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Versions: 00 01 02 03 04 05 RFC 6934

     Network Working Group                     Nabil Bitar(ed.)
                                               Verizon
     Internet Draft
     Intended Status: Informational            Sanjay Wadhwa (ed.)
                                               Alcatel-Lucent
     Expires: January 16, 2013
                                               Thomas Haag
                                               Deutsche Telekom

                                               Hongyu Li
                                               Huawei Technologies

                                               July 16, 2012




            Applicability of Access Node Control Mechanism to
                     PON based Broadband Networks

                      draft-ietf-ancp-pon-03.txt


     Abstract


     The purpose of this document is to provide applicability of the
     Access Node Control mechanism to PON-based broadband access. The
     need for an Access Node Control mechanism between a Network
     Access Server (NAS) and an Access Node Complex (a combination of
     Optical Line Termination (OLT) and Optical Network Termination
     (ONT) elements) is described in a multi-service reference
     architecture in order to perform QoS-related, service-related and
     Subscriber-related operations. The Access Node Control mechanism
     is also extended for interaction between components of the Access
     Node Complex (OLT and ONT). The Access Node Control mechanism
     will ensure that the transmission of information between the NAS
     and Access Node Complex (ANX) and between the OLT and ONT within
     an ANX does not need to go through distinct element managers but
     rather uses a direct device-to-device communication and stays on
     net. This allows for performing access link related operations
     within those network elements to meet performance objectives.






     Status of this Memo



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     Copyright Notice



     Copyright (c) 2012 IETF Trust and the persons identified as
     the document authors. All rights reserved.



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     respect to this document. Code Components extracted from this
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     without warranty as described in the Simplified BSD License.



     Table of Contents

        1. Introduction..................................... 4
        2. Terminology......................................
5
        3. Motivation for explicit extension of ANCP to FTTx
        PON................................................. 7
        4. Reference Model for PON Based Broadband Access
        Network............................................. 8
        4.1. Functional Blocks.............................
11
        4.1.1. Home Gateway................................
11
        4.1.2. PON Access..................................
11
        4.1.3. Access Node Complex.........................
11
        4.1.4. Access Node Complex Uplink to the NAS....... 12
        4.1.5. Aggregation Network.........................
12
        4.1.6. Network Access Server....................... 12
        4.1.7. Regional Network............................
12
        4.2. Access Node Complex Control Reference
        Architecture Options...............................
13
        4.2.1. ANCP+OMCI ANX Control.......................
13
        4.2.2. All-ANCP ANX Control........................ 14
        5. Concept of Access Node Control Mechanism for PON
        Based Access.......................................
15
        6. Multicast....................................... 18
        6.1. Multicast Conditional Access..................
19
        6.2. Multicast Admission Control...................
22
        6.3. Multicast Accounting.......................... 34
        7. Remote Connectivity Check.......................
35
        8. Access Topology Discovery.......................
35
        9. Access Loop Configuration.......................
37
        10. Security Considerations........................
37
        11. Differences in ANCP applicability between DSL and
        PON................................................
38
        12. ANCP versus OMCI between the OLT and ONT/ONU... 40
        13. IANA Considerations............................
40
        14. Acknowledgements............................... 41
        15. References..................................... 41
        15.1. Normative References.........................
41
        15.2. Informative References.......................
41



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     1. Introduction


     Passive Optical Networks (PONs) based on BPON [G.983.1] and GPON
     [G.984.1] are being deployed across carrier networks. There are
     two models for PON deployment: Fiber to the building/curb
     (FTTB/FTTC), and Fiber to the Premises (FTTP). In the FTTB/C
     deployment, the last mile connectivity to the subscriber premises
     is provided over the local Copper loop, often using Very High
     Speed Digital Subscriber line (VDSL). In the FTTP case, PON
     extends to the premises of the subscriber. In addition, there are
     four main PON technologies: (1) Broadband PON (BPON), (2) Gigabit
     PON (GPON), (3) 10-Gigabit PON (XGPON), and (4) Ethernet PON
     (EPON). This document describes the applicability of Access Node
     Control Protocol (ANCP) in the context of FTTB/C and FTTP
     deployments, focusing on BPON, GPON and XPON. Architectural
     considerations lead to different ANCP compositions. Therefore,
     the composition of ANCP communication between Access Nodes and
     Network Access Server (NAS) is described using different models.

     BPON, GPON and XPON in FTTP deployments provide large bandwidth
     in the first mile, bandwidth that is an order of magnitude larger
     than that provided by xDSL. In the downstream direction, BPON
     provides 622 Mbps per PON while GPON provides 2.4 Gbps, and XPON
     provides 10 Gbps.

     In residential deployments, the number of homes sharing the same
     PON is limited by the technology and the network engineering
     rules. Typical deployments have 32-64 homes per PON.

     The motive behind BPON, GPON and XPON deployment is providing
     triple-play services over IP: voice, video and data. Voice is
     generally low bandwidth but has low-delay, low-jitter, and low
     packet-loss requirements. Data services (e.g., Internet services)
     often require high throughput and can tolerate medium latency.
     Data services may include multimedia content download such as
     video. However, in that case, the video content is not required
     to be real-time and/or it is low quality video. Video services,
     on the other hand, are targeted to deliver Standard Definition or
     High Definition video content in real-time or near-real time,
     depending on the service model. Standard Definition content using
     MPEG2 encoding requires on the order of 3.75 Mbps per stream
     while High definition content using MPEG2 encoding requires on
     the order of 15-19 Mbps depending on the level of compression
     used. Video services require low-jitter and low-packet loss with
     low start-time latency. There are two types of video services: on
     demand and broadcast (known also as liner programming content).


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     While linear programming content can be provided over Layer1 on
     the PON, the focus in this document is on delivering linear
     programming content over IP to the subscriber, using IP
     multicast. Video on demand is also considered for delivery to the
     subscriber over IP using a unicast session model.

     Providing simultaneous triple-play services over IP with unicast
     video and multicast video, VoIP and data requires an architecture
     that preserves the quality of service of each service.
     Fundamental to this architecture is ensuring that the video
     content (unicast and multicast) delivered to the subscriber does
     not exceed the bandwidth allocated to the subscriber for video
     services. Architecture models often ensure that data is
     guaranteed a minimum bandwidth and that VoIP is guaranteed its
     own bandwidth. In addition, QoS control across services is often
     performed at a Network Access Server (NAS), often referred to as
     Broadband Network Gateway (BNG) for subscriber management, per
     subscriber and shared link resources. Efficient multicast video
     services require enabling multicast services in the access
     network between the subscriber and the subscriber management
     platform. In the FTTP/B/C PON environment, this implies enabling
     IP multicast on the Access Node (AN) complex composed of the
     Optical Network Terminal (ONT) or Unit (ONU) and Optical Line
     Terminal (OLT), as applicable. This is as opposed to Digital
     Subscriber Line (DSL) deployments where multicast is enabled on
     the DSL Access Multiplexer (DSLAM) only. The focus in this
     document will be on the ANCP requirements needed for coordinated
     admission control of unicast and multicast video in FTTP/B/C PON
     environments between the AN complex (ANX) and the NAS,
     specifically focusing on bandwidth dedicated for multicast and
     shared bandwidth between multicast and unicast.

     [RFC5851] provides the framework and requirements for
     coordinated admission control between a NAS and an AN with
     special focus on DSL deployments. This document extends that
     framework and the related requirements to explicitly address
     PON deployments.



     2.  Terminology


     - PON (Passive Optical Network) [G.983.1][G.984.1]: a point-to-
     multipoint fiber to the premises network architecture in which
     unpowered splitters are used to enable the splitting of an
     optical signal from a central office on a single optical fiber to


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     multiple premises. Up to 32-128 may be supported on the same PON.
     A PON configuration consists of an Optical Line Terminal (OLT) at
     the Service Provider's Central Office (CO) and a number of
     Optical Network Units or Terminals (ONU/ONT) near end users, with
     an optical distribution network (ODN) composed of fibers and
     splitters between them. A PON configuration reduces the amount of
     fiber and CO equipment required compared with point-to-point
     architectures.

     - Access Node Complex (ANX): The Access Node Complex is composed
     of two geographically separated functional elements OLT and
     ONU/ONT. The general term Access Node Complex (ANX) will be used
     when describing a functionality which does not depend on the
     physical location but rather on the "black box" behavior of OLT
     and ONU/ONT.

     -Optical Line Terminal (OLT): is located in the Service
     provider's central office (CO). It terminates and aggregates
     multiple PONs (providing fiber access to multiple premises or
     neighborhoods) on the subscriber side, and interfaces with the
     Network Access server (NAS) that provides subscriber management.

     - Optical Network Terminal (ONT): terminates PON on the network
     side and provides PON adaptation. The subscriber side interface
     and the location of the ONT are dictated by the type of network
     deployment. For a Fiber-to-the-Premise (FTTP) deployment (with
     Fiber all the way to the apartment or living unit), ONT has
     Ethernet (FE/GE/MoCA) connectivity with the Home Gateway
     (HGW)/Customer Premise Equipment(CPE). In certain cases, one ONT
     may provide connections to more than one Home Gateway at the same
     time.

     -Optical Network Unit (ONU): A generic term denoting a device
     that terminates any one of the distributed (leaf) endpoints of an
     Optical Distribution Node (ODN), implements a PON protocol, and
     adapts PON PDUs to subscriber service interfaces. In case of an
     MDU multi-dwelling or multi-tenant unit, a multi-subscriber ONU
     typically resides in the basement or a wiring closet (FTTB case),
     and has FE/GE/Ethernet over native Ethernet link or over xDSL
     (typically VDSL) connectivity with each CPE at the subscriber
     premises. In the case where fiber is terminated outside the
     premises (neighborhood or curb side) on an ONT/ONU, the last-leg-
     premises connections could be via existing or new Copper, with
     xDSL physical layer (typically VDSL). In this case, the ONU
     effectively is a "PON fed DSLAM".




