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Versions: (draft-cuspdt-rtgwg-cu-separation-bng-protocol) 00 01 02 03 04

INTERNET-DRAFT                                                     S. Hu
Intended status: Informational                              China Mobile
                                                             D. Eastlake
                                                  Futurewei Technologies
                                                                 M. Chen
                                                     Huawei Technologies
                                                                  F. Qin
                                                                   Z. Li
                                                            China Mobile
                                                                 T. Chua
                                            Singapore Telecommunications
Expires: December 13, 2019                                 June 14, 2019


                 The China Mobile, Huawei, and ZTE BNG
       Simple Control and User Plane Separation Protocol (S-CUSP)
             draft-chz-simple-cu-separation-bng-protocol-01



Abstract

   To support Control Plane (CP) and User Plane (UP) Separation (CUPS)
   for fixed network Broadband Network Gateway (BNG) service providers,
   China Mobile, Huawei Technologies, and ZTE have developed a simple
   CUPS control channel Protocol (S-CUSP).

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


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.

   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."





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   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
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Table of Contents

      1.  Introduction...........................................6

      2.  Terminology............................................7
        2.1.  Implementation Requirement Keywords................7
        2.2.  Terms..............................................7

      3.  BNG CUPS Overview.....................................10
        3.1.  BNG CUPS Motivation...............................10
        3.2.  BNG CUPS Architecture Overview....................10
        3.3.  BNG CUPS Interfaces...............................12
        3.3.1.  Service Interface...............................13
        3.3.2.  Control Interface...............................14
        3.3.3.  Management Interface............................14
        3.4.  BNG CUPS Procedure Overview.......................14

      4.  S-CUSP Protocol Overview..............................18
        4.1.  Control Channel Related Procedures................18
        4.1.1.  S-CUSP Session Establishment....................18
        4.1.2.  Keep Alive......................................19
        4.2.  Node Related Procedures...........................20
        4.2.1.  UP Resource Report..............................20
        4.2.2.  Enable BAS Function on Access Interface.........20
        4.2.3.  Update Subscriber Network Routing...............21
        4.2.4.  CGN Public IP Address Allocation................21
        4.2.5.  Data Synchronization between the CP and UP......23
        4.3.  Subscriber Session Related Procedures.............24
        4.3.1.  Create Subscriber Session.......................25
        4.3.2.  Update Subscriber Session.......................26
        4.3.3.  Delete Subscriber Session.......................26
        4.3.4.  Subscriber Session Events Report................27

      5.  S-CUSP Call Flows.....................................28
        5.1.  IPoE..............................................28
        5.1.1.  DHCPv4 Access...................................28
        5.1.2.  DHCPv6 Access...................................29
        5.1.3.  IPv6 SLAAC Access...............................31
        5.1.4.  DHCPv6 + SLAAC Access...........................32
        5.1.5.  DHCP Dual Stack Access..........................34
        5.1.6.  L2 Static Subscriber Access.....................36
        5.2.  PPPoE.............................................39
        5.2.1.  IPv4 PPPoE Access...............................39
        5.2.2.  IPv6 PPPoE Access...............................40
        5.2.3.  PPPoE Dual Stack Access.........................42
        5.3.  WLAN Access.......................................44
        5.4.  L2TP..............................................46
        5.4.1.  L2TP LAC Access.................................46
        5.4.2.  L2TP LNS IPv4 Access............................48
        5.4.3.  L2TP LNS IPv6 Access............................50
        5.5.  CGN (Carrier Grade NAT)...........................52

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Table of Contents (continued)

        5.6.  L3 Leased Line Access.............................54
        5.6.1.  Web Authentication..............................54
        5.6.2.  User Traffic Trigger............................56
        5.7.  Multicast Access..................................57

      6.  S-CUSP Message Formats................................59
        6.1.  Common Message Header.............................59
        6.2.  Control Messages..................................60
        6.2.1.  Hello Message...................................60
        6.2.2.  Keepalive Message...............................61
        6.2.3.  Sync_Request Message............................61
        6.2.4.  Sync_Begin Message..............................61
        6.2.5.  Sync_Data Message...............................62
        6.2.6.  Sync_End Message................................62
        6.2.7.  Update_Request Message..........................63
        6.2.8.  Update_Response Message.........................63
        6.3.  Event Message.....................................64
        6.4.  Report Message....................................65
        6.5.  CGN Messages......................................65
        6.5.1.  Addr_Allocation_Req Message.....................65
        6.5.2.  Addr_Allocation_Ack Message.....................65
        6.5.3.  Addr_Renew_Req Message..........................66
        6.5.4.  Addr_Renew_Ack Message..........................66
        6.5.5.  Addr_Release_Req Message........................66
        6.5.6.  Addr_Release_Ack Message........................66
        6.6.  Vendor Message....................................66
        6.7 Error Message.......................................67

      7.  S-CUSP TLVs and Sub-TLVs..............................68
        7.1.  Common TLV Header.................................68
        7.2.  Basic Data Fields.................................69
        7.3.  Sub-TLV Format and Sub-TLVs.......................70
        7.3.1.  Name sub-TLVs...................................70
        7.3.2.  Ingress-CAR sub-TLV.............................71
        7.3.3.  Egress-CAR sub-TLV..............................71
        7.3.4.  If-Desc sub-TLV.................................72
        7.3.5.  IPv6 Address List sub-TLV.......................74
        7.3.6.  Vendor sub-TLV..................................74
        7.4.  The Hello TLV.....................................76
        7.5.  The Keep Alive TLV................................77
        7.6.  The Error Information TLV.........................78
        7.7.  BAS Function Enabler TLV..........................78
        7.8.  Routing TLVs......................................81
        7.8.1.  IPv4 Routing TLV................................81
        7.8.2.  IPv6 Routing TLV................................82
        7.9.  Subscriber TLVs...................................84
        7.9.1.  Basic Subscriber TLV............................84
        7.9.2.  PPP Subscriber TLV..............................87
        7.9.3.  IPv4 Subscriber TLV.............................88

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Table of Contents (continued)

        7.9.4.  IPv6 Subscriber TLV.............................89
        7.9.5.  IPv4 Static Subscriber Detect TLV...............90
        7.9.6.  IPv6 Static Subscriber Detect TLV...............91
        7.9.7.  L2TP-LAC Subscriber TLV.........................93
        7.9.8.  L2TP-LNS Subscriber TLV.........................93
        7.9.9.  L2TP-LAC Tunnel TLV.............................94
        7.9.10.  L2TP-LNS Tunnel TLV............................95
        7.9.11.  Update Response TLV............................96
        7.9.12.  Subscriber Policy TLV..........................97
        7.9.13.  Subscriber CGN Port Range TLV..................99
        7.10.  Device Status TLVs...............................99
        7.10.1.  Interface Status TLV..........................100
        7.10.2.  Board Status TLV..............................100
        7.11.  CGN TLVs........................................101
        7.11.1.  Address Allocation Request TLV................101
        7.11.2.  Address Allocation Response TLV...............102
        7.11.3.  Address Renewal Request TLV...................103
        7.11.4.  The Address Renewal Response TLV..............104
        7.11.5.  Address Release Request TLV...................105
        7.11.6.  The Address Release Response TLV..............105
        7.12.  Event TLVs......................................106
        7.12.1. Subscriber Traffic Statistics TLV..............106
        7.12.2.  Subscriber Detection Result TLV...............108
        7.13.  Vendor TLV......................................109

      8.  Implementation Status................................111
        8.1.  Implementations..................................111
        8.1.1.  Huawei Technologies............................111
        8.1.2.  ZTE............................................112
        8.1.3.  H3C............................................112
        8.2.  Hackathon........................................112
        8.3.  EANTC Testing....................................113

      9.  Summary of Major S-CUSP Codepoints...................114
        9.1.  Message Types....................................114
        9.2.  TLV Types........................................114
        9.3.  TLV Operation Codes..............................116
        9.4.  Sub-TLV Types....................................116
        9.5.  Error Codes......................................117

      10.  IANA Considerations.................................119
      11.  Security Considerations.............................120

      Contributors.............................................121
      Normative References.....................................122
      Informative References...................................122
      Authors' Addresses.......................................124



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1.  Introduction

   A fixed network 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
   framework is described in [TR-384].  The CU separated service Control
   Plane (CP), which is responsible for user access authentication and
   setting forwarding entries in User Planes (UPs), can be virtualized
   and centralized.  The routing control and forwarding plane, i.e. the
   BNG user plane (local), can be distributed across the infrastructure.
   Other structures can also be supported such as both CP and UP being
   virtual or both being physical.

   This document specifies the Simple CU Separation BNG control channel
   Protocol (S-CUSP) for communications between a BNG Control Plane (CP)
   and a set of User Planes (UPs).  S-CUSP is designed to be flexible
   and extensible so as to easily allow for additional messages and data
   items, should further requirements be expressed in the future.

   This document is not an IETF standard and does not have IETF
   consensus.  S-CUSP was designed by China Mobile, Huawei Technologies,
   and ZTE, it is presented here to make the S-CUSP specification
   conveniently available to the Internet community to enable diagnosis
   and interoperability.


























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2.  Terminology

   This section specifies implementation requirement keywords and terms
   used in this document. S-CUSP messages are described in this document
   using Routing Backus-Naur Form (RBNF) as defined in [RFC5511].



2.1.  Implementation Requirement Keywords

   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.



2.2.  Terms

   This section specifies terms used in this document.

   AAA: Authentication Authorization Accounting.

   ACK: Acknowledgement message.

   BAS: Broadband Access Server (BRAS, BNG).

   BNG: Broadband Network Gateway.  A broadband remote access server
       (BRAS (BRoadband Access Server), 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).

   BRAS: BRoadband Access Server (BNG).

   CAR: Committed Access Rate.

   CBS: Committed Burst Size.

   CGN: Carrier Grade NAT.

   Ci: Control Interface.

   CIR: Committed Information Rate.

   CoA: Change of Authorization.

   CP: Control Plane.


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       CP is a user control management component which supports the
       management of the UP's resources such as the user entry and
       forwarding policy.

   CPE: Customer Premises Equipment.

   CU: Control-plane / User-plane.

   CUSP: Control and User plane Separation Protocol.

   DEI: Drop Eligibility Indicator. A bit in a VLAN tag after the
       priority and before the  VLAN ID. (This bit was formerly the CFI
       (Canonical Format Indicator).) [802.1Q]

   DHCP: Dynamic Host Configuration Protocol [RFC2131].

   dial-up: This refers to the initial connection messages when a new
       user appears. The name is left over from when users literally
       dialed up on a modem equipped phone line but herein is applied to
       other initial connection techniques. Initial connection is
       frequently indicated by the receipt of packets over PPPoE or
       IPoE.

   EMS: Element Management System.

   IPoE: IP over Ethernet.

   L2TP: Layer 2 Tunneling Protocol [RFC2661].

   LAC: L2TP Access Concentrator.

   LNS: L2TP Network Server.

   MAC: 48-bit Media Access Control address [RFC7042].

   MANO: Management and Orchestration.

   Mi: Management Interface.

   MSS: Maximum Segment Size.

   MRU: Maximum Receive Unit.

   NAT: Network Address Translation [RFC3022].

   ND: Neighbor Discovery.

   NFV: Network Function Virtualization.

   NFVI: NFV Infrastructure


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   PBS: Peak Burst Size.

   PD: Prefix Delegation.

   PIR: Peak Information Rate.

   PPP: Point to Point Protocol [RFC1661].

   PPPoE: PPP over Ethernet.

   RBNF: Routing Backus-Naur Form [RFC5511].

   RG: Residential Gateway.

   S-CUSP: Simple Control and User Plane Separation Protocol.

   Si: Service Interface.

   TLV: Type, Length, Value.  See Sections 7.1 and 7.3.

   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.

   URPF: Unicast Reverse Path Forwarding.

   User: Equivalent to "customer" or "subscriber".

   VRF: Virtual Routing and Forwarding.






















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3.  BNG CUPS Overview



3.1.  BNG CUPS 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 Control Plane and User Plane (CU) separation is
   described in [TR-384].  The main idea of CU 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).



3.2.  BNG CUPS Architecture Overview

   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. The user management function can be centralized and
   deployed as a concentrated module or device, called the BNG Control
   Plane (BNG-CP). The other functions, such as the router function and
   forwarding engine, can be deployed in the form of the BNG User Plane
   (BNG-UP).

   The following figure shows the architecture of CU separated BNG:



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    +------------------------------------------------------------------+
    |        Neighboring policy and resource management systems        |
    |                                                                  |
    |   +-------------+   +-----------+   +---------+   +----------+   |
    |   |AAA    Server|   |DHCP Server|   |   EMS   |   |   MANO   |   |
    |   +-------------+   +-----------+   +---------+   +----------+   |
    +------------------------------------------------------------------+

    +------------------------------------------------------------------+
    |                       CU-separated BNG system                    |
    | +--------------------------------------------------------------+ |
    | |   +----------+  +----------+ +------++------++-----------+   | |
    | |   | Address  |  |Subscriber| | AAA  ||Access||    UP     |   | |
    | |   |management|  |management| |      || Mgt  ||management |   | |
    | |   +----------+  +----------+ +------++------++-----------+   | |
    | |                              CP                              | |
    | +--------------------------------------------------------------+ |
    |                                                                  |
    |                                                                  |
    |                                                                  |
    | +---------------------------+      +--------------------------+  |
    | |  +------------------+     |      |  +------------------+    |  |
    | |  | Routing control  |     |      |  | Routing control  |    |  |
    | |  +------------------+     | ...  |  +------------------+    |  |
    | |  +------------------+     |      |  +------------------+    |  |
    | |  |Forwarding engine |     |      |  |Forwarding engine |    |  |
    | |  +------------------+  UP |      |  +------------------+  UP|  |
    | +---------------------------+      +--------------------------+  |
   +------------------------------------------------------------------+

                Figure 1:  Architecture of CU Separated BNG

   As shown in Figure 1, the BNG Control Plane could be virtualized and
   centralized, which provides 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, 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


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   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 is responsible for the following:

    1. Address management: unified address pool management and CGN
       subscriber address traceability 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. Access management: process user dial-up packets, such as PPPoE,
       DHCP, L2TP, etc.

    5. UP management: management of UP interface status, and the setup,
       deletion, and maintenance of channels between CP and UP.

   The User Plane is responsible for the following:

    1. Routing control functions: responsible for constructing routing
       forwarding plane (e.g., routing, multicast, MPLS, etc.).

    2. Routing and Service Forwarding plane functions: responsible
       including traffic forwarding, QoS and traffic statistics
       collection.

    Subscriber detection: responsible for detecting whether a subscriber
       is still online.



3.3.  BNG CUPS Interfaces

   To support the communication between the Control Plane and User
   Plane, three interfaces are assumed.  These are referred to as the
   Service Interface (Si), Control Interface (Ci), and Management
   Interface (Mi) as shown in Figure 2.




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             +-----------------------------------+
             |                                   |
             |               BNG-CP              |
             |                                   |
             +--+--------------+--------------+--+
                |              |              |
     1. Service |   2. Control | 3. Management|
      Interface |    Interface |    Interface |
           (Si) |         (Ci) |         (Mi) |
                |              |              |
                |           ___|___           |
                |       ___(       )___       |
               _|______(               )______|_
              (                                 )
             (         Network/Internet         )
              (________                 ________)
                |      (___         ___)      |
                |          (_______)          |
                |              |              |
                |              |              |
             +--+--------------+--------------+--+
             |                                   |
             |               BNG-UP              |
             |                                   |
             +-----------------------------------+

           Figure 2: Interfaces Between the CP and UP of the BNG



3.3.1.  Service Interface

   For a traditional BNG (without CU separation), the user dial-up
   signals are terminated and processed by the control plane of a BNG.
   When the CP and UP of a BNG are separated, there needs to be a way to
   relay these signals between the CP and the UP.

   The Service Interface (Si) is used to establish tunnels between the
   CP and UP. The tunnels are responsible for relaying the PPPoE, IPoE,
   and L2TP related control packets that are received from a Residential
   Gateway (RG) over those tunnels. An appropriate tunnel type is VXLAN
   [RFC7348].

   The detailed definition of Si is out of scope for this document.








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3.3.2.  Control Interface

   The CP uses the Control Interface to deliver subscriber session
   states, network routing entries, etc. to the UP (see Section 6.2.7)).
   The UP uses this interface to report subscriber service statistics,
   subscriber detection results, etc. to the CP (see Sections 6.3 and
   6.4). A carrying protocol for this interface is specified in this
   document.



3.3.3.  Management Interface

   NETCONF [RFC6241] is the protocol used on the Management Interface
   between a CP and UP. It is used to configure the parameters of the
   Control Interface, Service Interface, the Access interfaces and
   QoS/ACL Templates. It is expected that implementations will make use
   of existing YANG models where possible, but that new YANG models
   specific to S-CUSP will need to be defined. The definitions of the
   parameters are out of scope for this document.



3.4.  BNG CUPS Procedure Overview

   The following numbered sequences (Figure 3) gives a high level view
   of the main BNG CUPS procedures.

      RG              UP                      CP              AAA
      |               |                        |               |
      |               |Establish S-CUSP Channel|               |
      |              1|<---------------------->|               |
      |               |                        |               |
      |               |      Report Board      |               |
      |               |       interface        |               |
      |               |      information       |               |
      |              2|------to CP via Ci----->|               |
      |               |                        |               |
      |               | Enable BAS function    |               |
      |              3|<-----on UP via Ci------|               |
      |               |                        |               |
      |               | Notify UP to advertise |               |
      |               |   subscriber network   |               |
      |               |        routing         |               |
      |              4|<------- via Ci---------|               |
      |               |                        |               |
      |  Dial-up Req  |                        |               |
   5.1|-------------->|                        |               |
      |               | Relay the Dial-up Req  |               |
      |            5.2|-----to CP via Si------>| Authentication|


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      |               |                        |    Req/Rep    |
      |               |                     5.3|<------------->|
      |               | Send the Dial-up Rep   |               |
      |            5.4|<----to UP via Si-------|               |
      |  Dial-up Rep  |                        |               |
   5.5|<--------------|                        |               |
      |               | Create subscriber      |               |
      |               |    session on UP       |               |
      |            5.6|<--------via Ci-------->|               |
      |               |                        |  CoA Request  |
      |               |                     6.1|<--------------|
      |               | Update session on UP   |               |
      |            6.2|<--------via Ci-------->|               |
      |               |                        |  CoA Response |
      |               |                     6.3|-------------->|
      |               |                        |               |
      |  Offline Req  |                        |               |
   7.1|-------------->|                        |               |
      |               | Relay the Offline Req  |               |
      |            7.2|------to CP via Si----->|               |
      |               |                        |               |
      |               | Send the Offline Rep   |               |
      |            7.3|<-----to UP via Si------|               |
      |  Offline Rep  |                        |               |
   7.4|<--------------|                        |               |
      |               | Delete session on UP   |               |
      |            7.5|<--------via Ci-------->|               |
      |               |                        |               |
      |               | Event report           |               |
      |              8|---------via Ci-------->|               |
      |               |                        |               |
      |               | Data Synchronization   |               |
      |              9|<--------via Ci-------->|               |
      |               |                        |               |
      |               | CGN Address Allocation |               |
      |             10|<--------via Ci-------->|               |
      |               |                        |               |

                  Figure 3: BNG CUPS Procedures Overview
    1. S-CUSP session establishment: This is the first step of BNG CUPS
       procedures. Once the Control Interface parameters are configured
       on a UP. It will start to setup S-CUSP sessions with the
       specified CPs. The detailed definition of S-CUSP session
       establishment can be found in Section 4.1.1.

