GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc6934

Internet Engineering Task Force (IETF) N. Bitar, Ed. Request for Comments: 6934 Verizon Category: Informational S. Wadhwa, Ed. ISSN: 2070-1721 Alcatel-Lucent

                                                               T. Haag
                                                      Deutsche Telekom
                                                                 H. Li
                                                   Huawei Technologies
                                                             June 2013
       Applicability of the Access Node Control Mechanism to
    Broadband Networks Based on Passive Optical Networks (PONs)

Abstract

 The purpose of this document is to provide applicability of the
 Access Node Control Mechanism to broadband access based on Passive
 Optical Networks (PONs).  The need for an Access Node Control
 Mechanism between a Network Access Server (NAS) and an Access Node
 Complex, composed of 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 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

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Not all documents
 approved by the IESG are a candidate for any level of Internet
 Standard; see Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6934.

Bitar, et al. Informational [Page 1] RFC 6934 ANCP in PON-Based Networks June 2013

Copyright Notice

 Copyright (c) 2013 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1. Introduction ....................................................3
 2. Terminology .....................................................4
 3. Motivation for Explicit Extension of ANCP to FTTx PON ...........6
 4. Reference Model for PON-Based Broadband Access Network ..........7
    4.1. Functional Blocks ..........................................9
         4.1.1. Home Gateway ........................................9
         4.1.2. PON Access ..........................................9
         4.1.3. Access Node Complex ................................10
         4.1.4. Access Node Complex Uplink to the NAS ..............10
         4.1.5. Aggregation Network ................................10
         4.1.6. Network Access Server ..............................10
         4.1.7. Regional Network ...................................10
    4.2. Access Node Complex Control Reference Architecture
         Options ...................................................11
         4.2.1. ANCP+OMCI ANX Control ..............................11
         4.2.2. All-ANCP ANX Control ...............................12
 5. Concept of Access Node Control Mechanism for PON-Based Access ..13
 6. Multicast ......................................................16
    6.1. Multicast Conditional Access ..............................16
    6.2. Multicast Admission Control ...............................18
    6.3. Multicast Accounting ......................................30
 7. Remote Connectivity Check ......................................31
 8. Access Topology Discovery ......................................32
 9. Access Loop Configuration ......................................34
 10. Security Considerations .......................................34
 11. Differences in ANCP Applicability between DSL and PON .........35
 12. ANCP versus OMCI between the OLT and ONT/ONU ..................36
 13. Acknowledgements ..............................................37
 14. References ....................................................37
    14.1. Normative References .....................................37
    14.2. Informative References ...................................38

Bitar, et al. Informational [Page 2] RFC 6934 ANCP in PON-Based Networks June 2013

1. Introduction

 Passive Optical Networks (PONs) based on Broadband PON (BPON)
 [G.983.1] and Gigabit PON (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) BPON, (2) GPON, (3) 10-Gigabit PON
 (XG-PON), and (4) Ethernet PON (EPON).  This document describes the
 applicability of the Access Node Control Protocol (ANCP) in the
 context of FTTB/C and FTTP deployments, focusing on BPON, GPON, and
 XG-PON.  Architectural considerations lead to different ANCP
 compositions.  Therefore, the composition of ANCP communication
 between Access Nodes (ANs) and Network Access Servers (NASs) is
 described using different models.
 BPON, GPON, and XG-PON 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 Mbit/s per PON, GPON provides 2.4 Gbit/s, and XG-PON provides 10
 Gbit/s.
 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 XG-PON deployment is to provide
 triple-play services over IP: voice, video, and data.  Voice is
 generally low bandwidth but has requirements for low delay, low
 jitter, and low packet loss.  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 Mbit/s per stream while High Definition
 content using MPEG2 encoding requires 15-19 Mbit/s 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 linear
 programming content).  While linear programming content can be
 provided over Layer 1 on the PON, the focus in this document is on

Bitar, et al. Informational [Page 3] RFC 6934 ANCP in PON-Based Networks June 2013

 delivering linear programming content over IP to the subscriber using
 IP multicast.  Video on Demand (VoD) 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 ANX 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 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

  1. PON (Passive Optical Network) [G.983.1][G.984.1]: a point-to-

multipoint FTTP 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 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 (ONUs/ONTs) 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.