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     -Network Access Server (NAS): Network element which aggregates
     subscriber traffic from a number of ANs or ANXs. The NAS is often
     an injection point for policy management and IP QoS in the access
     network. It is also referred to as Broadband Network Gateway
     (BNG) or Broadband Remote Access Server (BRAS).

     -Home Gateway (HGW): Network element that connects subscriber
     devices to the AN or ANX and the access network. In case of xDSL,
     the Home Gateway is an xDSL network termination that could either
     operate as a Layer 2 bridge or as a Layer 3 router. In the latter
     case, such a device is also referred to as a Routing Gateway
     (RG). In the case of PON, it is often a Layer3 routing device
     with the ONT performing PON termination.

     -PON-Customer-ID: This is an identifier which uniquely identifies
     the ANX and the access loop logical port on the ANX to the
     subscriber (customer) premises, and is used in any interaction
     between NAS and ANX that relates to access-loops. Logically it is
     composed of information containing identification of the OLT (the
     OLT may be physically directly connected to the NAS), the PON
     port on the OLT, the ONT/ONU, and the port on the ONT/ONU
     connecting to the subscriber HGW. When acting as a DHCP relay
     agent, the OLT can encode PON-Customer-ID in the "Agent-Circuit-
     Identifier" Sub-option in Option-82 of the DHCP messages [RFC3046].

     3. Motivation for explicit extension of ANCP to FTTx PON


     The fundamental difference between PON and DSL is that a PON is
     an optical broadcast network by definition. That is, at the PON
     level, every ONT on the same PON sees the same signal. However,
     the ONT filters only those PON frames addressed to it. Encryption
     is used on the PON to prevent eavesdropping.

     The broadcast PON capability is very suitable to delivering
     multicast content to connected premises, maximizing bandwidth
     usage efficiency on the PON. Similar to DSL deployments, enabling
     multicast on the Access Node Complex (ANX) provides for bandwidth
     use efficiency on the path between the Access Node and the NAS as
     well as improves the scalability of the NAS by reducing the
     amount of multicast traffic being replicated at the NAS. However,
     the broadcast capability on the PON enables the AN (OLT) to send
     one copy on the PON as opposed to one copy to each receiver on
     the PON. The PON multicast capability can be leveraged in the
     case of GPON and BPON as discussed in this document.




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     Fundamental to leveraging the broadcast capability on the PON for
     multicast delivery is the ability to assign a single encryption
     key for all PON frames carrying all multicast channels or a key
     per set of multicast channels that correspond to service
     packages, or none. It should be noted that the ONT can be a
     multi-Dwelling Unit (MDU) ONT with multiple Ethernet ports, each
     connected to a living unit. Thus, the ONT must not only be able
     to receive a multicast frame, but must also be able to forward
     that frame only to the Ethernet port with receivers for the
     corresponding channel.

     In order to implement triple-play service delivery with necessary
     "quality-of-experience", including end-to-end bandwidth optimized
     multicast video delivery, there needs to be tight coordination
     between the NAS and the ANX. This interaction needs to be near
     real-time as services are requested via application or network
     level signaling by broadband subscribers. ANCP as defined in
     [RFC5851] for DSL based networks is very suitable to realize a
     control protocol (with transactional exchange capabilities),
     between PON enabled ANX and the NAS, and also between the
     components comprising the ANX, i.e., between OLT and the ONT.
     Typical use cases for ANCP in PON environment include the
     following:

            - Access topology discovery

            - Access Loop Configuration

            - Multicast

                 - Optimized multicast delivery

                 - Unified video resource control

                 - NAS based provisioning of ANX

            - Remote connectivity check


     4. Reference Model for PON Based Broadband Access Network


     An overall end-to-end reference architecture of a PON access
     network is depicted in Figure 1 and Figure 2 with ONT serving a
     single HGW, and ONT/ONU serving multiples HGWs, respectively. An
     OLT may provide FTTP and FTTB/C access at the same time but most
     likely not on the same PON port. Specifically, the following PON


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     cases are addressed in the context of this reference
     architecture:


             - BPON with Ethernet uplink to the NAS and ATM on the PON
     side.

             - GPON/XPON with Ethernet uplink to the NAS and Ethernet
     on the PON side

     In case of an Ethernet aggregation network that supports new QoS-
     enabled IP services (including Ethernet multicast replication),
     the architecture builds on the reference architecture specified
     in the Broadband Forum (BBF) [TR-101]. The Ethernet aggregation
     network between a NAS and an OLT may be degenerated to one or
     more direct physical Ethernet links.

     Given the industry move towards Ethernet as the new access and
     aggregation technology for triple play services, the primary
     focus throughout this document is on GPON/XPON and BPON with
     Ethernet between the NAS and the OLT.




























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                                            Access           Customer
                                <---------Aggregation-------><-Prem->
                                            Network           Network

                                         +------------------+
                                         |  Access Node     |
                                         |  Complex (ANX)   |
           +---------+   +---+  +-----+  |+---+       +---+ |  +---+
           |         | +-|NAS|--|Eth  |--||OLT|-<PON>-|ONT|-|--|HGW|
     NSP---+Regional | | +---+  |Agg  |  |+---+       +---+ |  +---+
           |Broadband| | +---+  +-----+  +------------------+
           |Network  |-+-|NAS|                  |
     ASP---+         | | +---+                  |
           |         | | +---+                  |
           +---------+ +-|NAS|                  |       +---+  +---+
                         +---|                  +-<PON>-|ONT|--|HGW|
                                                    |   +---+  +---+
                                                    |
                                                    |   +---+  +---+
                                                    +---|ONT|--|HGW|
                                                        +---+  +---+
           HGW      : Home Gateway
           NAS      : Network Access Server
           PON      : Passive Optical Network
           OLT      : Optical Line Terminal
           ONT      : Optical Network Terminal


                       Figure 1:  Access Network with PON.



                                                           FE/GE/VDSL
                                                           +---+ +---+
                                  +----------------+       |   |-|HGW|
           +---------+   +-----+  | +-----+  +----+|       |   | +---+
           |         | +-|NAS  |--| |Eth  |--|OLT||-<PON>- |   |
     NSP---+Regional | | +-----+  | |Agg  |  |    ||     | |ONT| +---+
           |         | |          | |     |  |    ||     | | or|-|HGW|
           |Broadband| | +-----+  | +-----+  +----+|     | |ONU| +---+
           |Network  |-+-|NAS  |  +----------------+     | |   |
     ASP---+         | | +-----+                         | |   | +---+
           |         | | +-----+                         | |   |-|HGW|
           +---------+ +-|NAS  |                         | +---+ +---+
                         +-----+                         |
                                                         | +---+ +---+
                                                         +-|ONT|-|HGW|
                                                           +---+ +---+

     Figure 2: FTTP/FTTB/C with multi-subscriber ONT/ONU serving
     MTUs/MDUs.



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     The following sections describe the functional blocks and network
     segments in the PON access reference architecture.


     4.1. Functional Blocks



     4.1.1. Home Gateway



     The Home Gateway (HGW) connects the different Customer Premises
     Equipment (CPE) to the ANX and the access network. In case of
     PON, the HGW is a layer 3 router. In this case, the HGW performs
     IP configuration of devices within the home via DHCP, and
     performs Network Address and Port Translation (NAPT) between the
     LAN and WAN side. In case of FTTP/B/C, the HGW connects to the
     ONT/ONU over an Ethernet interface. That Ethernet interface could
     be over an Ethernet physical port or over another medium. In case
     of FTTP, it is possible to have a single box GPON CPE solution,
     where the ONT encompasses the HGW functionality as well as the
     GPON adaptation function.

     4.1.2. PON Access


     PON access is composed of the ONT/ONU and OLT. PON ensures
     physical connectivity between the ONT/ONU at the customer
     premises and the OLT. PON framing can be BPON (in case of BPON)
     or GPON (in case of GPON). The protocol encapsulation on BPON is
     based on multi-protocol encapsulation over AAL5, defined in
     [RFC2684].  This covers PPP over Ethernet (PPPoE, defined in
     [RFC2516]), or bridged IP (IPoE). The protocol encapsulation on
     GPON is always IPoE. In all cases, the connection between the AN
     (OLT) and the NAS (or BNG) is assumed to be Ethernet in this
     document.

     4.1.3. Access Node Complex



     This is composed of OLT and ONT/ONU and is defined in section 2.





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     4.1.4. Access Node Complex Uplink to the NAS



     The ANX uplink connects the OLT to the NAS. The fundamental
     requirements for the ANX uplink are to provide traffic
     aggregation, Class of Service distinction and customer separation
     and traceability. This can be achieved using an ATM or an
     Ethernet based technology. The focus in this document is on
     Ethernet as stated earlier.

     4.1.5. Aggregation Network


     The aggregation network provides traffic aggregation towards the
     NAS. The Aggregation network is assumed to be Ethernet in this
     document.

     4.1.6. Network Access Server


     The NAS is a network device which aggregates multiplexed
     Subscriber traffic from a number of ANXs. The NAS plays a central
     role in per-subscriber policy enforcement and QoS. It is often
     referred to as a Broadband Network Gateway (BNG) or Broadband
     Remote Access Server (BRAS). A detailed definition of the NAS is
     given in [RFC2881]. The NAS interfaces to the aggregation network
     by means of 802.1Q or 802.1 Q-in-Q Ethernet interfaces, and
     towards the Regional Network by means of transport interfaces
     (e.g., GigE, PPP over SONET). The NAS functionality corresponds
     to the BNG functionality described in BroadBand Forum (BBF) TR-
     101 [TR-101]. In addition, the NAS supports the Access Node
     Control functionality defined for the respective use cases in
     this document.