    2. Board and interface report: Once the S-CUSP session is
       established between the UP and a CP, the UP will report status
       information on the boards and subscriber side interfaces of this
       UP to the CP. A board can also be called a Line/Service Process
       Unit (LPU/SPU) card. The subscriber side interfaces refer to the


Hu, et al                                                      [Page 15]


INTERNET-DRAFT                                           Simple BNG CUSP


       interfaces that connect the Acess Network nodes (e.g., OLT:
       Optical Line Terminal, DSLAM: Digital Subscriber Line Access
       Multiplexer, etc.). The CP can use this information to enable the
       Broadband Access Service (BAS) function (e.g., IPoE, PPPoE, etc.)
       on the specified interfaces. See Sections 4.2.1 and 7.10 for more
       details on Resource reporting.

    3. BAS (Broadband Access Service) function enable: To enable the BAS
       function on the specified interfaces of a UP.

    4. Subscriber network route advertisement: The CP will allocate one
       or more IP address blocks to a UP. Each address block contains a
       series of IP addresses. Those IP addresses will be allocated to
       subscribers who are dialing up from the UP. To enable other nodes
       in the network to learn how to reach the subscribers, the CP
       needs to notify the UP to advertise to the network the routes
       that can reach those IP addresses.

    5. 5.1-5.6 is a complete call flow of a subscriber dial-up process.
       When a UP receives a dial-up request, it will relay the request
       packet to a CP through the Service Interface. The CP will parse
       the request. If everything is OK, it will send an authentication
       request to the AAA server to authenticate the subscriber. Once
       the subscriber passes the authentication, the AAA server will
       return a positive response to the CP. Then the CP will send the
       dial-up response packet to the UP and the UP will forward the
       response packet to the subscriber (RG). At the same time, the CP
       will create a subscriber session on the UP, which enables the
       subscriber to access the network.  For different access types,
       the process may be a bit different. But the high-level process is
       similar. For each access type, the detail process can be found in
       Section 5.

    6. 6.1-6.3 is the sequence when updating an existing subscriber
       session. The AAA server initiates a Change of Authorization (CoA)
       and sends the CoA to the CP. The CP will then update the session
       according to the CoA.  See Section 4.3.2 for more detail on CP
       messages updating UP tables.

    7. 7.1-7.5 is the sequence for deleting an existing subscriber
       session. When a UP receives an offline request, it will relay the
       request to a CP through the Service Interface. The CP will send
       back a response to the UP through the Service Interface. The UP
       will then forward the offline response to the subscriber.  Then
       the CP will delete the session on the UP through the Control
       Interface.

    8. Event reports include the following two parts (more detail can be
       found in Section 4.3.4) Both are reported using the Event
       message.


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INTERNET-DRAFT                                           Simple BNG CUSP


        8.1. Subscriber Traffic Statistics Report

        8.2.  Subscriber Detection Result Report

   9. Data synchronization: See Sections 4.2.5 for more detail on CP and
       UP Synchronization.

   10. CGN address allocation: See Sections 4.2.4 for more detail on CGN
       Address Allocation.











































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4.  S-CUSP Protocol Overview



4.1.  Control Channel Related Procedures



4.1.1.  S-CUSP Session Establishment

   A UP is associated with a CP and is controlled by that CP. In the
   case of a hot-standby or warm-standby, a UP is associated with two
   CPs, one called the Master CP and the other called the Standby CP.
   The association between a UP and its CPs is implemented by dynamic
   configuration.

   Once a UP knows its CPs, the UP starts to establish S-CUSP sessions
   with those CPs as shown in Figure 4.

             UP                               CP
             |                                 |
             |   TCP Session Establishment     |
             |<------------------------------->|
             |                                 |
             |   HELLO (version, capability)   |
             |-------------------------------->|
             |                                 |
             |   HELLO (version, capability)   |
             |<--------------------------------|
             |                                 |

                  Figure 4: S-CUSP Session Establishment

   The S-CUSP session establishment consists of two successive steps:

    1. Establishment of a TCP [RFC793] connection (3-way handshake)
       between the CP and the UP using port tbd1.

    2. Establishment of a S-CUSP session over the TCP connection.

   Once the TCP connection is established, the CP and the UP initialize
   the S-CUSP session during which the version and Keepalive timers are
   negotiated.

   The version information (Hello TLV, see section 7.4) is carried
   within Hello messages (see Section 6.2.1).  A CP can support multiple
   versions, but a UP can only support one version.  So, the version
   negotiation is based on whether a version can be support by both the
   CP and the UP.  For a CP or UP, if a Hello message is received that
   does not indicate a version supported by both, a subsequent Hello


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INTERNET-DRAFT                                           Simple BNG CUSP


   message with an Error Information TLV will be sent to the peer to
   notify the peer of the "Version-Mismatch" error and the session
   establishment phase fails.

   Keepalive negotiation is performed by carrying a Keepalive TLV in the
   Hello message.  The Keepalive TLV includes a Keepalive timer and Dead
   Timer field. The CP and UP have to agree on the Keepalive Timer and
   Dead Timer.  Otherwise, a subsequent Hello message with an Error
   Information TLV will be sent to its peer and the session
   establishment phase fails.

   The S-CUSP session establishment phase fails if the CP or UP disagree
   on the version and keepalive parameters or if one of the CP or UP
   does not answer after the expiration of the establishment timer.
   When the S-CUSP session establishment fails, the TCP connection is
   promptly closed. Successive retries are permitted but an
   implementation SHOULD make use of an exponential back-off session
   establishment retry procedure.



4.1.2.  Keep Alive

   Once an S-CUSP session has been established, a UP or CP may want to
   know that its S-CUSP peer is still available for use.

   Each end of a S-CUSP session runs a Keepalive timer.  It restarts the
   timer every time it sends a message on the session.  When the timer
   expires, it sends a Keepalive message.

   The ends of the S-CUSP session also run DeadTimers, and they restart
   the timers whenever a message is received on the session.  If one end
   of the session receives no message after the DeadTimer expires, it
   declares the session dead. The session will be closed.

   The minimum value of the Keepalive timer is 1 second, and it is
   specified in units of 1 second.  The recommended default value is 30
   seconds.  The timer may be disabled by setting it to zero.

   The recommended default for the DeadTimer is 4 times the value of the
   Keepalive timer used by the remote peer.  This implies there is
   essentially no risk of TCP congestion due to excessive Keepalive
   messages.

   The Keepalive timer and DeadTimer are initially negotiated through
   the Keepalive TLV carried in the Hello Message.






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INTERNET-DRAFT                                           Simple BNG CUSP


4.2.  Node Related Procedures



4.2.1.  UP Resource Report

   Once an S-CUSP session has been established between a CP and an UP.
   The UP reports the information of the Boards and access side
   interfaces on this UP to the CP as shown in Figure 5. Report messages
   are unacknowledged and are assumed to be delivered because the
   session runs over TCP.

   The CP can use that information to activate/enable the Broadband
   Access Service (BAS) functions (e.g., IPoE, PPPoE, etc.) on the
   specified interfaces.

   In addition, the UP resource report may trigger a UP warm-standby
   process.  In the case of warm-standby, a failure on an UP may trigger
   the CP to start a warm-standby process, by moving the on-line
   subscriber sessions to a standby UP and then direct the affected
   subscribers to access the Internet through the standby UP.

                        UP                      CP
                        |                        |
                        |  Report Board Status   |
                        |------to CP via Ci----->|
                        |                        |
                        | Report Interface Status|
                        |------to CP via Ci----->|
                        |                        |

                  Figure 5: UP Board and Interface Report

   Board status information is carried in the Board Status TLV (Section
   7.10.2) and Interface status information is carried in Interface
   Status TLV (Section 7.10.1). Both Board and Interface Status TLVs are
   carried in the Report Message (Section 6.4).



4.2.2.  Enable BAS Function on Access Interface

   Once the CP collects the interface status of a UP, it will
   activate/enable the BAS functions on specified interfaces through the
   Update_Request and Update_Response message (Section 6.2) exchanges
   carrying the BAS Function Enabler TLV (Section 7.7).






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INTERNET-DRAFT                                           Simple BNG CUSP


                        UP                       CP
                        |                         |
                        |   Enable BAS function   |
                        |         Request         |
                        |<-----on UP via Ci-------|
                        |                         |
                        |   Enable BAS function   |
                        |         Response        |
   |------on UP via Ci------>|
   |                         |

                       Figure 6: Enable BAS Function



4.2.3.  Update Subscriber Network Routing

   The CP will allocate one or more address blocks to a UP. Each address
   block contains a series of IP addresses. Those IP addresses will be
   allocated to subscribers who are dialing up to the UP. To enable the
   other nodes in the network to learn how to reach the subscribers, the
   CP needs to install the routes on the UP and notify the UP to
   advertise the routes to the network.

                        UP                       CP
                        |                         |
                        | Subscriber network route|
                        |      update request     |
                        |<------- via Ci----------|
                        |                         |
                        | Subscriber network route|
                        |      update response    |
                        |-------- via Ci--------->|
                        |                         |

                Figure 7: Update Subscriber Network Routing

   The subscriber network routing update request and response are
   achieved through the Update Request and Response Message exchanges by
   carrying the IPv4/IPv6 Routing Information TLVs (Section 7.8).



4.2.4.  CGN Public IP Address Allocation

   The following sequences describe the CGN address management related
   procedures.  Three independent procedures are defined, one each for
   CGN address allocation request/response, CGN address renewal
   request/response, and CGN address release request/response.



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INTERNET-DRAFT                                           Simple BNG CUSP


   CGN address allocation/renew/release procedures are designed for the
   case where the CGN function is running on the UP.  The UP has to map
   the subscriber private IP addresses to a public IP addresses, and
   such mapping is performed by the UP locally when a subscriber dials-
   up.  That means the UP has to ask for public IPv4 address blocks for
   CGN subscribers from the CP.

   In addition, when a public IP address is allocated to a UP, there
   will be a lease time (e.g., one day). Before the lease time expires,
   the UP can ask for renewal of the IP address lease from the CP. It is
   achieved by the exchange of the Addr_Renew_Req and Addr_Renew_Ack
   messages.

   If the public IP address will not be used anymore, the UP SHOULD
   release the address by sending an Addr_Release_Req message to the CP.

   If the CP wishes to withdraw addresses that it has previously leased
   to a UP, it uses the same procedures as above.  The "Oper" code in
   the IPv4/IPv6 Routing TLV (see Section 7.1) determines whether the
   request is an update or withdraw.

   The relevant messages are defined in Section 6.5.

                UP                       CP
                |                         |
                | CGN Address Allocation  |
                |         Request         |
             1.1|-------- via Ci--------->|
                | CGN Address Allocation  |
                |         Response        |
             1.2|<------- via Ci----------|
                |                         |
                | CGN Address Renew       |
                |         Request         |
             2.1|-------- via Ci--------->|
                | CGN Address Renew       |
                |         Response        |
             2.2|<------- via Ci----------|
                |                         |
                | CGN Address Release     |
                |         Request         |
             3.1|-------- via Ci--------->|
                | CGN Address Release     |
                |         Response        |
             3.3|<------- via Ci----------|
                |                         |

                Figure 8: CGN Public IP Address Allocation




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INTERNET-DRAFT                                           Simple BNG CUSP


4.2.5.  Data Synchronization between the CP and UP

   For a CU separated BNG, the UP will continue to function using the
   state that has been installed in it even if the CP fails or the
   session between the UP and CP fails.

   Under some circumstances it is necessary to synchronize state between
   the CP and UP, for example if a CP fails and the UP is switched to a
   different CP.

   Synchronization includes two directions.  One direction is from UP to
   CP; in that case, the synchronization information is mainly about the
   board/interface status of the UP.  The other direction is from CP to
   UP; in that case, the subscriber sessions, subscriber network routes,
   L2TP tunnels, etc. will be synchronized to the UP.

   The synchronization is triggered by a Sync_Request message, to which
   the receiver will (1) reply with a Sync_Begin message to notify the
   requester that synchronization will begin, and (2) then start the
   synchronization using the Sync_Data message.  When synchronization
   finished, a Sync_End message will be sent.

   The following figure shows the process of data synchronization
   between a UP and a CP.




























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                           UP                       CP
                           |                         |
                           | Synchronization Request |
                           |<------- via Ci----------|
                           |                         |
                           | Synchronization Begin   |
                           |-------- via Ci--------->|
                           |                         |
                           | Board/Interface Report  |
                           |-------- via Ci--------->|
                           |                         |
                           | Synchronization End     |
                           |-------- via Ci--------->|
                           |                         |
                          1) Synchronization from UP to CP

                           UP                       CP
                           |                         |
                           | Synchronization Request |
                           |-------- via Ci--------->|
                           |                         |
                           | Synchronization Begin   |
                           |<-------- via Ci---------|
                           |                         |
                           |      Synchronizes       |
                           |Subscriber Session States|
                           |  Network Route Entries  |
                           |<------- via Ci----------|
                           |                         |
                           | Synchronization End     |
                           |<-------- via Ci---------|
                           |                         |
                          2) Synchronization from CP to UP

                      Figure 9: Data Synchronization



4.3.  Subscriber Session Related Procedures

   A subscriber session consists of a set of forwarding states,
   policies, and security rules that are applied to the subscriber.  It
   is used for forwarding subscriber traffic in a UP.  To initialize a
   session on a UP, a set of hardware resource have to be allocated
   (e.g., NP, TCAM etc.) to a session.

   Subscriber session related procedures include subscriber session
   create, update, delete, and statistics report.  The following sub-
   sections give a high level view of the procedures.



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INTERNET-DRAFT                                           Simple BNG CUSP


4.3.1.  Create Subscriber Session

   The below sequence describes the DHCP IPv4 dial-up process, it is an
   example that shows how a subscriber session is created. (An example
   for IPv6 appears in Section 5.1.2.)

        RG              UP                       CP             AAA
        |               |                        |               |
        | Online Request|                        |               |
       1|-------------->|                        |               |
        |               |Relay the Online Request|               |
        |              2|-----to CP via Si------>| Authentication|
        |               |                        |    Req/Rep    |
        |               |                       3|<------------->|
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              4|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              5|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                       6|<------------->|
        |               |                        |               |
        |               |  Send Online Response  |               |
        |              7|<----to UP via Si-------|               |
        |               |                        |               |
        |Online Response|                        |               |
      12|<--------------|                        |               |
        |               |                        |               |

                   Figure 10: Subscriber Session Create

   The request starts from an Online Request message (step 1) from the
   RG (for example, a DHCP Discovery packet).  When the UP receives the
   Online Request from the RG, it will tunnel the Online Request to the
   CP through the Service Interface (Step 2).  The Service Interface is
   implemented by a tunneling technology.

   When the CP receives the Online Request from the UP, it will send an
   authentication request to the AAA server to authenticate and
   authorize the subscriber (step 3).  When a positive reply is received
   from the AAA sever, the CP starts to create a subscriber session for
   the request.  Relevant resources (e.g., IP address, bandwidth, etc.)
   will be allocated to the subscriber, policies and security rules will
   be generated for the subscriber Then the CP sends a session create
   request to the UP through the Control Interface (Ci) (step 4), and a
   response is expected from the UP to confirm the creation (step 5).



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INTERNET-DRAFT                                           Simple BNG CUSP


   Finally, the CP will notify the AAA server to start accounting (step
   6).  At the same time, an Online Response message (for example, a
   DHCP Ack packet) will be sent to the UP through the Si (step 7).  And
   the UP will forward the Online Response to the RG (step 8).

   This completes the subscriber online process.



4.3.2.  Update Subscriber Session

   The following numbered sequence shows the process of subscriber
   session update.

                     UP                       CP             AAA
                     |                        |  COA Request  |
                     |                       1|<--------------|
                     | Session update Request |               |
                    2|<--------via Ci---------|               |
                     |                        |               |
                     | Session update Response|               |
                    3|---------via Ci-------->|               |
                     |                        |  COA Response |
                     |                       4|-------------->|
                     |                        |               |

                   Figure 11: Subscriber Session Update

   When a subscriber session has been created on a UP, there may be
   requirements to update the session with new parameters (e.g.,
   Bandwidth, QoS, policies, etc.).

   This procedure is triggered by a Change of Authorization (COA)
   request message sent by the AAA server.  The CP will update the
   session on the UP according to the new parameters through the Control
   Interface.



4.3.3.  Delete Subscriber Session

   The below call flow shows generally how S-CUPS deals with a
   subscriber offline request.

             RG               UP                       CP
              |                |                        |
              |Offline Request |                        |
             1|--------------->|                        |
              |                |    Relay the Offline   |
              |                |        Request         |


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INTERNET-DRAFT                                           Simple BNG CUSP


              |               2|------to CP via Si----->|
              |                |                        |
              |                |    Send the Offline    |
              |                |        Response        |
              |               3|<-----to UP via Si------|
              |Offline Response|                        |
             4|<---------------|                        |
              |                |     Session delete     |
              |                |        Request         |
              |                |<--------via Ci---------|
              |                |     Session delete     |
              |                |       Response         |
              |                |---------via Ci-------->|
              |                |                        |

                   Figure 12: Subscriber Session Delete

   Similar to the session creation process, when a UP receives an
   offline request from a RG, it will tunnel the request to a CP through
   the Si.

   When the CP receives the offline request, it will withdraw/release
   the resources (e.g., IP address, bandwidth) that have been allocated
   to the subscriber.  Then, it sends a reply to the UP through the
   Service Interface and the UP will forward the reply to the RG.  At
   the same time, it will delete all the status of the session on the UP
   through the Ci.



4.3.4.  Subscriber Session Events Report

                      UP                       CP
                      |                        |
                      | Statistic/Detect report|
                      |---------via Ci-------->|
                      |                        |

                         Figure 13: Events Report

   When a session is created on an UP, the UP will periodically report
   statistics information and detect results of the session to the CP.










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INTERNET-DRAFT                                           Simple BNG CUSP


5.  S-CUSP Call Flows

   The subsections below give an overview of various "dial-up"
   interactions over the Service Interface followed by an overview of
   the setting of various information in the UP by the CP using S-CUSP
   over the Control Interface.

   S-CUSP messages are described in this document using Routing Backus
   Naur Form (RBNF) as defined in [RFC5511].



5.1.  IPoE



5.1.1.  DHCPv4 Access

   The following sequence shows detailed procedures for DHCPv4 access.

