Network Working Group N. Bitar Internet-Draft Verizon Intended status: Informational S. Wadhwa Expires: September 10, 2009 Juniper Networks March 9, 2009 Applicability of Access Node Control Mechanism to PON based Broadband Networks draft-bitar-wadhwa-ancp-pon-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on September 10, 2008. Bitar & Wadhwa Expires September 10, 2009 [Page 1] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Copyright Notice Copyright (c) 2009 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. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Abstract The purpose of this document is to provide applicability of Access Node Control Mechanism, as described in [ANCP-FRAMEWORK], to PON based broadband access. The need for an Access Node Control Mechanism between a Network Access Server (NAS) and an Access Node Complex (a combination of Optical Line Termination (OLT) and Optical Network Termination (ONT) elements), is described in a multi-service reference architecture in order to perform QoS-related, service- related and Subscriber-related operations. The Access Node Control Mechanism is also extended for interaction between components of the Access Node Complex (OLT and ONT). The Access Node Control mechanism will ensure that the transmission of the information does not need to go through distinct element managers but rather uses a direct device- device communication. This allows for performing access link related operations within those network elements to meet performance objectives. Table of Contents 1 Specification Requirements 4 2 Introduction 4 2.1 Terminology..............................................5 3 Reference Architecture for PON Based Broadband Access Network 7 3.1 Home Gateway.............................................8 3.2 PON Access...............................................9 3.3 Access Node Complex......................................9 3.4 Access Node Complex Uplink to the BNG....................9 3.5 Aggregation Network......................................9 3.6 Network Access Server....................................9 3.7 Regional Network........................................10 4 Motivation for explicit extension of ANCP to FTTP PON 10 5 Concept of Access Node Control Mechanism for PON based access 11 6 Multicast 13 6.1 Multicast Conditional Access............................13 6.2 Multicast Admission Control.............................15 6.3 Multicast Accounting....................................26 7 Remote Connectivity Check 27 8 Access Topology Discovery 27 9 Security Considerations 28 10 Differences in ANCP applicability between DSL and PON 29 11 ANCP versus OMCI between the OLT and ONT 30 Bitar-Wadhwa Expires September 10, 2009 [Page 2] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 12 Acknowledgements 31 13 References 31 13.1 Normative References....................................31 13.2 Informative References..................................31 Author's Addresses 32 Bitar-Wadhwa Expires September 10, 2009 [Page 3] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 1 Specification Requirements The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. 2 Introduction Passive Optical Networks (PONs) based on BPON and GPON are being deployed across carrier networks. There are two models for PON deployment: Fiber to the curb (FTTC), and Fiber to the Premise (FTTP). In the FTTC deployment, the last mile connectivity is provided over the local loop using Very High Speed DSL. In the FTTP case, PON extends to the premise. In addition, there are three main PON technologies: (1) Broadband PON (BPON), (2) Gigabit PON (GPON), and (3) Ethernet PON (EPON). The focus in the document will be on BPON and GPON in the context of FTTP deployment. BPON and GPON in FTTP deployments provide large bandwidth in the first mile, bandwidth that is an order of magnitude larger than that provided by xDSL. In the downstream direction BPON provides 622 Mbps per PON while GPON provides 2.4 Gbps. 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 homes per PON. The motive behind BPON and GPON deployment is providing triple-play services over IP: voice, video and data. Voice is generally low bandwidth but has low-delay, low-jitter, and low packet-loss requirements. Data services (e.g., Internet services) often require high throughput and can tolerate medium latency. Data services may include multimedia content download such as video. However, in that case, the video content is not required to be real-time and/or it is low quality video. Video services, on the other hand, are targeted to deliver Standard Definition or High Definition video content in real- time or near-real time, depending on the service model. Standard Definition content using MPEG2 encoding requires on the order of 3.75 Mbps per stream while High definition content requires using MPEG2 encoding requires on the order of 15-19 Mbps depending on the level of compression used. Video services require low-jitter and low-packet loss with low start-time latency. There are two types of video services: on demand and broadcast (known also as liner programming content). While linear programming content can be provided over Layer1 on the PON, the focus in this document is on delivering linear programming content over IP to the home, using IP multicast. Video on demand is also considered for delivery over IP using a unicast session model. Bitar-Wadhwa Expires September 10, 2009 [Page 4] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 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 the video content (unicast and multicast delivered to the user does not exceed the bandwidth allocated to the user 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 PON environment, this implies enabling IP multicast on the Access Node (AN) complex composed of the ONT and OLT, as applicable. This is as opposed to DSL deployments where multicast is enabled on the 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 PON environments between the AN complex and the NAS. [ANCP-FRAMEWORK] provides the framework and requirements for coordinated admission control between a NAS and an AN with special focus on DSL deployments. This document proposes the extension of that framework and the related requirements to explicitly address BPON and GPON deployments. 