     4.1.7. Regional Network


     The Regional Network connects one or more NAS and associated
     Access Networks to Network Service Providers (NSPs) and
     Application Service Providers (ASPs). The NSP authenticates
     access and provides and manages the IP address to Subscribers. It
     is responsible for overall service assurance and includes
     Internet Service Providers (ISPs). The ASP provides application
     services to the application Subscriber (gaming, video, content on
     demand, IP telephony, etc.). The NAS can be part of the NSP
     network. Similarly, the NSP can be the ASP.


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     4.2. Access Node Complex Control Reference Architecture Options


     Section 3 details the differences between xDSL access and PON
     access and the implication of these differences on DSLAM control
     vs. OLT and ONT/ONU (access node complex (ANX)) control. The
     following sections describe two reference models: (1) ANCP+OMCI
     ANX control, and (2) all-ANCP ANX control. That is, the two
     models differ in the ONT/ONU control within the ANX.
     Implementations, out of the scope of this document, may choose to
     implement one or the other based on the ONT/ONU type and the
     capabilities of the ONT/ONU and OLT. It is possible for an OLT or
     an OLT PON port to connect to ONTs/ONUs with different
     capabilities and for these two models to co-exist on the same OLT
     and same PON. Section 12 describes the differences between OMCI
     and ANCP in controlling the ONU/ONT.

     OMCI is designed as a protocol between the OLT and ONT/ONU. It
     enables the OLT to configure and administer capabilities on the
     ONT/ONU in BPON, GPON and XPON. ANCP is designed as a protocol
     between the NAS and access node. It enables the NAS to enforce
     dynamic policies on the access node, and the access node to
     report events to the NAS among other functions.

     4.2.1. ANCP+OMCI ANX Control


     Figure 3 depicts the reference model for ANCP+OMCI ANX control.
     In this model, ANCP is enabled between the NAS and a connected
     OLT, and OMCI is enabled between the OLT and an attached ONT/ONU.
     NAS communicates with the ANX via ANCP. The OLT acts as an
     ANCP/OMCI gateway for communicating necessary events and policies
     between the OLT and ONT/ONU within the ANX and for communicating
     relevant policies and events between the ONT/ONU and the NAS. The
     functionality performed by the OLT as ANCP/OMCI gateway will be
     application dependent (e.g., multicast control, topology
     discovery) and should be specified in a related specification. It
     should be noted that some applications are expected to require
     extensions. Such extensions are expected to be outside of ANCP
     scope, and may need to be defined by the ITU-T. It should be
     noted that OMCI, in addition to configuration and administration,
     provides the capability to report status changes on an ONT/ONU
     with AVC (Attribute Value Change) notifications. When ONT/ONU's
     DSL or Ethernet UNI attributes change, a related ME (management
     Entity) will send a corresponding notification (AVC) to the OLT.
     The OLT interworks such notification into an ANCP report and


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     sends it to the connected NAS via the ANCP session between the
     OLT and the NAS. As the ANCP report contains information of
     ONT/ONU's UNI and OLT's PON port, NAS can obtain accurate
     information of access topology.



                                       +----------------------+
                                       |         ANX          |
           +---------+   +---+  +---+  |+---+       +-------+ | +---+
           |         | +-|NAS|--|Eth|--||OLT|-<PON>-|ONU/ONT|-|-|HGW|
     NSP---+Regional | | +---+  |Agg|  |+---+       +-------+ | +---+
           |Broadband| | +---+  +---+  +----------------------+
           |Network  |-+-|NAS|               |
     ASP---+         | | +---+               |
           |         | | +---+               |
           +---------+ +-|NAS|               |       +-------+ +---+
                         +---|               +-<PON>-|ONU/ONT|-|HGW|
                                                  |  +-------+ +---+
                                                  |  +---+     +---+
                                                  +--|ONT|-----|HGW|
                                                     +---+     +---+
                                ANCP                 OMCI
                       +<--------------->+<----------->+

        HGW: Home Gateway
        NAS: Network Access Server
        PON: Passive Optical Network
        OLT: Optical Line Terminal
        ONT: Optical Network Terminal
        ONU: Optical Network Unit

     Figure 3: Access Network with single ANCP+OMCI access control



     4.2.2. All-ANCP ANX Control



     Figure 4 depicts the All-ANCP ANX control reference model. In
     this model, an ANCP session is enabled between a NAS and a
     connected OLT, and another ANCP session is enabled between the
     OLT and a connected ONT/ONU. ANCP enables communication of
     policies and events between the OLT and the ANX. The OLT acts as
     a gateway to relay policies and events between the NAS and
     ONT/ONU within the ANX in addition to communicating policies and
     events between the OLT and ONT/ONU. It should be noted that in
     this model, OMCI(not shown) is expected to be simultaneously
     enabled between the ONT and OLT, supporting existing OMCI


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     capabilities and applications on the PON, independent of ANCP or
     applications intended to be supported by ANCP.





                                       +----------------------+
                                       | Access Node Complex  |
                                       |      (ANX)           |
           +---------+   +---+  +---+  |+---+       +-------+ |  +---+
           |         | +-|NAS|--|Eth|--||OLT|-<PON>-|ONU/ONT| |--|HGW|
     NSP---+Regional | | +---+  |Agg|  |+---+       +-------+ |  +---+
           |Broadband| | +---+  +---+  +----------------------+
           |Network  |-+-|NAS|                |
     ASP---+         | | +---+                |
           |         | | +---+                |
           +---------+ +-|NAS|                |       +-------+  +---+
                         +---|                +-<PON>-|ONU/ONT|--|HGW|
                                                  |   +-------+  +---+
                                                  |
                                                  |   +-------+  +---+
                                                  +---|ONU/ONT|--|HGW|
                                                      +-------+  +---+

                                ANCP               ANCP
                       +<----------------->+<---------->+

         HGW: Home Gateway
         NAS: Network Access Server
         PON: Passive Optical Network
         OLT: Optical Line Terminal
         ONT: Optical Network Terminal
         ONU: Optical Network Unit

                   Figure 4:  All-ANCP ANX Reference Model


     5. Concept of Access Node Control Mechanism for PON Based
        Access


     The high-level communication framework for an Access Node Control
     mechanism is shown in Figure 5 for the ALL-ANCP ANX control
     model. The Access Node Control mechanism defines a quasi real-
     time, general-purpose method for multiple network scenarios with
     an extensible communication scheme, addressing the different use
     cases that are described in the sections that follow. The access
     node control mechanism is also extended to run between OLT and
     ONT/ONU. The mechanism consists of control function, and
     reporting and/or enforcement function. Controller function is

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     used to receive status information or admission requests from the
     reporting function. It is also used to trigger a certain behavior
     in the network element where the reporting and/or enforcement
     function resides.

     The reporting function is used to convey status information to
     the controller function that requires the information for
     executing local functions. The enforcement function can be
     contacted by the controller function to enforce a specific policy
     or trigger a local action. The messages shown in Figure 5 show
     the conceptual message flow. The actual use of these flows, and
     the times or frequencies when these messages are generated depend
     on the actual use cases, which are described in later sections.





































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       +--------+
       | Policy |                               +----+
       | Server |                    +--<PON>---|ONT |------- HGW
       +--------+                   +           +----+  +---+
            |                      +         +----------|ONT|----HGW
            |                     +          |          +---+
            |               +----------------|-------------+
         +----+             | +----+         |     +-----+ |    +---+
         |NAS |---------------|    |         |     |     |-|----|HGW|
         |    |<------------->|    |         |     | ONU | |    +---+
         +----+     ANCP    | |OLT |------<PON>----|     | |
            |               | |    |               |     | |    +---+
            |               | |    |<------------->|     |------|HGW|
            |               | +----+    ANCP       +-----+ |    +---+
            |               +------------------------------+
            |                    |    Access Node      |
            | Control Request    |                     |
            | ------------------>| Control Request     |
            |                    |-------------------->|
            |                    | Control Response    |
            | Control Response   |<------------------- |
            |<-------------------|                     |
            |                    |Admission Request    |
            | Admission Request  |<--------------------|
            |<-------------------|                     |
            |Admission Response  |                     |
            |------------------->|Admission Response   |
            |                    |-------------------->|
            |Information Report  |                     |
            |<-------------------|                     |
            Access Node Control     Access Node Control
                Mechanism                Mechanism
            <--------------------><-------------------->

                                   PPP, DHCP, IP
            <------------------------------------------------------>

     Figure 5: Conceptual message flow for Access Node Control
     mechanism in all-ANCP ANX control model.

     As discussed previously, in different PON deployment scenarios,
     ANCP may be used in variant ways and may interwork with other
     protocols, e.g., OMCI. In the ANCP+OMCI model described earlier,
     the NAS maintains ANCP adjacency with the OLT while the OLT
     controls the ONT/ONU via OMCI. The messages shown in Figure 6
     show the conceptual message flow for this model.  The actual use
     of these flows, and the times or frequencies when these messages
     are generated depend on the actual use cases.