        RG              UP                       CP             AAA
        |               |                        |               |
        | DHCP Discovery|                        |               |
       1|-------------->|                        |               |
        |               |Relay the DHCP Discovery|               |
        |              2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                       3|<------------->|
        |               |                        |               |
        |               |  Send the DHCP Offer   |               |
        |              4|<----to UP vis Si-------|               |
        |  DHCP Offer   |                        |               |
       5|<--------------|                        |               |
        |  DHCP Request |                        |               |
       6|-------------->|                        |               |
        |               |  Relay the DHCP Request|               |
        |              7|-----to CP via Si------>|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              8|<--------via Ci---------|               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              9|---------via Ci-------->|               |
        |               |                        |   Accounting  |
        |               |                      10|<------------->|
        |               |                        |               |
        |               |  Send DHCP ACK         |               |
        |             11|<----to UP via Si-------|               |
        |               |                        |               |


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INTERNET-DRAFT                                           Simple BNG CUSP


        |  DHCP ACK     |                        |               |
      12|<--------------|                        |               |
        |               |                        |               |

                         Figure 14: DHCPv4 Access

   Step 8 and 9 are implemented by the S-CUSP protocol.

   When a subscriber is authenticated and authorized by the AAA server,
   the CP will create a subscriber session on the UP.  This is achieved
   by sending an Update_Request message to the UP.

   The format of the Update_Request message is shown as follows using
   RBNF:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   The UP will reply with an Update_Response message, the format of the
   Update_Response message is as follows:

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]



5.1.2.  DHCPv6 Access

   The following sequence shows detailed procedures for DHCPv6 access.

        RG              UP                       CP             AAA
        |               |                        |               |
        |  Solicit      |                        |               |
       1|-------------->|                        |               |
        |               |  Relay the Solicit     |               |
        |              2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                       3|<------------->|
        |               |                        |               |
        |               |  Send the Advertise    |               |
        |              4|<----to UP vis Si-------|               |
        |  Advertise    |                        |               |
       5|<--------------|                        |               |
        |               |                        |               |
        |  Request      |                        |               |
       6|-------------->|                        |               |


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        |               |  Relay the Request     |               |
        |              7|-----to CP via Si------>|               |
        |               |                        |               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              8|<--------via Ci-------->|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              9|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                      10|<------------->|
        |               |                        |               |
        |               |  Send Reply            |               |
        |             11|<----to UP via Si-------|               |
        |               |                        |               |
        |  Reply        |                        |               |
      12|<--------------|                        |               |
        |               |                        |               |

                         Figure 15: DHCPv6 Access

   Steps 1-7 are a standard DHCP IPv6 access process.  The subscriber
   creation is triggered by a DHCP IPv6 request message.  When this
   message is received, it means that the subscriber has passed the AAA
   authentication and authorization.  Then the CP will create a
   subscriber session on the UP.  This is achieved by sending an
   Update_Request message to the UP (Step 8).

   The format of the Update_Request message is as follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   The UP will reply with an Update_Response message (Step 9). The
   format of the Update_Response message is as follows:

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>








Hu, et al                                                      [Page 30]


INTERNET-DRAFT                                           Simple BNG CUSP


5.1.3.  IPv6 SLAAC Access

   The following flow shows the IPv6 SLAAC access process.

        RG              UP                       CP             AAA
        |               |                        |               |
        |      RS       |                        |               |
       1|-------------->|                        |               |
        |               |  Relay the Router      |               |
        |               |    Solicit (RS)        |               |
        |              2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                       3|<------------->|
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              4|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              5|---------via Ci-------->|               |
        |               |                        |               |
        |               |  Send Router Advertise |               |
        |               |         (RA)           |               |
        |              6|<----to UP vis Si-------|               |
        |      RA       |                        |               |
       7|<--------------|                        |               |
        |               |                        |               |
        |      NS       |                        |               |
       8|-------------->|                        |               |
        |               |  Relay the Neighbor    |               |
        |               |     Solicit (NS)       |               |
        |              9|-----to CP via Si------>|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                      10|<------------->|
        |               |                        |               |
        |               |  Send a Neighbor       |               |
        |               |     Advertise (NA)     |               |
        |             11|<----to UP via Si-------|               |
        |               |                        |               |
        |      NA       |                        |               |
      12|<--------------|                        |               |
        |               |                        |               |

                       Figure 16: IPv6 SLAAC Access

   It starts with a Router Solicit (RS) request from an RG that is
   tunneled to the CP by the UP.  After the AAA authentication and
   authorization, the CP will create a subscriber session on the UP.


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   This is achieved by sending an Update_Request message to the UP (step
   4).

   The format of the Update_Request message is as follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   The UP will reply with an Update_Response message (step 5), the
   format of the Update_Response message is as follows:

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.1.4.  DHCPv6 + SLAAC Access

   The following call flow shows the DHCP IPv6 and SLAAC access process.

        RG              UP                       CP             AAA
        |               |                        |               |
        |      RS       |                        |               |
       1|-------------->|                        |               |
        |               |  Relay the Router      |               |
        |               |    Solicit (RA)        |               |
        |              2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                       3|<------------->|
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              4|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              5|---------via Ci-------->|               |
        |               |                        |               |
        |               |  Send Router Advertise |               |
        |               |         (RA)           |               |
        |              6|<----to UP vis Si-------|               |
        |      RA       |                        |               |
       7|<--------------|                        |               |
        |               |                        |               |
        |DHCPv6 Solicit |                        |               |
       8|-------------->|                        |               |
        |               |  Relay DHCPv6 Solicit  |               |


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        |              9|-----to CP via Si------>|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Request      |               |
        |             10|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Response     |               |
        |             11|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                      12|<------------->|
        |               |                        |               |
        |               |  Send DHCPv6 Reply     |               |
        |             13|<----to UP via Si-------|               |
        |               |                        |               |
        | DHCPv6 Reply  |                        |               |
      14|<--------------|                        |               |
        |               |                        |               |

                     Figure 17: DHCPv6 + SLAAC Access

   When a subscriber passes AAA authentication, the CP will create a
   subscriber session on the UP.  This is achieved by sending an
   Update_Request message to the UP (step 4).

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   The UP will reply with an Update_Response message (step 5). The
   format of the Update_Response is as follows:

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   After receiving a DHCPv6 Solicit, the CP will update the subscriber
   session by sending an Update_Request message with new parameters to
   the UP (Step 10).

   The format of the Update_Request message is as follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]



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   The UP will reply with an Update_Response message (step 11).  The
   format of the Update_Response is as follows:

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.1.5.  DHCP Dual Stack Access

   The following sequence is a combination of DHCP IPv4 and DHCP IPv6
   access processes.

        RG              UP                       CP             AAA
        |               |                        |               |
        | DHCP Discovery|                        |               |
       1|-------------->|                        |               |
        |               |Relay the DHCP Discovery|               |
        |              2|-----to CP via Si------>|               |
        |               |                        |  Accounting   |
        |               |                       3|<------------->|
        |               |                        |               |
        |               |  Send the DHCP Offer   |               |
        |              4|<----to UP vis Si-------|               |
        |  DHCP Offer   |                        |               |
       5|<--------------|                        |               |
        |  DHCP Request |                        |               |
       6|-------------->|                        |               |
        |               |  Relay the DHCP Request|               |
        |              7|-----to CP via Si------>|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              8|<--------via Ci-------->|               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              9|---------via Ci-------->|               |
        |               |                        |   Accounting  |
        |               |                      10|<------------->|
        |               |  Send DHCP ACK         |               |
        |             11|<----to UP via Si-------|               |
        |               |                        |               |
        |  DHCP ACK     |                        |               |
      12|<--------------|                        |               |
        |      RS       |                        |               |
      13|-------------->|                        |               |
        |               |  Relay the Router      |               |
        |               |    Solicit (RA)        |               |
        |             14|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |


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        |               |                      15|<------------->|
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |             16|<--------via Ci---------|               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |             17|---------via Ci-------->|               |
        |               |                        |               |
        |               |  Send Router Advertise |               |
        |               |         (RA)           |               |
        |             18|<----to UP vis Si-------|               |
        |      RA       |                        |               |
      19|<--------------|                        |               |
        |               |                        |               |
        |DHCPv6 Solicit |                        |               |
      20|-------------->|                        |               |
        |               |  Relay DHCPv6 Solicit  |               |
        |             21|-----to CP via Si------>|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Request      |               |
        |             22|<--------via Ci---------|               |
        |               |  Update subscriber     |               |
        |               |   session Response     |               |
        |             23|---------via Ci-------->|               |
        |               |                        |   Accounting  |
        |               |                      24|<------------->|
        |               |  Send DHCPv6 Reply     |               |
        |             25|<----to UP via Si-------|               |
        | DHCPv6 Reply  |                        |               |
      26|<--------------|                        |               |
        |               |                        |               |

                     Figure 18: DHCP Dual Stack Access

   The DHCP dual stack access includes three sets of Update_Request/
   Update_Response exchanges to create/update DHCPv4/v6 subscriber
   session.

   1.  Create DHCPv4 session (step 8 and 9)

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>


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                    [<Subscriber CGN Port Range TLV>]

   2.  Create DHCPv6 session (step 16 and 17)

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   3.  Update DHCPv6 session (step 22 and 23)

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Subscriber Session Update Response TLV>



5.1.6.  L2 Static Subscriber Access

   L2 static subscriber access processes are as follows:

        RG              UP                      CP              AAA
        |               |                        |               |
        |               |    Static Subscriber   |               |
        |               |     Detection Req.     |               |
        |              1|<-----to UP via Ci------|               |
        |               |    Static Subscriber   |               |
        |               |     Detection Rep.     |               |
        |              2|<-----to UP via Ci----->|               |
        |  ARP/ND(REQ)  |                        |               |
     3.1|<--------------|                        |               |
        |  ARP/ND(ACK)  |                        |               |
     3.2|-------------->|                        |               |
        |               |  Relay the ARP/ND      |               |
        |            3.3|-----to CP via Si------>|       AAA     |
        |               |                        |    Req/Rep    |
        |               |                     3.4|<------------->|
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |            3.5|<--------via Ci-------->|               |
        |               |  Create subscriber     |               |


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        |               |   session Response     |               |
        |            3.6|---------via Ci-------->|               |
        |               |                        |               |
        |  ARP/ND(REQ)  |                        |               |
     4.1|-------------->|                        |               |
        |               |  Relay the ARP/ND      |               |
        |            4.2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                     4.3|<------------->|
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |            4.4|<--------via Ci-------->|               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |            4.5|---------via Ci-------->|               |
        |  ARP/ND(ACK)  |                        |               |
     4.6|<--------------|                        |               |
        |               |                        |               |
        |   IP Traffic  |                        |               |
     5.1|-------------->|                        |               |
        |               |  Relay the IP Traffic  |               |
        |            5.2|-----to CP via Si------>|      AAA      |
        |               |                        |    Req/Rep    |
        |               |                     5.3|<------------->|
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |            5.4|<--------via Ci-------->|               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |            5.5|---------via Ci-------->|               |
        |               |                        |               |
        |  ARP/ND(REQ)  |                        |               |
     5.6|<--------------|                        |               |
        |  ARP/ND(ACK)  |                        |               |
     5.7|-------------->|                        |               |
        |               |                        |               |

                  Figure 19: L2 Static Subscriber Access

   For L2 static subscriber access, the process starts with a CP
   installing a static subscriber detection list on an UP.  The list
   determines which subscribers will be detected.  This is implemented
   by exchanging Update_Request and Update_Response messages between CP
   and UP.  The format of the messages are as follows:

   <Update_Request Message> ::= <Common Header>
                     <IPv4 Static Subscriber Detect TLVs>
                     <IPv6 Static Subscriber Detect TLVs>

   <Update_Response Message> ::= <Common Header>


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                    <Update Response TLV>

   For L2 Static subscriber access, there are three ways to trigger the
   access process:

    1. Triggered by UP (3.1-3.6): This assumes that the UP knows the IP
       address, the access interface, and VLAN of the RG.  The UP will
       actively trigger the access flow by sending an ARP/ND packet to
       the RG.  If the RG is online, it will reply with an ARP/ND to the
       UP.  The UP will tunnel the ARP/ND to the CP through the Si.  The
       CP then triggers the authentication process.  If the
       authentication result is positive.  The CP will create a
       corresponding subscriber session on the UP.

    2. Triggered by RG ARP/ND (4.1-4.6): Most of the process is same as
       option 1 (triggered by UP).  The difference is that the RG will
       actively send the ARP/ND to trigger the process.

    3. Triggered by RG IP traffic (5.1-5.7): This is for the case where
       the RG has the ARP/ND information, but the subscriber session on
       the UP is lost (e.g., due to failure on the UP, or the UP
       restarted).  That means the RG may keep sending IP packets to the
       UP.  The packets will trigger the UP to start a new access
       process.

   From a subscriber session point of view, the procedures and the
   message formats for the above three cases are the same, as follows:

   IPv4 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>




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5.2.  PPPoE



5.2.1.  IPv4 PPPoE Access

   The following figure shows the IPv4 PPPoE access call flow.

        RG              UP                      CP              AAA
        |               |                        |               |
        |  PPPoE Disc   |        PPPoE Disc      |               |
       1|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |  PPP LCP      |        PPP LCP         |               |
       2|<------------->|<---------via Si------->|               |
        |               |                        |      AAA      |
        |  PPP PAP/CHAP |        PPP PAP/CHAP    |    Req/Rep    |
       3|<------------->|<---------via Si------->|<------------->|
        |               |                        |               |
        |  PPP IPCP     |        PPP IPCP        |               |
       4|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              5|<--------via Ci-------->|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              6|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                       7|<------------->|
        |               |                        |               |

                       Figure 20: IPv4 PPPoE Access

   From the above sequence, step 1-4 are the standard PPPoE call flow.
   The UP is responsible for redirecting the PPPoE control packets to
   the CP or RG.  The PPPoE control packets are transmitted between the
   CP and UP through the Si.

   After the PPPoE call flow, if the subscriber passed the AAA
   authentication and authorization, the CP will create a corresponding
   session on the UP through the Ci.  The formats of the messages are as
   follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv4 Subscriber TLV>


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                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]



5.2.2.  IPv6 PPPoE Access

   The following figure describes the IPv6 PPPoE access call flow.

        RG              UP                      CP              AAA
        |               |                        |               |
        |  PPPoE Disc   |        PPPoE Disc      |               |
       1|<------------->|<--------via Si-------->|               |
        |               |                        |               |
        |  PPP LCP      |        PPP LCP         |               |
       2|<------------->|<---------via Si------->|               |
        |               |                        |      AAA      |
        |  PPP PAP/CHAP |        PPP PAP/CHAP    |    Req/Rep    |
       3|<------------->|<---------via Si------->|<------------->|
        |               |                        |               |
        |  PPP IP6CP    |        PPP IP6CP       |               |
       4|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Request      |               |
        |              5|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Create subscriber     |               |
        |               |   session Response     |               |
        |              6|---------via Ci-------->|               |
        |               |                        |               |
        | ND Negotiation|        ND Negotiation  |               |
       7|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Request      |               |
        |              8|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Response     |               |
        |              9|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                      10|<------------->|
        |               |                        |               |
        |    DHCPv6     |        DHCPv6          |               |


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        |  Negotiation  |      Negotiation       |               |
      7'|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Request      |               |
        |             8'|---------via Ci-------->|               |
        |               |                        |               |
        |               |  Update subscriber     |               |
        |               |   session Response     |               |
        |             9'|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                     10'|<------------->|
        |               |                        |               |

                       Figure 21: IPv6 PPPoE Access

   From the above sequence, steps 1-4 are the standard PPPoE call flow.
   The UP is responsible for redirecting the PPPoE control packets to
   the CP or RG.  The PPPoE control packets are transmitted between the
   CP and UP through the Si.

   After the PPPoE call flow, if the subscriber passed the AAA
   authentication and authorization, the CP will create a corresponding
   session on the UP through the Ci.  The formats of the messages are as
   follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   Then, the RG will initialize a ND/DHCPv6 negotiation process with the
   CP (see step 7 and 7'), after that, it will trigger an update (8-9,
   8'-9') to the subscriber session. The formats of the update messages
   are as follows:

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>


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                    <Update Response TLV>



5.2.3.  PPPoE Dual Stack Access

   The following figure shows a combination of IPv4 and IPv6 PPPoE
   access call flow.

        RG              UP                      CP              AAA
        |               |                        |               |
        |PPPoE Discovery|      PPPoE Discovery   |               |
       1|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |  PPP LCP      |        PPP LCP         |               |
       2|<------------->|<---------via Si------->|               |
        |               |                        |      AAA      |
        |  PPP PAP/CHAP |        PPP PAP/CHAP    |    Req/Rep    |
       3|<------------->|<---------via Si------->|<------------->|
        |               |                        |               |
        |  PPP IPCP     |        PPP IPCP        |               |
       4|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Create v4 subscriber  |               |
        |               |   session Request      |               |
        |              5|<--------via Ci---------|               |
        |               |  Create v4 subscriber  |               |
        |               |   session Response     |               |
        |              6|---------via Ci-------->|               |
        |               |                        |   Accounting  |
        |               |                       7|<------------->|
        |  PPP IP6CP    |        PPP IP6CP       |               |
      4'|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Create V6 subscriber  |               |
        |               |   session Request      |               |
        |             5'|<--------via Ci---------|               |
        |               |  Create v6 subscriber  |               |
        |               |   session Response     |               |
        |             6'|---------via Ci-------->|               |
        |               |                        |               |
        | ND Negotiation|     ND Negotiation     |               |
       8|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Update v6 subscriber  |               |
        |               |   session Request      |               |
        |              9|---------via Ci-------->|               |
        |               |  Update v6 subscriber  |               |
        |               |   session Response     |               |
        |             10|---------via Ci-------->|               |


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        |               |                        |   Accounting  |
        |               |                      7'|<------------->|
        |    DHCPv6     |        DHCPv6          |               |
        |  Negotiation  |      Negotiation       |               |
      8'|<------------->|<---------via Si------->|               |
        |               |                        |               |
        |               |  Update v6 subscriber  |               |
        |               |   session Request      |               |
        |             9'|<--------via Ci---------|               |
        |               |                        |               |
        |               |  Update v6 subscriber  |               |
        |               |   session Response     |               |
        |            10'|---------via Ci-------->|               |
        |               |                        |               |
        |               |                        |   Accounting  |
        |               |                      7"|<------------->|
        |               |                        |               |

                    Figure 22: PPPoE Dual Stack Access

   PPPoE dual stack is a combination of IPv4 PPPoE and IPv6 PPPoE
   access.  The process is as above.  The formats of the messages are as
   follows:

   1.  Create an IPv4 PPPoE subscriber session (5-6)

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   2.  Create an IPv6 PPPoE subscriber session (5'-6')

   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   3.  Update the IPv6 PPPoE subscriber session (9-10, 9'-10')


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   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.3.  WLAN Access

   The following figure shows the WLAN access call flow.

