. Updating a non-existent object creates it. The remaining bits of the Type field indicate the TLV's type (4-15 bits) which is the object to which it applies. The following objects / types are currently defined: Value Meaning ----- -------------- 0 USER_BASIC_INFO 1 USER_PPP_INFO 2 ACCESS_IFSRV_INFO 3 USER_IPV4_INFO 4 USER_IPV6_INFO 5 USER_QOS_AUTH_INFO 6 ROUTEV4_INFO 7 ROUTEV6_INFO 8 STATIC_USER_INFO Hu, et al [Page 12] INTERNET-DRAFT CU Separation Protocol The TLV-Length field defines the length of the value portion in bytes. The TLV is padded to 4-bytes alignment; padding is not included in the Length field (so a 3-byte value would have a length of 3, but the total size of the TLV would be 8 bytes). Unrecognized TLVs MUST be ignored. IANA management of the CUSP Object TLV type identifier codespace is described in Section 11. The details of the attributes of the Objective TLV are specified in Section 4.1 of [InforModel]. Hu, et al [Page 13] INTERNET-DRAFT CU Separation Protocol 6. Control Message Format CUSP Control messages have a common format. They begin with the CUSP common header (see Section 4) followed by control TLVs fields for the different control operations. It may also include one or more type- length-value (TLV) encoded control data sets. Each TLV has the same structure as described in Section 6.1. For each CUSP message type, rules are defined that specify the set of objects that the message can carry. We use the Backus-Naur Form (BNF) (see [RFC5511]) to specify such rules. Square brackets refer to optional sub-sequences. An implementation MUST form the CUSP messages using the object ordering specified in this document. 6.1 Control TLV Format A CUSP control may include a set of one or more optional TLVs. All CUSP control TLVs have the following format: Type: 2 bytes TLV-Length: 2 bytes Value: variable A CUSP control TLV consists of 2 bytes for the type, 2 bytes specifying the TLV length, and a value field. Control Type (8 bits): The following message types are currently defined: Value Meaning ----- ---------- 0 Hello 1 Statistics The Length field defines the length of the value portion in bytes. The TLV is padded to 4-bytes alignment; padding is not included in the Length field (so a 3-byte value would have a length of 3, but the total size of the TLV would be 8 bytes). Unrecognized TLVs MUST be ignored. IANA management of the CUSP Object TLV type identifier codespace is described in Section 11. Hu, et al [Page 14] INTERNET-DRAFT CU Separation Protocol 6.2 Hello Message The Hello message is a CUSP message sent by a UP to a CP and by a CP to a UP in order to establish a CUSP session. The Type field of the CUSP common header for the Hello message is set to 2. Once the TCP connection has been successfully established, the first message sent by the UP to the CP or by the CP to the UP MUST be a Hello message. Any message received prior to a Hello message MUST trigger a protocol error condition causing an ERROR message to be sent with Error-Type Version_ Negotiation_Failed and the CUSP session establishment attempt MUST be terminated by closing the TCP connection. The Hello message is used to establish a CUSP session between the CUSP peers. During the establishment phase, the CUSP peers exchange version information. If both parties agree on such version negotiation, the CUSP session is successfully established. The format of a Hello message is as follows: ::= :: = Version (4 bytes): specifies the CP/UP supported CUSP's version, currently, the version is 1. 6.3 Statistics Message If the CUSP session goes down, the CU separation BNG is required to preserve the users' information. If the CUSP session restarts, the CP may request the UP to report the previous session's statistics to synchronize user information. The Type field of the CUSP common header for the Statistics messages is set to 3, 4, 5, or 6. The format of a Statistics message is as follows: ::= ::= ClassID (2 bytes): This field specifies the statistics type of CUS session, the following statistics types are currently defined: Hu, et al [Page 15] INTERNET-DRAFT CU Separation Protocol Value Meaning ----- ------------------------------- 0 objective message statistic 1 Source report message statistic 2 Event report message statistic Event (2 bytes): specified the Statistics message's subtypes, the following subtypes are currently defined: Value Meaning ----- ------- 0 request Statistics message 1 begin Statistics message 2 Statistics data message 3 End Statistics message Note that, the event value MUST be synchronized with the type of comment header. Hu, et al [Page 16] INTERNET-DRAFT CU Separation Protocol 7. Event TLV Format CUSP Event TLVs have a common format. They begin with a CUSP common header (see Section 4). It is followed by Event TLV fields defined for each different Events. It may also include one or more type- length-value (TLV) encoded Event data sets. Each TLV has the same structure as described in Section 7.1. For each CUSP message type, rules are defined that specify the set of objects that the message can carry. We use the Backus-Naur Form (BNF) (see [RFC5511]) to specify such rules. Square brackets refer to optional sub-sequences. An implementation MUST form the CUSP messages using the object ordering specified in this document. 