Bitar, et al. Informational [Page 4] RFC 6934 ANCP in PON-Based Networks June 2013

  1. Access Node Complex (ANX): 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 that does not depend on the physical location but
    rather on the "black box" behavior of OLT and ONU/ONT.
  1. 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.
  1. 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 an FTTP deployment (with fiber all the way to the
    apartment or living unit), ONT has Ethernet (Fast Ethernet (FE) /
    Gigabit Ethernet (GE) / Multimedia over Coax Alliance (MoCA))
    connectivity with the Home Gateway (HGW) / Customer Premises
    Equipment (CPE).  In certain cases, one ONT may provide
    connections to more than one Home Gateway at the same time.
  1. Optical Network Unit (ONU): a generic term denoting a device that

terminates any one of the distributed (leaf) endpoints of an

    Optical Distribution Network (ODN), implements a PON protocol, and
    adapts PON PDUs to subscriber service interfaces.  In the case of
    a multi-dwelling unit (MDU) or multi-tenant unit (MTU), 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".
  1. Network Access Server (NAS): network element that 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).
  1. Home Gateway (HGW): network element that connects subscriber

devices to the AN or ANX and the access network. In the 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

Bitar, et al. Informational [Page 5] RFC 6934 ANCP in PON-Based Networks June 2013

    latter case, such a device is also referred to as a Routing
    Gateway (RG).  In the case of PON, it is often a Layer 3 routing
    device with the ONT performing PON termination.
  1. PON-Customer-ID: identifier that 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 and 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 ID" 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 for 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.
 Fundamental to leveraging the broadcast capability on the PON for
 multicast delivery is the ability to assign no key, a single
 encryption key for all PON frames carrying all multicast channels, or
 a key per set of multicast channels that correspond to a service
 package.  When supporting encryption for multicast channels, the
 encryption key is generated by the OLT and sent by the OLT to each
 targeted ONT via the ONT Management and Control Interface (OMCI) as
 described in Section 15.5.2 of ITU-T G.987.3 [G.987.3] for XG-PON.
 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.

Bitar, et al. Informational [Page 6] RFC 6934 ANCP in PON-Based Networks June 2013

 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 the PON-
 enabled ANX and the NAS and also between the components comprising
 the ANX, i.e., between the OLT and the ONT.  Typical use cases for
 ANCP in the PON environment include the following:
  1. Access topology discovery
  2. Access loop configuration
  3. Multicast
    1. Optimized multicast delivery
    2. Unified video resource control
    3. NAS-based provisioning of ANX
  4. 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 Figures 1 and 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 cases are addressed
 in the context of this reference architecture:
  1. BPON with Ethernet uplink to the NAS and ATM on the PON side
  2. GPON/XG-PON with Ethernet uplink to the NAS and Ethernet on the

PON side

 In the 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/XG-PON and BPON with Ethernet
 between the NAS and the OLT.

Bitar, et al. Informational [Page 7] RFC 6934 ANCP in PON-Based Networks June 2013

                                        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

Bitar, et al. Informational [Page 8] RFC 6934 ANCP in PON-Based Networks June 2013

                                                       FE/GE/VDSL
                                                       +---+ +---+
                              +----------------+       |   |-|HGW|
       +---------+   +-----+  | +-----+  +----+|       |   | +---+
       |         | +-|NAS  |--| |Eth  |--|OLT||-<PON>- |   |
 NSP---+Regional | | +-----+  | |Agg  |  |    ||     | |ONT| +---+
       |Broadband| |          | |     |  |    ||     | | or|-|HGW|
       |Network  | | +-----+  | +-----+  +----+|     | |ONU| +---+
       |         |-+-|NAS  |  +----------------+     | |   |
 ASP---+         | | +-----+                         | |   | +---+
       |         | | +-----+                         | |   |-|HGW|
       +---------+ +-|NAS  |                         | +---+ +---+
                     +-----+                         |
                                                     | +---+ +---+
                                                     +-|ONT|-|HGW|
                                                       +---+ +---+
 Figure 2: FTTP/FTTB/C with Multi-Subscriber ONT/ONU Serving MTUs/MDUs
 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 CPEs to the ANX and the
 access network.  In the 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 the 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 the 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 or GPON.  The protocol encapsulation on
 BPON is based on multi-protocol encapsulation over ATM Adaptation
 Layer 5 (AAL5), defined in [RFC2684].  This covers PPP over Ethernet
 (PPPoE, defined in [RFC2516]) or IP over Ethernet (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.

Bitar, et al. Informational [Page 9] RFC 6934 ANCP in PON-Based Networks June 2013

4.1.3. Access Node Complex

 The Access Node Complex (ANX) is composed of OLT and ONT/ONU and is
 defined in Section 2.

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, customer separation, and traceability.
 This can be achieved using an ATM or an Ethernet-based technology.
 As stated earlier, the focus in this document is on Ethernet.