        RG            UP              CP         AAA      WEB Server
        |             |                |          |           |
        |    DHCP     |                |          |           |
        |  Discovery  |                |          |           |
       1|------------>|                |          |           |
        |             |      DHCP      |          |           |
        |             |    Discovery   |          |           |
        |            2|-----via Si---->|   AAA    |           |
        |             |   DHCP Offer   |<-------->|           |
        |            3|<----via Si-----|          |           |
        |  DHCP Offer |                |          |           |
       4|<------------|                |          |           |
        |     DHCP    |                |          |           |
        |    Request  |                |          |           |
       5|------------>|                |          |           |
        |             |  DHCP Request  |          |           |
        |            6|-----via Si---->|          |           |
        |             |                |          |           |
        |             | Create session |          |           |
        |             |    Request     |          |           |
        |            7|<----via Ci-----|          |           |
        |             | Create session |          |           |
        |             |    Response    |          |           |
        |            8|----via Ci----->|          |           |
        |             |                |          |           |
        |             |  DHCP ACK      |          |           |
        |            9|<----via Si-----|          |           |
        |             |                |          |           |
        |  DHCP ACK   |                |          |           |
      10|<------------|                |          |           |
        |             |                |          |           |
        | Subscriber  |                |          |           |
        | HTTP Traffic|                |          |           |
      11|------------>|-->             |          |           |


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        |             |  | WEB URL     |          |           |
        |  Traffic    |  | Redirect    |          |           |
        | Redirection |  |             |          |           |
      12|<------------|<-+             |          |           |
        |                              |          |           |
        |                                                     |
      13|-----------------Redirect to Web server------------->|
        |                                                     |
      14|<----------------Push HTTP log-in page---------------|
        |                                                     |
      15|-----------------User Authentication---------------->|
        |                                                     |
        |             |                |  Portal Interchange  |
        |             |              16|<-------------------->|
        |             |                |                      |
        |             |                |   AAA    |           |
        |             |                |  Req/Rep |           |
        |             |              17|<-------->|           |
        |             |                |          |           |
        |             | Update session |          |           |
        |             |    Request     |          |           |
        |           18|<----via Ci-----|          |           |
        |             |                |          |           |
        |             | Update session |          |           |
        |             |    Response    |          |           |
        |           19|-----via Ci---->|          |           |
        |             |                |          |           |

                          Figure 23: WLAN Access

   WLAN access starts with the DHCP dial-up process (steps 1-6), after
   that the CP will create a subscriber session on the UP (steps 7-8).
   The formats of the session creation messages are as follows:

   IPv4 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>


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                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   After step 10, the RG will be allocated an IP address and its first
   HTTP packet will be redirected to a WEB server for subscriber
   authentication (steps 11-17).  After the WEB authentication, if the
   result is positive, the CP will update the subscriber session by
   using the following message exchanges:

   IPv4 Case: <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case: <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.4.  L2TP



5.4.1.  L2TP LAC Access

        RG         UP(LAC)      CP(LAC)     AAA        LNS
        |            |              |        |          |
        |    PPPoE   |    PPPoE     |        |          |
        |  Discovery |   Discovery  |        |          |
       1|<---------->|<---via Si--->|        |          |
        |            |              |        |          |
        |  PPP LCP   |   PPP LCP    |        |          |
       2|<---------->|<---via Si--->|        |          |
        |            |              |   AAA  |          |
        |PPP PAP/CHAP| PPP PAP/CHAP | Req/Rep|          |
       3|<---------->|<---via Si--->|<------>|          |
        |            |              |        |          |


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        |  PPP IPCP  |  PPP IPCP    |        |          |
       4|<---------->|<---via Si--->|        |          |
        |            |              |        |          |
        |            | L2TP tunnel  |        |          |
        |            | negotiation  |        |          |
        |            |   SCCRQ/     |        |          |
        |            |   SCCRP/     |        |          |
        |            |   SCCCN      |        |          |
        |           5|<---via Si--->|        |          |
        |            | /\                               |
        |            | || forward                       |
        |            | \/                               |
        |            |<-----------via routing---------->|
        |            |                                  |
        |            | L2TP session |        |          |
        |            | negotiation  |        |          |
        |            |    ICRQ/     |        |          |
        |            |    ICRP/     |        |          |
        |            |    ICCN      |        |          |
        |           6|<---via Si--->|        |          |
        |            | /\                               |
        |            | || forward                       |
        |            | \/                               |
        |            |<-----------via routing---------->|
        |            |                                  |
        |            |    Create    |         |         |
        |            |   subscriber |         |         |
        |            |    session   |         |         |
        |            |    Request   |         |         |
        |           7|<---via Ci----|         |         |
        |            |              |         |         |
        |            |    Create    |         |         |
        |            |   subscriber |         |         |
        |            |    session   |         |         |
        |            |    Response  |         |         |
        |           8|----via Ci--->|         |         |
        |            |              |         |         |
        |                                               |
        |         PAP/CHAP (Triggered by LNS)           |
       9|<-----------------via routing?---------------->|
        |                                               |

                        Figure 24: L2TP-LAC Access

   Steps 1-4 are a standard PPPoE access process.  After that the LAC-CP
   starts to negotiate an L2TP session and tunnel with the LNS.  After
   the negotiation, the CP will create an L2TP LAC subscriber session on
   the UP through the following messages:

   <Update_Request Message> ::= <Common Header>


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                     <Basic Subscriber TLV>
                     <L2TP-LAC Subscriber TLV>
                     <L2TP-LAC Tunnel TLV>

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.4.2.  L2TP LNS IPv4 Access

        RG          LAC            UP(LNS)  AAA      CP(LNS)
        |            |              |        |          |
        |    PPPoE   |              |        |          |
        |  Discovery |              |        |          |
       1|<---------->|              |        |          |
        |            |              |        |          |
        |  PPP LCP   |              |        |          |
       2|<---------->|                       |          |
        |            |          AAA          |          |
        |PPP PAP/CHAP|        Req/Rep        |          |
       3|<---------->|<--------------------->|          |
        |            |                                  |
        |            |                                  |
        |            | L2TP tunnel  |     L2TP tunnel   |
        |            | negotiation  |     negotiation   |
        |            |   SCCRQ/     |       SCCRQ/      |
        |            |   SCCRP/     |       SCCRP/      |
        |            |   SCCCN      |       SCCCN       |
        |           4|<------------>|<------via Si----->|
        |            |              |                   |
        |            | L2TP session |     L2TP session  |
        |            | negotiation  |     negotiation   |
        |            |    ICRQ/     |        ICRQ/      |
        |            |    ICRP/     |        ICRP/      |
        |            |    ICCN      |        ICCN       |
        |           5|<------------>|<------via Si----->|
        |            |              |                   |
        |            |              |    Create         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Request        |
        |            |             6|<-----via Ci-------|
        |            |              |    Create         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Response       |
        |            |             7|------via Ci------>|
        |                                               |
        |          PAP/CHAP (Triggered by LNS)          |


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       8|<--------------------------------------------->|
        |                                               |
        |            |              |        |    AAA   |
        |            |              |        |  Req/Rep |
        |            |              |       9|<-------->|
        |            |              |                   |
        |                                               |
        |                   PPP IPCP                    |
      10|<--------------------------------------------->|
        |                                               |
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Request        |
        |            |            11|<-----via Ci-------|
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Response       |
        |            |            12|------via Ci------>|
        |            |              |                   |

                      Figure 25: IPv4 L2TP-LNS Access

   In this case, the BNG is running as an LNS and separated into LNS-CP
   and LNS-UP.  Steps 1-5 finish the normal L2TP dial-up process.  When
   the L2TP session and tunnel negotiations are finished, the LNS-CP
   will create an L2TP LNS subscriber session on the LNS-UP.  The format
   of messages are as follows:

   <Update_Request Message> ::= <Common Header>
                     <L2TP-LNS Subscriber TLV>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     <L2TP-LNS Tunnel TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   After that, the LNS-CP will trigger an AAA authentication.  If the
   authentication result is positive, a PPP IPCP process will follow,
   then the CP will update the session with the following message
   exchanges:

   <Update_Request Message> ::= <Common Header>
                     <L2TP-LNS Subscriber TLV>


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                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     <L2TP-LNS Tunnel TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]



5.4.3.  L2TP LNS IPv6 Access

        RG          LAC          UP(LNS)    AAA      CP(LNS)
        |            |              |        |          |
        |    PPPoE   |              |        |          |
        |  Discovery |              |        |          |
       1|<---------->|              |        |          |
        |            |              |        |          |
        |  PPP LCP   |              |        |          |
       2|<---------->|                       |          |
        |            |          AAA          |          |
        |PPP PAP/CHAP|        Req/Rep        |          |
       3|<---------->|<--------------------->|          |
        |            |                                  |
        |            |                                  |
        |            | L2TP tunnel  |     L2TP tunnel   |
        |            | negotiation  |     negotiation   |
        |            |   SCCRQ/     |       SCCRQ/      |
        |            |   SCCRP/     |       SCCRP/      |
        |            |   SCCCN      |       SCCCN       |
        |           4|<------------>|<------via Si----->|
        |            |              |                   |
        |            | L2TP session |     L2TP session  |
        |            | negotiation  |     negotiation   |
        |            |    ICRQ/     |        ICRQ/      |
        |            |    ICRP/     |        ICRP/      |
        |            |    ICCN      |        ICCN       |
        |           5|<------------>|<------via Si----->|
        |            |              |                   |
        |            |              |    Create         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Request        |
        |            |             6|<-----via Ci-------|
        |            |              |    Create         |
        |            |              |   subscriber      |
        |            |              |    session        |


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        |            |              |    Response       |
        |            |             7|------via Ci------>|
        |                                               |
        |          PAP/CHAP (Triggered by LNS)          |
       8|<--------------------------------------------->|
        |                                               |
        |            |              |        |    AAA   |
        |            |              |        |  Req/Rep |
        |            |              |       9|<-------->|
        |            |              |        |          |
        |                                               |
        |                   PPP IP6CP                   |
      10|<--------------------------------------------->|
        |                                               |
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Request        |
        |            |            11|<-----via Ci-------|
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Response       |
        |            |            12|------via Ci------>|
        |            |              |                   |
        |                           |                   |
        |       ND negotiation      |   ND negotiation  |
      13|<------------------------->|<-----via Si------>|
        |                           |                   |
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Request        |
        |            |            14|<-----via Ci-------|
        |            |              |    Update         |
        |            |              |   subscriber      |
        |            |              |    session        |
        |            |              |    Response       |
        |            |            15|------via Ci------>|
        |            |              |                   |

                      Figure 26: L2TP-LNS IPv6 Access

   Steps 1-12 are the same as L2TP and LNS IPv4 Access.  Steps 1-5
   finish the normal L2TP dial-up process.  When the L2TP session and
   tunnel negotiations are finished, the LNS-CP will create an L2TP LNS
   subscriber session on the LNS-UP.  The format of the messages is as
   follows:

   <Update_Request Message> ::= <Common Header>


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                     <L2TP-LNS Subscriber TLV>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     <L2TP-LNS Tunnel TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   After that, the LNS-CP will trigger a AAA authentication. If the
   authentication result is positive, a PPP IP6CP process will follow,
   then the CP will update the session with the following message
   exchanges:

   <Update_Request Message> ::= <Common Header>
                     <L2TP-LNS Subscriber TLV>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     <L2TP-LNS Tunnel TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>

   Then, an ND negotiation will be triggered by the RG.  After the ND
   negotiation, the CP will update the session with the following
   message exchanges:

   <Update_Request Message> ::= <Common Header>
                     <L2TP-LAC Subscriber TLV>
                     <Basic Subscriber TLV>
                     <PPP Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     <L2TP-LNS Tunnel TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.5.  CGN (Carrier Grade NAT)

          RG              UP                       CP             AAA
          |               |                        |               |


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          |               |  Public Address Block  |               |
          |               |   Allocation Request   |               |
          |              1|<--------via Ci-------->|               |
          |               |  Public Address Block  |               |
          |               |   Allocation Reply     |               |
          |              2|---------via Ci-------->|               |
          |               |                        |               |
          |   Subscriber  |                        |               |
          | access request|        Subscriber      |               |
         3|-------------->|      access request    |               |
          |              4|----------via Si------->|               |
          |               |                        |      AAA      |
          |               |       Subscriber       |    Req/Rep    |
          |  Subscriber   |      access reply     5|<------------->|
          | access reply 6|<---------via Si--------|               |
         7|<--------------|                        |               |
          |               |                        |               |
          |               |  Create subscriber     |               |
          |               |   session Request      |               |
          |              8|<--------via Ci-------->|               |
          |               |                        |               |
          |               |  Create subscriber     |               |
          |               |   session Response     |               |
          |               | (with NAT information) |               |
          |              9|---------via Ci-------->|               |
          |               |                        |               |
          |               |                        |   Accounting  |
          |               |                        |  with source  |
          |               |                        |   information |
          |               |                      10|<------------->|
          |               |                        |  Public IP +  |
          |               |                        |  Port range   |
          |               |                        |  to Private IP|
          |               |                        |  mapping      |
          |               |                        |               |

                           Figure 27: CGN Access

   The first steps allocate one or more CGN address blocks to the UP
   (steps 1-2).  This is achieved by the following message exchanges
   between CP and UP.

   <Addr_Allocation_Req Message> ::= <Common Header>
                     <Request Address Allocation TLV>

   <Addr_Allocation_Ack Message> ::= <Common Header>
                    <Address Assignment Response TLV>

   Steps 3-9 show the general dial-up process in the case of CGN mode.
   The specific processes (e.g., IPoE, PPPoE, L2TP, etc.) are defined in


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   above sections.

   If a subscriber is a CGN subscriber, once the subscriber session is
   created/updated, the UP will report the NAT information to the CP.
   This is achieved by carrying the "Subscriber CGN Port Range TLV" in
   the Update_Response message.



5.6.  L3 Leased Line Access



5.6.1.  Web Authentication

        RG            UP              CP         AAA      WEB Server
        |             |                |          |           |
        |    User     |                |          |           |
        |   traffic   |                |          |           |
       1|------------>|                |          |           |
        |             |      User      |          |           |
        |             |    traffic     |          |           |
        |            2|-----via Si---->|    AAA   |           |
        |             |                |  Req/Rep |           |
        |             |               3|<-------->|           |
        |             | Create session |          |           |
        |             |    Request     |          |           |
        |            4|<----via Ci-----|          |           |
        |             |                |          |           |
        |             | Create session |          |           |
        |             |    Response    |          |           |
        |            5|----via Ci----->|          |           |
        |    HTTP     |                |          |           |
        |   traffic   |                |          |           |
       6|------------>|                |          |           |
        |             |                |          |           |
        | Redirect to |                |          |           |
        |   Web URL   |                |          |           |
       7|<------------|                |          |           |
        |             |                |          |           |
        |                                                     |
       8|-----------------Redirected to Web server----------->|
        |                                                     |
       9|<----------------Push HTTP Log-in page---------------|
        |                                                     |
      10|-----------------User Authentication---------------->|
        |                                                     |
        |             |                |  Portal Interchange  |
        |             |              11|<-------------------->|
        |             |                |                      |


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        |             |                |   AAA    |           |
        |             |                |  Req/Rep |           |
        |             |              12|<-------->|           |
        |             |                |          |           |
        |             |                |          |           |
        |             | Update session |          |           |
        |             |    Request     |          |           |
        |           13|<----via Ci-----|          |           |
        |             |                |          |           |
        |             | Update session |          |           |
        |             |    Response    |          |           |
        |           14|----via Ci----->|          |           |
        |             |                |          |           |

         Figure 28: Web Authentication based L3 Leased Line Access

   In this case, IP traffic from the RG will trigger the CP to
   authenticate the RG by checking the source IP and the exchanges with
   the AAA server.  Once the RG passed the authentication, the CP will
   create a corresponding subscriber session on the UP through the
   following message exchanges:

   IPv4 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Subscriber Session Update Response TLV>

   Then, the HTTP traffic from the RG will be redirected to a WEB server
   to finish the WEB authentication.  Once the WEB authentication is
   passed, the CP will trigger another AAA authentication.  After the
   AAA authentication, the CP will update the session with the following
   message exchanges:

   IPv4 Case:


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   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.6.2.  User Traffic Trigger

        RG            UP              CP         AAA
        |             |                |          |
        |             |   L3 access    |          |
        |             |  control list  |          |
        |            1|<----via Ci-----|          |
        |    User     |                |          |
        |   traffic   |                |          |
       2|------------>|                |          |
        |             |      User      |          |
        |             |    traffic     |          |
        |            3|-----via Si---->|          |
        |             |                |   AAA    |
        |             |                |  Req/Rep |
        |             |               4|<-------->|
        |             |                |          |
        |             | Create session |          |
        |             |    Request     |          |
        |            5|<----via Ci-----|          |
        |             | Create session |          |
        |             |    Response    |          |
        |            6|----via Ci----->|          |
        |             |                |          |

          Figure 29: User Traffic Triggered L3 Leased Line Access

   In this user traffic triggered case, the CP must install an access


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   control list on the UP, which is used by the UP to determine whether
   an RG is legal or not.  If the traffic is from a legal RG, it will be
   redirected to the CP though the Si.  The CP will trigger a AAA
   interchange with the AAA server.  After that, the CP will create a
   corresponding subscriber session on the UP with the following message
   exchanges:

   IPv4 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv4 Subscriber TLV>
                     <IPv4 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>
                    [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                     <Basic Subscriber TLV>
                     <IPv6 Subscriber TLV>
                     <IPv6 Routing TLV>
                     [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                    <Update Response TLV>



5.7.  Multicast Access

          RG            UP              CP         AAA
          |             |                |          |
          | User access |  User access   |   AAA    |
          |   request   |    request     |  Req/Rep |
         1|<----------->|<----via Si---->|<-------->|
          |             |      User      |          |
          |             |                |          |
          |             |                |          |
          |             | Create session |          |
          |             |    Request     |          |
          |            2|<----via Ci---->|          |
          |             |                |          |
          |             | Create session |          |
          |             |    Response    |          |
          |            3|----via Ci----->|          |
          |             |                |          |
          |  Multicast  |                |          |
          | negotiation |                |          |


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         4|<----------->|                |          |
          |             |                |          |

                        Figure 30: Multicast Access

   Multicast access starts with an user access request from the RG. The
   request will be redirected to the CP by the Si.  A follow-up AAA
   interchange between the CP and the AAA server will be triggered.
   After the authentication, the CP will create a multicast subscriber
   session on the UP through the following messages:

   IPv4 Case:
   <Update_Request Message> ::= <Common Header>
                  <Multicast Group Information TLV>
                  <Basic Subscriber TLV>
                  <IPv4 Subscriber TLV>
                  <IPv4 Routing TLV>
                  [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                 <Update Response TLV>
                 [<Subscriber CGN Port Range TLV>]

   IPv6 Case:
   <Update_Request Message> ::= <Common Header>
                  <Multicast Group Information TLV>
                  <Basic Subscriber TLV>
                  <IPv6 Subscriber TLV>
                  <IPv6 Routing TLV>
                  [<Subscriber Policy TLV>]

   <Update_Response Message> ::= <Common Header>
                 <Update Response TLV>



















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INTERNET-DRAFT                                           Simple BNG CUSP


6.  S-CUSP Message Formats

   An S-CUSP message consists of a common header followed by a variable-
   length body consisting entirely of TLVs.  Receiving an S-CUSP message
   with an unknown message type or missing mandatory TLV MUST trigger an
   Error message (see Section 6.7) or a response message with an Error
   Information TLV (see Section 7.6).