7.1 Event TLV Format A CUSP Event may include a set of one or more optional TLVs. All CUSP Event TLVs have the following format: Type: 2 bytes Length: 2 bytes Value: variable A CUSP Event TLV consists of 2 bytes for the type, 2 bytes specifying the TLV length, and a value field. Event Type (8 bits): The following message types are currently defined: Type Meaning ----- ------------------------------ 0 USER_TRAFFIC_INFORMATION 1 USER_DETECT_RESULT_INFORMATION The Length field defines the length of the value portion in bytes. The TLV is padded to 4-bytes alignment; padding is not included in the Length field (so a 3-byte value would have a length of 3, but the total size of the TLV would be 8 bytes). Unrecognized TLVs MUST be ignored. IANA management of the CUSP Object TLV type identifier codespace is described in Section 11. Hu, et al [Page 17] INTERNET-DRAFT CU Separation Protocol 7.2 USER_TRAFFIC_INFORMATION Message The USER_TRAFFIC_INFORMATION Message be used by the UP to reported the user's traffic statistics. The format of a USER_TRAFFIC_INFORMATION message is as follows: ::= ::= USER_ID (4 bytes): is the identifier of user. This parameter is unique and mandatory. This attribute is used to distinguish different users. StatisticsType (4 bytes): be used to indicate the Statistics type, the following types are currently defined: Value Meaning ----- ----------------------- 0 IPv4 traffic statistics 1 IPv6 traffic statistics IngressPackets (8 bytes): be used to present the ingress packets. IngressBytes (8 bytes): be used to present the ingress bytes. EgressPackets (8 bytes): be used to present the egress packets. EgressBytes (8 bytes): be used to present the egress bytes. 7.3 USER_DETECT_RESULT_INFORMATION Message The USER_TRAFFIC_INFORMATION Message is used to reported the failure of user detection by the UP. The format of a USER_DETECT_RESULT_INFORMATION message is as follows: ::= ::= USER_ID (4 bytes): is the identifier of user. This parameter is unique and mandatory. This attribute is used to distinguish different users. Hu, et al [Page 18] INTERNET-DRAFT CU Separation Protocol DetectFail (2 bytes): be used to indicate that the user detect fail. Hu, et al [Page 19] INTERNET-DRAFT CU Separation Protocol 8. Resource Report TLV Format CUSP Resource Report TLVs have a common format. They begin with a CUSP common header (see Section 4). It is followed by Event TLV fields defined for each different Resource. It may also include one or more type-length-value (TLV) encoded Resource Report data sets. Each TLV has the same structure as described in Section 7.1. 8.1 Resource Report TLV Format A CUSP Resource Report may include a set of one or more optional TLVs. All CUSP Resource Report TLVs have the following format: Type: 2 bytes Length: 2 bytes Value: variable A CUSP Resource Report TLV is comprised of 2 bytes for the type, 2 bytes specifying the TLV length, and a value field. Resource Type (8 bits): The following message types are currently defined: Value Meaning ----- ------- 0 RESOURCE_IF_INFO 1 RESOURCE_SLOT_INFO The Length field defines the length of the value portion in bytes. The TLV is padded to 4-bytes alignment; padding is not included in the Length field (so a 3-byte value would have a length of 3, but the total size of the TLV would be 8 bytes). Unrecognized TLVs MUST be ignored. IANA management of the CUSP Object TLV type identifier codespace is described in Section 11. The details about the attributes of Resource Report TLV are specified in Section 4.2 of [InforModel] Hu, et al [Page 20] INTERNET-DRAFT CU Separation Protocol 9. Error Message Format Error messages are used by the CP or UPs to notify the other side of the connection of problems. They are mostly used by the UPs to indicate a failure of a request initiated by the CP. The format of an Error message is as follows: ::= ERRID (4 bytes): Used to indicate the error type. The following types are currently defined: Value Meaning ------- -------------------------------- 00~1000 Reserved 1001 version negotiation failed 1002 TLV type cannot be recognized 1003 TLV length Anomaly 1004 TLV objective Anomaly 1005 Statistics failed 1006 Statistics request not supported Hu, et al [Page 21] INTERNET-DRAFT CU Separation Protocol 10. Security Considerations TBD. 11. IANA Considerations IANA is registered to assign a port for CUSP as follows: Service Port Transport Name Number Protocol Description Reference ------- ------ --------- ------------ --------------- cusp tbd1 tcp Control User [this document] Separation Protocol IANA is requested to create a "CUSP Parameters" web page and include there of the registries set up below in this Section. 11.1 Message Types TBD. 11.2 TLV Types Values TBD. 11.3 ERRID Codes TBD. Hu, et al [Page 22] INTERNET-DRAFT CU Separation Protocol Normative References [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 (work in progress), October 2017. [InforModel] 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 (work in progress), October 2018. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000, . [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax Used to Form Encoding Rules in Various Routing Protocol Specifications", RFC 5511, DOI 10.17487/RFC5511, April 2009, . [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 [cuspdt-rtgwg-cusp-requirements] Hu, S., Gu, R., Lopezalvarez, V., Song, J., and Z. Wang, "Requirements for Control Plane and User Plane Separated BNG Protocol", draft-cuspdt-rtgwg- cusp-requirements (work in progress), October 2018. [TR-384] Broadband Forum, "Cloud Central Office Reference Architectural Framework", BBF TR-384, 2018. Hu, et al [Page 23] INTERNET-DRAFT CU Separation Protocol Authors' Addresses Shujun Hu China Mobile 32 Xuanwumen West Ave, Xicheng District Beijing, Beijing 100053 China Email: hushujun@chinamobile.com Donald Eastlake, 3rd Huawei 1424 Pro Shop Court Davenport, FL 33896 USA Phone: +1-508-333-2270 Email: d3e3e3@gmail.com Zitao Wang Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: wangzitao@huawei.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 Jun Song Huawei Hu, et al [Page 24] INTERNET-DRAFT CU Separation Protocol 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: song.jun@huawei.com Tee Mong Chua Singapore Telecommunications Limited 31 Exeter Road, #05-04 Comcentre Podium Block Singapore City 239732 Singapore Email: teemong@singtel.com Hu, et al [Page 25] INTERNET-DRAFT CU Separation Protocol Copyright, Disclaimer, and Additional IPR Provisions 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 (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 26]