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 that 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 Synchronous Optical
 Network (SONET)).  The NAS functionality corresponds to the BNG
 functionality described in 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 NASs 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.

Bitar, et al. Informational [Page 10] RFC 6934 ANCP in PON-Based Networks June 2013

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 versus OLT
 and ONT/ONU (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.  Choosing which model to implement may be based on
 the ONT/ONU type and the capabilities of the ONT/ONU and OLT; this is
 an implementation-specific decision that is outside the scope of this
 document.  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 XG-PON.  ANCP is designed as a protocol
 between the NAS and Access Node.  Among other functions, it enables
 the NAS to enforce dynamic policies on the Access Node and the Access
 Node to report events to the NAS.

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 an 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 ANCP and/or OMCI
 extensions to map messages between OMCI and ANCP.  OMCI extensions
 are likely to be defined by the ITU-T.  It should also be noted that
 in addition to configuration and administration, OMCI provides the
 capability to report status changes on an ONT/ONU with AVC (Attribute
 Value Change) notifications.  When the ONT/ONU's DSL or Ethernet
 User-Network Interface (UNI) attributes change, a related Management
 Entity will send a corresponding notification (AVC) to the OLT.  The
 OLT interworks such a notification into an ANCP report and 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.

Bitar, et al. Informational [Page 11] RFC 6934 ANCP in PON-Based Networks June 2013

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

Bitar, et al. Informational [Page 12] RFC 6934 ANCP in PON-Based Networks June 2013

                                   +----------------------+
                                   | 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 Control 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 a controller function and a reporting and/or
 enforcement function.  The controller function is 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

Bitar, et al. Informational [Page 13] RFC 6934 ANCP in PON-Based Networks June 2013

 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.
   +--------+
   | 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

Bitar, et al. Informational [Page 14] RFC 6934 ANCP in PON-Based Networks June 2013

 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 control 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.
   +--------+
   | 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

Bitar, et al. Informational [Page 15] RFC 6934 ANCP in PON-Based Networks June 2013

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)
 becoming multicast aware by implementing an IGMP [RFC3376] snooping
 and/or proxy function [RFC4605].  The replication thus needs to be
 distributed between NAS, aggregation nodes, and ANX.  In the case of
 GPON and in the 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

Bitar, et al. Informational [Page 16] RFC 6934 ANCP in PON-Based Networks June 2013

 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.
 Where network-based channel conditional access is desired, there are
 two approaches.  First, 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.  A second 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 of this document, 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 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 is
 known at the ONT/ONU and OLT.  If the ONT/ONU has a white list and/or

Bitar, et al. Informational [Page 17] RFC 6934 ANCP in PON-Based Networks June 2013

 a black list per premises, the OLT need not have such a list.  If the
 ONT/ONU does not have such a list, the OLT may be programmed with
 such a list for each premises.  In the 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:
  1. An exact match for a (*,G) Any-Source Multicast (ASM) group (e.g.,

<G=g.h.i.l>)

  1. An exact match for a (S,G) Source-Specific Multicast (SSM) channel

(e.g., <S=s.t.u.v,G=g.h.i.l>)

  1. A mask-based range match for a (*,G) ASM group (e.g.,

<G=g.h.i.l/Mask>)

  1. 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.

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-

Bitar, et al. Informational [Page 18] RFC 6934 ANCP in PON-Based Networks June 2013

 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 that 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 is 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.
 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:

Bitar, et al. Informational [Page 19] RFC 6934 ANCP in PON-Based Networks June 2013

 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 the 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 the 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 the
 "Agent Circuit ID" 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 can track the changes in available bandwidth on the PON
 under all conditions.  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

Bitar, et al. Informational [Page 20] RFC 6934 ANCP in PON-Based Networks June 2013

 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.

Bitar, et al. Informational [Page 21] RFC 6934 ANCP in PON-Based Networks June 2013

                                                  +----+
                              +---<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
                                                  forwarded 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

Bitar, et al. Informational [Page 22] RFC 6934 ANCP in PON-Based Networks June 2013

                                                  +----+
                              +---<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:
  1. 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

Bitar, et al. Informational [Page 23] RFC 6934 ANCP in PON-Based Networks June 2013

    passes the conditional access check, the ONT will forward the IGMP
    join and will send a bandwidth admission control request to the
    OLT.  If 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 until it has received a positive admission
    control response from the OLT.
  1. 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 available multicast 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
    available PON 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's 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 available multicast video
 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 activates the corresponding multicast entry if not

Bitar, et al. Informational [Page 24] RFC 6934 ANCP in PON-Based Networks June 2013

 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 was 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 available PON 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 available PON 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.  After authorizing the request, the policy server 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 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

Bitar, et al. Informational [Page 25] RFC 6934 ANCP in PON-Based Networks June 2013

 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.
 It should be noted that similar functionality to that described in
 this section and depicted in Figures 9, 10, and 11 will be required
 when OMCI is enabled between the OLT and ONT/ONU in the ANCP+OMCI ANX
 control model.  In the latter case, the OLT will act as an ANCP-OMCI
 gateway.