   Conversely, if a TLV is optional, the TLV may or may not be present.
   Optional TLVs are indicated in the message formats shown in this
   document by being enclosed in square brackets.

   This section specifies the format of the common S-CUSP message header
   and lists the defined messages.

   Network byte order is used for all multi-byte fields.



6.1.  Common Message Header

   S-CUSP Common Message 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Ver  |  Resv | Message-Type  |        Message-Length         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            Reserved           |        Transaction-ID         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 6.1: S-CUSP Message Common Header


      o  Ver (4 bits): The major version of the protocol. This document
         specifies version 1. Different major versions of the protocol
         may have significantly different message structure and format
         except that the Ver field will always be in the same place at
         the beginning of each message. A successful S-CUSP session
         depends on the CP and the UP both using the same major version
         of the protocol.

      o  Resv (4 bits):  Reserved. MUST be sent as zero and ignored on
         receipt.

      o  Message-Type (8 bits):  The set of message types specified in
         this document is listed in Section 9.1.

      o  Message-Length (16 bits):  Total length of the S-CUSP message
         including the common header, expressed in number of bytes as an
         unsigned integer.


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      o  Transaction ID (16 bits): This field is used to identify
         requests. It is echoed back in any corresponding ACK / response
         / Error message. It is RECOMMENDED that a monotonically
         increasing value be used in successive message and that value
         wrap back to zero after 0xFFFF.  The contents of this field is
         an opaque value that the receiver MUST NOT use for any purpose
         except to echo back in a corresponding response and,
         optionally, for logging.



6.2.  Control Messages

   This document defines the following control messages:

   Type  Name               Notes and TLVs that can be carried
   ----  ----               ------------------------------------
      1  Hello              Hello TLV, Keep-Alive TLV.
      2  Keepalive          A common header with the Keepalive message
                                type.
      3  Sync_Request       Synchronization request.
      4  Sync_Begin         Synchronization starts.
      5  Sync_Data          Synchronization data: TLVs specified in
                            Section 5.
      6  Sync_End           End synchronization.
      7  Update_Request     TLVs specified in Sections 7.6-7.9.
      8  Update_Response    TLVs specified in Sections 7.6-7.9.



6.2.1.  Hello Message

   Hello message is used for S-CUSP session establishment and version
   negotiation.  The detail of S-CUSP session establishment and version
   negotiation can be found in Section 4.1.1.

   The format of Hello message is as follows:

   <Hello Message> ::= <Common Header>
                        <Hello TLV>
                        <Keepalive TLV>
                        [<Error Information TLV>]

   The return code and negotiation result will be carried in the Error
   Information TLV.  They are listed as follows:

      0: Success, version negotiation success.

      1: Failure, malformed message received.



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      2: One or more of the TLVs was not understood.

      1001: The version negotiation fails.  The S-CUSP session
      establishment phase fails.

      1002: The keepalive negotiation fails.  The S-CUSP session
      establishment phase fails.

      1003: The establishment timer expires.  session establishment
      phase fails.



6.2.2.  Keepalive Message

   The Keepalive message is periodically sent by each end of an S-CUSP
   session.  It is used to detect whether the peer end is still alive.
   The Keepalive procedures are defined Section 4.1.2.

   The format of the Keepalive message is as follows:

   <Keepalive Message> ::= <Common Header>



6.2.3.  Sync_Request Message

   The Sync_Request message is used to request synchronization from an
   S-CUSP peer.  Both CP and UP can request their peer to synchronize
   data.

   The format of the Sync_Request message is as follows:

   <Sync_Request Message> ::= <Common Header>

   A Sync_Request message may result in a Sync_Begin message from its
   peer.  The Sync_Begin message is defined in Section 6.2.4.



6.2.4.  Sync_Begin Message

   The Sync_Begin message is a reply to a Sync_Request message.  It is
   used to notify the synchronization requester whether the
   synchronization can be started.

   The format of Sync_Begin message is as follows:

   <Sync_Begin Message> ::= <Common Header>
                           <Error Information TLV>


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   The return codes are carried in the Error Information TLV.  The codes
   are listed below:

      0: Success, be ready to synchronize.

      1: Failure, malformed message received.

      2: One or more of the TLVs was not understood.

      2001: Synch-NoReady.  The data to be synchronized is not ready.

      2002: Synch-Unsupport.  The data synchronization is not supported.



6.2.5.  Sync_Data Message

   The Sync_Data message is used to send data being synchronized between
   the CP and UP.  The Sync_Data message has the same function and
   format as the Update_Request message.  The difference is that there
   is no ACK for a Sync_Data message.  An error caused by the Sync_Data
   message will result in a Sync_End message.

   There are two scenarios:

      Synchronization from UP to CP: Synchronize the resource data to
      CP.

         <Sync_Data Message> ::= <Common Header>
                                 [<Resource Reporting TLVs>]

      Synchronization from CP to UP: Synchronize all subscriber sessions
      to UP.  As for which TLVs should be carried, it depends on the
      specific session data to be synchronized.  This is equivalent to
      create the specific session.  Refer to Section 5 to see more
      details.

         <Sync_Data Message> ::= <Common Header>
                              [<User Routing TLVs>]
                              [<User Information TLVs>]
                              [<L2TP Subscriber TLVs>]
                              [<Subscriber CGN Port Range TLV>]
                              [<Subscriber Policy TLV>]



6.2.6.  Sync_End Message

   The Sync_End message is used to indicate the end of a synchronization
   process.  The format of a Sync_End message is as follows:


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   <Sync_End Message> ::= <Common Header>
                           <Error Information TLV>

   The return/error codes are listed as follows:

      0: Success, synchronization finished.

      1: Failure, malformed message received.

      2: One or more of the TLVs was not understood.



6.2.7.  Update_Request Message

   The Update_Request message is a multi-task message, it can be used to
   create, update, and delete subscriber sessions on a UP.

   For session operations, the specific operation is controlled by the
   "Oper" field of the carried TLVs.  As defined in Section 7.1, the
   "Oper" can be set to either "update" or "delete" when a TLV is
   carried in an Update_Request message.

   When the "Oper" set to update, it means to create or update a
   subscriber session, if the "Oper" set to delete, it indicates to
   delete a corresponding session on an UP.

   The format of Update_Request message is as follows:

   <Update_Request Message> ::= <Common Header>
                           [<User Routing TLVs>]
                           [<User Information TLVs>]
                           [<L2TP Subscriber TLVs>]
                           [<Subscriber CGN Port Range TLV>]
                           [<Subscriber Policy TLV>]

   Each Update_Request message will result in an Update_Response message
   that is defined in Section 6.2.8.



6.2.8.  Update_Response Message

   The Update_Response message is a response to an Update_Request
   message.  It is used to confirm the update request (or reject it in
   the case of an error).  The format of an Update_Response message is
   as follows:

   <Update_Response Message> ::= <Common Header>
                           [<Subscriber CGN Port Range TLV>]


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                           <Error Information TLV>

   The return/error codes are carried in the Error Information TLV.
   They are listed as follows:

      0: Success.

      1: Failure, malformed message received.

      2: One or more of the TLVs was not understood.

      3001(Pool-Mismatch): The corresponding address pool cannot be
      found.

      3002 (Pool-Full): The address pool is fully allocated and no
      address segment is available.

      3003 (Subnet-Mismatch): The address pool subnet cannot be found.

      3004 (Subnet-Conflict): Subnets in the address pool have been
      classified into other clients.

      4001 (Update-Fail-No-Res): The forwarding table fails to be
      delivered because the forwarding resources are insufficient.

      4002 (QoS-Update-Success): The QoS policy takes effect.

      4003 (QoS-Update-Sq-Fail): Failed to process the queue in the QoS
      policy.

      4004 (QoS-Update-CAR-Fail): Processing of the CAR in the QoS
      policy fails.

      4005 (Statistic-Fail-No-Res): Statistics processing failed due to
      insufficient statistics resources.



6.3.  Event Message

   The Event message is used to report subscriber session traffic
   statistics and detection information.  The format of Event message is
   as follows:

   <Event Message> ::= <Common Header>
                           [<User Traffic Statistics Report TLV>]
                           [<User Detection Result Report TLV>]





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6.4.  Report Message

   The Report message is used to report board and interface status on a
   UP.  The format of Report message is as follows:

   <Report Message> ::= <Common Header>
                           [<Board Status TLVs>]
                           [<Interface Status TLVs>]



6.5.  CGN Messages

   This document defines the following resource allocation messages:

   Type  Name                   TLV that is carried
   ----  -------------------  ------------------------
    200  Addr_Allocation_Req  Address Allocation Request
    201  Addr_Allocation_Ack  Address Allocation Response
    202  Addr_Renew_Req       Address Renewal Request
    203  Addr_Renew_Ack       Address Renewal Response
    204  Addr_Release_Req     Address Release Request
    205  Addr_Release_Ack     Address Release Response



6.5.1.  Addr_Allocation_Req Message

   The Addr_Allocation_Req message is used to request CGN address
   allocation.  The format of Addr_Allocation_Req message is as follows:

   <Addr_Allocation_Req Message> ::= <Common Header>
                           <Address Allocation Request TLV>



6.5.2.  Addr_Allocation_Ack Message

   The Addr_Allocation_Ack message is a response to an
   Addr_Allocation_Req message.  The format of Addr_Allocation_Ack
   message is as follows:

   <Addr_Allocation_Ack Message> ::= <Common Header>
                           <Address Allocation Response TLV>








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INTERNET-DRAFT                                           Simple BNG CUSP


6.5.3.  Addr_Renew_Req Message

   The Addr_Renew_Req message is used to request address renewal.  The
   format of Addr_Renew_Req message is as follows:

   <Addr_Renew_Req Message> ::= <Common Header>
                           <Address Renewal Request TLV>



6.5.4.  Addr_Renew_Ack Message

   The Addr_Renew_Ack message is a response to an Addr_Renew_Req
   message.  The format of Addr_Renew_Req message is as follows:

   <Addr_Renew_Ack Message> ::= <Common Header>
                           <Address Renewal Response TLV>



6.5.5.  Addr_Release_Req Message

   The Addr_Release_Req message is used to request address release.  The
   format of Addr_Release_Req message is as follows:

   <Addr_Release_Req Message> ::= <Common Header>
                           <Address Release Request TLV>



6.5.6.  Addr_Release_Ack Message

   The Addr_Release_Ack message is a response to an Addr_Release_Req
   message.  The format of Addr_Release_Ack message is as follows:

   <Addr_Release_Ack Message> ::= <Common Header>
                           <Address Renewal Response TLV>



6.6.  Vendor Message

   The Vendor message is, in conjunction with the vendor TLV and vendor
   sub-TLV, can be used by vendors to extend the S-CUSP protocol. It's
   message type is 11. If the receiver does not recognize the message,
   an Error message will be returned to the sender.

   The format of the Vendor message is as follows:

   <Vendor Message> ::= <Common Header>


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                        <Vendor TLV>
                        [<any other TLVs as specified by the vendor>]



6.7 Error Message

   The Error message is defined to return some critical error
   information to the sender.  If a receiver does not know the message
   type of a received message, it MUST return an Error message to the
   sender.

   The format of the Error message is as below:

   <Error Message> ::= <Common Header>
                       <Error Information TLV>




































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7.  S-CUSP TLVs and Sub-TLVs

   This section specifies the following:

   o   the format of the TLVs that appear in S-CUSP messages,

   o   the format of the sub-TLVs that appear within the values of some
      TLVs, and

   o   the format of some basic data fields that appear within TLVs or
      sub-TLVs.

   See Section 9 for a list of all defined TLVs and sub-TLVs.



7.1.  Common TLV Header

   S-CUSP messages consist of the common header specified in Section 6.1
   followed by TLVs formatted as specified in this section.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Oper  |      TLV-Type         |       TLV-Length              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                             Value                             ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 32: Common TLV Header

   o  Oper (4 bits): For Message-Types that indicate an operation on a
      data set, the Oper field is interpreted as Update, Delete, or
      Reserved as specified in Section 9.3. For all other Message-Types,
      the Oper field MUST be sent as zero and ignored on receipt.

   o  TLV-Type (12 bits): The Type of a TLV, that is the meaning and
      format of the Value part, are determined by the TLV-Type of the
      TLV.  See Section 9.2.

   o  TLV-Length (2 bytes):  The length of the Value portion of the TLV
      in bytes as an unsigned integer.

   o  Value (variable length):  This is the value portion of the TLV
      whose size is given by TLV-Length. The value portion consists of
      fields, frequently using one of the basic data field types (see
      Section 7.2) and sub-TLVs (see Section 7.3).





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7.2.  Basic Data Fields

   This section specifies the binary format of several standard basic
   data fields that are used within other data structures in this
   specification.

   o  STRING: 0 to 255 octets. Will be encoded as a sub-TLV (see Section
      7.3) to provide the length. The use of this data type in S-CUSP is
      to provide convenient labels for use by network operators in
      configuring and debugging their networks and interpreting S-CUSP
      messages. These labels should not be seen by subscribers. They are
      normally interpreted as ASCII [RFC20].

   o  MAC-Addr: 6 octets. Ethernet MAC Address [RFC7042].

   o  IPv4-Address: 8 octets. 4 octets of the IPv4 address value
      followed by a 4 octet address mask in the format XXX.XXX.XXX.XXX.

   o  IPv6-Address: 20 octets. 16 octets of IPv6 address followed by a 4
      octet integer n in the range of 0 to 128 which gives the address
      mask as the one's complement of 2**(128-n) - 1.

   o  VLAN ID: 2 octets. As follows [802.1Q]:

          0                   1
          0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
         | PRI |D|      VLAN-ID          |
         +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

         PRI: Priority. Default value 7.

         D: Drop Eligibility Indicator (DEI). Default value 0.

         VLAN-ID: Unsigned integer in the range 1-4094. (0 and 4095 are
         not valid VLAN IDs [802.1Q].)
















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7.3.  Sub-TLV Format and Sub-TLVs

   In some cases, the Value portion of a TLV, as specified above, can
   contain one or more Sub-TLVs formatted as follows:

       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             |          Length               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Value                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...

                          Figure 33: Sub-TLV Header

      o  Type (2 bytes): The Type of a Sub-TLV, that is the meaning and
         format of the Value part, are determined by the Type of the
         TLV. Sub-TLV Types numbers have the same meaning regardless of
         the TLV Type of the TLV within which the sub-TVL occurs. See
         Section 9.4.

      o  Length (2 bytes): The length of the Value portion of the sub-
         TLV in bytes as an unsigned integer.

      o  Value (variable length): This is the value portion of the sub-
         TLV whose size is given by Length.

   The sub-TLVs currently specified are defined in the following
   subsections.



7.3.1.  Name sub-TLVs

   This document defines the following name sub-TLVs that are used to
   carry the name of the corresponding object.  The length of each of
   these sub-TLV is variable from 1 to 255 octets.  The value is of type
   STRING padded with zeros octets to 4-octet alignment.

    Type   Sub-TLV Name            Meaning
   -----   --------------------    -------------------
      1    VRF-Name                The name of a VRF
      2    Ingress-QoS-Profile     The name of an ingress QoS profile
      3    Egress-QoS-Profile      The name of an egress QoS profile
      4    User-ACL-Policy         The name of an ACL policy
      5    Multicast-ProfileV4     The name of an IPv4 multicast profile
      6    Multicast-ProfileV6     The name of an IPv6 multicast profile
      7    NAT-Instance            The name of a NAT instance
      8    Pool-Name               The name of an address pool



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7.3.2.  Ingress-CAR sub-TLV

   The Ingress-CAR sub-TLV indicates the authorized upstream Committed
   Access Rate (CAR) parameters. The sub-TLV type of the Ingress-CAR
   sub-TLV is 9 and the sub-TLV length is 16. The format is as shown in
   Figure 34.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  CIR (Committed Information Rate)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  PIR (Peak Information Rate)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  CBS (Committed Burst Size)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  PBS (Peak Burst Size)                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 34: Ingress-CAR sub-TLV

   Where:

      CIR (4 bytes): Guaranteed rate in bits/second.

      PIR (4 bytes): Burst rate in bits/second.

      CBS (4 bytes): The token bucket in bytes.

      PBS (4 bytes): Burst token bucket in bytes.

   These fields are unsigned integers. More details about CIR, PIR, CBS,
   and PBS can be found in [RFC2698].



7.3.3.  Egress-CAR sub-TLV

   The Egress-CAR sub-TLV indicates the authorized downstream Committed
   Access Rate (CAR) parameters. The sub-TLV type of the Egress-CAR sub-
   TLV is 10 and its sub-TLV length is 16 octets. The format of the
   value part is as defined below.










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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  CIR (Committed Information Rate)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  PIR (Peak Information Rate)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  CBS (Committed Burst Size)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  PBS (Peak Burst Size)                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 35: Egress-CAR sub-TLV


   Where:

      CIR (4 bytes): Guaranteed rate in bits/second.

      PIR (4 bytes): Burst rate in bits/second.

      CBS (4 bytes): The token bucket in bytes.

      PBS (4 bytes): Burst token bucket in bytes.

   These fields are unsigned integers. More details about CIR, PIR, CBS,
   and PBS can be found in [RFC2698].



7.3.4.  If-Desc sub-TLV

   The If-Desc sub-TLV is defined to designate an interface.  It is an
   optional sub-TLV that may be carried in those TLVs that have an "if-
   index" or "out-if-index" field. The If-Desc sub-TLV is used as a
   local unique identifier within a BNG.

   The sub-TLV type is 11 and the sub-TLV length is 12 octets.  The
   format depends on the If-Type. The format of the value part is as
   follows:












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    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  If-Type (1-5)|    Chassis    |             Slot              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Sub-Slot            |            Port Number        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Sub-Port Number                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    If-Desc sub-TLV (Physical Port)

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | If-Type (6-7) |                Reserved                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                            Logic-ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Sub-Port Number                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     If-Desc sub-TLV (Virtual Port)

                    Figure 36: If-Desc sub-TLV Formats

   Where:

      If-Type: 8 bits in length, indicates the type of an interface.
      Following types are defined in this document:

         0: Reserved
         1: Fast Ethernet (FE)
         2: GE
         3: 10GE
         4: 100GE
         5: Eth-Trunk
         6: Tunnel
         7: VE
         8-255: Reserved.

      Chassis (8 bits): Identifies the chassis that the interface
      belongs to.

      Slot (16 bits): Identifies the slot that the interface belongs to.

      Sub-slot (16 bits): Identifies the sub-slot the interface belongs
      to.

      Port Number (16 bits): An identifier of a physical port/interface
      (e.g., If-Type: 1-5). It is locally significant within the
      slot/sub-slot.


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      Sub-port Number (32 bits): An identifier of the sub-port. Locally
      significant within its "parent" port (physical or virtual).