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       +--------+
       | Policy |
       | Server |
       +--------+                                  +---+        +---+
            |                                +---- |ONT|--------|HGW|
            |                                |     +---+        +---+
            |               +--------------- |-------------+
         +----+             | +----+         |     +-----+ |    +---+
         |NAS |---------------|    |         |     |     |-|----|HGW|
         |    |<------------->|    |         |     | ONU | |    +---+
         +----+     ANCP    | |OLT |------<PON>----|     | |
            |               | |    |               |     | |    +---+
            |               | |    |<------------->|     |------|HGW|
            |               | +----+    OMCI       +-----+ |    +---+
            |               +-----------------------------+
            |                    |    Access Node      |
            | Control Request    |                     |
            | ------------------>| Control Request     |
            |                    |-------------------->|
            |                    | Control Response    |
            | Control Response   |<------------------- |
            |<-------------------|                     |
            |                    |Admission Request    |
            | Admission Request  |<--------------------|
            |<-------------------|                     |
            |Admission Response  |                     |
            |------------------->|Admission Response   |
            |                    |-------------------->|
            |Information Report  |                     |
            |<-------------------|                     |
            Access Node Control     Operating Maintenance
                Mechanism          Control Interface (OMCI)
            <--------------------><-------------------->

                                   PPP, DHCP, IP
            <------------------------------------------------------->

     Figure 6: Conceptual Message Flow for ANCP+OMCI ANX control
     model.

     6. Multicast


     With the rise of supporting IPTV services in a resource-efficient
     way, multicast services are becoming increasingly important.

     In order to gain bandwidth optimization with multicast, the
     replication of multicast content per access-loop needs to be
     distributed to the ANX. This can be done by ANX (OLT and ONT/ONU)

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     becoming multicast aware by implementing an IGMP snooping and/or
     proxy function. The replication thus needs to be distributed
     between NAS, aggregation nodes, and ANX. In case of GPON, and in
     case of BPON with Ethernet uplink, this is very viable. By
     introducing IGMP processing on the ANX and aggregation nodes, the
     multicast replication process is now divided between the NAS, the
     aggregation node(s) and ANX. This is in contrast to the ATM-based
     model where NAS is the single element responsible for all
     multicast control and replication. In order to ensure backward
     compatibility with the ATM-based model, the NAS, aggregation node
     and ANX need to behave as a single logical device. This logical
     device must have exactly the same functionality as the NAS in the
     ATM access/aggregation network. The Access Node Control Mechanism
     can be used to make sure that this logical/functional equivalence
     is achieved by exchanging the necessary information between the
     ANX and the NAS.

     An alternative to multicast awareness in the ANX is for the
     subscriber to communicate the IGMP "join/leave" messages with the
     NAS, while the ANX is being transparent to these messages. In
     this scenario, the NAS can use ANCP to create replication state
     in the ANX for efficient multicast replication. The NAS sends a
     single copy of the multicast stream towards the ANX. The NAS can
     perform network-based conditional access and multicast admission
     control on multicast joins, and create replication state in the
     ANX if the request is admitted by the NAS.

     The following sections describe various use cases related to
     multicast.

    6.1. Multicast Conditional Access


     In a Broadband FTTP/B/C access scenario, Service Providers may
     want to dynamically control, at the network level, access to some
     multicast flows on a per user basis. This may be used in order to
     differentiate among multiple Service Offers or to
     realize/reinforce conditional access based on customer
     subscription. Note that, in some environments, application layer
     conditional access by means of Digital Rights Management (DRM)
     for instance may provide sufficient control so that network-based
     Multicast conditional access may not be needed. However, network
     level access control may add to the service security by
     preventing the subscriber from receiving a non-subscribed
     channel. In addition, it enhances network security by preventing
     a multicast stream from being sent on a link or a PON based on a
     non-subscriber request.


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     Where network-based channel conditional access is desired, there
     are two approaches. It can be done on the NAS along with
     bandwidth-based admission control. The NAS can control the
     replication state on the ANX based on the outcome of access and
     bandwidth based admission control. This is covered in a later
     section. The other approach is to provision the necessary
     conditional access information on the ANX (ONT/ONU and/or OLT) so
     the ANX can perform the conditional access decisions
     autonomously.  For these cases, the NAS can use ANCP to provision
     black and white lists as defined in [RFC5851] on the ANX so that
     the ANX can decide locally to honor a join or not. It should be
     noted that in the PON case, the ANX is composed of the ONT/ONU
     and OLT. Thus, this information can be programmed on the ONT/ONU
     and/or OLT. Programming this information on the ONT/ONU prevents
     illegitimate joins from propagating further into the network. A
     third approach, outside of the scope, may be to program the HGW
     with the access list. A White list associated with an Access Port
     identifies the multicast channels that are allowed to be
     replicated to that port. A Black list associated with an Access
     Port identifies the multicast channels that are not allowed to be
     replicated to that port. It should be noted that the black list
     if not explicitly programmed is the complement of the white list
     and vice versa.

     If the ONT/ONU performs IGMP snooping and it is programmed with a
     channel access list, the ONT/ONU will first check if the
     requested multicast channel is part of a White list or a Black
     list associated with the access port on which the IGMP join is
     received. If the channel is part of a White list, the ONT/ONU
     will pass the join request upstream towards the NAS. The ONT/ONU
     must not start replicating the associated multicast stream to the
     access port if such a stream is received until it gets
     confirmation that it can do so from the upstream node (NAS or
     OLT). Passing the channel access list is one of the admission
     control criteria whereas bandwidth-based admission control is
     another. If the channel is part of a Black list, the ONT/ONU can
     autonomously discard the message because the channel is not
     authorized for that subscriber.

     The ONT/ONU, in addition to forwarding the IGMP join, sends an
     ANCP admission request to the OLT identifying the channel to be
     joined and the premises. Premises identification to the OLT can
     be based on a Customer-Port-ID that maps to the access port on
     the ONT/ONU and known at the ONT/ONU and OLT. If the ONT/ONU has
     a white list and/or a black list per premises, the OLT need not
     have such a list. If the ONT/ONU does not have such a list, the


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     OLT may be programmed with such a list for each premises. In this
     latter case, the OLT would perform the actions described earlier
     on the ONT/ONU. Once the outcome of admission control
     (conditional access and bandwidth based admission control) is
     determined by the OLT (either by interacting with the NAS or
     locally), it is informed to the ONT/ONU. OLT Bandwidth based
     admission control scenarios are defined in a later section.

     The White List and Black List can contain entries allowing:

          -  An exact match for a (*,G) Any Source Multicast (ASM)
     group (e.g., <G=g.h.i.l>);

          -  An exact match for a (S,G) Source Specific Multicast
     (SSM)channel (e.g., <S=s.t.u.v,G=g.h.i.l>);

          -  A mask-based range match for a (*,G) ASM group (e.g.,
       <G=g.h.i.l/Mask>);

          - A mask-based range match for a (S,G) SSM channel (e.g.,
            <S=s.t.u.v,G=g.h.i.l/Mask>);

     The use of a White list and Black list may be applicable, for
     instance, to regular IPTV services (i.e., Broadcast TV) offered
     by an Access Provider to broadband (e.g., FTTP) subscribers.  For
     this application, the IPTV subscription is typically bound to a
     specific FTTP home, and the multicast channels that are part of
     the subscription are well-known beforehand. Furthermore, changes
     to the conditional access information are infrequent, since they
     are bound to the subscription.  Hence the ANX can be provisioned
     with the conditional access information related to the IPTV
     service.

     Instead of including the channel list(s) at the ONT/ONU, the OLT
     or NAS can be programmed with these access lists. Having these
     access lists on the ONT/ONU prevents forwarding of unauthorized
     joins to the OLT or NAS, reducing unnecessary control load on
     these network elements. Similarly, performing the access control
     at the OLT instead of the NAS, if not performed on the ONT/ONU,
     will reduce unnecessary control load on the NAS.









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     6.2. Multicast Admission Control


     The successful delivery of Triple Play Broadband services is
     quickly becoming a big capacity planning challenge for most of
     the Service Providers nowadays. Solely increasing available
     bandwidth is not always practical, cost-economical and/or
     sufficient to satisfy end-user experience given not only the
     strict QoS requirements of unicast applications like VoIP and
     Video on Demand, but also the fast growth of multicast
     interactive applications such as "video conferencing", digital
     TV, and digital audio. These applications typically require low
     delay, low jitter, low packet loss and high bandwidth. These
     applications are also typically "non-elastic", which means that
     they operate at a fixed bandwidth, which cannot be dynamically
     adjusted to the currently available bandwidth.

     An Admission Control (AC) mechanism covering admission of
     multicast traffic for the FTTP/B/C access is required in order to
     avoid over-subscribing the available bandwidth and negatively
     impacting the end-user experience. Before honoring a user request
     to join a new multicast flow, the combination of ANX and NAS must
     ensure admission control is performed to validate that there is
     enough video bandwidth remaining on the PON, and on the uplink
     between the OLT and NAS to carry the new flow (in addition to all
     other existing multicast and unicast video traffic) and that
     there is enough video bandwidth for the subscriber to carry that
     flow. The solution needs to cope with multiple flows per premises
     and needs to allow bandwidth to be dynamically shared across
     multicast and unicast video traffic per subscriber, PON, and
     uplink (irrespective of whether unicast AC is performed by the
     NAS, or by some off-path Policy Server). It should be noted that
     the shared bandwidth between multicast and unicast video is under
     operator control. That is, in addition to the shared bandwidth,
     some video bandwidth could be dedicated to Video on Demand, while
     other video bandwidth could be dedicated for multicast.

     The focus in this document will be on multicast-allocated
     bandwidth including the shared unicast and multicast bandwidth.
     Thus, supporting admission control requires some form of
     synchronization between the entities performing multicast AC
     (e.g., the ANX and/or NAS), the entity performing unicast AC
     (e.g., the NAS or a Policy Server), and the entity actually
     enforcing the multicast replication (i.e., the NAS and the ANX).
     This synchronization can be achieved in a number of ways:




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       - One approach is for the NAS to perform bandwidth based
          admission control on all multicast video traffic and
          unicast video traffic that requires using the shared
          bandwidth with multicast. Based on the outcome of admission
          control, NAS then controls the replication state on the
          ANX. The subscriber generates an IGMP join for the desired
          stream on its logical connection to the NAS. The NAS
          terminates the IGMP message, and performs conditional
          access and bandwidth based admission control on the IGMP
          request. The bandwidth admission control is performed
          against the following:

            1. Available video bandwidth on the link to OLT

            2. Available video bandwidth on the PON interface

            3. Available video bandwidth on the last mile (access-port
     on the ONT/ONU).

     The NAS can locally maintain and track video bandwidth it manages
     for all the three levels mentioned above. The NAS can maintain
     identifiers corresponding to the PON interface and the last mile
     (customer interface). It also maintains a channel map,
     associating every channel (or a group of channels sharing the
     same bandwidth requirement) with a data rate. For instance, in
     case of 1:1 VLAN representation of the premises, the outer tag
     (S-VLAN) could be inserted by the ANX to correspond to the PON
     interface on the OLT, and the inner-tag could be inserted by the
     ANX to correspond to the access-line towards the customer.
     Bandwidth tracking and maintenance for the PON interface and the
     last-mile could be done on these VLAN identifiers. In case of N:1
     representation, the single VLAN inserted by ANX could correspond
     to the PON interface on the OLT. The access loop is represented
     via Customer-Port-ID received in "Agent Circuit Identifier" sub-
     option in DHCP messages.

     The NAS can perform bandwidth accounting on received IGMP
     messages. The video bandwidth is also consumed by any unicast
     video being delivered to the CPE. NAS can perform video bandwidth
     accounting and control on both IGMP messages and on requests for
     unicast video streams when either all unicast admission control
     is done by the NAS or an external policy server makes a request
     to the NAS for using shared bandwidth with multicast as described
     later in the document.

     This particular scenario assumes the NAS is aware of the
     bandwidth on the PON, and under all conditions can track the


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     changes in available bandwidth on the PON. On receiving an IGMP
     Join message, NAS will perform bandwidth check on the subscriber
     bandwidth. If this passes, and the stream is already being
     forwarded on the PON by the OLT (which also means that it is
     already forwarded by the NAS to the OLT), NAS will admit the
     JOIN, update the available subscriber bandwidth, and transmit an
     ANCP message to the OLT and in turn to the ONT/ONU to start
     replication on the customer port. If the stream is not already
     being replicated to the PON by the OLT, the NAS will also check
     the available bandwidth on the PON, and if it is not already
     being replicated to the OLT it will check the bandwidth on the
     link towards the OLT. If this passes, the available PON bandwidth
     and the bandwidth on the link towards the OLT are updated. The
     NAS adds the OLT as a leaf to the multicast tree for that stream.
     On receiving the message to start replication, the OLT will add
     the PON interface to its replication state if the stream is not
     already being forwarded on that PON. Also, the OLT will send an
     ANCP message to direct the ONT/ONU to add or update its
     replication state with the customer port for that channel. The
     interaction between ANX and NAS is shown in Figures 7 and 8. For
     unicast video streams, application level signaling from the CPE
     typically triggers an application server to request bandwidth
     based admission control from a policy server. The policy server
     can in turn interact with the NAS to request the bandwidth for
     the unicast video flow if it needs to use shared bandwidth with
     multicast. If the bandwidth is available, NAS will reserve the
     bandwidth, update the bandwidth pools for subscriber bandwidth,
     the PON bandwidth, and the bandwidth on the link towards the OLT,
     and send a response to the policy server, which is propagated
     back to the application server to start streaming. Otherwise, the
     request is rejected.


















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                                                      +----+
                                  +---<PON>---------- |ONT |------ HGW
                                 +                    +----+
                                +                     +----+
                               +           +--------- |ONT |------ HGW
       +----+               +----+        +           +----+
       |NAS |---------------|    |------<PON>
       |    |<------------->|    |        +           +-----+
       +----+     ANCP      |OLT |         +--------- |     |----- HGW
         |                  |    |                    |     |
         |                  |    |<------------------>| ONU |------HGW
         |                  +----+    ANCP            |     |     +---+
         |                     |                      |     |-----|HGW|
         |                     |                      +-----+     +---+
         |           1.IGMP JOIN(S/*,G)                |              |
         |<---------------------------------------------------------- |
       2.|                     |                       |              |
       +=======================+                       |              |
       [Access Control &       ]                       |              |
       [Subscriber B/W         ]                       |              |
       [PON B/W & OLT link B/W ]                       |              |
       [based Admission Control]                       |              |
       +=======================+                       |              |
         |                     |                       |              |
         |-------------------> |                       |              |
       3.ANCP Replication-Start|                       |              |
         (<S/*,G> or Multicast |                       |              |
         |MAC,Customer-Port-ID>| --------------------> |              |
         |                     |4.ANCP Replication-Start              |
         |                  (<S/*,G> or Multicast MAC,Customer-Port-ID)
         |-------------------> |                       |              |
         |5.Multicast Flow(S,G)|                       |              |
         |On Multicast VLAN    |---------------------> |              |
         |                     |6.Multicast Flow (S,G) |              |
         |                     |forwarded on           |              |
         |                     |Unidirectional         |              |
         |                     |<Multicast GEM-PORT>   |              |
         |                     |on the PON by OLT      |------------->|
                                                      7. Multicast Flow
                                                       orwarded on    |
                                                      Customer-Port by|
                                                       |ONT/OLT.      |
                                                       |              |

     Figure 7: Interactions for NAS based Multicast Admission Control
     (no IGMP processing on ANX, and NAS maintains available video
     bandwidth for PON) upon channel join.







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                                                      +----+
                                  +---<PON>---------- |ONT |----- HGW
                                 +                    +----+
                                +                     +----+
                               +           +--------- |ONT |----- HGW
       +----+               +----+        +           +----+
       |NAS |---------------|    |------<PON>
       |    |<------------->|    |        +           +-----+
       +----+     ANCP      |OLT |         +--------- |     |---- HGW
         |                  |    |                    |     |
         |                  |    |<------------------>| ONU |-----HGW
         |                  +----+    ANCP            |     |     +---+
         |                     |                      |     |-----|HGW|
         |                     |                      +-----+     +---+
         |                     |                       |              |
         |            IGMP LEAVE(S/*,G)                |              |
         |<-----------------------------------------------------------|
         |                     |                       |              |
       +====================+  |                       |              |
       [Admission Control   ]  |                       |              |
       [<Resource Released> ]  |                       |              |
       +====================+  |                       |              |
         |                     |                       |              |
         |                     |                       |              |
         |                     |                       |              |
         |-------------------> |                       |              |
        ANCP Replication-Stop  |                       |              |
         (<S/*,G> or Multicast MAC,Customer-Port-ID)   |              |
         |                     |                       |              |
         |                     |---------------------> |              |
         |                     | ANCP Replication-Stop |              |
                           (<S/*,G> or Multicast MAC,Customer-Port-ID)


     Figure 8: Interactions for NAS based Multicast Admission Control
     (no IGMP processing on ANX, and NAS maintains available video
     bandwidth for PON) upon channel leave.


         - An alternate approach is required if the NAS is not aware
     of the bandwidth on the PON. In this case the OLT does the PON
     bandwidth management, and requests NAS to perform bandwidth
     admission control on subscriber bandwidth and the bandwidth on
     the link to the OLT. Following are operations of various
     elements:

            ANX operation:

            - ONT/ONU can snoop IGMP messages. If conditional access
     is configured and the channel is in the Black list (or it is not
     on the  White list), ONT will drop the IGMP Join. If the channel
     passes the conditional access check, the ONT will forward the

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     IGMP Join, and will send a bandwidth admission control request to
     the OLT. In case the multicast stream is already being received
     on the PON, the ONT/ONU does not forward the stream to the access
     port where IGMP is received till it has received a positive
     admission control response from the OLT.

          - OLT can snoop IGMP messages.  It also receives a bandwidth
     admission control request from the ONT/ONU for the requested
     channel. It can be programmed with a channel bandwidth map. If
     the multicast channel is already being streamed on the PON, or
     the channel bandwidth is less than the multicast available
     bandwidth on the PON, the OLT forwards the IGMP request to the
     NAS and keeps track of the subscriber (identified by customer-
     Port-ID) as a receiver. If the channel is not already being
     streamed on the PON, but the PON has sufficient bandwidth for
     that channel, the OLT reduces the PON multicast video bandwidth
     by the channel bandwidth and may optionally add the PON to the
     multicast tree without activation for that channel. This is
     biased towards a forward expectation that the request will be
     accepted at the NAS. The OLT forwards the IGMP join to the NAS.
     It also sends a bandwidth admission request to the NAS
     identifying the channel, and the premises for which the request
     is made. It sets a timer for the subscriber multicast entry
     within which it expects to receive a request from the NAS that
     relates to this request.  If the PON available bandwidth is less
     than the bandwidth of the requested channel, the OLT sends an
     admission response (with a reject) to the ONT/ONU, and does not
     forward the IGMP join to the NAS.

     NAS operation:

     The NAS receives the IGMP join from the subscriber on the
     subscriber connection. When NAS receives the admission control
     request from ANX (also signifying the bandwidth on the PON is
     available), it performs admission control against the subscriber
     available multicast bandwidth. If this check passes, and the NAS
     is already transmitting that channel to the OLT, the request is
     accepted. If the check passes and the NAS is not transmitting the
     channel to the OLT yet, it performs admission control against the
     multicast video available bandwidth (this includes the dedicated
     multicast bandwidth and the shared bandwidth between multicast
     and video on demand) on the link(s) to the OLT. If the check
     passes, the request is accepted, the available video bandwidth
     for the subscriber and downlink to the OLT are reduced by the
     channel bandwidth, and the NAS sends an ANCP admission control
     response (indicating accept) to the OLT, requesting the addition
     of the subscriber to the multicast tree for that channel. The OLT


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     activates the corresponding multicast entry if not active and
     maintains state of the subscriber in the list of receivers for
     that channel. The OLT also sends an ANCP request to the ONT/ONU
     to enable reception of the multicast channel and forwarding to
     the subscriber access port. Otherwise, if the request is
     rejected, the NAS will send an admission reject to the OLT, which
     in turn removes the subscriber as a receiver for that channel (if
     it were added), and credits back the channel bandwidth to the PON
     video bandwidth if there is no other receiver on the PON for that
     channel. The interactions between ANX and NAS are shown in
     Figures 9 and 10.

     If the OLT does not receive a response from the NAS within a set
     timer, the OLT removes the subscriber from the potential list of
     receivers for the indicated channel. It also returns the
     allocated bandwidth to the PON available bandwidth if there are
     no other receivers. In this case, the NAS may send a response to
     the OLT with no matching entry as the entry has been deleted. The
     OLT must perform admission control against the PON available
     bandwidth and may accept the request and send an ANCP request to
     the ONT/ONU to activate the corresponding multicast entry as
     described earlier. If it does not accept the request, it will
     respond back to the NAS with a reject. The NAS shall credit back
     the channel bandwidth to the subscriber. It shall also stop
     sending the channel to the OLT if that subscriber was the last
     leaf on the multicast tree towards the OLT.

     On processing an IGMP leave, the OLT will send an ANCP request to
     NAS to release resources. NAS will release the subscriber
     bandwidth. If this leave causes the stream to be no longer
     required by the OLT, the NAS will update its replication state
     and release the bandwidth on the NAS to OLT link.

     If the subscriber makes a request for a unicast video stream
     (i.e., Video on Demand), the request results in appropriate
     application level signaling, which typically results in an
     application server requesting a policy server for bandwidth-based
     admission control for the VoD stream. The policy server after
     authorizing the request, can send a request to the NAS for the
     required bandwidth if it needs to use bandwidth that is shared
     with multicast. This request may be based on a protocol outside
     of the scope of this document. The NAS checks if the available
     video bandwidth (accounting for both multicast and unicast) per
     subscriber and for the link to the OLT is sufficient for the
     request. If it is, it temporarily reserves the bandwidth and
     sends an ANCP admission request to the OLT for the subscriber,
     indicating the desired VoD bandwidth. If the OLT has sufficient


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     bandwidth on the corresponding PON, it reserves that bandwidth
     and returns an accept response to the NAS. If not, it returns a
     reject to the NAS. If the NAS receives an accept, it returns an
     accept to the policy server which in turn returns an accept to
     the application server, and the video stream is streamed to the
     subscriber. This interaction is shown in Figure 11. If the NAS
     does not accept the request from the policy server, it returns a
     reject. If the NAS receives a reject from the OLT, it returns the
     allocated bandwidth to the subscriber and the downlink to the
     OLT.







































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                                                     +----+
                                           +-------- |ONT |-------- HGW
       +----+               +----+         +         +----+
       |NAS |---------------|    |------<PON>
       |    |<------------->|    |         +          +-----+
       +----+     ANCP      |OLT |         +--------- |     |------ HGW
         |                  |    |    ANCP            | ONU |
         |                  +----+<------------------>+-----+-------HGW
         |                     |                        |             |
         |1.IGMP Join(s/*,G) +=============+         +=============+  |
         |<------------------[IGMP Snooping]---------[IGMP snooping]--|
         |                   +=============+         +=============+  |
         |                     |2.Admission-Request     |             |
         |                     |(Flow,Customer-Port-ID) |             |
         |                     |<---------------------- |             |
         |                3.+===============+           |             |
         |                  [ Access Ctrl   ]           |             |
         |                  [ & PON B/W     ]           |             |
         |                  [ Admission Ctrl]           |             |
         |                  +===============+ PASS      |             |
         |4.Admission-Request  |                        |             |
         | <Flow,              |                        |             |
         |  Customer-Port-ID>  |                        |             |
         |<--------------------|                        |             |
       5.|                     |                        |             |
       +=================+     |                        |             |
       [Subscriber B/W   ]     |                        |             |
       [& OLT link B/W   ]     |                        |             |
       [Admission Ctrl   ]     |                        |             |
       +=================+PASS |                        |             |
         |6.Admission-Reply-Pass                        |             |
         |<Flow,Customer-Port-ID>                       |             |
         |-------------------->|                        |             |
         |            7.+========================+      |             |
         |              [Update Replication State]      |             |
         |              +========================+      |             |
         |                     | 8.Admission-Reply-Pass |             |
         |                     |(<Flow,Cust-Port-ID>    |             |
         |                     |----------------------> |             |
         |                     |                 9.+============+     |
         |                     |                   [Update Repl.]     |
         |                     |                   [   State    ]     |
         |                     |                   +============+     |


     Figure 9: Interaction between NAS & ANX for Multicast Bandwidth
     Admission Control in the All-ANCP ANX control model upon success.
     Similar functionality will be required when OMCI is enabled between
     the OLT and ONT/ONU in the ANCP+OMCI ANX control model. In this
     latter case, the OLT will act as ANCP-OMCI gateway.




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                                                      +----+
                                           +--------- |ONT |------ HGW
       +----+               +----+        +           +----+
       |NAS |---------------|    |------<PON>
       |    |<------------->|    |        +           +-----+
       +----+     ANCP      |OLT |         +--------- |     |----- HGW
         |                  |    |    ANCP            |ONU  |
         |                  +----+<------------------>+-----+------HGW
         |                     |                        |             |
         |1.IGMP Join(s/*,G) +=============+        +=============+   |
         |<------------------[IGMP Snooping]--------[IGMP snooping]-- |
         |                   +=============+        +=============+   |
         |                     |2.Admission-Request     |             |
         |                     |(Flow,Customer-Port-ID) |             |
         |                     |<---------------------- |             |
         |                2.+===============+           |             |
         |                  [ Access Ctrl   ]           |             |
         |                  [ & PON B/W     ]           |             |
         |                  [ Admission Ctrl]           |             |
         |                  +===============+ PASS      |             |
         |3.Admission-Request  |                        |             |
         | <Flow,Customer-Port-ID>                      |             |
         |<--------------------|                        |             |
       4.|                     |                        |             |
       +==================+    |                        |             |
       [Subscriber B/W    ]    |                        |             |
       [& OLT link B/W    ]    |                        |             |
       [Admission Ctrl    ]    |                        |             |
       +==================+FAIL                         |             |
         |                     |                        |             |
         |5.Admission-Reply-Fail                        |             |
         |<Flow,Cust-Port-ID>  |                        |             |
         |-------------------->|                        |             |
         |            6.+==================+            |             |
         |              [Release PON B/W   ]            |             |
         |              [Remove Repl.State ]            |             |
         |              +==================+            |             |
         |                     | 7.Admission-Reply-Fail |             |
         |                     |<Flow,Cust-Port-ID>     |             |
         |                     |----------------------> |             |
         |                     |                 8.+============+     |
         |                     |                   [Remove Repl.]     |
         |                     |                   [   State    ]     |
         |                     |                   +============+     |


     Figure 10: Interaction between NAS and ANX for Multicast Bandwidth
     Admission Control in the All-ANCP ANX control model upon failure.
     Similar functionality will be required when OMCI is enabled between
     the OLT and ONT/ONU in the ANCP+OMCI ANX control model. In this
     latter case, the OLT will act as ANCP-OMCI gateway.



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       +------------+              1. VoD Request
       | App. Server|<-----------------------------------------------
       | Server     |
       +------------+
         | 2. Admission-Request (VoD-Flow)
       +-------+
       |Policy |
       |Server |
       +-------+
        |  +
        |<-|---3. Admission-Request
        |  |
        +  | 8. Admission-Reply
       +----+        +      +----+                  +-----+
       |NAS |---------------|OLT |------<PON>-------|ONT  |---HGW--CPE
       |    |<------------->|    |                  +-----+    |
       +----+     ANCP      +----+                      |      |
         |                     |                        |      |
       4.|                     |                        |      |
       +=================+     |                        |      |
       [Subscriber B/W   ]     |                        |      |
       [& OLT link B/W   ]     |                        |      |
       [Admission Ctrl   ]     |                        |      |
       +=================+PASS |                        |      |
         |                     |                        |      |
         | 5.Admission-Request |                        |      |
         |(Bandwidth,PON-Port-ID)                       |      |
         |-------------------> |                        |      |
         |                     |                        |      |
         |                6.+===============+           |      |
         |                  [   PON B/W     ]           |      |
         |                  [ Admission Ctrl]           |      |
         |                  +===============+ PASS      |      |
         |7.Admission-Reply    |                        |      |
         | <PON-Port-ID>       |                        |      |
         |<------------------- |                        |      |
         |                     |                        |      |
         |                     |                        |      |


     Figure 11: Interactions for VoD Bandwidth Admission Control in
     the All-ANCP ANX control model. Similar functionality will be
     required when OMCI is enabled between the OLT and ONT in the
     ANCP+OMCI ANX control model. In this latter case, the OLT will
     act as ANCP-OMCI gateway.


     -A third possible approach is where the ANX is assumed to have a
     full knowledge to make an autonomous decision on admitting or
     rejecting a multicast and a unicast join. With respect to the
     interaction between ONT/ONU and OLT, the procedure is similar to

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     the first approach (i.e., NAS controlled replication). However,
     when the OLT receives an IGMP request from a subscriber, it
     performs admission control against that subscriber multicast
     video bandwidth (dedicated and shared with Video on Demand), the
     PON and uplink to the GWR. It should be noted in this case that
     if there are multiple NAS-OLT links, either the link on which the
     multicast stream must be sent is pre-determined, needs to be
     selected by the OLT based on downstream bandwidth from NAS to OLT
     and the selection is communicated to the NAS, or the OLT has to
     be ready to receive the stream on any link. If the check passes,
     the OLT updates the video available bandwidth per PON and
     subscriber. The OLT adds the subscriber to the list of receivers
     and the PON to the multicast tree, if it is not already on it. It
     also sends an ANCP request to the ONT/ONU to add the subscriber
     access port to that channel multicast tree, and sends an ANCP
     message to the NAS informing it of the subscriber and link
     available video bandwidth and the channel the subscriber joined.
     The NAS upon receiving the ANCP information message, updates the
     necessary information, including the OLT to the multicast tree if
     it is not already on it. It should be noted in this case that the
     ANCP message from the OLT to the NAS is being used to add the OLT
     to a multicast tree as opposed to an IGMP message. The IGMP
     message can also be sent by the OLT with the OLT acting as an
     IGMP proxy at the expense of added messages. In this option, the
     OLT acts as the network IGMP router for the subscriber.

     For unicast video streams, the policy server receiving an
     admission request from an application server, as described
     before, may query the OLT for admission control as it has all
     information. If the OLT has sufficient bandwidth for the stream
     it reserves that bandwidth for the subscriber, PON and OLT uplink
     to the NAS and returns an accept to the policy server. It also
     updates the NAS via an ANCP message of the subscriber available
     video bandwidth. If the OLT rejects the policy server request, it
     will return a reject to the policy server.

     It should be noted that if the policy server adjacency is with
     the NAS, the policy server may make the admission request to the
     NAS. The NAS then sends an ANCP admission request to the OLT on
     behalf of the policy server. The NAS returns an accept or reject to
     the policy server if it gets a reject or accept, respectively,
     from the OLT.






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     6.3. Multicast Accounting


     It may be desirable to perform accurate per-user or per Access
     Loop time or volume based accounting. In case the ANX is
     performing the traffic replication process, it knows when
     replication of a multicast flow to a particular Access Port or
     user starts and stops. Multicast accounting can be addressed in
     two ways:

     - ANX keeps track of when replication starts or stops, and
     reports this information to the NAS for further processing. In
     this case, ANCP can be used to send the information from the ANX
     to the NAS. This can be done with the Information Report message.
     The NAS can then generate the appropriate time and/or volume
     accounting information per Access Loop and per multicast flow, to
     be sent to the accounting system. The ANCP requirements to
     support this approach are specified in [RFC5851]. If the
     replication function is distributed between the OLT and ONT/ONU,
     a query from the NAS will result in OLT generating a query to the
     ONT/ONU.

     - ANX keeps track of when replication starts or stops, and
     generates the time and/or volume based accounting information per
     Access Loop and per multicast flow, before sending it to a
     central accounting system for logging. Since ANX communicates
     with this accounting system directly, the approach does not
     require the use of ANCP. It is therefore beyond the scope of this
     document; It may also be desirable for the NAS to have the
     capability to asynchronously query the ANX to obtain an
     instantaneous status report related to multicast flows currently
     replicated by the ANX. Such a reporting functionality could be
     useful for troubleshooting and monitoring purposes. If the
     replication function in the ANX is distributed between the OLT
     and the ONT/ONU, then for some of the information required by the
     NAS (such as the list of access-ports on which a flow is being
     forwarded or list of flows being forwarded on an access-port), a
     query to the OLT from the NAS will result in a query from OLT to
     ONT/ONU. The OLT responds back to the NAS when it receives the
     response from the ONT/ONU. Also, if the list of PONs on which
     replication is happening for a multicast channel or the list of
     channels being replicated on a PON is what is desired, the OLT
     can return this information.






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     7. Remote Connectivity Check


     In an end-to-end Ethernet aggregation network, end-to-end
     Ethernet OAM as specified in IEEE 802.1ag and ITU-T
     Recommendation Y.1730/1731 can provide Access Loop connectivity
     testing and fault isolation. However, most HGWs do not yet
     support these standard Ethernet OAM procedures. Also, in a mixed
     Ethernet and ATM access network (e.g., Ethernet based aggregation
     upstream from the OLT, and BPON downstream), interworking
     functions for end-to-end OAM are not yet standardized or widely
     available. Until such mechanisms become standardized and widely
     available, Access Node Control mechanism between NAS and ANX can
     be used to provide a simple mechanism to test connectivity of an
     access-loop from the NAS.

     Triggered by a local management interface, the NAS can use the
     Access Node Control Mechanism (Control Request Message) to
     initiate an Access Loop test between Access Node and HGW or
     ONT/ONU. On reception of the ANCP message, the OLT can trigger
     native OAM procedures defined for BPON in [G.983.1] and for GPON
     in [G.984.1]. The Access Node can send the result of the test to
     the NAS via a Control Response message.

     8. Access Topology Discovery


     In order to avoid congestion in the network, manage and utilize
     the network resources better, and ensure subscriber fairness, NAS
     performs hierarchical shaping and scheduling of the traffic by
     modeling different congestion points in the network (such as the
     last-mile, access Node uplink, and the access facing port).

     Such mechanisms require that the NAS gains knowledge about the
     topology of the access network, the various links being used and
     their respective rates. Some of the information required is
     somewhat dynamic in nature (e.g., DSL line rate in case the last
     mile is xDSL based, e.g., in case of "PON fed DSLAMs" for
     FTTC/FTTB scenarios), hence cannot come from a provisioning
     and/or inventory management OSS system. Some of the information
     varies less frequently (e.g., capacity of the OLT uplink), but
     nevertheless needs to be kept strictly in sync between the actual
     capacity of the uplink and the image the NAS has of it.

     OSS systems are rarely able to enforce in a reliable and scalable
     manner the consistency of such data, notably across
     organizational boundaries under certain deployment scenarios.


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     The Access Topology Discovery function allows the NAS to perform
     these advanced functions without having to depend on an error-
     prone and possibly complex integration with an OSS system.

     The rate of the access-loop can be communicated via ANCP
     (Information Report Message) from the ONT/ONU to the OLT in the
     All-ANCP ANX control model or via OMCI in the ANCP+OMCI ANX
     control model, and then from OLT to the NAS via ANCP.
     Additionally, during the time the DSL NT is active, data rate
     changes can occur due to environmental conditions (the DSL Access
     Loop can get "out of sync" and can retrain to a lower value, or
     the DSL Access Loop could use Seamless Rate Adaptation making the
     actual data rate fluctuate while the line is active). In this
     case, ANX sends an additional Information Report to the NAS each
     time the Access Loop attributes change above a threshold value.
     Existing DSL procedures are not applicable in this case because
     an adapted message flow and additional TLVs are needed.


       +--------+
       | Policy |
       | Server |
       +--------+                                        +---+   +---+
            |                                +-----------|ONT|---|HGW|
            |                                |           +---+   +---+
            |               +--------------- |-----------------+
         +----+             | +----+         |         +-----+ | +---+
         |NAS |------------ | |    |         |         |     |-|-|HGW|
         |    |<----------> | |    |         |         |ONT/ | | +---+
         +----+     ANCP    | |OLT |------<PON>--------|ONU  | |
            |               | |    |                   |     | | +---+
            |               | |    |<----------------->|     |---|HGW|
            |               | +----+       OMCI        +-----+ | +---+
            |               +----------------------------------+
            |                    |      Access Node       |
            |                    |                        |
            |                    |------GPON Ranging------|
            | Port Status Message|      ONT Port UP       |
            |<------------------ |<-----------------------|
            |Port Configuration  GPON Line/Service Profile|
            |------------------> |<---------------------->|
            |     ONT/ONI Port UP|                        |
            |<------------------ |                        |
            |                    |                        |
            |      ANCP          |         OMCI           |
            <-------------------><----------------------->|
                                   PPP, DHCP, IP
            <------------------------------------------------------>

     Figure 12: Message Flow for the use case of Topology Discovery
     for the ANCP+OMCI access control model.


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     Figure 12 depicts a message flow for topology discovery when
     using the ANCP+OMCI access control model. Basically, when an
     ONT/ONU gets connected to a PON, the OLT detects a new device and
     a GPON Ranging process starts. During this process the ONT/ONU
     becomes authorized by the OLT and identified by ONT/ONU ID, PON
     Port ID and max Bandwidth. This port status is reported via ANCP
     to the NAS and then potentially the policy server via another
     mechanism that is out of scope of this document. In a second step
     after GPON Service profile is assigned from OLT to ONT/ONU, the
     OLT reports the final status to NAS with information about
     service profile and other information such as the ONT/ONU port
     rate to the subscriber for instance.

     9. Access Loop Configuration


     Topology Discovery reports access port identification to NAS when
     sending an Access Port Discovery message. This informs NAS
     identification of PON port on an Access Node. Based on Access
     Port Identification and on customer identification, service
     related parameters could be configured on an OLT and an ONU/ONT.

