The China Mobile, Huawei, and ZTE Broadband Network Gateway (BNG) Simple Control and User Plane Separation Protocol (S-CUSP)
RFC 8772

Document Type RFC - Informational (May 2020; No errata)
Last updated 2020-05-11
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Independent Submission                                             S. Hu
Request for Comments: 8772                                  China Mobile
Category: Informational                                  D. Eastlake 3rd
ISSN: 2070-1721                                   Futurewei Technologies
                                                                  F. Qin
                                                            China Mobile
                                                                 T. Chua
                                            Singapore Telecommunications
                                                                D. Huang
                                                                     ZTE
                                                                May 2020

The China Mobile, Huawei, and ZTE Broadband Network Gateway (BNG) Simple
          Control and User Plane Separation Protocol (S-CUSP)

Abstract

   A Broadband Network Gateway (BNG) in a fixed wireline access network
   is an Ethernet-centric IP edge router and the aggregation point for
   subscriber traffic.  Control and User Plane Separation (CUPS) for
   such a BNG improves flexibility and scalability but requires various
   communication between the User Plane (UP) and the Control Plane (CP).
   China Mobile, Huawei Technologies, and ZTE have developed a simple
   CUPS control channel protocol to support such communication: the
   Simple Control and User Plane Separation Protocol (S-CUSP).  S-CUSP
   is defined in this document.

   This document is not an IETF standard and does not have IETF
   consensus.  S-CUSP is presented here to make its specification
   conveniently available to the Internet community to enable diagnosis
   and interoperability.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not candidates for any level of Internet Standard;
   see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8772.

Copyright Notice

   Copyright (c) 2020 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.

Table of Contents

   1.  Introduction
   2.  Terminology
     2.1.  Implementation Requirement Keywords
     2.2.  Terms
   3.  BNG CUPS Overview
     3.1.  BNG CUPS Motivation
     3.2.  BNG CUPS Architecture Overview
     3.3.  BNG CUPS Interfaces
       3.3.1.  Service Interface (Si)
       3.3.2.  Control Interface (Ci)
       3.3.3.  Management Interface (Mi)
     3.4.  BNG CUPS Procedure Overview
   4.  S-CUSP Protocol Overview
     4.1.  Control Channel Procedures
       4.1.1.  S-CUSP Session Establishment
       4.1.2.  Keepalive Timer and DeadTimer
     4.2.  Node Procedures
       4.2.1.  UP Resource Report
       4.2.2.  Update BAS Function on Access Interface
       4.2.3.  Update Network Routing
       4.2.4.  CGN Public IP Address Allocation
       4.2.5.  Data Synchronization between the CP and UP
     4.3.  Subscriber Session Procedures
       4.3.1.  Create Subscriber Session
       4.3.2.  Update Subscriber Session
       4.3.3.  Delete Subscriber Session
       4.3.4.  Subscriber Session Events Report
   5.  S-CUSP Call Flows
     5.1.  IPoE
       5.1.1.  DHCPv4 Access
       5.1.2.  DHCPv6 Access
       5.1.3.  IPv6 Stateless Address Autoconfiguration (SLAAC) Access
       5.1.4.  DHCPv6 and SLAAC Access
       5.1.5.  DHCP Dual-Stack Access
       5.1.6.  L2 Static Subscriber Access
     5.2.  PPPoE
       5.2.1.  IPv4 PPPoE Access
       5.2.2.  IPv6 PPPoE Access
       5.2.3.  PPPoE Dual-Stack Access
     5.3.  WLAN Access
     5.4.  L2TP
       5.4.1.  L2TP LAC Access
       5.4.2.  L2TP LNS IPv4 Access
       5.4.3.  L2TP LNS IPv6 Access
     5.5.  CGN (Carrier Grade NAT)
     5.6.  L3 Leased Line Access
       5.6.1.  Web Authentication
       5.6.2.  User Traffic Trigger
     5.7.  Multicast Service Access
   6.  S-CUSP Message Formats
     6.1.  Common Message Header
     6.2.  Control Messages
       6.2.1.  Hello Message
       6.2.2.  Keepalive Message
       6.2.3.  Sync_Request Message
       6.2.4.  Sync_Begin Message
       6.2.5.  Sync_Data Message
       6.2.6.  Sync_End Message
       6.2.7.  Update_Request Message
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