      Logic-ID (32 bits): An identifier of a virtual interface (e.g.,
      If-Type: 6-7)



7.3.5.  IPv6 Address List sub-TLV

   The IPv6 Address List sub-TLV is used to convey one or more IPv6
   addresses.  It is carried in the IPv6 Subscriber TLV.  The sub-TLV
   type is 12, the sub-TLV length is variable.

   The format of IPv6 Addresses sub-TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        IPv6 Address                           ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        IPv6 Address                           ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                            ...                                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        IPv6 Address                           ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 37: IPv6 Address List sub-TLV

   Where:

      IP Address (IPv6-Address): Each IP Address is an IP-Address type,
      carries an IPv6 address.



7.3.6.  Vendor sub-TLV

   The Vendor sub-TLV is intended to be used inside the value portion of
   the Vendor TLV (Section 7.13). It provides a Sub-Type that
   effectively extends the sub-TLV type in the sub-TLV header and
   provides for versioning of vendor sub-TLVs.

   The value part of the Vendor sub-TLV is formatted as follows:







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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Vendor ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Sub-Type            |       Sub-Type-Version        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~             value (other as specified by vendor)              ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 38: Vendor sub-TLV

   Where:

      The sub-TLV type: 13.

      The sub-TLV length: variable.

      Vendor-ID (4 bytes): Vendor ID as defined in RADIUS [RFC2865].

      Sub-Type (2 bytes): Used by the Vendor to distinguish multiple
      different sub-TLVs.

      Sub-Type-Version (2 bytes): Used by the Vendor to distinguish
      different versions of a Vendor Defined sub-TLV sub-Type.

      value: as specified by the vendor.

   Since Vendor code will be handling the sub-TLV after the Vendor ID
   field is recognized, the remainder of the sub-TLV can be organized
   however the vendor wants. But it desirable for a vendor to be able to
   define multiple different vendor sub-TLVs and to keep track of
   different versions of its vendor defined sub-TLVs. Thus, it is
   RECOMMENDED that the vendor assign a Sub-Type value for each of that
   vendor's sub-TLVs that is different from other Sub-Type values that
   vendor has used. Also, when modifying a vendor defined sub-TLV in a
   way potentially incompatible with a previous definition, the vendor
   SHOULD increase the value it is using in the Sub-Type-Version field.














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7.4.  The Hello TLV

   The Hello TLV is defined to be carried in the Hello message for
   version and capabilities negotiation.  It indicates the S-CUSP sub-
   version and capabilities supported.  The format of Hello TLV is as
   follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          VerSupported                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Vendor ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Capabilities                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             Figure 39: Hello TLV

   Where:

      The TLV type is 100.

      The TLV length is 12 octets.

      The value field consists of three parts:

         VerSupported: 32 bits in length.  This is a bit map of the Sub-
         Versions of the S-CUSP protocol that the sender supports.  This
         document specifies Sub-Version zero of Major Version 1, that
         is, Version 1.0.  The VerSupported field MUST be non-zero.  The
         VerSupported bits are numbered from 0 as the most significant
         bit. Bit 0 indicates support of Sub-Version zero, bit 1
         indicates support of Sub-Version one, etc.

         Vendor-ID: 4 bytes in length.  Vendor ID, as defined in RADIUS
         [RFC2865].

         Capabilities: 32 bits in length. Flags that indicate the
         support of particular capabilities by the sender of the Hello.
         No Capabilities are defined in this document and so
         implementations will set this field to zero. The Capabilities
         field of the Hello TLV MUST be checked before any other TLVs in
         the Hello because capabilities defined in the future might
         extend existing TLVs or permit new TLVs.

   After the exchange of Hello messages, the CP and UP each perform a
   logical AND of the Sub-Version supported by the CP and the UP and
   separately perform a logical AND of the Capabilities bits fields for
   the CP and the UP.


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   If the result of the AND of the Sub-Versions supported is zero, then
   no session can be established and the connection is torn down. If the
   result of the AND of the Sub-Versions supported is non-zero, then the
   session uses the highest Sub-Version supported by both the CP and UP.

   For example, if one side supports Sub-Versions 1, 3, 4, and 5
   (VerSupported = 0x5C000000) and the other side supports 2, 3, and 4
   (VerSupported = 0x38000000) then 3 and 4 are the Sub-Versions in
   common and 4 is the highest Sub-Version supported by both sides. So
   Sub-Version 4 is used for the session that has been negotiated.

   The result of the logical AND of the Capabilities bits will show what
   additional capabilities both sides support. If this result is zero,
   there are no such capabilities so none can be used during the
   session. If this result is non-zero, it shows the additional
   capabilities that can be used during the session. The CP and the UP
   MUST NOT use a capability unless both advertise support.



7.5.  The Keep Alive TLV

   The Keep Alive TLV is defined to be carried in the Hello message.  It
   provides timing information for the keep alive feature.  The format
   of Hello TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Keepalive   | DeadTimer     |            Reserved           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 40: Keep Alive TLV

   Where:

      The TLV type: 102.

      The value of length: 4 octets.

      Keepalive (8 bits): Indicates the maximum period of time (in
      seconds) between two consecutive S-CUSP messages sent by the
      sender of the message containing this TLV as an unsigned integer.
      The minimum value for the Keepalive is 1 second. When set to 0,
      once the session is established, no further Keepalive messages are
      sent to the remote peer. A RECOMMENDED value for the Keepalive
      frequency is 30 seconds.

      DeadTimer (8 bits in length): Specifies the amount of time as an
      unsigned integer number of seconds after the expiration of which


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      the S-CUSP peer can declare the session with the sender of the
      Hello message to be down if no S-CUSP message has been received.
      The DeadTimer SHOULD be set to 0 and MUST be ignored if the
      Keepalive is set to 0. A RECOMMENDED value for the DeadTimer is 4
      times the value of the Keepalive.

      The Reserved bits MUST be sent as zero and ignored on receipt.



7.6.  The Error Information TLV

   The Error Information TLV is a common TLV that can be used in many
   Response (e.g., Update_Response message) and ACK messages (e.g.,
   Addr_Allocation_Ack message, etc.).  It is used to convey the
   information about an error in the received S-CUSP message.  The
   format of the Error Information TLV is as follows:

       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  |  Reserved             |  TLV-Type             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Error Code                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 41: Error Information TLV

   Where:

      The TLV type: 101.

      The value of length: 8 octets.

      Message-Type(1 byte): This parameter is the message type of the
      message containing an error.

      Reserved (1 byte): MUST be sent as zero and ignored on receipt.

      TLV-Type (2 bytes): Indicates which TLV caused the error.

      Error Code: 4 bytes in length.  Indicate the specific Error Code
      (see Section 9.5).



7.7.  BAS Function Enabler TLV

   The BAS Function Enabler TLV is used by a CP to control the access
   mode, authentication methods, and other related functions of an


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   interface on a UP.

   The format of the BAS Function Enabler TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          If-Index                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Access-Mode  |  Auth-Method4 |  Auth-Method6 |    Reserved   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Flags                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         sub-TLVs (optional)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 42: BAS Function Enabler TLV

   Where:

      The TLV type: 1.

      The value of length: variable.

      If-Index: 4 bytes in length, a unique identifier of an interface
      of a BNG.

      Access-Mode: 1 byte in length, indicates the access mode of the
      interface.  This document defines following values:

         0: Layer 2 subscriber;
         1: Layer 3 subscriber;
         2: Layer 2 leased line;
         3: Layer 3 leased line;
         4-255: Reserved.

      Auth-Method4: 1 byte in length, for IPv4 scenario, it indicates
      the authentication on this interface; this field is defined as a
      bitmap, this document defines following values (other bits are
      reserved and MUST be sent as zero and ignored on receipt):

         0x1: PPPoE authentication;
         0x2: DOT1X authentication;
         0x4: Web authentication;
         0x8: Web fast authentication;
         0x10: Binding authentication.

      Auth-Method6: 1 byte in length, for IPv6 scenario, it indicates
      the authentication on this interface; this field is defined as a
      bitmap, this document defines following values (other bits are


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      reserved and MUST be sent as zero and ignored on receipt):

         0x1: PPPoE authentication;
         0x2: DOT1X authentication;
         0x4: Web authentication;
         0x8: Web fast authentication;
         0x10: Binding authentication;

      sub-TLVs: The IF-Desc sub-TLV can be carried.
         If-Desc sub-TLV: carries the interface information.

      The flags field is defined as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                MBZ                            |Y|X|P|I|N|A|S|F|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 43: Interface Flags

      Where:

         F (IPv4 Trigger) bit: Indicates whether IPv4 packets can
         trigger a subscriber to go online. 1: enabled, 0: disabled.

         S (IPv6 Trigger) bit: Indicates whether IPv6 packets can
         trigger a subscriber to go online. 1: enabled, 0: disabled.

         A (ARP Trigger) bit: Indicates whether ARP packets can trigger
         a subscriber to go online. 1: enabled, 0: disabled.

         N (ND Trigger) bit: Indicates whether ND packets can trigger a
         subscriber to go online. 1: enabled, 0: disabled.

         I (IPoE-Flow-Check): Used for UP detection.  IPoE 1: Enable
         traffic detection. 0: Disable traffic detection.

         P (PPP-Flow-Check) bit: Used for UP detection.  PPP 1: Enable
         traffic detection. 0: Disable traffic detection.

         X (ARP-Proxy) bit: 1: The interface is enabled with ARP proxy
         and can process ARP requests across different Port+VLANs. 0:
         The ARP proxy is not enabled on the interface, and only the ARP
         requests of the same Port+VLAN are processed.

         Y (ND-Proxy) bit: 1: The interface is enabled with ND proxy and
         can process ND requests across different Port+VLANs. 0: The ND
         proxy is not enabled on the interface, and only the ND requests
         of the same Port+VLAN are processed.


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         MBZ: Reserved bits that MUST be sent as zero and ignored on
         receipt.



7.8.  Routing TLVs

   Normally, after an S-CUSP session is established between a UP and a
   CP, the CP will allocate one or more blocks of IP addresses to the
   UP.  Those IP addresses will be allocated to subscribers who will
   dial-up to the UP.  In order to make sure that other nodes within the
   network learn how to reach those IP addresses, the CP needs to
   install one or more routes that can reach those IP addresses on the
   UP and notify the UP to advertise the routes to the network.

   The Routing TLVs are used by a CP to notify a UP of the network
   routing.  They can be carried in the Update_Request message and
   Sync_Data message.



7.8.1.  IPv4 Routing TLV

   The IPv4 Routing TLV is used to carry IPv4 network routing related
   information.

   The format of the TLV value part is as below:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Dest-Address                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Next-Hop                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Out-If-Index                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Cost                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Tag                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Route Type             |          Reserved           |A|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          sub-TLVs  (optional)                 ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 44: IPv4 Routing TLV



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   Where:

      The TLV Type: 7

      The TLV Length: Variable

      User-ID: 4 bytes in length.  Carries the user identifier.  This
      field is filled with all Fs when a non-user route is delivered to
      the UP.

      Dest-Address (IPv4-Address type):  Identifies the destination
      address.

      Next-Hop: (IPv4-Address type):  Identifies the next hop address.

      Out-If-Index (4 bytes):  Indicates the interface index.

      Cost (4 bytes):  The cost value of the route.

      Tag (4 bytes):  The tag value of the route.

      Route-Type (2 bytes):  Indicates the route type.  The options are
      as follows:

         0: User host route
         1: Radius authorization FrameRoute
         2: Network segment route
         3: Gateway route
         4: Radius authorized IP route
         5: L2TP LNS side user route

      Advertise-Flag: 1 bit.  Indicates whether the route should be
      advertised by the UP.  Following flags are defined:
         0: Not advertised,
         1: advertised.

      sub-TLVs: The VRF-Name  and/or If-Desc sub-TLVs can be carried.
         VRF-Name sub-TLV: indicates which VRF the route belongs to.
         If-Desc sub-TLV: carries the interface information.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.8.2.  IPv6 Routing TLV

   The IPv6 Routing TLV is used to carry IPv6 network routing
   information.

   The format of this TLV is as follows:


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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          IPv6 Dest-Address                    ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          IPv6 Next-Hop                        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Out-If-Index                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Cost                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Tag                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Route Type             |          Reserved           |A|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          sub-TLVs (optional)                  ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                         Figure 45: IPv6 Routing TLV

   Where:

      The TLV Type: 7

      The TLV Length: Variable

      User-ID: 4 bytes in length.  Carries the user identifier.  This
      field is filled with all Fs when a non-user route is delivered to
      the UP.

      IPv6 Dest-Address (IPv6-Address type):  Identifies the destination
      address.

      IPv6 Next-Hop: (IPv6-Address type):  Identifies the next hop
      address.

      Out-If-Index (4 bytes):  Indicates the interface index.

      Cost (4 bytes):  The cost value of the route.

      Tag (4 bytes):  The tag value of the route.

      Route-Type: (2 bytes):  Indicates the route type.  The options are
      as follows:






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         0: User host route
         1: Radius authorization FrameRoute
         2: Network segment route
         3: Gateway route
         4: Radius authorized IP route
         5: L2TP LNS side user route

      Advertise-Flag: 1 bit.  Indicates whether the route should be
      advertised by the UP.  Following flags are defined:
         0: Not advertised,
         1: advertised.

      sub-TLVs: If-Desc and VRF-Name sub-TLVs can be carried.
         VRF-Name sub-TLV: Indicates the VRF to which the subscriber
      belongs.
         If-Desc sub TLV: carries the interface information.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.  Subscriber TLVs

   The Subscriber TLVs are defined for a CP to send the basic
   information about a user to a UP.



7.9.1.  Basic Subscriber TLV

   The Basic Subscriber TLV is used to carry the basic common
   information for all kinds of access subscribers.  It is carried in an
   Update_Request message.



















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   The format of the Basic Subscriber TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Session ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User MAC                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             User MAC          |   Oper ID     |    Reserved   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Access Type   |Sub-access Type|  Account Type | Address Family|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               C-VID           |          P-VID                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Detect Times    |          Detect Interval      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            If-Index                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                            sub-TLVs (optional)                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 46: Basic Subscriber TLV

   Where:

      The TLV Type: 2.

      The TLV Length: variable in length.

      User-ID (4 bytes): The identifier of a subscriber.

      Session-ID (4 bytes): Session ID of a PPPoE subscriber.  Zero
      means non-PPPoE subscriber.

      User-Mac (MAC-Addr type): The MAC Address of a subscriber.

      Oper-ID (1 byte): Indicates the ID of an operation performed by a
      user.  This field is carried in the response from the UP.

      Reserved (1 byte): MUST be sent as zero and ignored on receipt.

      Access-Type (1 byte):

         1: PPP access (PPP)
         2: PPP over Ethernet over ATM access (PPPoEoA)
         3: PPP over ATM access (PPPoA)
         4: PPP over Ethernet access (PPPoE)


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         5: PPPoE over VLAN access (PPPoEoVLAN)
         6: PPP over LNS access (PPPoLNS)
         7: IP over Ethernet DHCP access (IPoE_DHCP)
         8: IP over Ethernet EAP authentication access (IPoE_EAP)
         9: IP over Ethernet Layer 3 access (IPoE_L3)
         10: IP over Ethernet Layer 2 Static access (IPoE_L2_STATIC)
         11: Layer 2 Leased Line access (L2_Leased_Line)
         12: Layer 2 VPN Leased Line access (L2VPN_Leased_Line)
         13: Layer 3 Leased Line access (L3_Leased_Line)
         14: Layer 2 Leased line Sub-User access
                 (L2_Leased_Line_SUB_USER)
         15: L2TP LAC tunnel access (L2TP_LAC)
         16: L2TP LNS tunnel access (L2TP_LNS)

      Sub-Access-Type (1 byte): Indicates whether PPP termination or PPP
      relay is used.
         0: Reserved
         1: PPP Relay (for LAC)
         2: PPP termination (for LNS)

      Account-Type(1 byte):
         0: Collects statistics on IPv4 and IPv6 traffic of terminals
                 independently.
         1: Collects statistics on IPv4 and IPv6 traffic of terminals.

      Address Family (1 byte)
         1: IPv4
         2: IPv6
         3: dual stack

      C-VID (VLAN-ID): Indicates the inner VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  The default value of PRI
      is 7, the value of DEI is 0, and the value of VID is 1~4094.  The
      PRI value can also be obtained by parsing terminal packets.

      P-VID (VLAN-ID): Indicates the outer VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  The format is the same as
      that for C-VID.

      Detect-Times (2 bytes): Number of detection timeout times.  The
      value 0 indicates that no detection is performed.

      Detect-Interval (2 bytes): Detection interval in seconds.

      If-Index (4 bytes): Interface index.

      Sub-TLVs: VRF-Name sub-TLV and If-Desc sub-TLV can be carried.
         VRF-Name sub-TLV: Indicates the VRF to which the subscriber
      belongs.
         If-Desc sub-TLV: carries the interface information.


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      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.2.  PPP Subscriber TLV

   The PPP Subscriber TLV is defined to carry PPP information of a User
   from a CP to a UP. It will be carried in an Update_Request message
   when PPPoE or L2TP access is used.

   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        MSS                    |        Reserved             |M|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        MRU                    |        Reserved               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Magic Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Peer Magic Number                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 47: PPP Subscriber TLV

   Where:

      The TLV type: 3.

      The TLV length: 12 octets.

      User-ID (4 bytes): The identifier of a subscriber.

      MSS-Value (2 bytes): Indicates the MSS value (in bytes).

      MSS-Enable (M) (1 bit): Indicates whether the MSS is enabled.
         0: Disabled.
         1: Enabled.

      MRU (2 bytes): PPPoE local MRU (in bytes).

      Magic-Number (4 bytes): Local magic number in PPP negotiation
      packets.

      Peer-Magic-Number (4 bytes): Remote peer magic number.

      The Reserved fields MUST be sent as zero and ignored on receipt.


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7.9.3.  IPv4 Subscriber TLV

   The IPv4 Subscriber TLV is defined to carry IPv4 related information
   for a BNG user.  It will be carried in an Update_Request message when
   IPv4 IPoE, or PPPoE access is used.

   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User IPv4 Address                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Gateway IPv4 Address                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          MTU                  |   Reserved            |U|E|W|P|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          VRF-Name sub-TLV                     ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 48: IPv4 Subscriber TLV

   Where:

      The TLV type: 4.

      The TLV length: variable.

      User-ID (4 bytes): The identifier of a subscriber.

      User-IPv4 (IPv4-Address): The IPv4 address of the subscriber.

      Gateway-IPv4 (IPv4-Address): The gateway address of the
      subscriber.

      Portal Force (P) (1 bit ): Push advertisement, 0: off, 1: on.

      Web-Force (W) (1 bit): Push IPv4 Web. 0: off, 1: on.

      Echo-Enable (E) (1 bit): UP returns ARP Req or PPP Echo. 0: off,
      1: on.

      IPv4-URPF (U) (1 bit): User Unicast Reverse Path Forwarding (URPF)
      flag. 0: off, 1: on.

      MTU 2 bytes MTU value.  The default value is 1500.

      VRF-Name Sub-TLV: Indicates the subscriber belongs to which VRF.