2.1 Terminology o PON (Passive Optical Network): a point-to-multipoint fiber to the premises network architecture in which unpowered splitters are used to enable the splitting of an optical signal from a central office on a single optical fiber to multiple premises. Up to 32- 128 may be supported on the same PON. A PON configuration consists of an Optical Line Termination (OLT) at the Service Provider's CO and a number of Optical Network Units or Terminals (ONU/ONT) near end users, with an optical distribution network (ODN) composed of fibers and splitters between them. A PON configuration reduces the amount of fiber and CO equipment required compared with point to point architectures. o Access Node Complex (ANX): The Access Node is decomposed by two geographical functions, performed by OLT and ONU/ONT. The general term Access Node (ANX) will be used when describing a functionality which doesn't depend on the physical location but rather on the "black box" behaviour of OLT and ONU/ONT. o Optical Line Terminal (OLT): is located in the Service provider's central office. It terminates and aggregates Bitar-Wadhwa Expires September 10, 2009 [Page 5] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 multiple PONs (providing fiber access to multiple premises or neighborhoods) on the user side, and interfaces with the service element (NAS) providing subscriber management. o Optical Network Terminal (ONT): terminates PON on the network side and provides PON adaptation. The user side interface and the location of the ONT is dictated by the type of network deployment. For a Fiber-to-the-Premise (FTTP) deployment (with Fiber all the way to the apartment or living unit), ONT has Ethernet (FE/GE) connectivity with the Home Gateway (HGW)/Customer Premise Equipment (CPE). In case of an MDU (multi-dwelling or multi-tenant unit), a multi-subscriber ONU typically resides in the basement or a wiring closet, and has FE/GE connectivity with each CPE. In the case where fiber is terminated outside the premise (neighborhood or curb side) on an ONT/ONU, the last-leg-premise connections could be via existing or new Copper, with xDSL physical layer (typically VDSL). In this case, the Access Node (OLT & ONT together) effectively is a "PON fed DSLAM". Bitar-Wadhwa Expires September 10, 2009 [Page 6] o Network Access Server (NAS): Network element which aggregates subscriber traffic from a number of ANs or ANXs. The NAS is often an injection point for policy management and IP QoS in the access network. It is also referred to as Broadband Network Gateway (BNG) or Broadband Remote Access Server (BRAS). o Home Gateway (HGW): Network element that connects subscriber devices to the AN or ANX and the access network. In case of DSL, the Home Gateway is a DSL network termination that could either operate as a Layer 2 bridge or as a Layer 3 router. In the latter case, such a device is also referred to as a Routing Gateway (RG). In the case of PON, it is often a Layer3 routing device with the ONT performing PON termination. o PON-Customer-ID: This is an identifier which uniquely identifies the ANX and the access loop logical port on the ANX to the customer premise, and is used in any interaction between NAS and ANX that relates to access-loops. Logically it is composed of information containing identification of the OLT (the OLT may be physically directly connected to the NAS), the PON port on the OLT, the ONT, and the port on the ONT. When acting as an intermediate agent, the OLT can encode PON-Customer-ID in the "Agent-Circuit-Identifier" Sub-option in Option-82 of the DHCP messages. 3 Reference Architecture for PON Based Broadband Access Network The reference architecture used in this document is based on Ethernet aggregation for both of BPON and GPON. Specifically, the following cases are addressed: o BPON with Ethernet uplink to the BNG and ATM on the PON side. o GPON with Ethernet uplink to the BNG and Ethernet on the PON side. In case of an Ethernet aggregation network that supports new QoS- enabled IP services (including Ethernet multicast replication), the architecture builds on the reference architecture specified in DSL Forum [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's move towards Ethernet as the new access and aggregation technology for triple play services, the primary focus throughout this document is on GPON and BPON with Ethernet between the BNG and the OLT. Figures 1 and 2 depict an end-to-end broadband network with PON access. Bitar-Wadhwa Expires September 10, 2009 [Page 7] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Access Customer <------------Aggregation-------><-Premise-> Network Network +---------------------+ |Access Node (ANX) | +----------+ +----+ +----+ |+---+ +-------+| +---+ | | +-|NAS |--|Eth |-||OLT|--|ONT/ONU||--|HGW| NSP---+Regional | | +----+ |Agg | |+---+ +-------+| +---+ |Broadband | | +----+ +----+ +---------------------+ |Network |-+-|NAS | | ASP---+ | | +----+ | | | | +----+ | +----------+ +-|NAS | | +--------+ +---+ +----+ +---|ONT/ONU |--|HGW| | +--------+ +---+ |............... | +--------+ +---+ +---|ONT/ONU |--|HGW| +--------+ +---+ HGW : Home Gateway NAS : Network Access Server PON : Passive Optical Network OLT : Optical Line Terminal ONT/ONU : Optical Network Terminal/Unit Figure 1. Access Network with PON FE/GE or VDSL +-------+ +---+ +--------------+ | |--|HGW| +----------+ +-----+ | +---+ +---+ | | | +---+ | | +-|NAS |--| |Eth|--|OLT| |--| | +---+ NSP---+Regional | | +-----+ | |Agg| | | | | |ONT/ONU|--|HGW| |Broadband | | +-----+ | +---+ +---+ | | | | +---+ |Network |-+-|NAS | +--------------+ | | | . ASP---+ | | +-----+ | | | +---+ | | | +-----+ | | |--|HGW| +----------+ +-|NAS | | +-------+ +---+ +-----+ | | +-------+ +---+ +--|ONT/ONU|--|HGW| +-------+ +---+ Figure 2. FTTP/FTTC with multi-subscriber ONU serving MTUs/MDUs 3.1 Home Gateway The Home Gateway (HGW) connects the different Customer Premises Equipment (CPE) to the ANX and the access network. In case of PON, the HGW is a layer 3 router. In this case, the HGW performs DHCP assignment to devices within the home, and performs Network Address and Port Translation (NAPT) between the LAN and WAN side. In case of FTTP, the HGW connects to the ONT over an Ethernet interface. That Bitar-Wadhwa Expires September 10, 2009 [Page 8] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Ethernet interface could be a physical port or over another medium. In case of FTTP, it is possible to have a single box GPON CPE solution, where the ONT encompasses the HGW functionality as well as the GPON adaptation function. 