Bitar, et al. Informational [Page 26] RFC 6934 ANCP in PON-Based Networks June 2013

                                                 +----+
                                       +-------- |ONT |-------- HGW
   +----+               +----+         +         +----+
   |NAS |---------------|    |------<PON>
   |    |<------------->|OLT |         +          +-----+
   +----+     ANCP      |    | ANCP    +--------- | ONU |------ HGW
     |                  +----+<------------------>+-----+-------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

Bitar, et al. Informational [Page 27] RFC 6934 ANCP in PON-Based Networks June 2013

                                                  +----+
                                       +--------- |ONT |------ HGW
   +----+               +----+        +           +----+
   |NAS |---------------|    |------<PON>
   |    |<------------->|OLT |        +          +-----+
   +----+     ANCP      |    | ANCP   +----------| ONU |----- HGW
     |                  +----+<----------------->+-----+------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

Bitar, et al. Informational [Page 28] RFC 6934 ANCP in PON-Based Networks June 2013

   +------------+              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
 A third possible approach is where the ANX is assumed to have 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 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

Bitar, et al. Informational [Page 29] RFC 6934 ANCP in PON-Based Networks June 2013

 and shared with Video on Demand), the PON, and uplink to the NAS.  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 available video 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, the 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's 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.

6.3. Multicast Accounting

 It may be desirable to perform accurate time- or volume-based
 accounting per user or per access loop.  If 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:

Bitar, et al. Informational [Page 30] RFC 6934 ANCP in PON-Based Networks June 2013

  1. 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.
  1. 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 the OLT to the 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.

7. Remote Connectivity Check

 In an end-to-end Ethernet aggregation network, end-to-end Ethernet
 Operations, Administration, and Maintenance (OAM), as specified in
 IEEE 802.1ag [802.1ag] and ITU-T Recommendation Y.1730/1731 [Y.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, the 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.

Bitar, et al. Informational [Page 31] RFC 6934 ANCP in PON-Based Networks June 2013

 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 an Access Node and a 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 if the last mile is xDSL
 based, such as in the case of "PON-fed DSLAMs" for FTTC/FTTB
 scenarios) and hence cannot come from a provisioning and/or inventory
 management Operations Support System (OSS).  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.
 OSSs are rarely able to enforce the consistency of such data in a
 reliable and scalable manner, notably across organizational
 boundaries under certain deployment scenarios.  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.
 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 to make 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.

Bitar, et al. Informational [Page 32] RFC 6934 ANCP in PON-Based Networks June 2013

   +--------+
   | 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 Control Model
 Figure 12 depicts a message flow for topology discovery when using
 the ANCP+OMCI 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 the GPON service
 profile is assigned from OLT to ONT/ONU, the OLT reports the final
 status to NAS with information about the service profile and other
 information such as the ONT/ONU port rate to the subscriber, for
 instance.

Bitar, et al. Informational [Page 33] RFC 6934 ANCP in PON-Based Networks June 2013

9. Access Loop Configuration

 Topology Discovery provides Access Port Identification to the NAS
 when sending an Access Port Discovery message.  This informs NAS
 identification of a 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 the User-Network Interface (UNI), which is the
 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.
 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 a 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).

Bitar, et al. Informational [Page 34] RFC 6934 ANCP in PON-Based Networks June 2013

 User activity logging for accounting or tracking purposes could raise
 privacy concerns if not appropriately protected.  To protect such
 information, logging/accounting information can be exchanged with the
 corresponding server over a secure channel, and the information can
 be stored securely with policy-driven controlled access.