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      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.4.  IPv6 Subscriber TLV

   The IPv6 Subscriber TLV is defined to carry IPv6 related information
   for a BNG user.  It will be carried in an Update_Request message when
   IPv6 IPoE, or PPPoE access is used.

   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~           User PD-Address (IPv6 Address List sub-TLV)         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~        Gateway ND-Address (IPv6 Address List sub-TLV)         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User IANA Address                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          IPv6 Interface ID                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          IPv6 Interface ID (cont.)            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          MTU                  |   Reserved            |U|E|W|P|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                    VRF Name sub-TLV (optional)                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 749: IPv6 Subscriber TLV

   Where:

      The TLV type: 5.

      The TLV length: variable.

      User-ID (4 bytes): The identifier of a subscriber.

      User PD-Addresses (IPv6 Address List): Carries a list of Prefix
      Delegation (PD) addresses of the subscriber.

      User ND-Addresses (IPv6 Address List): Carries a list of Neighbor
      Discovery (ND) addresses of the subscriber.

      User IANA-Address (IPv6-Address): The IANA address of the
      subscriber.


Hu, et al                                                      [Page 89]


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      IPv6 Interface ID (8 bytes): The identifier of an IPv6 interface.

      Portal Force 1 bit (P): Push advertisement, 0: off, 1: on.

      Web-Force 1 bit (W): Push IPv6 Web, 0: off, 1: on.

      Echo-Enable 1 bit (E): The UP returns ARP Req or PPP Echo. 0: off;
      1: on.

      IPv6-URPF 1 bit (U): User Reverse Path Forwarding (URPF) flag, 0:
      off; 1: on.

      MTU (2 bytes): The MTU value.  The default value is 1500.

      VRF-Name Sub-TLV: Indicates the VRF to which the subscriber
      belongs.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.5.  IPv4 Static Subscriber Detect TLV

   The IPv4 Static Subscriber Detect TLV is defined to carry IPv4
   related information for a static access subscriber.  It will be
   carried in an Update_Request message when IPv4 static access on a UP
   needs to be enabled.

   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          If-Index                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           C-VID               |           P-VID               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User Address                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Gateway Address                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User MAC                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        User MAC (cont.)       |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       sub-TLVs (optional)                     ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 750: IPv4 Static Subscriber TLV



Hu, et al                                                      [Page 90]


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   Where:

      The TLV type: 6.

      The TLV length: variable.

      If-Index (4 bytes): The interface index of the interface from
      which the subscriber will dial-up.

      C-VID (VLAN-ID): Indicates the inner VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  A valid value is 1~4094.

      P-VID (VLAN-ID): Indicates the outer VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  The format is the same as
      that of the C-VID.  A valid value is 1~4094.  For a single-layer
      VLAN, set this parameter to PeVid.

      User Address (IPv4-Addr): The user's IPv4 address.

      Gateway Address (IPv4-Addr): The gateway's IPv4 Address.

      User-MAC (MAC-Addr type): The MAC address of the subscriber.

      Sub-TLVs: VRF-Name and If-Desc sub-TLVs may be carried.
         VRF-Name sub-TLV: Indicates the VEF to which the subscriber
      belongs.
         If-Desc sub-TLV: Carries the interface information.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.6.  IPv6 Static Subscriber Detect TLV

   The IPv6 Static Subscriber Detect TLV is defined to carry IPv6
   related information for a static access subscriber.  It will be
   carried in an Update_Request message when needed to enable IPv6
   static subscriber detection on a UP.














Hu, et al                                                      [Page 91]


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   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          If-Index                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           C-VID               |           P-VID               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          User Address                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          Gateway Address                      ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User MAC                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        User MAC (cont.)       |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        sub-TLVs (optional)                     ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 51: IPv6 Static Subscriber Detect TLV

   Where:

      The TLV type: 6.

      The TLV length: variable.

      If-Index (4 bytes): The interface index of the interface from
      which the subscriber will dial-up.

      C-VID (VLAN-ID): Indicates the inner VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  A valid value is 1~4094.

      P-VID (VLAN-ID): Indicates the outer VLAN ID.  The value 0
      indicates that the VLAN ID is invalid.  The format is the same as
      that the of C-VID.  A valid value is 1~4094.  For a single-layer
      VLAN, set this parameter to PeVid.

      User Address (IPv6-Address type): The subscriber's IPv6 address.

      Gateway Address (IPv6-Address type): The gateway's IPv6 Address.

      User-MAC (MAC-Addr type): The MAC address of the subscriber.

      sub-TLVs: VRF-Name and If-Desc sub-TLVs may be carried
         VRF-Name Sub-TLV: Indicates the VRF to which the subscriber
      belongs.
         If-Desc sub-TLV: Carries the interface information.



Hu, et al                                                      [Page 92]


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      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.7.  L2TP-LAC Subscriber TLV

   The L2TP-LAC Subscriber TLV is defined to carry the related
   information for a L2TP LAC access subscriber.  It will be carried in
   an Update_Request message when L2TP LAC access is used.

   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Local Tunnel ID          |     Local Session ID          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Remote Tunnel ID         |     Remote Session ID         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 52: L2TP-LAC Subscriber TLV

   Where:

      The TLV type: 11.

      The TLV length: 12 octets.

      User-ID (4 bytes): The identifier of a user/subscriber.

      Local-Tunnel-ID (2 bytes): The local ID of the L2TP tunnel.

      Local-Session-ID (2 bytes): The local session ID with the L2TP
      tunnel.

      Remote-Tunnel-ID (2 bytes): The remote ID of the L2TP tunnel.

      Remote-Session-ID (2 bytes): The remote session ID of the L2TP
      tunnel.



7.9.8.  L2TP-LNS Subscriber TLV

   The L2TP-LNS Subscriber TLV is defined to carry the related
   information for a L2TP LNS access subscriber.  It will be carried in
   an Update_Request message when L2TP LNS access is used.



Hu, et al                                                      [Page 93]


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   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Local Tunnel ID          |     Local Session ID          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      Remote Tunnel ID         |     Remote Session ID         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 53: L2TP-LNS Subscriber TLV

   Where:

      The TLV type: 12.

      The TLV length: 12 octets.

      User-ID (4 bytes): The identifier of a user/subscriber.

      Local-Tunnel-ID (2 bytes): The local ID of the L2TP tunnel.

      Local-Session-ID (2 bytes): The local session ID with the L2TP
      tunnel.

      Remote-Tunnel-ID (2 bytes): The remote ID of the L2TP tunnel.

      Remote-Session-ID (2 bytes): The remote session ID of the L2TP
      tunnel.



7.9.9.  L2TP-LAC Tunnel TLV

   The L2TP-LAC Tunnel TLV is defined to carry the L2TP LAC tunnel
   related information.  It will be carried in the Update_Request
   message when L2TP LAC access is used.

   The format of the TLV value part is as follows:











Hu, et al                                                      [Page 94]


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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Local Tunnel ID         |       Remote Tunnel ID        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Source Port         |        Destination Port       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          Tunnel Source Address                ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          Tunnel Destination Address           ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          VRF Name sub-TLV                     ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 54: L2TP-LAC Tunnel TLV

   Where:

      The TLV type: 13.

      The TLV length: variable.

      Local-Tunnel-ID (2 bytes): The local ID of the L2TP tunnel.

      Remote-Tunnel-ID (2 bytes): The remote ID of the L2TP tunnel.

      Source-Port (2 bytes): The source UDP port number of an L2TP
      subscriber.

      Dest-Port (2 bytes): The destination UDP port number of an L2TP
      subscriber.

      Source-IP (IPv4/v6): The source IP address of the tunnel.

      Dest-IP (IPv4/v6): The destination IP address of the tunnel.

      VRF-Name Sub-TLV: The VRF name to which the L2TP subscriber tunnel
      belongs.



7.9.10.  L2TP-LNS Tunnel TLV

   The L2TP-LNS Tunnel TLV is defined to carry the L2TP LNS tunnel
   related information.  It will be carried in the Update_Request
   message when L2TP LNS access is used.

   The format of the TLV value part is as follows:

       0                   1                   2                   3


Hu, et al                                                      [Page 95]


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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Local Tunnel ID        |       Remote Tunnel ID        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Source Port            |       Destination Port        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       Tunnel Source Address                   ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       Tunnel Destination Address              ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                       VRF Name sub-TLV                        ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 55: L2TP-LNS Tunnel TLV

   Where:

      The TLV type: 14.

      The TLV length: variable.

      Local-Tunnel-ID (2 bytes): The local ID of the L2TP tunnel.

      Remote-Tunnel-ID (2 bytes): The remote ID of the L2TP tunnel.

      Source-Port (2 bytes): The source UDP port number of an L2TP
      subscriber.

      Dest-Port (2 bytes): The destination UDP port number of an L2TP
      subscriber.

      Source-IP (IPv4/v6): The source IP address of the tunnel.

      Dest-IP (IPv4/v6): The destination IP address of the tunnel.

      VRF-Name Sub-TLV: The VRF name to which the L2TP subscriber tunnel
      belongs.



7.9.11.  Update Response TLV

   The Update Response TLV is used to return the operation result of an
   update request.  It is carried in the Update_Response message as a
   response to the Update_Request message.







Hu, et al                                                      [Page 96]


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   The format of Session Update Response TLV is as follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                          User-ID                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | User-Trans-ID |   Oper-Code   |   Oper-Result |  Reserved     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Error-Code                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 56: Session Update Response TLV

   Where:

      The TLV type: 302.

      The TLV length: 12.

      User-ID (4 bytes): A unique identifier of an user/subscriber.

      User-Trans-ID (1 byte): In the case of dual-stack access or when
      modifying a session, User-Trans-ID is used to identify a user
      operation transaction.  It is used by the CP to correlate a
      response to a specific request.

      Oper-Code (1 byte): Operation code. 1: update, 2: delete.

      Oper-Result (1 byte): Operation Result. 0: Success, Others:
      Failure.

      Error-Code (4 bytes): Operation failure cause code.  for details,
      see Section 9.5.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.12.  Subscriber Policy TLV

   The Subscriber Policy TLV is used to carry the policies that will be
   applied to a subscriber.  It is carried in the Update_Request
   message.








Hu, et al                                                      [Page 97]


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   The format of the TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   I-Priority  |   E-Priority  |   Reserved                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          sub-TLVs                             ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 57: User QoS Policy Information TLV

   Where:

      The TLV type: 6.

      The TLV length: variable.

      User-ID (4 bytes): The identifier of a user/subscriber.

      Ingress-Priority (1 byte): Indicates the upstream priority.  The
      value range is 0~7.

      Egress-Priority (1 byte): Indicates the downstream priority.  The
      value range is 0~7.

      sub-TLVs: The sub-TLVs that are present can occur in any order.

         Ingress-CAR sub-TLV: Upstream CAR.

         Egress-CAR sub-TLV: Downstream CAR.

         Ingress-QoS-Profile sub-TLV: Indicates the name of the QoS-
         Profile profile in the upstream direction.

         Egress-QoS-Profile Sub-TLV: Indicates the name of the QoS-
         Profile profile in the downstream direction.

         User-ACL-Policy Sub-TLV: All ACL user policies, including
         v4ACLIN, v4ACLOUT, v6ACLIN, v6ACLOUT, v4WEBACL, v6WEBACL,
         v4SpecialACL, and v6SpecialACL.

         Multicast-Profile4 Sub-TLV: IPv4 multicast policy name.

         Multicast-Profile6 Sub-TLV: IPv6 multicast policy name.

         NAT-Instance Sub-TLV: Indicates the instance ID of a NAT user.



Hu, et al                                                      [Page 98]


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      The Reserved field MUST be sent as zero and ignored on receipt.



7.9.13.  Subscriber CGN Port Range TLV

   The Subscriber CGN Port Range TLV is used to carry the NAT public
   address and port range.  It will be carried in the Update_Response
   message when CGN is used.

   The format of this TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            User ID                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           NAT-Port-Start      |          NAT-Port-End         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            NAT-Address                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 58: Subscriber CGN Port Range TLV

   Where:

      The TLV type: 15.

      The TLV length: 12 octets.

      User-ID (4 bytes): The identifier of a user/subscriber.

      NAT-Port-Start (2 bytes): The start port number.

      NAT-Port-End (2 bytes): The end port number.

      NAT-Address (4 bytes): The NAT public network address.



7.10.  Device Status TLVs

   The TLVs in this section are for reporting Interface and Board level
   information from the UP to the CP.








Hu, et al                                                      [Page 99]


INTERNET-DRAFT                                           Simple BNG CUSP


7.10.1.  Interface Status TLV

   The Interface Status TLV is used to carry the status information of
   an interface on a UP.  It is carried in a Report message.

   The format of the value part of this TLV is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          If-Index                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          MAC Address (upper part)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   MAC Address (lower part)    |   Phy-State   |   Reserved    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          MTU                                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          sub-TLVs (optional)                  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 59: Interface Status TLV

   Where:

      The TLV type: 200.

      The TLV length: variable.

      If-Index (4 bytes): Indicates the interface index.

      MAC-Address (MAC-Addr type): Interface MAC address.

      Phy-State (1 byte): Physical status of the interface. 0: down, 1:
      Up

      MTU (4 bytes): Interface MTU value.

      sub-TLVs: The If-Desc and VRF-Name sub-TLVs can be carried.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.10.2.  Board Status TLV

   The Board Status TLV is used to carry the status information of a
   board on an UP.  It is carried in a Report message.

   The format of Board Status TLV is as follows:


Hu, et al                                                     [Page 100]


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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Board-Type  | Board-State   |   Reserved    |   Chassis     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Slot            |           Reserved            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 60: Interface Resource TLV

   Where:

      The TLV type: 201.

      The TLV length: 8 octets.

      Chassis (1 byte): The chassis number of the Board.

      Slot (1 byte): The slot number of the Board.

      Sub-Slot (1 byte): The sub-slot number of the Board.

      Board-Type (1 byte):
         1: CGN Service Process Unit (SPU) board.
         2: Line Process Unit (LPU) Board.

      Board-State (1 byte):
         0: Normal.
         1: Abnormal.

      The reserved field MUST be sent as zero and ignored on receipt.



7.11.  CGN TLVs



7.11.1.  Address Allocation Request TLV

   The Address Allocation Request TLV is used to request address
   allocation from CP.  An address Pool-Name sub-TLV is carried to
   indicate from which address pool to allocate addresses.  The Address
   Allocation Request TLV is carried in the Addr_Allocation_Req message.

   The format of the value part of this TLV is as follows:






Hu, et al                                                     [Page 101]


INTERNET-DRAFT                                           Simple BNG CUSP


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                          Pool-Name sub-TLV                    ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 61: Address Allocation Request TLV

   Where:

      The TLV type: 400.

      The TLV length: variable.

      Pool-Name sub-TLV: Indicates from which Address pool to allocate
      address.



7.11.2.  Address Allocation Response TLV

   The Address Allocation Response TLV is used to return the address
   allocation result, it is carried the Addr_Allocation_Ack message.

   The value part of the Address Allocation Response TLV is formatted as
   follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Lease Time                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        IPv4 Addr and Mask                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        IPv4 Addr and Mask continued           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Error-Code                             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                        Pool-Name sub-TLV                      ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 62: Address Assignment Response TLV

   Where:

      The TLV type: 401.

      The TLV length: variable.

      Lease Time (4 bytes): Duration of address lease in seconds.


Hu, et al                                                     [Page 102]


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      IPv4 Addr and Mask (IPv4-Address type): The allocated IPv4
      address.

      Error-Code (4 bytes): Indicates success or an error.

         0: Success.

         1: Failure.

         3001 (Pool-Mismatch): The corresponding address pool cannot be
         found.

         3002 (Pool-Full): The address pool is fully allocated and no
         address segment is available.

      Pool-Name sub-TLV: A Pool-Name sub-TLV to indicate from which
      Address pool the address is allocated.



7.11.3.  Address Renewal Request TLV

   The Address Renewal Request TLV is used to request address renewal
   from the CP.  It is carried the Addr_Renew_Req message.

   The format of this TLV value is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask continued           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Pool-Name sub-TLV                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 63: Address Renewal Request TLV

   Where:

      The TLV type: 402.

      The TLV length: variable.

      IPv4 Addr and Mask (IPv4-Addr): The IPv4 address to be renewed.

      Pool Name sub-TLV: A Pool-Name sub-TLV to indicate from which
      Address pool to renew the address.



Hu, et al                                                     [Page 103]


INTERNET-DRAFT                                           Simple BNG CUSP


7.11.4.  The Address Renewal Response TLV

   The Address Renewal Response TLV is used to return the address
   renewal result.  It is carried in the Addr_Renew_Ack message.

   The format of this TLV value is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask continued           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Error-Code                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Pool-Name sub-TLV                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 64: Address Renewal Response TLV

   Where:

      The TLV type: 403.

      The TLV length: variable.

      Client-IP (IPv4-Address type): The renewed IPv4 address.

      Error Code (4 bytes): Indicates success or an error:

         0: Renew success.

         1: Renew failed.

         3001 (Pool-Mismatch): The corresponding address pool cannot be
         found.

         3002 (Pool-Full): The address pool is fully allocated and no
         address segment is available.

         3003 (Subnet-Mismatch): The address pool subnet cannot be
         found.

         3004 (Subnet-Conflict): Subnets in the address pool have been
         assigned to other clients.

      Pool Name sub-TLV: A Pool-Name Sub-TLV to indicate from which
      Address pool to renew the address.



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7.11.5.  Address Release Request TLV

   The Address Release Request TLV is used to release an IPv4 address.
   It is carried in the Addr_Release_Req message.

   The value part of this TLV is formatted as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask continued           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Pool-Name sub-TLV                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 65: Address Release Request TLV

   Where:

      The TLV type: 404.

      The TLV length: variable.

      IPv4 Address and Mask (IPv4-Address type): The IPv4 address be
      released.

      Pool-Name sub-TLV: A Pool-Name Sub-TLV to indicate from which
      Address pool to release the address.



7.11.6.  The Address Release Response TLV

   The Address Release Response TLV is used to return the address
   release result.  It is carried in the Addr_Release_Ack message.

   The format of this TLV is as follows:













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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     IPv4 Address and Mask continued           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Error-Code                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     Pool-Name sub-TLV                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 66: Address Renewal Response TLV

   Where:

      The TLV type: 405.

      The TLV length: variable.

      Client-IP (IPv4-Address type): The released IPv4 address.

      Error-Code (4 bytes): Indicates success or an error.

         0: Address release success.

         1: Address release failed.

         3001 (Pool-Mismatch): The corresponding address pool cannot be
         found.

         3003 (Subnet-Mismatch): The address cannot be found.

         3004 (Subnet-Conflict): The address has been allocated to
         another subscriber.

      Pool-Name sub-TLV: A Pool-Name Sub-TLV to indicate from which
      address pool to release the address.