3.2 PON Access PON access is composed of the ONT and OLT. PON ensures physical connectivity between the ONT at the customer premises and the OLT. PON framing can be BPON (in case of BPON) or GPON (in case of GPON). The protocol encapsulation on BPON is based on multi-protocol encapsulation over AAL5, defined in [RFC2684]. This covers PPP over Ethernet (PPPoE, defined in [RFC2516]), or bridged IP (IPoE). The protocol encapsulation on GPON is always IPoE. In all cases, the connection between the AN (OLT) and the NAS (BNG) is assumed to be Ethernet in this document. 3.3 Access Node Complex This is composed of OLT and ONT and is defined in section 2.1. 3.4 Access Node Complex Uplink to the BNG The ANX uplink connects the OLT to the NAS. The fundamental requirements for the ANX uplink are to provide traffic aggregation, Class of Service distinction and customer separation and traceability. This can be achieved using an ATM or an Ethernet based technology. The focus in this document is on Ethernet as stated earlier. 3.5 Aggregation Network The aggregation network provides traffic aggregation towards the NAS. The Aggregation network is assumed to be Ethernet in this document. 3.6 Network Access Server The NAS is a network device which aggregates multiplexed Subscriber traffic from a number of ANXs. The NAS plays a central role in per- subscriber policy enforcement and QoS. It is often referred to as a Broadband Network Gateway (BNG) or Broadband Remote Access Server (BRAS). A detailed definition of the NAS is given in [RFC2881]. The NAS interfaces to the aggregation network by means of 802.1Q or 802.1 Q-in-Q Ethernet interfaces, and towards the Regional Network by means of transport interfaces (e.g. GigE, PPP over SONET). The NAS functionality corresponds to the BNG functionality described in DSL Forum TR-101. In addition to this, the NAS supports the Access Node Control functionality defined for the respective use cases in this document. Bitar-Wadhwa Expires September 10, 2009 [Page 9] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 3.7 Regional Network The Regional Network connects one or more NAS and associated Access Networks to Network Service Providers (NSPs) and Application Service Providers (ASPs). The NSP authenticates access and provides and manages the IP address to Subscribers. It is responsible for overall service assurance and includes Internet Service Providers (ISPs).The ASP provides application services to the application Subscriber (gaming, video, content on demand, IP telephony etc.). The NAS can be part of the NSP network. Similarly, the NSP can be the ASP. 4 Motivation for explicit extension of ANCP to FTTP PON The fundamental difference between PON and DSL is that a PON is an optical broadcast network by definition. That is, at the PON level, every ONT on the same PON sees the same signal. However, the ONT filters only those PON frames addressed to it. Encryption is used on the PON to prevent eavesdropping. The broadcast PON capability is very suitable to delivering multicast content to connected premises, maximizing bandwidth usage efficiency on the PON. Similar to DSL deployments, enabling multicast on the Access Node Complex (ANX) provides for bandwidth use efficiency on the path between the Access Node and the NAS as well as improves the scalability of the NAS by reducing the amount of multicast traffic being replicated at the NAS. However, the broadcast capability on the PON enables the AN (OLT) to send one copy on the PON as opposed to N copies of a multicast channel on the PON serving N premises being receivers. 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 a single encryption key for all PON frames carrying all multicast channels or a key per set of multicast channels that correspond to service packages, or none. It should be noted that the ONT can be a multi-Dwelling Unit (MDU) ONT with multiple Ethernet ports, each connected to a living unit. Thus, the ONT must not only be able to receive a multicast frame, but must also be able to forward that frame only to the Ethernet port with receivers for the corresponding channel. In order to implement triple-play service delivery with necessary "quality-of-experience", including end-to-end bandwidth optimized multicast video delivery, there needs to be tight coordination between the NAS and the ANX. This interaction needs to be near real- time as services are requested via application or network level signaling by broadband subscribers. ANCP as defined in [ANCP- FRAMEWORK] for DSL based networks is very suitable to realize a control protocol (with transactional exchange capabilities), between Bitar-Wadhwa Expires September 10, 2009 [Page 10] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 PON enabled ANX and the NAS, and also between the components comprising the ANX i.e. between OLT and the ONT. Typical use cases for ANCP in PON environment include the following: o Multicast o Optimized multicast delivery o Unified video resource control o NAS based provisioning of ANX o Access topology discovery o Remote connectivity check 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 3. 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. The mechanism consists of control function, and reporting and/or enforcement function. 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 controller function to enforce a specific policy or trigger a local action. The messages shown in Figure 3 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 case, which are described in later sections. Bitar-Wadhwa Expires September 10, 2009 [Page 11] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +--------+ | Policy | +----+ | Server | +-----|ONT |------- HGW +--------+ + +----+ +---+ | + +----------|ONT|------ HGW | + | +---+ | +----------------|-------------+ +----+ | +----+ | +-----+ | +---+ |NAS |---------------| | | | |---------|HGW| | |<------------->| | | | ONT | | +---+ +----+ ANCP | |OLT |----------| | | | | | | | | | +----+ | | | |<------------->| |---------|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 3. Conceptual Message Flow for Access Node Control Mechanism Bitar-Wadhwa Expires September 10, 2009 [Page 12] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 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) becoming multicast aware by implementing an IGMP snooping and/or proxy function. The replication thus needs to be distributed between NAS, aggregation nodes, and ANX. In case of GPON, and in case of BPON with Ethernet uplink, this is very viable. By introducing IGMP processing on the ANX and aggregation nodes, the multicast replication process is now divided between the NAS, the aggregation node(s) and ANX. This is in contrast to the ATM-based model, where NAS is the single element responsible for all multicast control and replication). In order to ensure backward compatibility with the ATM- based model, the NAS, aggregation node and ANX need to behave as a single logical device. This logical device must have exactly the same functionality as the NAS in the ATM access/aggregation network. The Access Node Control Mechanism can be used to make sure that this logical/functional equivalence is achieved by exchanging the necessary information between the ANX and the NAS. An alternative to multicast awareness in the ANX is for the subscriber to communicate the IGMP "join/leave" messages with the NAS, while the ANX is being transparent to these messages. In this scenario, the NAS can use ANCP to create replication state in the ANX for efficient multicast replication. The NAS sends a single copy of the multicast stream towards the ANX. The NAS can perform network- based conditional access and multicast admission control on multicast joins, and create replication state in the ANX if the flow is admitted by the NAS. The following sections describe various use cases related to multicast. 6.1 Multicast Conditional Access In a Broadband FTTP 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 Bitar-Wadhwa Expires September 10, 2009 [Page 13] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Digital Rights Management (DRM) for instance may provide sufficient control, so that network-based Multicast conditional access may not be needed. However, network level access control may add to the service security by preventing the subscriber from receiving a non- subscribed channel. In addition, it enhances network security by preventing a multicast stream from being sent on a link or a PON based on a non-subscriber request. Where network-based channel conditional access is desired, there are two approaches. It can be done on the NAS along with bandwidth based admission control. The NAS can control the replication state on the ANX based on the outcome of access and bandwidth based admission control. This is covered later in section 3.4. The other approach is to provision the necessary conditional access information on the ANX (ONT 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 [ANCP-FRAMEWORK], 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 and OLT. Thus, this information can be programmed on the ONT and/or OLT. Programming this information on the ONT prevents illegitimate joins from propagating further into the network. A White list associated with an Access Port identifies the multicast flows that are allowed to be replicated to that port. A Black list associated with an Access Port identifies the multicast flows 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 performs IGMP snooping and it is programmed with a channel access list, the ONT 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 will pass the join request upstream towards the NAS. The ONT 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 can autonomously discard the message because the channel is not authorized. The ONT, in addition to forwarding the IGMP join, sends an ANCP admission request to the OLT identifying the channel to be joined and the premise. Premise identification to the OLT can be based on a Customer-Port-ID that maps to the access port on the ONT and known Bitar-Wadhwa Expires September 10, 2009 [Page 14] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 at the ONT and OLT. If the ONT has a white list and/or a black list per premise, the OLT need not have such a list. If the ONT does not have such a list, the OLT may be programmed with such a list for each premise. In this latter case, the OLT would perform the actions described earlier on the ONT. 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. OLT Bandwidth based admission control scenarios are defined in section 3.4. The White List and Black List can contain entries allowing: o An exact match for a (*,G) ASM group (e.g. ); o An exact match for a (S,G) SSM channel (e.g. ); o A mask-based range match for a (*,G) ASM group (e.g. ); o A mask-based range match for a (S,G) SSM channel (e.g. ); 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, the OLT or NAS can be programmed with these access lists. Having these access lists on the ONT 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, 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- user experience given not only the strict requirements of unicast Bitar-Wadhwa Expires September 10, 2009 [Page 15] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 delay sensitive 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 packet loss and high bandwidth. These applications are also typically "non-elastic", which means that they operate at a fixed bandwidth, which cannot be dynamically adjusted to the currently available bandwidth. An Admission Control (AC) mechanism covering admission of multicast traffic for the FTTP 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 premise 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). 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 video traffic (unicast or multicast) that is being delivered to the subscriber. 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, performs conditional access, and bandwidth based admission control on the IGMP request. The bandwidth admission control is performed against the following: 1. Available video bandwidth on the link to OLT 2. Available video bandwidth on the PON interface 3. Available video bandwidth on the last mile (access-port on the ONT/ONU). The NAS can locally maintain and track video bandwidth for all the three levels mentioned above. The NAS can maintain identifiers corresponding to the PON interface and the last mile (customer interface). It also maintains a channel map, associating every channel (or a group of channels sharing the same bandwidth requirement) with a data rate. For instance, in case of 1:1 VLAN representation of the premise, the outer tag (S-VLAN) could be Bitar-Wadhwa Expires September 10, 2009 [Page 16] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 inserted by the ANX to correspond to the PON interface on the OLT, and the inner-tag could be inserted by the ANX to correspond to the access-line towards the customer. Bandwidth tracking and maintenance for the PON interface and the last-mile could be done on these VLAN identifiers. In case if N:1 representation, the single VLAN inserted by ANX could correspond to the PON interface on the OLT. The access loop is represented via Customer-Port-ID received in "Agent Circuit Identifier" sub-option in DHCP messages. The NAS can perform bandwidth accounting on received IGMP messages. The video bandwidth is also consumed by any unicast video being delivered to the CPE. NAS can perform video bandwidth accounting and control on both IGMP messages and on requests for unicast video streams. This particular scenario assumes the NAS is aware of the bandwidth on the PON, and under all conditions can track the changes in available bandwidth on the PON. On receiving an IGMP Join message, NAS will perform bandwidth check on the subscriber bandwidth. If this passes, and the stream is already being forwarded on the PON by the OLT (which also means that it is already forwarded by the NAS to the OLT), NAS will admit the JOIN, update the available subscriber bandwidth, and transmit an ANCP message to the OLT and in turn to the ONT 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 is updated. The NAS adds the OLT as a leaf to the multicast tree for that stream. On receiving the message to start replication, the OLT will add the PON interface to its replication state if the stream is not already being forwarded on that PON. Also, the OLT will send an ANCP message to direct the ONT to add or update its replication state with the customer port for that channel. The interaction between ANX and NAS is shown in Figures 4 and 5. 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 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-Wadhwa Expires September 10, 2009 [Page 17] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +----+ +--------------|ONT |-------- HGW + +----+ + +----+ + +--------- |ONT |-------- HGW +----+ +----+ + +----+ |NAS |---------------| |------ | |<------------->| | + +-----+ +----+ 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| | | (,Customer-Port-ID> | | | | | | | | --------------------->| | | |4.ANCP Replication-Start | | |(,Customer-Port-ID) | |-------------------->| | | |5.Multicast Flow(S,G)| | | |On Multicast VLAN |---------------------->| | | |6.Multicast Flow (S,G) | | | |forwarded on | | | |Unidirectional | | | | | | | |on the PON by OLT |--------------->| |7. Multicast Flow |forwarded on | |Customer-Port by| |ONT/OLT. | | | Figure 4. Interactions for NAS based Multicast Admission Control (no IGMP processing on ANX, and NAS maintains available video bandwidth for PON). Bitar-Wadhwa Expires September 10, 2009 [Page 18] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +----+ +--------------|ONT |-------- HGW + +----+ + +----+ + +--------- |ONT |-------- HGW +----+ +----+ + +----+ |NAS |---------------| |------ | |<------------->| | + +-----+ +----+ ANCP |OLT | +--------- | |------- HGW | | | | | | | |<------------------>| ONU |--------HGW | +----+ ANCP | | +---+ | | | |--------|HGW| | | +-----+ +---+ | | | | | IGMP LEAVE(S/*,G) | | |<-------------------------------------------------------------| | | | | +====================+ | | | [Admission Control ] | | | [ ] | | | +====================+ | | | | | | | | | | | | | | | |-------------------->| | | ANCP Replication-Stop | | | (,Customer-Port-ID) | | | | | | | | --------------------->| | | | ANCP Replication-Stop | | | |(,Customer-Port-ID) | Figure 5. Interactions for NAS based Multicast Admission Control (no IGMP processing on ANX, and NAS maintains available video bandwidth for PON). 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. ANX operation: o ONT can snoop IGMP messages. If conditional access is configured and the channel is in the Black list (or it is it not on the White list), ONT will drop the IGMP Join. If the channel passes the conditional access check, the ONT will forward the IGMP Join, and will send a bandwidth admission control request to the OLT. In case the multicast stream is already being received on the PON, the ONT does not forward the stream to the access port where IGMP is received, till it has received a positive admission control response from the OLT. Bitar-Wadhwa Expires September 10, 2009 [Page 19] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 o OLT can snoop IGMP messages. It also receives a bandwidth admission control request from the ONT 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 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 PON video bandwidth is reduced by the channel bandwidth and the PON can be added to the multicast tree without activation for that channel. This is biased towards a forward expectation that the request will be accepted. The OLT forwards the IGMP join to the NAS. It also sends a bandwidth admission request to the NAS identifying the channel, and the premise for which the request is made. It sets a timer for the subscriber multicast entry within which it expects to receive a request from the NAS that relates to this request. If the PON available bandwidth is less than the bandwidth of the requested channel, the OLT sends an admission response (with a reject) to the ONT, and does not forward the IGMP join to the NAS. NAS operation: The NAS receives the IGMP join from the subscriber on the subscriber connection. When NAS receives the admission control request from ANX (also signifying the bandwidth on the PON is available), it performs admission control against the subscriber available 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 video available bandwidth on the link(s) to the OLT. If the check passes, the request is accepted, the available video bandwidth for the Bitar-Wadhwa Expires September 10, 2009 [Page 20] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 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 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 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 turns removes the subscriber as a receiver for that channel 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 show in Figures 6 and 7. If the OLT does not receive a response from the NAS within a set timer, the OLT removes the subscriber from the potential list of receivers for the indicated channel. It also returns the allocated bandwidth to the PON available bandwidth if there are no other receivers. In this case, the NAS may send a response to the OLT with no matching entry as the entry has been deleted. The OLT must perform admission control against the PON available bandwidth and may accept the request and send an ANCP request to the ONT 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), it results in appropriate application level signaling, which typically results in an application server requesting a policy server for bandwidth-based admission control for the VoD stream. The policy server after authorizing the request, can send a request to the NAS for the required bandwidth. 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 admission response to the NAS. If not, it returns a reject to the NAS. If the NAS receives an accept, it returns an accept to the policy server which in turn returns an accept to the application server, and the video stream is streamed to the subscriber. This interaction is shown in Figure 8. If the NAS does not accept the request from the policy Bitar-Wadhwa Expires September 10, 2009 [Page 21] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 server, it returns a reject. If the NAS receives a reject from the OLT, it returns the allocated bandwidth pool to the subscriber and the downlink to the OLT. Bitar-Wadhwa Expires September 10, 2009 [Page 22] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +----+ +----------|ONT |-------- HGW +----+ +----+ + +----+ |NAS |---------------| |------ | |<------------->| | + +-----+ +----+ ANCP |OLT | +--------- | |--------- HGW | | | ANCP | | | | |<------------------>| ONU |----------HGW | +----+ +-----+ | | | | |1.IGMP Join(s/*,G) +=============+ +=============+ | |<------------------[IGMP Snooping]---------[IGMP snooping]----| | +=============+ +=============+ | | |2.Admission-Request | | (Flow, Customer-Port-ID)| | | |<-----------------------| | | 3.+===============+ | | | [ Access Ctrl ] | | | [ & PON B/W ] | | | [ Admission Ctrl] | | | +===============+ PASS | | |4.Admission-Request | | | | | | | |<--------------------| | | 5.| | | | +=================+ | | | [Subscriber B/W ] | | | [& OLT link B/W ] | | | [Admission Ctrl ] | | | +=================+PASS | | | | | | | |6.Admission-Reply-Pass | | | | | |-------------------->| | | | 7.+========================+ | | | [Update Replication State] | | | +========================+ | | | | 8.Admission-Reply-Pass | | | |( | | | |----------------------->| | | | 9.+============+ | | | [Update Repl.] | | | [ State ] | | | +============+ | Figure 6. Interaction between NAS & ANX for Multicast B/W Admission Control Bitar-Wadhwa Expires September 10, 2009 [Page 23] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +----+ +--------- |ONT |-------- HGW +----+ +----+ + +----+ |NAS |---------------| |------ | |<------------->| | + +-----+ +----+ ANCP |OLT | +--------- | |--------- HGW | | | ANCP | | | | |<------------------>| ONU |----------HGW | +----+ +-----+ | | | | |1.IGMP Join(s/*,G) +=============+ +=============+ | |<------------------[IGMP Snooping]--------[IGMP snooping]-----| | +=============+ +=============+ | | |2.Admission-Request | | | |(Flow, Customer-Port-ID)| | | |<-----------------------| | | 2.+===============+ | | | [ Access Ctrl ] | | | [ & PON B/W ] | | | [ Admission Ctrl] | | | +===============+ PASS | | |3.Admission-Request | | | | | | |<--------------------| | | 4.| | | | +==================+ | | | [Subscriber B/W ] | | | [& OLT link B/W ] | | | [Admission Ctrl ] | | | +==================+FAIL | | | | | | |5.Admission-Reply-Fail | | | | | | |-------------------->| | | | 6.+==================+ | | | [Release PON B/W ] | | | [Remove Repl.State ] | | | +==================+ | | | | 7.Admission-Reply-Fail | | | | | | | |----------------------->| | | | 8.+============+ | | | [Remove Repl.] | | | [ State ] | | | +============+ | Figure 7. Interaction between NAS and ANX for Multicast B/W Admission Control Bitar-Wadhwa Expires September 10, 2009 [Page 24] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 +------------+ 1. VoD Request | App. Server|<---------------------------------------------------- | Server | +------------+ | 2. Admission-Request (VoD-Flow) +-------+ |Policy | |Server | +-------+ | + |<-|---3. Admission-Request | | + | 8. Admission-Reply +----+ + +----+ +-----+ |NAS |---------------|OLT |-------------|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 | | | | | | | |<--------------------| | | | | | | | | | | Figure 8. Interactions for VoD Bandwidth Admission Control . A third possible approach is where the NAX is assumed to have a full knowledge to make an autonomous decision on admitting or rejecting a multicast and a unicast join. With respect to the interaction between ONT and OLT, the procedure is similar to the first approach (i.e. NAS controlled replication). However, when the OLT receives an IGMP request for a subscriber, it performs admission control against that subscriber video bandwidth, the PON and uplink to the GWR. It should be noted in this case that if Bitar-Wadhwa Expires September 10, 2009 [Page 25] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 there are multiple NAS-OLT links, either the link on which the multicast stream must be sent is pre-determined or needs to be selected by the OLT based on downstream bandwidth from NAS to OLT and the selection is communicated to the NAS. If the check passes, the OLT updates the video available bandwidth per PON and subscriber. The OLT adds the subscriber to the list of receivers and the PON to the multicast tree, if it is not already on it. It also sends an ANCP request to the ONT 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. For unicast video streams, the policy server receiving an admission request from an application server, as described before, may query the OLT for admission control as it has all information. If the OLT has sufficient bandwidth for the stream it reserves that bandwidth for the subscriber, PON and OLT uplink to the NAS and returns an accept to the policy server. It also updates the NAS via an ANCP message of the subscriber available video bandwidth. If the OLT rejects the policy server request, it will return a reject to the policy server. It should be noted that if the policy server adjacency is with the NAS, the policy server may make the admission request to the NAS. The NAS then sends an ANCP admission request to the OLT on behalf of the policy server. The NAS returns an accept or reject to the policy server if it gets a reject or accept, respectively, from the OLT. 6.3 Multicast Accounting It may be desirable to perform accurate per-user or per Access Loop time or volume based accounting. In case the ANX is performing the traffic replication process, it knows when replication of a multicast flow to a particular Access Port or user starts and stops. Multicast accounting can be addressed in two ways: o 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 [ANCP-FRAMEWORK]. If the replication function is distributed between the OLT and ONT a query from the NAS will result in OLT generating a query to the ONT. o 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 Bitar-Wadhwa Expires September 10, 2009 [Page 26] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 central accounting system for logging. Since ANX communicates with this accounting system directly, the approach doesn't 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, then for some of the information required by the NAS (such as the list of access-ports on which a flow is being forwarded or list of flows being forwarded on an access-port), a query to the OLT from the NAS will result in a query from OLT to ONT. The OLT responds back to the NAS when it receives the response from the ONT. 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 OAM as specified in IEEE 802.1ag and ITU-T Recommendation Y.1730/1731 can provide Access Loop connectivity testing and fault isolation. However, most HGWs do not yet support these standard Ethernet OAM procedures. Also, in a mixed Ethernet and ATM access network (e.g. Ethernet based aggregation upstream from the OLT, and BPON downstream), interworking functions for end-to-end OAM are not yet standardized and widely available. Until such mechanisms become standardized and widely available, Access Node Control mechanism between NAS and ANX can be used to provide a simple mechanism to test connectivity of an access-loop from the NAS. Triggered by a local management interface, the NAS can use the Access Node Control Mechanism (Control Request Message) to initiate an Access Loop test between Access Node and HGW. 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, and 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). Bitar-Wadhwa Expires September 10, 2009 [Page 27] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Such mechanisms require that the NAS gains knowledge about the topology of the access network, the various links being used and their respective rates. Some of the information required is somewhat dynamic in nature (e.g. DSL line rate in case the last mile is xDSL based e.g. in case of "PON fed DSLAMs" for FTTC/FTTN scenarios), hence cannot come from a provisioning and/or inventory management OSS system. Some of the information varies less frequently (e.g. capacity of the OLT uplink), but nevertheless needs to be kept strictly in sync between the actual capacity of the uplink and the image the NAS has of it. OSS systems are rarely able to enforce in a reliable and scalable manner the consistency of such data, notably across organizational boundaries under certain deployment scenarios. The Access Topology Discovery function allows the NAS to perform these advanced functions without having to depend on an error-prone and possibly complex integration with an OSS system. The rate of the access-loop can be communicated via ANCP (Information Report Message) from the ONT to the OLT, and from OLT to the NAS. Additionally, during the time the DSL NT is active, data rate changes can occur due to environmental conditions (the DSL Access Loop can get "out of sync" and can retrain to a lower value, or the DSL Access Loop could use Seamless Rate Adaptation making the actual data rate fluctuate while the line is active). In this case, ANX sends an additional Information Report to the NAS each time the Access Loop attributes change above a threshold value. 9 Security Considerations [ANCP-SECURITY] 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 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-Wadhwa Expires September 10, 2009 [Page 28] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 10 Differences in ANCP applicability between DSL and PON As it currently stands, both ANCP framework [ANCP-FRAMEWORK] and protocol [ANCP-PROTOCOL] are defined in context of DSL access. Due to inherent differences between PON and DSL access technologies, ANCP needs a few extensions for supporting the use-cases outlined in this document for PON based access. These specific differences and extensions are outlined below. o 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 ONT and the NAS (e.g. admission-request messages).This is illustrated in the generic message flow in Figure 3 of section 5. In case of DSL, the ANCP exchange is contained between two network elements (NAS and the DSLAM). o The PON connection to the ONT is a shared medium between multiple ONTs on the same PON. The local-loop in case of DSL is point-to- point. In case of DSL access network, the access facing port on the NAS (i.e. port to the network between NAS and the DSLAM), and the access-facing ports on the DSLAM (i.e. customer's local-loop) are the two bandwidth constraint points that need to be considered for performing bandwidth based admission control for multicast video and VOD delivered to the customer. In case of PON access, in addition to the bandwidth constraint on the NAS to OLT facing ports, and the subscriber allocated bandwidth for video services, the bandwidth available on the PON for video is an additional constraint that needs to be considered for bandwidth based admission control. If the bandwidth control is centralized in NAS (as described in option 1 of section 6.2), then the NAS needs to support additional logic to consider available PON bandwidth before admitting a multicast request or a VOD request by the user. Accordingly, ANCP needs to identify the customer access port and the PON on which the customer ONT is. If the PON bandwidth control is performed on the OLT (as defined in second option in section 6.2), then additional ANCP request and response messages are required for NAS to query the OLT to determine available PON bandwidth when a request to admit a VOD flow is received on the NAS (as shown in figure 8 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). o In PON, the multicast replication can potentially be performed on three different network elements: (1) on the NAS (2) on the OLT for replication to multiple PON ports and (3) on the ONT/ONU for replication to multiple customer ports. In case of DSL, the replication can potentially be performed on NAS and/or the DSLAM. Section 6.2 defines options for multicast replication in case of PON. In the first option, the multicast replication is done on the AN, but is controlled from NAS via ANCP (based on the reception of per- customer IGMP messages on the NAS). In this option, the NAS needs to Bitar-Wadhwa Expires September 10, 2009 [Page 29] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 supply to the OLT the set of PON-customer-IDs (as defined in section 2.1) to which the multicast stream needs to be replicated. The PON- customer-ID identifies the OLT and the PON ports on the OLT as well as the ONT and the access-ports on the ONT where the multicast stream needs to be replicated. Upon receiving the request to update its multicast replication state, the OLT MUST update its replication state with the indicated PON ports, but MAY also need to interact with the ONT via ANCP to update the multicast replication state on the ONT with the set of access-ports (as indicated by the NAS).In case of DSL, the DSLAM only needs to update its own replication state based on the set of access-ports indicated by the NAS. o 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 premise. In 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. 11 ANCP versus OMCI between the OLT and ONT ONT Management and Control Interface (OMCI) [OMCI] is specified for in-band ONT management via the OLT. This includes configuring parameters on the ONT. 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, albeit it may not be suitable protocol for dynamic transactions as required for the multicast application. If OMCI is selected to be enabled between the OLT and ONT 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 that can be used by an ANCP client and accordingly it requires that the ONT be IP addressable for ANCP. Most ONTs today have a TCP/IP stack used by certain applications (e.g., VoIP, IGMP snooping). ANCP may use the same IP address that is often assigned to SIP or depending on the implementation may require a different address. Sharing the same IP address between SIP and ANCP may have other network implications on traffic routing. Using a separate IP address for the purpose of ONT 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 sends unsolicited requests to the OLT rather than being queried or configured by OLT requests. 12. IANA Considerations This document does not require actions by IANA. Bitar-Wadhwa Expires September 10, 2009 [Page 30] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 12 Acknowledgements 13 References 13.1 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. 13.2 Informative References [RFC2881] Mitton, D. and M. Beadles, "Network Access Server Requirements Next Generation (NASREQNG) NAS Model", RFC 2881, Jul 2000. [ANCP-FRAMEWORK] "Framework for Access Node Control Mechanism in Broadband Networks", draft-ietf-ancp-framework-08.txt, work in progress. [G.983.1] ITU-T recommendation G.983.1, Broadband optical access systems based on Passive Optical Networks (PON). [G.984.1] ITU-T recommendation G.984.1 Gigabit-capable Passive Optical Networks (G-PON): General characteristics [TR-101] Cohen, A. and E. Shrum, "Migration to Ethernet-Based DSL Aggregation", DSL Forum TR-101, May 2006. [ANCP-SECURITY] Moustafa, H., Tschofenig, H., and S. De Cnodder, "Security Threats and Security Requirements for the Access Node Control Protocol (ANCP)", draft-ietf-ancp-security-threats-07.txt, March 2004, work in progress. [OMCI] ITU-T recommendation G.984.4 GPON ONT Management and Control Interface (OMCI) Specifications. [ANCP-PROTOCOL] Wadhwa, S et al, "Protocol for Access Node Control Mechanism in Broadband Networks", draft-ietf-ancp-protocol-04.txt, November 3, 2008, work in progress. Bitar-Wadhwa Expires September 10, 2009 [Page 31] Internet-Draft draft-bitar-wadhwa-ancp-pon-01 March 2009 Authors' Addresses Nabil Bitar Verizon 117 West Street Waltham, MA 02451 Phone: Email: nabil.n.bitar@verizon.com Sanjay Wadhwa Juniper Networks 10 Technology Park Drive Westford, MA 01886 Phone: Email: swadhwa@juniper.net Bitar-Wadhwa Expires September 10, 2009 [Page 32]