     Service related parameters could be sent to OLT via ANCP before
     or after an ONU/ONT is up. Sending of ANCP loop Configuration
     messages from NAS can be triggered by a management system or by
     customer identification and authentication after Topology
     Discovery. It may be used for first time configuration (zero
     touch) or for updating/upgrading customer's profile like C-VLAN
     ID, S-VLAN ID, and service bandwidth.

     Parameters of UNI (subscriber interface to HGW/CPE) of ONU/ONT
     can also be configured via ANCP. When the ONU/ONT supports ANCP,
     parameters of the UNI on ONU/ONT are sent to the ONU/ONT via
     ANCP. If the ONU/ONT does not support ANCP, but only OMCI,
     parameters have to be sent from the NAS to the OLT via ANCP
     first. Then, the OLT translates such configuration into OMCI and
     sends it to the ONU/ONT.


     10. Security Considerations


     [RFC5713] lists the ANCP related security threats that could be
     encountered on the Access Node and the NAS. It develops a threat
     model for ANCP security, and lists the security functions that
     are required at the ANCP level.


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     With Multicast handling as described in this document, ANCP
     protocol activity between the ANX and the NAS is triggered by
     join/leave requests coming from the end-user equipment. This
     could potentially be used for denial of service attack against
     the ANX and/or the NAS.

     To mitigate this risk, the NAS and ANX may implement control
     plane protection mechanisms such as limiting the number of
     multicast flows a given user can simultaneously join, or limiting
     the maximum rate of join/leave from a given user.

     Protection against invalid or unsubscribed flows can be deployed
     via provisioning black lists as close to the subscriber as
     possible (e.g., in the ONT).


     11. Differences in ANCP applicability between DSL and PON


     As it currently stands, both ANCP framework [RFC5851] and
     protocol [RFC6320] are defined in context of DSL access. Due to
     inherent differences between PON and DSL access technologies,
     ANCP needs a few extensions for supporting the use-cases outlined
     in this document for PON based access. These specific differences
     and extensions are outlined below.

     - In PON, the access-node functionality is split between OLT and
     ONT. Therefore, ANCP interaction between NAS and AN translates to
     transactions between NAS and OLT and between OLT and ONT. The
     processing of ANCP messages (e.g., for multicast replication
     control) on the OLT can trigger generation of ANCP messages from
     OLT to ONT. Similarly, ANCP messages from ONT to the OLT can
     trigger ANCP exchange between the OLT and the NAS (e.g.,
     admission-request messages). This is illustrated in the generic
     message flows in Figures 5 and 6 of section 5. In case of DSL,
     the ANCP exchange is contained between two network elements (NAS
     and the DSLAM).

     - The PON connection to the ONT is a shared medium between
     multiple ONTs on the same PON. The local-loop in case of DSL is
     point-to-point. In case of DSL access network, the access facing
     port on the NAS (i.e., port to the network between NAS and the
     DSLAM), and the access-facing ports on the DSLAM (i.e.,
     customer's local-loop) are the two bandwidth constraint points
     that need to be considered for performing bandwidth based
     admission control for multicast video and VoD delivered to the
     customer. In case of PON access, in addition to the bandwidth


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     constraint on the NAS to OLT facing ports, and the subscriber
     allocated bandwidth for video services, the bandwidth available
     on the PON for video is an additional constraint that needs to be
     considered for bandwidth based admission control. If the
     bandwidth control is centralized in NAS (as described in option 1
     of section 6.2), then the NAS needs to support additional logic
     to consider available PON bandwidth before admitting a multicast
     request or a VoD request by the user. Accordingly, ANCP needs to
     identify the customer access port and the PON on which the
     customer ONT is. If the PON bandwidth control is performed on the
     OLT (as defined in second option in section 6.2), then additional
     ANCP request and response messages are required for NAS to query
     the OLT to determine available PON bandwidth when a request to
     admit a VOD flow is received on the NAS (as shown in Figure 9 in
     section 6.2) or for the OLT to inform the NAS what stream
     bandwidth is sent to the subscriber for the NAS to take
     appropriate action (e.g., bandwidth adjustment for various types
     of traffic).

     - In PON, the multicast replication can potentially be performed
     on three different network elements: (1) on the NAS (2) on the
     OLT for replication to multiple PON ports, and (3) on the ONT/ONU
     for replication to multiple customer ports. In case of DSL, the
     replication can potentially be performed on NAS and/or the DSLAM.
     Section 6.2 defines options for multicast replication in case of
     PON. In the first option, the multicast replication is done on
     the AN, but is controlled from NAS via ANCP (based on the
     reception of per-customer IGMP messages on the NAS). In this
     option, the NAS needs to supply to the OLT the set of PON-
     customer-IDs (as defined in section 2) to which the multicast
     stream needs to be replicated. The PON-customer-ID identifies the
     OLT and the PON ports on the OLT as well as the ONT and the
     access-ports on the ONT where the multicast stream needs to be
     replicated. Upon receiving the request to update its multicast
     replication state, the OLT must update its replication state with
     the indicated PON ports, but may also need to interact with the
     ONT via ANCP to update the multicast replication state on the ONT
     with the set of access-ports (as indicated by the NAS). In case
     of DSL, the DSLAM only needs to update its own replication state
     based on the set of access-ports indicated by the NAS.

     - For reporting purposes, ANCP must enable the NAS to query the
     OLT for channels replicated on a PON or a list of PONs and to
     specific access ports. The latter should trigger the OLT to query
     the ONT for a list of channels being replicated on all access
     ports or on specific access ports to the premises. In DSL case,



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     Internet-Draft          draft-ietf-ancp-pon-03          July 2012


     it is sufficient to query the DSLAM for a list of channels being
     replicated on an access port or a list of access ports.

     12. ANCP versus OMCI between the OLT and ONT/ONU


     ONT Management and Control Interface (OMCI) [OMCI] is specified
     for in-band ONT management via the OLT. This includes configuring
     parameters on the ONT/ONU. Such configuration can include adding
     an access port on the ONT to a multicast tree and the ONT to a
     multicast tree. Thus, OMCI can be a potential replacement for
     ANCP between the OLT and ONT/ONU, albeit it may not a be suitable
     protocol for dynamic transactions as required for the multicast
     application.

     If OMCI is selected to be enabled between the OLT and ONT/ONU to
     carry the same information elements that would be carried over
     ANCP, the OLT must perform the necessary translation between ANCP
     and OMCI for replication control messages received via ANCP. OMCI
     is an already available control channel, while ANCP requires a
     TCP/IP stack on the ONT/ONU that can be used by an ANCP client
     and accordingly it requires that the ONT/ONU be IP addressable
     for ANCP. Most ONTs/ONUs today have a TCP/IP stack used by
     certain applications (e.g., VoIP, IGMP snooping). ANCP may use
     the same IP address that is often assigned for VoIP or depending
     on the implementation may require a different address. Sharing
     the same IP address between VoIP and ANCP may have other network
     implications on traffic routing. Using a separate IP address for
     the purpose of ONT/ONU management or ANCP specifically may often
     be required when supporting ANCP. These considerations may favor
     OMCI in certain environments. However, OMCI will not allow some
     of the transactions required in approach 2, where the ONT/ONU
     sends unsolicited requests to the OLT rather than being queried or
     configured by OLT requests.

     13. IANA Considerations



        This document does not require actions by IANA.








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     14. Acknowledgements



     The authors are thanksful to Rajesh Yadav and Francois Le
     Faucheur for valuable comments and discussions.





     15. References



     15.1. Normative References


     [RFC2516]  Mamakos, L., Lidl, K., Evarts, J., Carrel, D., Simone,
     D., and R. Wheeler, "A Method for Transmitting PPP Over
     Ethernet (PPPoE)", RFC 2516, February 1999.

     [RFC2684]  Grossman, D. and J. Heinanen, "Multiprotocol
     Encapsulation over ATM Adaptation Layer 5", RFC 2684, September
     1999.

     15.2. Informative References


     [RFC2881] Mitton, D. and M. Beadles, "Network Access Server
     Requirements Next Generation (NASREQNG) NAS Model", RFC 2881, Jul
     2000.

     [RFC5851] Ooghe, S., et al., "Framework and Requirements
     for Access Node Control Mechanism in Broadband Networks", RFC
     5851, May 2010.

     [G.983.1] ITU-T recommendation G.983.1, Broadband optical access
     systems based on Passive Optical Networks (PON).

     [G.984.1] ITU-T recommendation G.984.1 Gigabit-capable Passive
     Optical Networks (G-PON): General characteristics.

     [RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
     RFC3046, January 2011.



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     Internet-Draft          draft-ietf-ancp-pon-03          July 2012


     [TR-101] Cohen, A. and E. Shrum, "Migration to Ethernet-Based DSL
     Aggregation", DSL Forum TR-101, May 2006.

     [RFC5713] Moustafa, H., Tschofenig, H., and S. De Cnodder,
     "Security Threats and Security Requirements for the Access Node
     Control Protocol (ANCP)", RFC 5713, January 2010.

     [OMCI] ITU-T recommendation G.984.4 GPON ONT Management and
     Control Interface (OMCI) Specifications.

     [RFC6320] Taylor, T., et al, "Protocol for Access Node Control
     Mechanism in Broadband Networks", RFC 6320, October 2011.


     Authors' Addresses

     Nabil Bitar
     Verizon
     60 Sylvan Road
     Waltham, MA 02451
     Email: nabil.n.bitar@verizon.com


     Sanjay Wadhwa
     Alcatel-Lucent
     701 East Middlefield Road
     Mountain View, CA, 94043
     Email: sanjay.wadhwa@alcatel-lucent.com

     Hongyu Li
     Email: hongyu.lihongyu@huawei.com

     Thomas Haag
     Email: HaagT@telekom.de














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