7.12.  Event TLVs



7.12.1. Subscriber Traffic Statistics TLV

   The Subscriber Traffic Statistics TLV is used to return the traffic
   statistics of a user/subscriber.  The format of this TLV is as
   follows:


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       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                User-ID                                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Statistics Type                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Packets (upper part)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Packets (lower part)                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Bytes (upper part)                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Bytes (lower part)                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Loss Packets (upper part)              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Loss Packets (lower part)              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Loss Bytes (upper part)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Ingress Loss Bytes (lower part)                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Packets (upper part)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Packets (lower part)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Bytes (upper part)                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Bytes (lower part)                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Loss Packets (upper part)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Loss Packets (lower part)               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Loss Bytes (upper part)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                Egress Loss Bytes (lower part)                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               Figure 67: Subscriber Traffic Statistics TLV

   Where:

      The TLV type: 300.

      The TLV length: 72 octets.

      User-ID (4 bytes): The user/subscriber identifier.



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      Statistics-Type (4 bytes): Traffic type.  It can be one of the
      following options:

         0: IPv4 traffic.
         1: IPv6 traffic.
         2: Dual stack traffic.

      Ingress Packets (8 bytes): The number of the packets in upstream
      direction.

      Ingress Bytes (8 bytes): The bytes of the upstream traffic.

      Ingress Loss Packets (8 bytes): The number of the lost packets in
      upstream direction.

      Ingress Loss Bytes (8 bytes): The bytes of the lost upstream
      packets.

      Egress Packets (8 bytes): The number of the packets in downstream
      direction.

      Egress Bytes (8 bytes): The bytes of the downstream traffic.

      Egress Loss Packets (8 bytes): The number of the lost packets in
      downstream direction.

      Egress Loss Bytes (8 bytes): The bytes of the lost downstream
      packets.



7.12.2.  Subscriber Detection Result TLV

   The Subscriber Detection Result TLV is used to return the detection
   result of a subscriber.  Subscriber detection is a function to detect
   whether a subscriber is online or not.  The result can be used by the
   CP to determine how to deal with the subscriber session.  (e.g.,
   delete the session if detection failed).

   The format of this TLV value part is as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          User-ID                              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Detect Type   | Detect Result |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                  Figure 68: Subscriber Detection Result TLV


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   Where:

      The TLV type: 301.

      The TLV length: 8 octets.

      User-ID (4 bytes): A user/subscriber identifier.

      Detect-Type (1 byte):

         0: IPv4 detection.

         1: IPv6 detection.

         2: PPP detection.

      Detect-Result (1 bytes):

         0: Indicates that the detection is successful.

         1: Detection failure.  The UP needs report only when the
         detection fails.

      The Reserved field MUST be sent as zero and ignored on receipt.



7.13.  Vendor TLV

   The Vendor ID TLV occurs as the first TLV in the Vendor message
   (Section 6.6). It provides a Sub-Type that effectively extends the
   message type in the message header, provides for versioning of vendor
   TLVs, and can accommodate sub-TLVs.

   The value part of the Vendor TLV is formatted as follows:

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Vendor ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Sub-Type            |       Sub-Type-Version        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                      sub-TLVs (optional)                      ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                            Figure 69: Vendor TLV

   Where:



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      The TLV type: 1024.

      The TLV length: variable.

      Vendor-ID (4 bytes): Vendor ID ass defined in RADIUS [RFC2865].

      Sub-Type (2 bytes): Used by the Vendor to distinguish multiple
      different vendor messages.

      Sub-Type-Version (2 bytes): Used by the Vendor to distinguish
      different versions of a Vendor Defined message sub-type.

      Sub-TLVs (variable): Sub-TLVs as specified by the vendor.

   Since Vendor code will be handling the TLV after the Vendor ID field
   is recognized, the remainder of the TLV value can be organized
   however the vendor wants. But it is desirable for a vendor to be able
   to define multiple different vendor messages and to keep track of
   different versions of its vendor defined messages. Thus, it is
   RECOMMENDED that the vendor assign a Sub-Type value for each vendor
   message that it defines different from other Sub-Type values that
   vendor has used. Also, when modifying a vendor defined message in a
   way potentially incompatible with a previous definition, the vendor
   SHOULD increase the value it is using in the Sub-Type-Version field.




























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8.  Implementation Status

   RFC Editor: Please remove this section before publication.

   This section discusses the status of implementations that have
   provided information and the testing of this protocol at the time of
   posting of this Internet-Draft, and is based on the proposal in
   [RFC7942] ("Improving Awareness of Running Code: The Implementation
   Status Section"). The description of implementations in this section
   is intended to assist in processing drafts to RFCs.

   Please note that the listing of any individual implementation or test
   results here does not imply endorsement by the RFC Editor or the
   IETF.  Furthermore, no effort has been spent to verify the
   information presented here that was supplied by contributors.  This
   is not intended as, and must not be construed to be, a catalog of
   available implementations or their testing or features.  Readers are
   advised to note that other implementations may exist.

   According to [RFC7942], "this will allow reviewers ... to assign due
   consideration to documents that have the benefit of running code,
   which may serve as evidence of valuable experimentation and feedback
   that have made the implemented protocols more mature.".



8.1.  Implementations

   Information on three S-CUSP implementations appears below.



8.1.1.  Huawei Technologies

      Name: Cloud-based BNG.

      Maturity: Production.

      Coverage: According to S-CUSP protocol.

      Contact information:
            Zhouyi Yu: yuzhouyi@huawei.com

      Date: 2018-11-01








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8.1.2.  ZTE

      Name: ZXR10 V6000 vBRAS

      Maturity: Production

      Coverage: According to S-CUSP protocol.

      Contact information:
            Yong Chen: 10056167@zte.com.cn
            Huaibin Wang: 10008729@zte.com.cn

      Date: 2018-12-01



8.1.3.  H3C

      Name: CUSP protocol for BRAS Control Plane and User Plan
      Separation

      Maturity: Research

      Coverage: According to S-CUSP protocol

      Contact information: mengdan@h3c.com; liuhanlei@h3c.com

      Date: 2019-1-30



8.2.  Hackathon

   Successful use of the protocol at the IETF-102 Hackathon, Montreal,
   Quebec, in 2018.

      Hackathon Project: Control Plane and User Plane Separation BNG
      control channel Protocol (CUSP)

      Champions: Zhenqiang Li, Michael Wang

      Report: See
      github.com/IETF-Hackathon/ietf102-project-presentations/blob/
         master/IETF102-hackathon-presentation-CUSP.pptx








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8.3.  EANTC Testing

   EANTC (European Advanced Networking Test Center (www.eantc.de))
   tested the Huawei implementation. Their summary was as follows:
   "EANTC tested advanced aspects of the Cloud-based Broadband Network
   Gateway (vBNG) with a focus on performance, scalability and high
   availability with up to 20 Million emulated subscribers. The solution
   performed very well across all test scenarios."

   See report at
   www.eantc.de/fileadmin/eantc/downloads/News/2018/EANTC-vBRAS-
   phase2.pdf








































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9.  Summary of Major S-CUSP Codepoints

   This section provides tables of the major S-CUSP codepoints,
   particularly message types, TLV types, TLV operation codes, sub-TLV
   types, and error codes. In most cases, references are provided to
   relevant sections elsewhere in this document.



9.1.  Message Types

        Type      Name              Section of this document
      -------    ----------------   ------------------------
           0      - Reserved
           1     Hello                 6.2.1.
           2     Keepalive             6.2.2.
           3     Sync_Request          6.2.3.
           4     Sync_Begin            6.2.4.
           5     Sync_Data             6.2.5.
           6     Sync_End              6.2.6.
           7     Update_Request        6.2.7.
           8     Update_Response       6.2.8.
           9     Report                6.4.
          10     Event                 6.3.
          11     Vendor                6.6.
          12     Error                 6.7.
      13-199      - Unassigned
         200     Addr_Allocation_Req   6.5.1.
         201     Addr_Allocation_Ack   6.5.2.
         202     Addr_Renew_Req        6.5.3.
         203     Addr_Renew_Ack        6.5.4.
         204     Addr_Release_Req      6.5.5.
         205     Addr_Release_Ack      6.5.6.
      206-254     - Unassigned
         255      - Reserved



9.2.  TLV Types

    Type     Name                         Usage Description
   ------   ------------                  --------------------------
       0    reserved                        -
       1   BAS Function Enabler           Carries the BNG access
                                          functions to be enabled or
                                          disabled on specified
                                          interfaces.
       2   Basic Subscriber               Carries the basic information
                                          about a BNG subscriber.
       3   PPP Subscriber                 Carries the PPP information


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                                          about a BNG subscriber.
       4   IPv4 Subscriber                Carries the IPv4 address of a
                                          BNG subscriber.
       5   IPv6 Subscriber                Carries the IPv6 address of a
                                          BNG subscriber.
       6   Subscriber Policy              Carries the policy information
                                          applied to a BNG subscriber.
       7   IPv4 Routing                   Carries the IPv4 network
                                          routing information.
       8   IPv6 Routing                   Carries the IPv6 network
                                          routing information.
       9   IPv4 Static Subscriber Detect  Carries the IPv4 static
                                          subscriber detect information.
      10   IPv6 Static Subscriber Detect  Carries the IPv6 static
                                          subscriber detect information.
      11   L2TP-LAC Subscriber            Carries the L2TP LAC
                                          subscriber information.
      12   L2TP-LNS Subscriber            Carries the L2TP LNS
                                          subscriber information.
      13   L2TP-LAC-Tunnel                Carries the L2TP LAC tunnel
                                          subscriber information.
      14   L2TP-LNS-Tunnel                Carries the L2TP LNS tunnel
                                          subscriber information.
      15   Subscriber CGN Port Range      Carries the public IPv4
                                          address and related port range
                                          of a BNG subscriber.
   16-99    unassigned                     -
     100   Hello                          Used for version and Keep
                                          Alive timers negotiation.
     101   Error Information              Carried in the Ack of the
                                          control message.  Carries the
                                          processing result, success, or
                                          error.
     102   Keep Alive                     Carried in the Hello message
                                          for Keep Alive timers
                                          negotiation.
   103-199  unassigned                     -
     200   Interface Status               Interfaces status reported by
                                          the UP including physical
                                          interfaces, sub-interfaces,
                                          trunk interfaces, and tunnel
                                          interfaces.
     201   Board Status                   Board information reported by
                                          the UP including the board
                                          type and in-position status.
   202-299  unassigned                     -
     300   Subscriber Traffic Statistics  User traffic statistics.
     301   Subscriber Detection Results   User detection information.
     302   Session Update Response        The processing result of a
                                          subscriber session update.


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   303-299  unassigned                     -
     400   Address Allocation Request     Request address allocation.
     401   Address Allocation Response    Address allocation response.
     402   Address Renewal Request        Request for address lease
                                          renewal.
     403   Address Renewal Response       Response to a request for
                                          extending an IP address lease.
     404   Address Release Request        Request to release the
                                          address.
     405   Address Release Response       Ack of a message releasing an
                                          IP address.
   406-1023 unassigned                     -
    1024   Vendor                         As implemented by vendor.
   1039-4095 unassigned                    -



9.3.  TLV Operation Codes

   TLV operation codes appear in the Oper field in the header of some
   TLVs. See Section 7.1.

      Code  Operation
      ----  ----------
         0   - reserved
         1  Update
         2  Delete
      3-15   - unassigned



9.4.  Sub-TLV Types

   See Section 7.3.


















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       Type  Name                 Reference
       ----  ------------------   ---------------.................
           0    - reserved
           1   VRF Name             7.3.1.
           2   Ingress-QoS-Profile  7.3.1.
           3   Egress-QoS-Profile   7.3.1.
           4   User-ACL-Policy      7.3.1.
           5   Multicast-ProfileV4  7.3.1.
           6   Multicast-ProfileV6  7.3.1.
           7   Ingress-CAR          7.3.2.
           8   Egress-CAR           7.3.3.
           9   NAT-Instance         7.3.1.
          10   Pool-Name            7.3.1.
          11   If-Desc              7.3.4.
          12   IPv6-Address List    7.3.5.
          13   Vendor               7.3.6.
      12-64534  - unassigned
       65535    - reserved



9.5.  Error Codes

    Value     Name             Remarks
   -------   -------          --------
        0    Success          Success

        1    Fail             Malformed message received.
        2    TLV-Unknown      One or more of the TLVs was not
                              understood.
        3    TLV-Length       The TLV length is abnormal.
    4-999     - unassigned    Unassigned basic error codes.
     1000     - reserved
     1001    Version-Mismatch The version negotiation fails. Terminate.
                              The subsequent service processes
                              corresponding to the UP are suspended.
     1002    Keepalive Error  The keepalive negotiation fails.
     1003    Timer Expires    The establishment timer expired.
   1004-1999  - unassigned    Unassigned error codes for version
                              negotiation.
     2000     - reserved
     2001    Synch-NoReady    The data to be smoothed is not ready.
     2002    Synch-Unsupport  The request for smooth data is not
                              supported.
   2003-2999  - unassigned    Unassigned data synchronization error
                              codes.
     3000     - reserved
     3001    Pool-Mismatch    The corresponding address pool cannot be
                              found.
     3002    Pool-Full        The address pool is fully allocated and no


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                              address segment is available.
     3003    Subnet-Mismatch  The address pool subnet cannot be found.
     3004    Subnet-Conflict  Subnets in the address pool have been
                              classified into other clients.
   3005-3999  - unassigned    Unassigned error codes for address
                              allocation.
     4000     - reserved
     4001    Update-Fail-No-Res  The forwarding table fails to be
                              delivered because the forwarding resources
                              are insufficient.
     4002    QoS-Update-Success  The QoS policy takes effect.
     4003    QoS-Update-Sq-Fail  Failed to process the queue in the QoS
                              policy.
     4004    QoS-Update-CAR-Fail  Processing of the CAR in the QoS
                              policy fails.
     4005    Statistic-Fail-No-Res  Statistics processing failed due to
                              insufficient statistics resources.
   4006-4999  - unassigned forwarding table delivery error codes.

   5000-4294967295 - reserved
































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10.  IANA Considerations

   IANA is requested to assign a service name and port for BNG S-CUSP as
   follows:

   Service  Port    Transport
   Name     Number  Protocol    Description        Reference
   -------  ------  ---------  -------------      ---------------
   s-cusp    tbd1    TCP       Control-plane and   [this document]
                               User-plane
                               Separation Protocol









































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11.  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.  Whether such protection is used is an operator decision.

   The S-CUSP messages do not provide security. Thus, if these messages
   are exchanged in an environment where security is a concern, that
   security MUST be provided by another protocol such as TLS 1.3
   [RFC8446] or IPSEC.  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 is in a more
   benign environment.





































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Contributors

      Zhouyi Yu
      Huawei Technologies

      Email: yuzhouyi@huawei.com


      Chengguang Niu
      Huawei Technologies

      Email: chengguang.niu@huawei.com

      Zitao Wang
      Huawei Technologies

      Email: wangzitao@huawei.com


      Jun Song
      Huawei Technologies

      Email: song.jun@huawei.com


      Dan Meng
      H3C Technologies
      No.1 Lixing Center
      No.8 guangxun south street, Chaoyang District,
      Beijing, 100102
      China

      Email: mengdan@h3c.com


      Hanlei Liu
      H3C Technologies
      No.1 Lixing Center
      No.8 guangxun south street, Chaoyang District,
      Beijing, 100102
      China

      Email: hanlei_liu@h3c.com









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Normative References

   [RFC20] Cerf, V., "ASCII format for network interchange", STD 80, RFC
             20, DOI 10.17487/RFC0020, October 1969, <https://www.rfc-
             editor.org/info/rfc20>.

   [RFC793] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
             DOI 10.17487/RFC0793, September 1981, <https://www.rfc-
             editor.org/info/rfc793>.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, DOI
             10.17487/RFC2119, March 1997, <https://www.rfc-
             editor.org/info/rfc2119>.

   [RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G.,
             and B. Palter, "Layer Two Tunneling Protocol "L2TP"", RFC
             2661, DOI 10.17487/RFC2661, August 1999, <https://www.rfc-
             editor.org/info/rfc2661>.

   [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
             "Remote Authentication Dial In User Service (RADIUS)", RFC
             2865, DOI 10.17487/RFC2865, June 2000, <https://www.rfc-
             editor.org/info/rfc2865>.

   [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
             and A. Bierman, Ed., "Network Configuration Protocol
             (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
             <https://www.rfc-editor.org/info/rfc6241>.

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119
             Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May
             2017, <https://www.rfc-editor.org/info/rfc8174>.



Informative References

   [802.1Q] IEEE, "IEEE Standard for Local and metropolitan area
             networks / Bridges and Bridged Networks", IEEE Std
             802.1Q-2014, 3 November 2013.

   [RFC1661] Simpson, W., Ed., "The Point-to-Point Protocol (PPP)", STD
             51, RFC 1661, DOI 10.17487/RFC1661, July 1994,
             <https://www.rfc-editor.org/info/rfc1661>.

   [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
             DOI 10.17487/RFC2131, March 1997, <https://www.rfc-
             editor.org/info/rfc2131>.



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   [RFC2698] Heinanen, J. and R. Guerin, "A Two Rate Three Color
             Marker", RFC 2698, DOI 10.17487/RFC2698, September 1999,
             <https://www.rfc-editor.org/info/rfc2698>.

   [RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
             Address Translator (Traditional NAT)", RFC 3022, DOI
             10.17487/RFC3022, January 2001, <https://www.rfc-
             editor.org/info/rfc3022>

   [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, <https://www.rfc-editor.org/info/rfc5511>.

   [RFC7042] Eastlake 3rd, D. and J. Abley, "IANA Considerations and
             IETF Protocol and Documentation Usage for IEEE 802
             Parameters", BCP 141, RFC 7042, DOI 10.17487/RFC7042,
             October 2013, <https://www.rfc-editor.org/info/rfc7042>.

   [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
             L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
             eXtensible Local Area Network (VXLAN): A Framework for
             Overlaying Virtualized Layer 2 Networks over Layer 3
             Networks", RFC 7348, DOI 10.17487/RFC7348, August 2014,
             <https://www.rfc-editor.org/info/rfc7348>.

   [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
             Code: The Implementation Status Section", BCP 205, RFC
             7942, DOI 10.17487/RFC7942, July 2016, <https://www.rfc-
             editor.org/info/rfc7942>.

   [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
             Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
             <https://www.rfc-editor.org/info/rfc8446>.

   [TR-384] Broadband Forum, "Cloud Central Office Reference
             Architectural Framework", BBF TR-384, 2018.















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Authors' Addresses

      Shujun Hu
      China Mobile
      32 Xuanwumen West Ave, Xicheng District
      Beijing, Beijing  100053
      China

      Email: hushujun@chinamobile.com


      Donald Eastlake, 3rd
      Futurewei Technologies
      1424 Pro Shop Court
      Davenport, FL  33896
      USA

      Phone: +1-508-333-2270
      Email: d3e3e3@gmail.com


      Mach (Guoyi) Chen
      Huawei Technologies
      Huawei Bldg., No. 156 Beiqing Road
      Beijing 100095 China

      Email: mach.chen@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







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      Tee Mong Chua
      Singapore Telecommunications Limited
      31 Exeter Road, #05-04 Comcentre Podium Block
      Singapore City  239732
      Singapore

      Email: teemong@singtel.com













































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