11. Differences in ANCP Applicability between DSL and PON

 As it currently stands, both ANCP framework [RFC5851] and protocol
 [RFC6320] are defined in the 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.
  1. 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 the case of DSL, the
    ANCP exchange is contained between two network elements (NAS and
    the DSLAM).
  1. The PON connection to the ONT is a shared medium between multiple

ONTs on the same PON. In the case of DSL, the local loop is

    point-to-point.  In the case of a 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 the case of PON access, in addition to the bandwidth
    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 the NAS (as described in the
    first approach in 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 the second approach
    in Section 6.2), then additional ANCP request and response

Bitar, et al. Informational [Page 35] RFC 6934 ANCP in PON-Based Networks June 2013

    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).
  1. 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 the case of DSL, the
    replication can potentially be performed on NAS and/or the DSLAM.
    Section 6.2 defines options for multicast replication in the 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 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 the case of DSL, the
    DSLAM only needs to update its own replication state based on the
    set of Access Ports indicated by the NAS.
  1. 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 a DSL case, 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 be a suitable protocol for dynamic
 transactions as required for the multicast application.

Bitar, et al. Informational [Page 36] RFC 6934 ANCP in PON-Based Networks June 2013

 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 and 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 how the VoIP
 agent is addressed and on traffic routing.  For instance, the VoIP
 traffic to/from the ONT is often encapsulated in a VLAN-tagged
 Ethernet frame and switched at Layer 2 through the OLT to the NAS
 where it is routed.  The VoIP agent in this case looks like another
 subscriber to the NAS.  On the other hand, the ANCP session between
 the ONT and OLT is terminated at the OLT.  Thus, the OLT must be able
 to receive/send IP traffic to/from the OLT, which will not work using
 this setting.  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. Acknowledgements

 The authors thank Rajesh Yadav and Francois Le Faucheur for their
 valuable comments and discussions.

14. References

14.1. 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.
 [RFC3376]  Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A.
            Thyagarajan, "Internet Group Management Protocol, Version
            3", RFC 3376, October 2002.

Bitar, et al. Informational [Page 37] RFC 6934 ANCP in PON-Based Networks June 2013

 [RFC4605]  Fenner, B., He, H., Haberman, B., and H. Sandick,
            "Internet Group Management Protocol (IGMP) / Multicast
            Listener Discovery (MLD)-Based Multicast Forwarding
            ("IGMP/MLD Proxying")", RFC 4605, August 2006.

14.2. Informative References

 [802.1ag]  IEEE 802.1ag, "Connectivity Fault Management", December
            2007.
 [RFC2881]  Mitton, D. and M. Beadles, "Network Access Server
            Requirements Next Generation (NASREQNG) NAS Model", RFC
            2881, July 2000.
 [RFC5851]  Ooghe, S., Voigt, N., Platnic, M., Haag, T., and S.
            Wadhwa, "Framework and Requirements for an Access Node
            Control Mechanism in Broadband Multi-Service Networks",
            RFC 5851, May 2010.
 [G.983.1]  ITU-T G.983.1, "Broadband optical access systems based on
            Passive Optical Networks (PON)", January 2005.
 [G.984.1]  ITU-T G.984.1, "Gigabit-capable Passive Optical Networks
            (GPON): General characteristics", March 2008.
 [RFC3046]  Patrick, M., "DHCP Relay Agent Information Option", RFC
            3046, January 2001.
 [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 G.984.4, "Gigabit-capable passive optical networks
            (G-PON): ONT management and control interface
            specification", February 2008.
 [RFC6320]  Wadhwa, S., Moisand, J., Haag, T., Voigt, N., and T.
            Taylor, Ed., "Protocol for Access Node Control Mechanism
            in Broadband Networks", RFC 6320, October 2011.
 [G.987.3]  ITU-T G.987.3, "10-Gigabit-capable passive optical
            networks(XG-PON): Transmission convergence (TC) layer
            specification", October 2010.

Bitar, et al. Informational [Page 38] RFC 6934 ANCP in PON-Based Networks June 2013

 [Y.1731]   ITU-T Y.1731, "OAM functions and mechanisms for Ethernet
            based networks", May 2006.

Authors' Addresses

 Nabil Bitar (editor)
 Verizon
 60 Sylvan Road
 Waltham, MA 02451
 EMail: nabil.n.bitar@verizon.com
 Sanjay Wadhwa (editor)
 Alcatel-Lucent
 701 East Middlefield Road
 Mountain View, CA, 94043
 EMail: sanjay.wadhwa@alcatel-lucent.com
 Thomas Haag
 Deutsche Telekom
 EMail: HaagT@telekom.de
 Hongyu Li
 Huawei Technologies
 EMail: hongyu.lihongyu@huawei.com

Bitar, et al. Informational [Page 39]

/data/webs/external/dokuwiki/data/pages/rfc/rfc6934.txt · Last modified: 2013/06/18 21:38 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki