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rfc:rfc4779

Network Working Group S. Asadullah Request for Comments: 4779 A. Ahmed Category: Informational C. Popoviciu

                                                         Cisco Systems
                                                             P. Savola
                                                             CSC/FUNET
                                                              J. Palet
                                                           Consulintel
                                                          January 2007
     ISP IPv6 Deployment Scenarios in Broadband Access Networks

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The IETF Trust (2007).

Abstract

 This document provides a detailed description of IPv6 deployment and
 integration methods and scenarios in today's Service Provider (SP)
 Broadband (BB) networks in coexistence with deployed IPv4 services.
 Cable/HFC, BB Ethernet, xDSL, and WLAN are the main BB technologies
 that are currently deployed, and discussed in this document.  The
 emerging Broadband Power Line Communications (PLC/BPL) access
 technology is also discussed for completeness.  In this document we
 will discuss main components of IPv6 BB networks, their differences
 from IPv4 BB networks, and how IPv6 is deployed and integrated in
 each of these networks using tunneling mechanisms and native IPv6.

Asadullah, et al. Informational [Page 1] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
 2.  Common Terminology . . . . . . . . . . . . . . . . . . . . . .  5
 3.  Core/Backbone Network  . . . . . . . . . . . . . . . . . . . .  5
   3.1.  Layer 2 Access Provider Network  . . . . . . . . . . . . .  5
   3.2.  Layer 3 Access Provider Network  . . . . . . . . . . . . .  6
 4.  Tunneling Overview . . . . . . . . . . . . . . . . . . . . . .  7
   4.1.  Access over Tunnels - Customers with Public IPv4
         Addresses  . . . . . . . . . . . . . . . . . . . . . . . .  7
   4.2.  Access over Tunnels - Customers with Private IPv4
         Addresses  . . . . . . . . . . . . . . . . . . . . . . . .  8
   4.3.  Transition a Portion of the IPv4 Infrastructure  . . . . .  8
 5.  Broadband Cable Networks . . . . . . . . . . . . . . . . . . .  9
   5.1.  Broadband Cable Network Elements . . . . . . . . . . . . .  9
   5.2.  Deploying IPv6 in Cable Networks . . . . . . . . . . . . . 10
     5.2.1.  Deploying IPv6 in a Bridged CMTS Network . . . . . . . 12
     5.2.2.  Deploying IPv6 in a Routed CMTS Network  . . . . . . . 14
     5.2.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . 23
     5.2.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . 24
     5.2.5.  IPv6 Security Considerations . . . . . . . . . . . . . 24
     5.2.6.  IPv6 Network Management  . . . . . . . . . . . . . . . 25
 6.  Broadband DSL Networks . . . . . . . . . . . . . . . . . . . . 26
   6.1.  DSL Network Elements . . . . . . . . . . . . . . . . . . . 26
   6.2.  Deploying IPv6 in IPv4 DSL Networks  . . . . . . . . . . . 28
     6.2.1.  Point-to-Point Model . . . . . . . . . . . . . . . . . 29
     6.2.2.  PPP Terminated Aggregation (PTA) Model . . . . . . . . 30
     6.2.3.  L2TPv2 Access Aggregation (LAA) Model  . . . . . . . . 33
     6.2.4.  Hybrid Model for IPv4 and IPv6 Service . . . . . . . . 36
   6.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 38
     6.3.1.  ASM-Based Deployments  . . . . . . . . . . . . . . . . 39
     6.3.2.  SSM-Based Deployments  . . . . . . . . . . . . . . . . 39
   6.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 40
   6.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 41
   6.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 42
 7.  Broadband Ethernet Networks  . . . . . . . . . . . . . . . . . 42
   7.1.  Ethernet Access Network Elements . . . . . . . . . . . . . 42
   7.2.  Deploying IPv6 in IPv4 Broadband Ethernet Networks . . . . 43
     7.2.1.  Point-to-Point Model . . . . . . . . . . . . . . . . . 44
     7.2.2.  PPP Terminated Aggregation (PTA) Model . . . . . . . . 46
     7.2.3.  L2TPv2 Access Aggregation (LAA) Model  . . . . . . . . 48
     7.2.4.  Hybrid Model for IPv4 and IPv6 Service . . . . . . . . 50
   7.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 52
   7.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 53
   7.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 54
   7.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 55

Asadullah, et al. Informational [Page 2] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 8.  Wireless LAN . . . . . . . . . . . . . . . . . . . . . . . . . 55
   8.1.  WLAN Deployment Scenarios  . . . . . . . . . . . . . . . . 55
     8.1.1.  Layer 2 NAP with Layer 3 termination at NSP Edge
             Router . . . . . . . . . . . . . . . . . . . . . . . . 56
     8.1.2.  Layer 3 Aware NAP with Layer 3 Termination at
             Access Router  . . . . . . . . . . . . . . . . . . . . 59
     8.1.3.  PPP-Based Model  . . . . . . . . . . . . . . . . . . . 61
   8.2.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 63
   8.3.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 65
   8.4.  IPv6 Security Considerations . . . . . . . . . . . . . . . 65
   8.5.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 67
 9.  Broadband Power Line Communications (PLC)  . . . . . . . . . . 67
   9.1.  PLC/BPL Access Network Elements  . . . . . . . . . . . . . 68
   9.2.  Deploying IPv6 in IPv4 PLC/BPL . . . . . . . . . . . . . . 69
     9.2.1.  IPv6 Related Infrastructure Changes  . . . . . . . . . 69
     9.2.2.  Addressing . . . . . . . . . . . . . . . . . . . . . . 69
     9.2.3.  Routing  . . . . . . . . . . . . . . . . . . . . . . . 70
   9.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 71
   9.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 71
   9.5.  IPv6 Security Considerations . . . . . . . . . . . . . . . 71
   9.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 71
 10. Gap Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 71
 11. Security Considerations  . . . . . . . . . . . . . . . . . . . 74
 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 74
 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 74
   13.1. Normative References . . . . . . . . . . . . . . . . . . . 74
   13.2. Informative References . . . . . . . . . . . . . . . . . . 76

Asadullah, et al. Informational [Page 3] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

1. Introduction

 This document presents the options available in deploying IPv6
 services in the access portion of a BB Service Provider (SP) network
 - namely Cable/HFC, BB Ethernet, xDSL, WLAN, and PLC/BPL.
 This document briefly discusses the other elements of a provider
 network as well.  It provides different viable IPv6 deployment and
 integration techniques, and models for each of the above-mentioned BB
 technologies individually.  The example list is not exhaustive, but
 it tries to be representative.
 This document analyzes how all the important components of current
 IPv4-based Cable/HFC, BB Ethernet, xDSL, WLAN, and PLC/BPL networks
 will behave when IPv6 is integrated and deployed.
 The following important pieces are discussed:
 A. Available tunneling options
 B. Devices that would have to be upgraded to support IPv6
 C. Available IPv6 address assignment techniques and their use
 D. Possible IPv6 Routing options and their use
 E. IPv6 unicast and multicast packet transmission
 F. Required IPv6 Quality of Service (QoS) parameters
 G. Required IPv6 Security parameters
 H. Required IPv6 Network Management parameters
 It is important to note that the addressing rules provided throughout
 this document represent an example that follows the current
 assignment policies and recommendations of the registries.  However,
 they can be adapted to the network and business model needs of the
 ISPs.
 The scope of the document is to advise on the ways of upgrading an
 existing infrastructure to support IPv6 services.  The recommendation
 to upgrade a device to dual stack does not stop an SP from adding a
 new device to its network to perform the necessary IPv6 functions
 discussed.  The costs involved with such an approach could be offset
 by lower impact on the existing IPv4 services.

Asadullah, et al. Informational [Page 4] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

2. Common Terminology

 BB: Broadband
 CPE: Customer Premise Equipment
 GWR: Gateway Router
 ISP: Internet Service Provider
 NAP: Network Access Provider
 NSP: Network Service Provider
 QoS: Quality of Service
 SP: Service Provider

3. Core/Backbone Network

 This section intends to briefly discuss some important elements of a
 provider network tied to the deployment of IPv6.  A more detailed
 description of the core network is provided in other documents
 [RFC4029].
 There are two types of networks identified in the Broadband
 deployments:
 A.  Access Provider Network: This network provides the broadband
     access and aggregates the subscribers.  The subscriber traffic is
     handed over to the Service Provider at Layer 2 or 3.
 B.  Service Provider Network: This network provides Intranet and
     Internet IP connectivity for the subscribers.
 The Service Provider network structure beyond the Edge Routers that
 interface with the Access provider is beyond the scope of this
 document.

3.1. Layer 2 Access Provider Network

 The Access Provider can deploy a Layer 2 network and perform no
 routing of the subscriber traffic to the SP.  The devices that
 support each specific access technology are aggregated into a highly
 redundant, resilient, and scalable Layer 2 core.  The network core
 can involve various technologies such as Ethernet, Asynchronous
 Transfer Mode (ATM), etc.  The Service Provider Edge Router connects
 to the Access Provider core.

Asadullah, et al. Informational [Page 5] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 This type of network may be transparent to the Layer 3 protocol.
 Some possible changes may come with the intent of supporting IPv6
 provisioning mechanisms, as well as filtering and monitoring IPv6
 traffic based on Layer 2 information such as IPv6 Ether Type Protocol
 ID (0x86DD) or IPv6 multicast specific Media Access Control (MAC)
 addresses (33:33:xx:xx:xx:xx).

3.2. Layer 3 Access Provider Network

 The Access Provider can choose to terminate the Layer 2 domain and
 route the IP traffic to the Service Provider network.  Access Routers
 are used to aggregate the subscriber traffic and route it over a
 Layer 3 core to the SP Edge Routers.  In this case, the impact of the
 IPv6 deployment is significant.
 The case studies in this document discuss only the relevant network
 elements of such a network: Customer Premise Equipment, Access
 Router, and Edge Router.  In real networks, the link between the
 Access Router and the Edge Router involves other routers that are
 part of the aggregation and the core layer of the Access Provider
 network.
 The Access Provider can forward the IPv6 traffic through its Layer 3
 core in three possible ways:
 A.  IPv6 Tunneling: As a temporary solution, the Access Provider can
     choose to use a tunneling mechanism to forward the subscriber
     IPv6 traffic to the Service Provider Edge Router.  This approach
     has the least impact on the Access Provider network; however, as
     the number of users increase and the amount of IPv6 traffic
     grows, the ISP will have to evolve to one of the scenarios listed
     below.
 B.  Native IPv6 Deployment: The Access Provider routers are upgraded
     to support IPv6 and can become dual stack.  In a dual-stack
     network, an IPv6 Interior Gateway Protocol (IGP), such as OSPFv3
     [RFC2740] or IS-IS [ISISv6], is enabled.  RFC 4029 [RFC4029]
     discusses the IGP selection options with their benefits and
     drawbacks.
 C.  MPLS 6PE Deployment [6PE]: If the Access Provider is running MPLS
     in its IPv4 core, it could use 6PE to forward IPv6 traffic over
     it.  In this case, only a subset of routers close to the edge of
     the network need to be IPv6 aware.  With this approach, BGP
     becomes important in order to support 6PE.
 The 6PE approach has the advantage of having minimal impact on the
 Access Provider network.  Fewer devices need to be upgraded and

Asadullah, et al. Informational [Page 6] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 configured while the MPLS core continues to switch the traffic,
 unaware that it transports both IPv4 and IPv6. 6PE should be
 leveraged only if MPLS is already deployed in the network.  At the
 time of writing this document, a major disadvantage of the 6PE
 solution is that it does not support multicast IPv6 traffic.
 The native approach has the advantage of supporting IPv6 multicast
 traffic, but it may imply a significant impact on the IPv4
 operational network in terms of software configuration and possibly
 hardware upgrade.
 More detailed Core Network deployment recommendations are discussed
 in other documents [RFC4029].  The handling of IPv6 traffic in the
 Core of the Access Provider Network will not be discussed for the
 remainder of this document.

4. Tunneling Overview

 If SPs are not able to deploy native IPv6, they might use tunneling-
 based transition mechanisms to start an IPv6 service offering, and
 move to native IPv6 deployment at a later time.
 Several tunneling mechanisms were developed specifically to transport
 IPv6 over existing IPv4 infrastructures.  Several of them have been
 standardized and their use depends on the existing SP IPv4 network
 and the structure of the IPv6 service.  The requirements for the most
 appropriate mechanisms are described in [v6tc] with more updates to
 follow.  Deploying IPv6 using tunneling techniques can imply as
 little changes to the network as upgrading software on tunnel end
 points.  A Service Provider could use tunneling to deploy IPv6 in the
 following scenarios:

4.1. Access over Tunnels - Customers with Public IPv4 Addresses

 If the customer is a residential user, it can initiate the tunnel
 directly from the IPv6 capable host to a tunnel termination router
 located in the NAP or ISP network.  The tunnel type used should be
 decided by the SP, but it should take into consideration its
 availability on commonly used software running on the host machine.
 Of the many tunneling mechanisms developed, such as IPv6 Tunnel
 Broker [RFC3053], Connection of IPv6 Domains via IPv4 Clouds
 [RFC3056], Generic Packet Tunneling in IPv6 [RFC2473], ISATAP
 [RFC4214], Basic Transition Mechanisms for IPv6 Hosts and Routers
 [RFC4213], and Transmission of IPv6 over IPv4 Domains without
 Explicit Tunnels [RFC2529], some are more popular than the others.
 At the time of writing this document, the IETF Softwire Working Group
 was tasked with standardizing a single tunneling protocol [Softwire]
 for this application.

Asadullah, et al. Informational [Page 7] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 If the end customer has a GWR installed, then it could be used to
 originate the tunnel, thus offering native IPv6 access to multiple
 hosts on the customer network.  In this case, the GWR would need to
 be upgraded to dual stack in order to support IPv6.  The GWR can be
 owned by the customer or by the SP.

4.2. Access over Tunnels - Customers with Private IPv4 Addresses

 If the end customer receives a private IPv4 address and needs to
 initiate a tunnel through Network Address Translation (NAT),
 techniques like 6to4 may not work since they rely on public IPv4
 address.  In this case, unless the existing GWRs support protocol-41-
 forwarding [Protocol41], the end user might have to use tunnels that
 can operate through NATs (such as Teredo [RFC4380]).  Most GWRs
 support protocol-41-forwarding, which means that hosts can initiate
 the tunnels - in which case the GWR is not affected by the IPv6
 service.
 The customer has the option to initiate the tunnel from the device
 (GWR) that performs the NAT functionality, similar to the GWR
 scenario discussed in Section 4.1.  This will imply hardware
 replacement or software upgrade and a native IPv6 environment behind
 the GWR.
 It is also worth observing that initiating an IPv6 tunnel over IPv4
 through already established IPv4 IPsec sessions would provide a
 certain level of security to the IPv6 traffic.

4.3. Transition a Portion of the IPv4 Infrastructure

 Tunnels can be used to transport the IPv6 traffic across a defined
 segment of the network.  As an example, the customer might connect
 natively to the Network Access Provider, where a tunnel is used to
 transit the traffic over IPv4 to the ISP.  In this case, the tunnel
 choice depends on its capabilities (for example, whether or not it
 supports multicast), routing protocols used (there are several types
 that can transport Layer 2 messages, such as GRE [RFC2784], L2TPv3
 [RFC3931], or pseudowire), manageability, and scalability (dynamic
 versus static tunnels).
 This scenario implies that the access portion of the network has been
 upgraded to support dual stack, so the savings provided by tunneling
 in this scenario are very small compared with the previous two
 scenarios.  Depending on the number of sites requiring the service,
 and considering the expenses required to manage the tunnels (some
 tunnels are static while others are dynamic [DynamicTunnel]) in this
 case, the SPs might find the native approach worth the additional
 investments.

Asadullah, et al. Informational [Page 8] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 In all the scenarios listed above, the tunnel selection process
 should consider the IPv6 multicast forwarding capabilities if such
 service is planned.  As an example, 6to4 tunnels do not support IPv6
 multicast traffic.
 The operation, capabilities, and deployment of various tunnel types
 have been discussed extensively in the documents referenced earlier
 as well as in [RFC4213] and [RFC3904].  Details of a tunnel-based
 deployment are offered in the next section of this document, which
 discusses the case of Cable Access, where the current Data Over Cable
 Service Interface Specification (DOCSIS 2.0) [RF-Interface] and prior
 specifications do not provide support for native IPv6 access.
 Although Sections 6, 7, 8, and 9 focus on a native IPv6 deployments
 over DSL, Fiber to the Home (FTTH), wireless, and PLC/BPL and because
 this approach is fully supported today, tunnel-based solutions are
 also possible in these cases based on the guidelines of this section
 and some of the recommendations provided in Section 5.

5. Broadband Cable Networks

 This section describes the infrastructure that exists today in cable
 networks providing BB services to the home.  It also describes IPv6
 deployment options in these cable networks.
 DOCSIS standardizes and documents the operation of data over cable
 networks.  DOCSIS 2.0 and prior specifications have limitations that
 do not allow for a smooth implementation of native IPv6 transport.
 Some of these limitations are discussed in this section.  For this
 reason, the IPv6 deployment scenarios discussed in this section for
 the existing cable networks are tunnel based.  The tunneling examples
 presented here could also be applied to the other BB technologies
 described in Sections 6, 7, 8, and 9.

5.1. Broadband Cable Network Elements

 Broadband cable networks are capable of transporting IP traffic to/
 from users to provide high speed Internet access and Voice over IP
 (VoIP) services.  The mechanism for transporting IP traffic over
 cable networks is outlined in the DOCSIS specification
 [RF-Interface].
 Here are some of the key elements of a cable network:
 Cable (HFC) Plant: Hybrid Fiber Coaxial plant, used as the underlying
 transport
 CMTS: Cable Modem Termination System (can be a Layer 2 bridging or
 Layer 3 routing CMTS)

Asadullah, et al. Informational [Page 9] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 GWR: Residential Gateway Router (provides Layer 3 services to hosts)
 Host: PC, notebook, etc., which is connected to the CM or GWR
 CM: Cable Modem
 ER: Edge Router
 MSO: Multiple Service Operator
 Data Over Cable Service Interface Specification (DOCSIS): Standards
 defining how data should be carried over cable networks
 Figure 5.1 illustrates the key elements of a Cable Network.
 |--- ACCESS  ---||------ HFC ------||----- Aggregation / Core -----|
 +-----+  +------+
 |Host |--| GWR  |
 +-----+  +--+---+
             |        _ _ _ _ _ _
          +------+   |           |
          |  CM  |---|           |
          +------+   |           |
                     |    HFC    |   +------+   +--------+
                     |           |   |      |   | Edge   |
 +-----+  +------+   |  Network  |---| CMTS |---|        |=>ISP
 |Host |--|  CM  |---|           |   |      |   | Router | Network
 +-----+  +--+---+   |           |   +------+   +--------+
                     |_ _ _ _ _ _|
          +------+         |
 +-----+  | GWR/ |         |
 |Host |--| CM   |---------+
 +-----+  |      |
          +------+
                            Figure 5.1

5.2. Deploying IPv6 in Cable Networks

 One of the motivators for an MSO to deploy IPv6 over its cable
 network is to ease management burdens.  IPv6 can be enabled on the
 CM, CMTS, and ER for management purposes.  Currently portions of the
 cable infrastructure use IPv4 address space [RFC1918]; however, there
 is a finite number of those.  Thus, IPv6 could have utility in the
 cable space implemented on the management plane initially and focused

Asadullah, et al. Informational [Page 10] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 on the data plane for end-user services later.  For more details on
 using IPv6 for management in cable networks, please refer to Section
 5.6.1.
 There are two different deployment modes in current cable networks: a
 bridged CMTS environment and a routed CMTS environment.  IPv6 can be
 deployed in both of these environments.
 1.  Bridged CMTS Network
 In this scenario, both the CM and CMTS bridge all data traffic.
 Traffic to/from host devices is forwarded through the cable network
 to the ER.  The ER then routes traffic through the ISP network to the
 Internet.  The CM and CMTS support a certain degree of Layer 3
 functionality for management purposes.
 2.  Routed CMTS Network
 In a routed network, the CMTS forwards IP traffic to/from hosts based
 on Layer 3 information using the IP source/destination address.  The
 CM acts as a Layer 2 bridge for forwarding data traffic and supports
 some Layer 3 functionality for management purposes.
 Some of the factors that hinder deployment of native IPv6 in current
 routed and bridged cable networks include:
 A.  Changes need to be made to the DOCSIS specification
     [RF-Interface] to include support for IPv6 on the CM and CMTS.
     This is imperative for deploying native IPv6 over cable networks.
 B.  Problems with IPv6 Neighbor Discovery (ND) on CM and CMTS.  In
     IPv4, these devices rely on Internet Group Multicast Protocol
     (IGMP) join messages to track membership of hosts that are part
     of a particular IP multicast group.  In order to support ND, a
     multicast-based process, the CM and CMTS will need to support
     IGMPv3/Multicast Listener Discovery Version 2 (MLDv2) or v1
     snooping.
 C.  Classification of IPv6 traffic in the upstream and downstream
     direction.  The CM and CMTS will need to support classification
     of IPv6 packets in order to give them the appropriate priority
     and QoS.  Service providers that wish to deploy QoS mechanisms
     also have to support classification of IPv6 traffic.
 Due to the above mentioned limitations in deployed cable networks, at
 the time of writing this document, the only option available for
 cable operators is to use tunneling techniques in order to transport
 IPv6 traffic over their current IPv4 infrastructure.  The following

Asadullah, et al. Informational [Page 11] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 sections will cover tunneling and native IPv6 deployment scenarios in
 more detail.

5.2.1. Deploying IPv6 in a Bridged CMTS Network

 In IPv4, the CM and CMTS act as Layer 2 bridges and forward all data
 traffic to/from the hosts and the ER.  The hosts use the ER as their
 Layer 3 next hop.  If there is a GWR behind the CM it can act as a
 next hop for all hosts and forward data traffic to/from the ER.
 When deploying IPv6 in this environment, the CM and CMTS will
 continue to act as bridging devices in order to keep the transition
 smooth and reduce operational complexity.  The CM and CMTS will need
 to bridge IPv6 unicast and multicast packets to/from the ER and the
 hosts.  If there is a GWR connected to the CM, it will need to
 forward IPv6 unicast and multicast traffic to/from the ER.
 IPv6 can be deployed in a bridged CMTS network either natively or via
 tunneling.  This section discusses the native deployment model.  The
 tunneling model is similar to ones described in Sections 5.2.2.1 and
 5.2.2.2.
 Figure 5.2.1 illustrates the IPv6 deployment scenario.
 +-----+  +-----+
 |Host |--| GWR |
 +-----+  +--+--+
             |              _ _ _ _ _ _
             |  +------+   |           |
             +--|  CM  |---|           |
                +------+   |           |
                           |   HFC     |   +------+  +--------+
                           |           |   |      |  | Edge   |
       +-----+  +------+   |  Network  |---| CMTS |--|        |=>ISP
       |Host |--|  CM  |---|           |   |      |  | Router |Network
       +-----+  +------+   |           |   +------+  +--------+
                           |_ _ _ _ _ _|
 |-------------||---------------------------------||---------------|
     L3 Routed              L2 Bridged                 L3 Routed
                           Figure 5.2.1

Asadullah, et al. Informational [Page 12] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.1.1. IPv6 Related Infrastructure Changes

 In this scenario, the CM and the CMTS bridge all data traffic so they
 will need to support bridging of native IPv6 unicast and multicast
 traffic.  The following devices have to be upgraded to dual stack:
 Host, GWR, and ER.

5.2.1.2. Addressing

 The proposed architecture for IPv6 deployment includes two components
 that must be provisioned: the CM and the host.  Additionally if there
 is a GWR connected to the CM, it will also need to be provisioned.
 The host or the GWR use the ER as their Layer 3 next hop.

5.2.1.2.1. IP Addressing for CM

 The CM will be provisioned in the same way as in currently deployed
 cable networks, using an IPv4 address on the cable interface
 connected to the MSO network for management functions.  During the
 initialization phase, it will obtain its IPv4 address using Dynamic
 Host Configuration Protocol (DHCPv4), and download a DOCSIS
 configuration file identified by the DHCPv4 server.

5.2.1.2.2. IP Addressing for Hosts

 If there is no GWR connected to the CM, the host behind the CM will
 get a /64 prefix via stateless auto-configuration or DHCPv6.
 If using stateless auto-configuration, the host listens for routing
 advertisements (RAs) from the ER.  The RAs contain the /64 prefix
 assigned to the segment.  Upon receipt of an RA, the host constructs
 its IPv6 address by combining the prefix in the RA (/64) and a unique
 identifier (e.g., its modified EUI-64 (64-bit Extended Unique
 Identifier) format interface ID).
 If DHCPv6 is used to obtain an IPv6 address, it will work in much the
 same way as DHCPv4 works today.  The DHCPv6 messages exchanged
 between the host and the DHCPv6 server are bridged by the CM and the
 CMTS.

5.2.1.2.3. IP Addressing for GWR

 The GWR can use stateless auto-configuration (RA) to obtain an
 address for its upstream interface, the link between itself and the
 ER.  This step is followed by a request via DHCP-PD (Prefix
 Delegation) for a prefix shorter than /64, typically /48 [RFC3177],
 which in turn is divided into /64s and assigned to its downstream
 interfaces connecting to the hosts.

Asadullah, et al. Informational [Page 13] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.1.3. Data Forwarding

 The CM and CMTS must be able to bridge native IPv6 unicast and
 multicast traffic.  The CMTS must provide IP connectivity between
 hosts attached to CMs, and must do so in a way that meets the
 expectation of Ethernet-attached customer equipment.  In order to do
 that, the CM and CMTS must forward Neighbor Discovery (ND) packets
 between ER and the hosts attached to the CM.
 Communication between hosts behind different CMs is always forwarded
 through the CMTS.  IPv6 communication between the different sites
 relies on multicast IPv6 ND [RFC2461] frames being forwarded
 correctly by the CM and the CMTS.
 In order to support IPv6 multicast applications across DOCSIS cable
 networks, the CM and bridging CMTS need to support IGMPv3/MLDv2 or v1
 snooping.  MLD is almost identical to IGMP in IPv4, only the name and
 numbers are changed.  MLDv2 is identical to IGMPv3 and also supports
 ASM (Any-Source Multicast) and SSM (Source-Specific Multicast)
 service models.  Implementation work on CM/CMTS should be minimal
 because the only significant difference between IPv4 IGMPv3 and IPv6
 MLDv2 is the longer addresses in the protocol.

5.2.1.4. Routing

 The hosts install a default route that points to the ER or the GWR.
 No routing protocols are needed on these devices, which generally
 have limited resources.  If there is a GWR present, it will also use
 static default route to the ER.
 The ER runs an IGP such as OSPFv3 or IS-IS.  The connected prefixes
 have to be redistributed.  If DHCP-PD is used, with every delegated
 prefix a static route is installed by the ER.  For this reason, the
 static routes must also be redistributed.  Prefix summarization
 should be done at the ER.

5.2.2. Deploying IPv6 in a Routed CMTS Network

 In an IPv4/IPv6 routed CMTS network, the CM still acts as a Layer 2
 device and bridges all data traffic between its Ethernet interface
 and cable interface connected to the cable operator network.  The
 CMTS acts as a Layer 3 router and may also include the ER
 functionality.  The hosts and the GWR use the CMTS as their Layer 3
 next hop.
 When deploying IPv6, the CMTS/ER will need to either tunnel IPv6
 traffic or natively support IPv6.

Asadullah, et al. Informational [Page 14] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 There are five possible deployment scenarios for IPv6 in a routed
 CMTS network:
 1.  IPv4 Cable (HFC) Network
 In this scenario, the cable network, including the CM and CMTS,
 remain IPv4 devices.  The host and ER are upgraded to dual stack.
 This is the easiest way for a cable operator to provide IPv6 service,
 as no changes are made to the cable network.
 2.  IPv4 Cable (HFC) Network, GWR at Customer Site
 In this case, the cable network, including the CM and CMTS, remain
 IPv4 devices.  The host, GWR, and ER are upgraded to dual stack.
 This scenario is also easy to deploy since the cable operator just
 needs to add GWR at the customer site.
 3.  Dual-stacked Cable (HFC) Network, CM, and CMTS Support IPv6
 In this scenario, the CMTS is upgraded to dual stack to support IPv4
 and IPv6.  Since the CMTS supports IPv6, it can act as an ER as well.
 The CM will act as a Layer 2 bridge, but will need to bridge IPv6
 unicast and multicast traffic.  This scenario is not easy to deploy
 since it requires changes to the DOCSIS specification.  The CM and
 CMTS may require hardware and software upgrades to support IPv6.
 4.  Dual-stacked Cable (HFC) Network, Standalone GWR, and CMTS
 Support IPv6
 In this scenario there is a stand-alone GWR connected to the CM.
 Since the IPv6 functionality exists on the GWR, the CM does not need
 to be dual stack.  The CMTS is upgraded to dual stack and it can
 incorporate the ER functionality.  This scenario may also require
 hardware and software changes on the GWR and CMTS.
 5.  Dual-stacked Cable (HFC) Network, Embedded GWR/CM, and CMTS
 Support IPv6
 In this scenario, the CM and GWR functionality exists on a single
 device, which needs to be upgraded to dual stack.  The CMTS will also
 need to be upgraded to a dual-stack device.  This scenario is also
 difficult to deploy in existing cable network since it requires
 changes on the Embedded GWR/CM and the CMTS.
 The DOCSIS specification will also need to be modified to allow
 native IPv6 support on the Embedded GWR/CM.

Asadullah, et al. Informational [Page 15] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.1. IPv4 Cable Network, Host, and ER Upgraded to Dual Stack

 This is one of the most cost-effective ways for a cable operator to
 offer IPv6 services to its customers.  Since the cable network
 remains IPv4, there is relatively minimal cost involved in turning up
 IPv6 service.  All IPv6 traffic is exchanged between the hosts and
 the ER.
 Figure 5.2.2.1 illustrates this deployment scenario.
                         +-----------+   +------+   +--------+
   +-----+  +-------+    |   Cable   |   |      |   |  Edge  |
   |Host |--|  CM   |----|  (HFC)    |---| CMTS |---|        |=>ISP
   +-----+  +-------+    |  Network  |   |      |   | Router |Network
                         +-----------+   +------+   +--------+
           _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
         ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                        IPv6-in-IPv4 tunnel
   |---------||---------------------------------------||------------|
   IPv4/v6                 IPv4 only                    IPv4/v6
                            Figure 5.2.2.1

5.2.2.1.1. IPv6 Related Infrastructure Changes

 In this scenario, the CM and the CMTS will only need to support IPv4,
 so no changes need to be made to them or the cable network.  The
 following devices have to be upgraded to dual stack: Host and ER.

5.2.2.1.2. Addressing

 The only device that needs to be assigned an IPv6 address at the
 customer site is the host.  Host address assignment can be done in
 multiple ways.  Depending on the tunneling mechanism used, it could
 be automatic or might require manual configuration.
 The host still receives an IPv4 address using DHCPv4, which works the
 same way in currently deployed cable networks.  In order to get IPv6
 connectivity, host devices will also need an IPv6 address and a means
 to communicate with the ER.

Asadullah, et al. Informational [Page 16] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.1.3. Data Forwarding

 All IPv6 traffic will be sent to/from the ER and the host device.  In
 order to transport IPv6 packets over the cable operator IPv4 network,
 the host and the ER will need to use one of the available IPv6 in
 IPv4 tunneling mechanisms.
 The host will use its IPv4 address to source the tunnel to the ER.
 All IPv6 traffic will be forwarded to the ER, encapsulated in IPv4
 packets.  The intermediate IPv4 nodes will forward this traffic as
 regular IPv4 packets.  The ER will need to terminate the tunnel
 and/or provide other IPv6 services.

5.2.2.1.4. Routing

 Routing configuration on the host will vary depending on the
 tunneling technique used.  In some cases, a default or static route
 might be needed to forward traffic to the next hop.
 The ER runs an IGP such as OSPFv3 or ISIS.

5.2.2.2. IPv4 Cable Network, Host, GWR and ER Upgraded to Dual Stack

 The cable operator can provide IPv6 services to its customers, in
 this scenario, by adding a GWR behind the CM.  Since the GWR will
 facilitate all IPv6 traffic between the host and the ER, the cable
 network, including the CM and CMTS, does not need to support IPv6,
 and can remain as IPv4 devices.
 Figure 5.2.2.2 illustrates this deployment scenario.
  +-----+
  |Host |
  +--+--+
     |                   +-----------+   +------+   +--------+
 +---+---+  +-------+    |   Cable   |   |      |   |  Edge  |
 |  GWR  |--|  CM   |----|  (HFC)    |---| CMTS |---|        |=>ISP
 +-------+  +-------+    |  Network  |   |      |   | Router |Network
                         +-----------+   +------+   +--------+
           _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
         ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                        IPv6-in-IPv4 tunnel
 |---------||--------------------------------------||-------------|
   IPv4/v6                 IPv4 only                    IPv4/v6
                            Figure 5.2.2.2

Asadullah, et al. Informational [Page 17] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.2.1. IPv6 Related Infrastructure Changes

 In this scenario, the CM and the CMTS will only need to support IPv4,
 so no changes need to be made to them or the cable network.  The
 following devices have to be upgraded to dual stack: Host, GWR, and
 ER.

5.2.2.2.2. Addressing

 The only devices that need to be assigned an IPv6 address at customer
 site are the host and GWR.  IPv6 address assignment can be done
 statically at the GWR downstream interface.  The GWR will send out RA
 messages on its downstream interface, which will be used by the hosts
 to auto-configure themselves with an IPv6 address.  The GWR can also
 configure its upstream interface using RA messages from the ER and
 use DHCP-PD for requesting a /48 [RFC3177] prefix from the ER.  This
 /48 prefix will be used to configure /64s on hosts connected to the
 GWR downstream interfaces.  The uplink to the ISP network is
 configured with a /64 prefix as well.
 The GWR still receives a global IPv4 address on its upstream
 interface using DHCPv4, which works the same way in currently
 deployed cable networks.  In order to get IPv6 connectivity to the
 Internet, the GWR will need to communicate with the ER.

5.2.2.2.3. Data Forwarding

 All IPv6 traffic will be sent to/from the ER and the GWR, which will
 forward IPv6 traffic to/from the host.  In order to transport IPv6
 packets over the cable operator IPv4 network, the GWR and the ER will
 need to use one of the available IPv6 in IPv4 tunneling mechanisms.
 All IPv6 traffic will need to go through the tunnel, once it comes
 up.
 The GWR will use its IPv4 address to source the tunnel to the ER.
 The tunnel endpoint will be the IPv4 address of the ER.  All IPv6
 traffic will be forwarded to the ER, encapsulated in IPv4 packets.
 The intermediate IPv4 nodes will forward this traffic as regular IPv4
 packets.  In case of 6to4 tunneling, the ER will need to support 6to4
 relay functionality in order to provide IPv6 Internet connectivity to
 the GWR, and hence, the hosts connected to the GWR.

5.2.2.2.4. Routing

 Depending on the tunneling technique used, additional configuration
 might be needed on the GWR and the ER.  If the ER is also providing a
 6to4 relay service then a default route will need to be added to the
 GWR pointing to the ER, for all non-6to4 traffic.

Asadullah, et al. Informational [Page 18] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 If using manual tunneling, the GWR and ER can use static routing or
 an IGP such as RIPng [RFC2080].  The RIPng updates can be transported
 over a manual tunnel, which does not work when using 6to4 tunneling
 since it does not support multicast.
 Customer routes can be carried to the ER using RIPng updates.  The ER
 can advertise these routes in its IGP.  Prefix summarization should
 be done at the ER.
 If DHCP-PD is used for address assignment, a static route is
 automatically installed on the ER for each delegated /48 prefix.  The
 static routes need to be redistributed into the IGP at the ER, so
 there is no need for a routing protocol between the ER and the GWR.
 The ER runs an IGP such as OSPFv3 or ISIS.

5.2.2.3. Dual-Stacked Cable (HFC) Network, CM, and CMTS Support IPv6

 In this scenario the cable operator can offer native IPv6 services to
 its customers since the cable network, including the CMTS, supports
 IPv6.  The ER functionality can be included in the CMTS or it can
 exist on a separate router connected to the CMTS upstream interface.
 The CM will need to bridge IPv6 unicast and multicast traffic.
 Figure 5.2.2.3 illustrates this deployment scenario.
                         +-----------+   +-------------+
   +-----+  +-------+    |   Cable   |   | CMTS / Edge |
   |Host |--|  CM   |----|  (HFC)    |---|             |=>ISP
   +-----+  +-------+    |  Network  |   |   Router    | Network
                         +-----------+   +-------------+
   |-------||---------------------------||---------------|
    IPv4/v6              IPv4/v6              IPv4/v6
                           Figure 5.2.2.3

5.2.2.3.1. IPv6 Related Infrastructure Changes

 Since the CM still acts as a Layer 2 bridge, it does not need to be
 dual stack.  The CM will need to support bridging of IPv6 unicast and
 multicast traffic and IGMPv3/MLDv2 or v1 snooping, which requires
 changes in the DOCSIS specification.  In this scenario, the following
 devices have to be upgraded to dual stack: Host and CMTS/ER.

Asadullah, et al. Informational [Page 19] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.3.2. Addressing

 In cable networks today, the CM receives a private IPv4 address using
 DHCPv4 for management purposes.  In an IPv6 environment, the CM will
 continue to use an IPv4 address for management purposes.  The cable
 operator can also choose to assign an IPv6 address to the CM for
 management, but the CM will have to be upgraded to support this
 functionality.
 IPv6 address assignment for the CM and host can be done via DHCP or
 stateless auto-configuration.  If the CM uses an IPv4 address for
 management, it will use DHCPv4 for its address assignment and the
 CMTS will need to act as a DHCPv4 relay agent.  If the CM uses an
 IPv6 address for management, it can use DHCPv6, with the CMTS acting
 as a DHCPv6 relay agent, or the CMTS can be statically configured
 with a /64 prefix and it can send out RA messages out the cable
 interface.  The CMs connected to the cable interface can use the RA
 messages to auto-configure themselves with an IPv6 address.  All CMs
 connected to the cable interface will be in the same subnet.
 The hosts can receive their IPv6 address via DHCPv6 or stateless
 auto-configuration.  With DHCPv6, the CMTS may need to act as a
 DHCPv6 relay agent and forward DHCP messages between the hosts and
 the DHCP server.  With stateless auto-configuration, the CMTS will be
 configured with multiple /64 prefixes and send out RA messages to the
 hosts.  If the CMTS is not also acting as an ER, the RA messages will
 come from the ER connected to the CMTS upstream interface.  The CMTS
 will need to forward the RA messages downstream or act as an ND
 proxy.

5.2.2.3.3. Data Forwarding

 All IPv6 traffic will be sent to/from the CMTS and hosts.  Data
 forwarding will work the same way it works in currently deployed
 cable networks.  The CMTS will forward IPv6 traffic to/from hosts
 based on the IP source/destination address.

5.2.2.3.4. Routing

 No routing protocols are needed between the CMTS and the host since
 the CM and host are directly connected to the CMTS cable interface.
 Since the CMTS supports IPv6, hosts will use the CMTS as their Layer
 3 next hop.
 If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
 IS-IS.

Asadullah, et al. Informational [Page 20] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.4. Dual-Stacked Cable (HFC) Network, Stand-Alone GWR, and CMTS

        Support IPv6
 In this case, the cable operator can offer IPv6 services to its
 customers by adding a GWR between the CM and the host.  The GWR will
 facilitate IPv6 communication between the host and the CMTS/ER.  The
 CMTS will be upgraded to dual stack to support IPv6 and can act as an
 ER as well.  The CM will act as a bridge for forwarding data traffic
 and does not need to support IPv6.
 This scenario is similar to the case described in Section 5.2.2.2.
 The only difference in this case is that the ER functionality exists
 on the CMTS instead of on a separate router in the cable operator
 network.
 Figure 5.2.2.4 illustrates this deployment scenario.
                                  +-----------+   +-----------+
 +------+  +-------+  +-------+   |   Cable   |   |CMTS / Edge|
 | Host |--| GWR   |--|  CM   |---|  (HFC)    |---|           |=>ISP
 +------+  +-------+  +-------+   |  Network  |   |   Router  |Network
                                  +-----------+   +-----------+
                    _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
                  ()_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _()
                           IPv6-in-IPv4 tunnel
 |-----------------||-----------------------------||--------------|
       IPv4/v6                      IPv4                  IPv4/v6
                             Figure 5.2.2.4

5.2.2.4.1. IPv6 Related Infrastructure Changes

 Since the CM still acts as a Layer 2 bridge, it does not need to be
 dual stack, nor does it need to support IPv6.  In this scenario, the
 following devices have to be upgraded to dual stack: Host, GWR, and
 CMTS/ER.

5.2.2.4.2. Addressing

 The CM will still receive a private IPv4 address using DHCPv4, which
 works the same way in existing cable networks.  The CMTS will act as
 a DHCPv4 relay agent.
 The address assignment for the host and GWR happens in a similar
 manner as described in Section 5.2.2.2.2.

Asadullah, et al. Informational [Page 21] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

5.2.2.4.3. Data Forwarding

 Data forwarding between the host and CMTS/ER is facilitated by the
 GWR and happens in a similar manner as described in Section
 5.2.2.2.3.

5.2.2.4.4. Routing

 In this case, routing is very similar to the case described in
 Section 5.2.2.2.4.  Since the CMTS now incorporates the ER
 functionality, it will need to run an IGP such as OSPFv3 or IS-IS.

5.2.2.5. Dual-Stacked Cable (HFC) Network, Embedded GWR/CM, and CMTS

        Support IPv6
 In this scenario, the cable operator can offer native IPv6 services
 to its customers since the cable network, including the CM/Embedded
 GWR and CMTS, supports IPv6.  The ER functionality can be included in
 the CMTS or it can exist on a separate router connected to the CMTS
 upstream interface.  The CM/Embedded GWR acts as a Layer 3 device.
 Figure 5.2.2.5 illustrates this deployment scenario.
                            +-----------+   +-------------+
  +-----+   +-----------+   |   Cable   |   | CMTS / Edge |
  |Host |---| CM / GWR  |---|  (HFC)    |---|             |=>ISP
  +-----+   +-----------+   |  Network  |   |   Router    |Network
                            +-----------+   +-------------+
  |---------------------------------------------------------|
                            IPv4/v6
                        Figure 5.2.2.5

5.2.2.5.1. IPv6 Related Infrastructure Changes

 Since the CM/GWR acts as a Layer 3 device, IPv6 can be deployed end-
 to-end.  In this scenario, the following devices have to be upgraded
 to dual stack: Host, CM/GWR, and CMTS/ER.

5.2.2.5.2. Addressing

 Since the CM/GWR is dual stack, it can receive an IPv4 or IPv6
 address using DHCP for management purposes.  As the GWR functionality
 is embedded in the CM, it will need an IPv6 address for forwarding
 data traffic.  IPv6 address assignment for the CM/GWR and host can be
 done via DHCPv6 or DHCP-PD.

Asadullah, et al. Informational [Page 22] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 If using DHCPv6, the CMTS will need to act as a DHCPv6 relay agent.
 The host and CM/GWR will receive IPv6 addresses from pools of /64
 prefixes configured on the DHCPv6 server.  The CMTS will need to
 glean pertinent information from the DHCP Offer messages, sent from
 the DHCP server to the DHCP clients (host and CM/GWR), much like it
 does today in DHCPv4.  All CM/GWR connected to the same cable
 interface on the CMTS belong to the same management /64 prefix.  The
 hosts connected to the same cable interface on the CMTS may belong to
 different /64 customer prefixes, as the CMTS may have multiple /64
 prefixes configured under its cable interfaces.
 It is also possible to use DHCP-PD for an IPv6 address assignment.
 In this case, the CM/GWR will use stateless auto-configuration to
 assign an IPv6 address to its upstream interface using the /64 prefix
 sent by the CMTS/ER in an RA message.  Once the CM/GWR assigns an
 IPv6 address to its upstream interface, it will request a /48
 [RFC3177] prefix from the CMTS/ER and chop this /48 prefix into /64s
 for assigning IPv6 addresses to hosts.  The uplink to the ISP network
 is configured with a /64 prefix as well.

5.2.2.5.3. Data Forwarding

 The host will use the CM/GWR as the Layer 3 next hop.  The CM/GWR
 will forward all IPv6 traffic to/from the CMTS/ER and hosts.  The
 CMTS/ER will forward IPv6 traffic to/from hosts based on the IP
 source/destination address.

5.2.2.5.4. Routing

 The CM/GWR can use a static default route pointing to the CMTS/ER or
 it can run a routing protocol such as RIPng or OSPFv3 between itself
 and the CMTS.  Customer routes from behind the CM/GWR can be carried
 to the CMTS using routing updates.
 If DHCP-PD is used for address assignment, a static route is
 automatically installed on the CMTS/ER for each delegated /48 prefix.
 The static routes need to be redistributed into the IGP at the
 CMTS/ER so there is no need for a routing protocol between the
 CMTS/ER and the GWR.
 If the CMTS is also acting as an ER, it runs an IGP such as OSPFv3 or
 IS-IS.

5.2.3. IPv6 Multicast

 In order to support IPv6 multicast applications across DOCSIS cable
 networks, the CM and bridging CMTS will need to support IGMPv3/MLDv2
 or v1 snooping.  MLD is almost identical to IGMP in IPv4, only the

Asadullah, et al. Informational [Page 23] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 name and numbers are changed.  MLDv2 is almost identical to IGMPv3
 and also supports ASM (Any-Source Multicast) and SSM (Source-Specific
 Multicast) service models.
 SSM is more suited for deployments where the SP intends to provide
 paid content to the users (video or audio).  These types of services
 are expected to be of primary interest.  Moreover, the simplicity of
 the SSM model often overrides the scalability issues that would be
 resolved in an ASM model.  ASM is, however, an option that is
 discussed in Section 6.3.1.  The Layer 3 CM, GWR, and Layer 3 routed
 CMTS/ER will need to be enabled with PIM-SSM, which requires the
 definition and support for IGMPv3/MLDv1 or v2 snooping, in order to
 track join/leave messages from the hosts.  Another option would be
 for the Layer 3 CM or GWR to support MLD proxy routing.  The Layer 3
 next hop for the hosts needs to support MLD.
 Refer to Section 6.3 for more IPv6 multicast details.

5.2.4. IPv6 QoS

 IPv6 will not change or add any queuing/scheduling functionality
 already existing in DOCSIS specifications.  But the QoS mechanisms on
 the CMTS and CM would need to be IPv6 capable.  This includes support
 for IPv6 classifiers, so that data traffic to/from host devices can
 be classified appropriately into different service flows and be
 assigned appropriate priority.  Appropriate classification criteria
 would need to be implemented for unicast and multicast traffic.
 Traffic classification and marking should be done at the CM for
 upstream traffic and the CMTS/ER for downstream traffic, in order to
 support the various types of services: data, voice, and video.  The
 same IPv4 QoS concepts and methodologies should be applied for IPv6
 as well.
 It is important to note that when traffic is encrypted end-to-end,
 the traversed network devices will not have access to many of the
 packet fields used for classification purposes.  In these cases,
 routers will most likely place the packets in the default classes.
 The QoS design should take into consideration this scenario and try
 to use mainly IP header fields for classification purposes.

5.2.5. IPv6 Security Considerations

 Security in a DOCSIS cable network is provided using Baseline Privacy
 Plus (BPI+).  The only part that is dependent on IP addresses is
 encrypted multicast.  Semantically, multicast encryption would work
 the same way in an IPv6 environment as in the IPv4 network.  However,

Asadullah, et al. Informational [Page 24] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 appropriate enhancements will be needed in the DOCSIS specification
 to support encrypted IPv6 multicast.
 There are limited changes that have to be done for hosts in order to
 enhance security.  The privacy extensions [RFC3041] for auto-
 configuration should be used by the hosts.  IPv6 firewall functions
 could be enabled, if available on the host or GWR.
 The ISP provides security against attacks that come from its own
 subscribers, but it could also implement security services that
 protect its subscribers from attacks sourced from the outside of its
 network.  Such services do not apply at the access level of the
 network discussed here.
 The CMTS/ER should protect the ISP network and the other subscribers
 against attacks by one of its own customers.  For this reason Unicast
 Reverse Path Forwarding (uRPF) [RFC3704] and Access Control Lists
 (ACLs) should be used on all interfaces facing subscribers.
 Filtering should be implemented with regard for the operational
 requirements of IPv6 [IPv6-Security].
 The CMTS/ER should protect its processing resources against floods of
 valid customer control traffic such as: Router and Neighbor
 Solicitations, and MLD Requests.
 All other security features used with the IPv4 service should be
 similarly applied to IPv6 as well.

5.2.6. IPv6 Network Management

 IPv6 can have many applications in cable networks.  MSOs can
 initially implement IPv6 on the control plane and use it to manage
 the thousands of devices connected to the CMTS.  This would be a good
 way to introduce IPv6 in a cable network.  Later, the MSO can extend
 IPv6 to the data plane and use it to carry customer traffic as well
 as management traffic.

5.2.6.1. Using IPv6 for Management in Cable Networks

 IPv6 can be enabled in a cable network for management of devices like
 CM, CMTS, and ER.  With the rollout of advanced services like VoIP
 and Video-over-IP, MSOs are looking for ways to manage the large
 number of devices connected to the CMTS.  In IPv4, an RFC1918 address
 is assigned to these devices for management purposes.  Since there is
 a finite number of RFC1918 addresses available, it is becoming
 difficult for MSOs to manage these devices.

Asadullah, et al. Informational [Page 25] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 By using IPv6 for management purposes, MSOs can scale their network
 management systems to meet their needs.  The CMTS/ER can be
 configured with a /64 management prefix that is shared among all CMs
 connected to the CMTS cable interface.  Addressing for the CMs can be
 done via stateless auto-configuration or DHCPv6.  Once the CMs
 receive a /64 prefix, they can configure themselves with an IPv6
 address.
 If there are devices behind the CM that need to be managed by the
 MSO, another /64 prefix can be defined on the CMTS/ER.  These devices
 can also use stateless auto-configuration to assign themselves an
 IPv6 address.
 Traffic sourced from or destined to the management prefix should not
 cross the MSO's network boundaries.
 In this scenario, IPv6 will only be used for managing devices on the
 cable network.  The CM will no longer require an IPv4 address for
 management as described in DOCSIS 3.0 [DOCSIS3.0-Reqs].

5.2.6.2. Updates to MIB Modules/Standards to Support IPv6

 The current DOCSIS, PacketCable, and CableHome MIB modules are
 already designed to support IPv6 objects.  In this case, IPv6 will
 neither add nor change any of the functionality of these MIB modules.
 The Textual Convention used to represent Structure of Management
 Information Version 2 (SMIv2) objects representing IP addresses was
 updated [RFC4001] and a new Textual Convention InetAddressType was
 added to identify the type of the IP address used for IP address
 objects in MIB modules.
 There are some exceptions; the MIB modules that might need to add
 IPv6 support are defined in the DOCSIS 3.0 OSSI specification
 [DOCSIS3.0-OSSI].

6. Broadband DSL Networks

 This section describes the IPv6 deployment options in today's high-
 speed DSL networks.

6.1. DSL Network Elements

 Digital Subscriber Line (DSL) broadband services provide users with
 IP connectivity over the existing twisted-pair telephone lines called
 the local-loop.  A wide range of bandwidth offerings are available
 depending on the quality of the line and the distance between the
 Customer Premise Equipment and the DSL Access Multiplexer (DSLAM).

Asadullah, et al. Informational [Page 26] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The following network elements are typical of a DSL network:
 DSL Modem: It can be a stand-alone device, be incorporated in the
 host, incorporate router functionalities, and also have the
 capability to act as a CPE router.
 Customer Premise Router (CPR): It is used to provide Layer 3 services
 for customer premise networks.  It is usually used to provide
 firewalling functions and segment broadcast domains for a small
 business.
 DSL Access Multiplexer (DSLAM): It terminates multiple twisted-pair
 telephone lines and provides aggregation to BRAS.
 Broadband Remote Access Server (BRAS): It aggregates or terminates
 multiple Permanent Virtual Circuits (PVCs) corresponding to the
 subscriber DSL circuits.
 Edge Router (ER): It provides the Layer 3 interface to the ISP
 network.
 Figure 6.1 depicts all the network elements mentioned.
 Customer Premise | Network Access Provider | Network Service Provider
        CP                     NAP                        NSP
 +-----+  +------+                +------+   +--------+
 |Hosts|--|Router|             +--+ BRAS +---+ Edge   |      ISP
 +-----+  +--+---+             |  |      |   | Router +==> Network
             |                 |  +------+   +--------+
          +--+---+             |
          | DSL  +-+           |
          |Modem | |           |
          +------+ |  +-----+  |
                   +--+     |  |
          +------+    |DSLAM+--+
 +-----+  | DSL  | +--+     |
 |Hosts|--+Modem +-+  +-----+
 +-----+  +--+---+
                                 Figure 6.1

Asadullah, et al. Informational [Page 27] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

6.2. Deploying IPv6 in IPv4 DSL Networks

 There are three main design approaches to providing IPv4 connectivity
 over a DSL infrastructure:
 1.  Point-to-Point Model: Each subscriber connects to the DSLAM over
     a twisted pair and is provided with a unique PVC that links it to
     the service provider.  The PVCs can be terminated at the BRAS or
     at the Edge Router.  This type of design is not very scalable if
     the PVCs are not terminated as close as possible to the DSLAM (at
     the BRAS).  In this case, a large number of Layer 2 circuits has
     to be maintained over a significant portion of the network.  The
     Layer 2 domains can be terminated at the ER in three ways:
     A.  In a common bridge group with a virtual interface that routes
         traffic out.
     B.  By enabling a Routed Bridged Encapsulation feature, all users
         could be part of the same subnet.  This is the most common
         deployment approach of IPv4 over DSL but it might not be the
         best choice in IPv6 where address availability is not an
         issue.
     C.  By terminating the PVC at Layer 3, each PVC has its own
         prefix.  This is the approach that seems more suitable for
         IPv6 and is presented in Section 6.2.1.
         None of these ways requires that the CPE (DSL modem) be
         upgraded.
 2.  PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
     between each subscriber and the BRAS.  The BRAS terminates the
     PPP sessions and provides Layer 3 connectivity between the
     subscriber and the ISP.  This model is presented in Section
     6.2.2.
 3.  Layer 2 Tunneling Protocol (L2TP) Access Aggregation (LAA) Model:
     PPP sessions are opened between each subscriber and the ISP Edge
     Router.  The BRAS tunnels the subscriber PPP sessions to the ISP
     by encapsulating them into L2TPv2 [RFC2661] tunnels.  This model
     is presented in Section 6.2.3.
 In aggregation models, the BRAS terminates the subscriber PVCs and
 aggregates their connections before providing access to the ISP.
 In order to maintain the deployment concepts and business models
 proven and used with existing revenue generating IPv4 services, the
 IPv6 deployment will match the IPv4 one.  This approach is presented

Asadullah, et al. Informational [Page 28] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 in Sections 6.2.1 - 6.2.3 that describe current IPv4 over DSL
 broadband access deployments.  Under certain circumstances where new
 service types or service needs justify it, IPv4 and IPv6 network
 logical architectures could be different as described in Section
 6.2.4.

6.2.1. Point-to-Point Model

 In this scenario, the Ethernet frames from the Host or the Customer
 Premise Router are bridged over the PVC assigned to the subscriber.
 Figure 6.2.1 describes the protocol architecture of this model.
      Customer Premise               NAP                 NSP
 |-------------------------|  |---------------| |------------------|
 +-----+  +-------+  +-----+  +--------+        +----------+
 |Hosts|--+Router +--+ DSL +--+ DSLAM  +--------+   Edge   |     ISP
 +-----+  +-------+  |Modem|  +--------+        |  Router  +=>Network
                     +-----+                    +----------+
                         |----------------------------|
                                    ATM
                                Figure 6.2.1

6.2.1.1. IPv6 Related Infrastructure Changes

 In this scenario, the DSL modem and the entire NAP is Layer 3
 unaware, so no changes are needed to support IPv6.  The following
 devices have to be upgraded to dual stack: Host, Customer Router (if
 present), and Edge Router.

6.2.1.2. Addressing

 The Hosts or the Customer Routers have the Edge Router as their Layer
 3 next hop.
 If there is no Customer Router, all the hosts on the subscriber site
 belong to the same /64 subnet that is statically configured on the
 Edge Router for that subscriber PVC.  The hosts can use stateless
 auto-configuration or stateful DHCPv6-based configuration to acquire
 an address via the Edge Router.
 However, as manual configuration for each customer is a provisioning
 challenge, implementers are encouraged to develop mechanism(s) that
 automatically map the PVC (or some other customer-specific
 information) to an IPv6 subnet prefix, and advertise the customer-
 specific prefix to all the customers with minimal configuration.

Asadullah, et al. Informational [Page 29] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 If a Customer Router is present:
 A.  It is statically configured with an address on the /64 subnet
     between itself and the Edge Router, and with /64 prefixes on the
     interfaces connecting the hosts on the customer site.  This is
     not a desired provisioning method being expensive and difficult
     to manage.
 B.  It can use its link-local address to communicate with the ER.  It
     can also dynamically acquire, through stateless auto-
     configuration, the prefix for the link between itself and the ER.
     The later option allows it to contact a remote DHCPv6 server, if
     needed.  This step is followed by a request via DHCP-PD for a
     prefix shorter than /64 that, in turn, is divided in /64s and
     assigned to its downstream interfaces.
 The Edge Router has a /64 prefix configured for each subscriber PVC.
 Each PVC should be enabled to relay DHCPv6 requests from the
 subscribers to DHCPv6 servers in the ISP network.  The PVCs providing
 access for subscribers that use DHCP-PD as well, have to be enabled
 to support the feature.  The uplink to the ISP network is configured
 with a /64 prefix as well.
 The prefixes used for subscriber links and the ones delegated via
 DHCP-PD should be planned in a manner that allows as much
 summarization as possible at the Edge Router.
 Other information of interest to the host, such as DNS, is provided
 through stateful DHCPv6 [RFC3315] and stateless DHCPv6 [RFC3736].

6.2.1.3. Routing

 The CPE devices are configured with a default route that points to
 the Edge Router.  No routing protocols are needed on these devices,
 which generally have limited resources.
 The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
 The connected prefixes have to be redistributed.  If DHCP-PD is used,
 with every delegated prefix a static route is installed by the Edge
 Router.  For this reason, the static routes must also be
 redistributed.  Prefix summarization should be done at the Edge
 Router.

6.2.2. PPP Terminated Aggregation (PTA) Model

 The PTA architecture relies on PPP-based protocols (PPPoA [RFC2364]
 and PPPoE [RFC2516]).  The PPP sessions are initiated by Customer
 Premise Equipment and are terminated at the BRAS.  The BRAS

Asadullah, et al. Informational [Page 30] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 authorizes the session, authenticates the subscriber, and provides an
 IP address on behalf of the ISP.  The BRAS then does Layer 3 routing
 of the subscriber traffic to the NSP Edge Router.
 When the NSP is also the NAP, the BRAS and NSP Edge Router could be
 the same piece of equipment and provide the above mentioned
 functionality.
 There are two types of PPP encapsulations that can be leveraged with
 this model:
 A. Connection using PPPoA
   Customer Premise               NAP                   NSP
 |--------------------| |----------------------| |----------------|
                                                 +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----------+
 +-----+  +-------+      +--------+ +----+-----+ +-----------+
 |Hosts|--+Router +------+ DSLAM  +-+   BRAS   +-+    Edge   |
 +-----+  +-------+      +--------+ +----------+ |   Router  +=>Core
              |--------------------------|       +-----------+
                           PPP
                            Figure 6.2.2.1
 The PPP sessions are initiated by the Customer Premise Equipment.
 The BRAS authenticates the subscriber against a local or a remote
 database.  Once the session is established, the BRAS provides an
 address and maybe a DNS server to the user; this information is
 acquired from the subscriber profile or from a DHCP server.
 This solution scales better then the Point-to-Point, but since there
 is only one PPP session per ATM PVC, the subscriber can choose a
 single ISP service at a time.

Asadullah, et al. Informational [Page 31] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 B. Connection using PPPoE
        Customer Premise               NAP                 NSP
 |--------------------------| |-------------------| |---------------|
                                                       +-----------+
                                                       |    AAA    |
                                               +-------+   Radius  |
                                               |       |   TACACS  |
                                               |       +-----------+
                                               |
 +-----+  +-------+           +--------+ +-----+----+ +-----------+
 |Hosts|--+Router +-----------+ DSLAM  +-+   BRAS   +-+    Edge   |  C
 +-----+  +-------+           +--------+ +----------+ |   Router  +=>O
                                                      |           |  R
             |--------------------------------|       +-----------+  E
                            PPP
                              Figure 6.2.2.2
 The operation of PPPoE is similar to PPPoA with the exception that
 with PPPoE multiple sessions can be supported over the same PVC, thus
 allowing the subscriber to connect to multiple services at the same
 time.  The hosts can initiate the PPPoE sessions as well.  It is
 important to remember that the PPPoE encapsulation reduces the IP MTU
 available for the customer traffic due to additional headers.
 The network design and operation of the PTA model is the same,
 regardless of the PPP encapsulation type used.

6.2.2.1. IPv6 Related Infrastructure Changes

 In this scenario the BRAS is Layer 3 aware and it has to be upgraded
 to support IPv6.  Since the BRAS terminates the PPP sessions it has
 to support the implementation of these PPP protocols with IPv6.  The
 following devices have to be upgraded to dual stack: Host, Customer
 Router (if present), BRAS, and Edge Router.

6.2.2.2. Addressing

 The BRAS terminates the PPP sessions and provides the subscriber with
 an IPv6 address from the defined pool for that profile.  The
 subscriber profile for authorization and authentication can be
 located on the BRAS or on an Authentication, Authorization, and
 Accounting (AAA) server.  The Hosts or the Customer Routers have the
 BRAS as their Layer 3 next hop.

Asadullah, et al. Informational [Page 32] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The PPP session can be initiated by a host or by a Customer Router.
 In the latter case, once the session is established with the BRAS and
 an address is negotiated for the uplink to the BRAS, DHCP-PD can be
 used to acquire prefixes for the Customer Router other interfaces.
 The BRAS has to be enabled to support DHCP-PD and to relay the DHCPv6
 requests of the hosts on the subscriber sites.
 The BRAS has /64 prefixes configured on the link to the Edge router.
 The Edge Router links are also configured with /64 prefixes to
 provide connectivity to the rest of the ISP network.
 The prefixes used for subscribers and the ones delegated via DHCP-PD
 should be planned in a manner that allows maximum summarization at
 the BRAS.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

6.2.2.3. Routing

 The CPE devices are configured with a default route that points to
 the BRAS router.  No routing protocols are needed on these devices,
 which generally have limited resources.
 The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
 addresses assigned to the PPP sessions are represented as connected
 host routes, connected prefixes have to be redistributed.  If DHCP-PD
 is used, with every delegated prefix a static route is installed by
 the Edge Router.  For this reason, the static routes must also be
 redistributed.  Prefix summarization should be done at the BRAS.
 The Edge Router is running the IGP used in the ISP network: OSPFv3 or
 IS-IS.
 A separation between the routing domains of the ISP and the Access
 Provider is recommended if they are managed independently.
 Controlled redistribution will be needed between the Access Provider
 IGP and the ISP IGP.

6.2.3. L2TPv2 Access Aggregation (LAA) Model

 In the LAA model, the BRAS forwards the CPE initiated session to the
 ISP over an L2TPv2 tunnel established between the BRAS and the Edge
 Router.  In this case, the authentication, authorization, and
 subscriber configuration are performed by the ISP itself.  There are
 two types of PPP encapsulations that can be leveraged with this
 model:

Asadullah, et al. Informational [Page 33] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 A. Connection via PPPoA
   Customer Premise              NAP                    NSP
 |--------------------| |----------------------| |----------------|
                                                 +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----+-----+
                                         |             |
 +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
 |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
 +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                 +-----------+
              |----------------------------------------|
                                 PPP
                                          |------------|
                                               L2TPv2
                         Figure 6.2.3.1
 B. Connection via PPPoE
       Customer Premise                NAP                   NSP
 |--------------------------| |--------------------| |---------------|
                                                      +-----------+
                                                      |    AAA    |
                                               +------+   Radius  |
                                               |      |   TACACS  |
                                               |      +-----+-----+
                                               |            |
 +-----+  +-------+           +--------+ +----+-----+ +----+------+
 |Hosts|--+Router +-----------+ DSLAM  +-+  BRAS    +-+    Edge   |  C
 +-----+  +-------+           +--------+ +----------+ |   Router  +=>O
                                                      |           |  R
                                                      +-----------+  E
             |-----------------------------------------------|
                                     PPP
                                              |--------------|
                                                    L2TPv2
                           Figure 6.2.3.2
 The network design and operation of the PTA model is the same,
 regardless of the PPP encapsulation type used.

Asadullah, et al. Informational [Page 34] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

6.2.3.1. IPv6 Related Infrastructure Changes

 In this scenario, the BRAS is forwarding the PPP sessions initiated
 by the subscriber over the L2TPv2 tunnel established to the L2TP
 Network Server (LNS), the aggregation point in the ISP network.  The
 L2TPv2 tunnel between the L2TP Access Concentrator (LAC) and LNS can
 run over IPv6 or IPv4.  These capabilities have to be supported on
 the BRAS.  The following devices have to be upgraded to dual stack:
 Host, Customer Router, and Edge Router.  If the tunnel is set up over
 IPv6, then the BRAS must be upgraded to dual stack.

6.2.3.2. Addressing

 The Edge Router terminates the PPP sessions and provides the
 subscriber with an IPv6 address from the defined pool for that
 profile.  The subscriber profile for authorization and authentication
 can be located on the Edge Router or on an AAA server.  The Hosts or
 the Customer Routers have the Edge Router as their Layer 3 next hop.
 The PPP session can be initiated by a host or by a Customer Router.
 In the latter case, once the session is established with the Edge
 Router, DHCP-PD can be used to acquire prefixes for the Customer
 Router interfaces.  The Edge Router has to be enabled to support
 DHCP-PD and to relay the DHCPv6 requests generated by the hosts on
 the subscriber sites.
 The BRAS has a /64 prefix configured on the link to the Edge Router.
 The Edge Router links are also configured with /64 prefixes to
 provide connectivity to the rest of the ISP network.  Other
 information of interest to the host, such as DNS, is provided through
 stateful [RFC3315] and stateless [RFC3736] DHCPv6.
 It is important to note here a significant difference between this
 deployment for IPv6 versus IPv4.  In the case of IPv4, the customer
 router or CPE can end up on any Edge Router (acting as LNS), where
 the assumption is that there are at least two of them for redundancy
 purposes.  Once authenticated, the customer will be given an address
 from the IP pool of the ER (LNS) it connected to.  This allows the
 ERs (LNSs) to aggregate the addresses handed out to the customers.
 In the case of IPv6, an important constraint that likely will be
 enforced is that the customer should keep its own address, regardless
 of the ER (LNS) it connects to.  This could significantly reduce the
 prefix aggregation capabilities of the ER (LNS).  This is different
 than the current IPv4 deployment where addressing is dynamic in
 nature, and the same user can get different addresses depending on
 the LNS it ends up connecting to.

Asadullah, et al. Informational [Page 35] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 One possible solution is to ensure that a given BRAS will always
 connect to the same ER (LNS) unless that LNS is down.  This means
 that customers from a given prefix range will always be connected to
 the same ER (primary, if up, or secondary, if not).  Each ER (LNS)
 can carry summary statements in their routing protocol configuration
 for the prefixes for which they are the primary ER (LNS), as well as
 for the ones for which they are the secondary.  This way the prefixes
 will be summarized any time they become "active" on the ER (LNS).

6.2.3.3. Routing

 The CPE devices are configured with a default route that points to
 the Edge Router that terminates the PPP sessions.  No routing
 protocols are needed on these devices, which generally have limited
 resources.
 The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
 Different processes should be used if the NAP and the NSP are managed
 by different organizations.  In this case, controlled redistribution
 should be enabled between the two domains.
 The Edge Router is running the IPv6 IGP used in the ISP network:
 OSPFv3 or IS-IS.

6.2.4. Hybrid Model for IPv4 and IPv6 Service

 It was recommended throughout this section that the IPv6 service
 implementation should map the existing IPv4 one.  This approach
 simplifies manageability and minimizes training needed for personnel
 operating the network.  In certain circumstances such mapping is not
 feasible.  This typically becomes the case when a Service Provider
 plans to expand its service offering with the new IPv6 deployed
 infrastructure.  If this new service is not well supported in a
 network design such as the one used for IPv4, then a different design
 might be used for IPv6.
 An example of such circumstances is that of a provider using an LAA
 design for its IPv4 services.  In this case all the PPP sessions are
 bundled and tunneled across the entire NAP infrastructure which is
 made of multiple BRAS routers, aggregation routers etc.  The end
 point of these tunnels is the ISP Edge Router.  If the provider
 decides to offer multicast services over such a design, it will face
 the problem of NAP resources being over utilized.  The multicast
 traffic can be replicated only at the end of the tunnels by the Edge
 Router and the copies for all the subscribers are carried over the
 entire NAP.

Asadullah, et al. Informational [Page 36] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 A Modified Point-to-Point (as described in Section 6.2.4.2) or PTA
 model is more suitable to support multicast services because the
 packet replication can be done closer to the destination at the BRAS.
 Such topology saves NAP resources.
 In this sense, IPv6 deployment can be viewed as an opportunity to
 build an infrastructure that might better support the expansion of
 services.  In this case, an SP using the LAA design for its IPv4
 services might choose a modified Point-to-Point or PTA design for
 IPv6.

6.2.4.1. IPv4 in LAA Model and IPv6 in PTA Model

 The coexistence of the two PPP-based models, PTA and LAA, is
 relatively straightforward.  The PPP sessions are terminated on
 different network devices for the IPv4 and IPv6 services.  The PPP
 sessions for the existing IPv4 service deployed in an LAA model are
 terminated on the Edge Router.  The PPP sessions for the new IPv6
 service deployed in a PTA model are terminated on the BRAS.
 The logical design for IPv6 and IPv4 in this hybrid model is
 presented in Figure 6.2.4.1.
 IPv6          |--------------------------|
                          PPP                    +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----+-----+
                                         |             |
 +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
 |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
 +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                 +-----------+
 IPv4          |----------------------------------------|
                                 PPP
                                          |------------|
                                               L2TPv2
                           Figure 6.2.4.1

6.2.4.2. IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

 In this particular scenario the Point-to-Point model used for the
 IPv6 service is a modified version of the model described in section
 6.2.1.

Asadullah, et al. Informational [Page 37] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 For the IPv4 service in the LAA model, the PVCs are terminated on the
 BRAS and PPP sessions are terminated on the Edge Router (LNS).  For
 IPv6 service in the Point-to-Point model, the PVCs are terminated at
 the Edge Router as described in Section 6.2.1.  In this hybrid model,
 the Point-to-Point link could be terminated on the BRAS, a NAP-owned
 device.  The IPv6 traffic is then routed through the NAP network to
 the NSP.  In order to have this hybrid model, the BRAS has to be
 upgraded to a dual-stack router.  The functionalities of the Edge
 Router, as described in Section 6.2.1, are now implemented on the
 BRAS.
 The other aspect of this deployment model is the fact that the BRAS
 has to be capable of distinguishing between the IPv4 PPP traffic that
 has to be bridged across the L2TPv2 tunnel and the IPv6 packets that
 have to be routed to the NSP.  The IPv6 Routing and Bridging
 Encapsulation (RBE) has to be enabled on all interfaces with PVCs
 supporting both IPv4 and IPv6 services in this hybrid design.
 The logical design for IPv6 and IPv4 in this hybrid model is
 presented in Figure 6.2.4.2.
 IPv6              |----------------|
                          ATM                    +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----+-----+
                                         |             |
 +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
 |Hosts|--+Router +------+ DSLAM  +-+  BRAS    +-+   Edge    |
 +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                 +-----------+
 IPv4          |----------------------------------------|
                                 PPP
                                          |------------|
                                               L2TPv2
                           Figure 6.2.4.2

6.3. IPv6 Multicast

 The deployment of IPv6 multicast services relies on MLD, identical to
 IGMP in IPv4 and on PIM for routing.  ASM (Any Source Multicast) and
 SSM (Single Source Multicast) service models operate almost the same
 as in IPv4.  Both have the same benefits and disadvantages as in
 IPv4.  Nevertheless, the larger address space and the scoped address
 architecture provide major benefits for multicast IPv6.  Through RFC
 3306, the large address space provides the means to assign global

Asadullah, et al. Informational [Page 38] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 multicast group addresses to organizations or users that were
 assigned unicast prefixes.  It is a significant improvement with
 respect to the IPv4 GLOP mechanism [RFC3180].
 This facilitates the deployment of multicast services.  The
 discussion of this section applies to all the multicast sections in
 the document.

6.3.1. ASM-Based Deployments

 Any Source Multicast (ASM) is useful for Service Providers that
 intend to support the forwarding of multicast traffic of their
 customers.  It is based on the Protocol Independent Multicast -
 Sparse Mode (PIM-SM) protocol and it is more complex to manage
 because of the use of Rendezvous Points (RPs).  With IPv6, static RP
 and Bootstrap Router [BSR] can be used for RP-to-group mapping
 similar to IPv4.  Additionally, the larger IPv6 address space allows
 for building up of group addresses that incorporate the address of
 the RP.  This RP-to-group mapping mechanism is called Embedded RP and
 is specific to IPv6.
 In inter-domain deployments, Multicast Source Discovery Protocol
 (MSDP) [RFC3618] is an important element of IPv4 PIM-SM deployments.
 MSDP is meant to be a solution for the exchange of source
 registration information between RPs in different domains.  This
 solution was intended to be temporary.  This is one of the reasons
 why it was decided not to implement MSDP in IPv6 [IPv6-Multicast].
 For multicast reachability across domains, Embedded RP can be used.
 As Embedded RP provides roughly the same capabilities as MSDP, but in
 a slightly different way, the best management practices for ASM
 multicast with embedded RP still remain to be developed.

6.3.2. SSM-Based Deployments

 Based on PIM-SSM, the Source-Specific Multicast deployments do not
 need an RP or related protocols (such as BSR or MSDP), but rely on
 the listeners to know the source of the multicast traffic they plan
 to receive.  The lack of RP makes SSM not only simpler to operate,
 but also robust; it is not impacted by RP failures or inter-domain
 constraints.  It also has a higher level of security (no RP to be
 targeted by attacks).  For more discussions on the topic of IPv6
 multicast, see [IPv6-Multicast].
 The typical multicast service offered for residential and very small
 businesses is video/audio streaming, where the subscriber joins a
 multicast group and receives the content.  This type of service model
 is well supported through PIM-SSM which is very simple and easy to

Asadullah, et al. Informational [Page 39] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 manage.  PIM-SSM has to be enabled throughout the SP network.  MLDv2
 is required for PIM-SSM support.  Vendors can choose to implement
 features that allow routers to map MLDv1 group joins to predefined
 sources.
 Subscribers might use a set-top box that is responsible for the
 control piece of the multicast service (does group joins/leaves).
 The subscriber hosts can also join desired multicast groups as long
 as they are enabled to support MLDv1 or MLDv2.  If a customer premise
 router is used, then it has to be enabled to support MLDv1 and MLDv2
 in order to process the requests of the hosts.  It has to be enabled
 to support PIM-SSM in order to send PIM joins/leaves up to its Layer
 3 next hop whether it is the BRAS or the Edge Router.  When enabling
 this functionality on a CPR, its limited resources should be taken
 into consideration.  Another option would be for the CPR to support
 MLD proxy routing.
 The router that is the Layer 3 next hop for the subscriber (BRAS in
 the PTA model or the Edge Router in the LAA and Point-to-Point model)
 has to be enabled to support MLDv1 and MLDv2 in order to process the
 requests coming from subscribers without CPRs.  It has to be enabled
 for PIM-SSM in order to receive joins/leaves from customer routers
 and send joins/leaves to the next hop towards the multicast source
 (Edge Router or the NSP core).
 MLD authentication, authorization and accounting are usually
 configured on the Edge Router in order to enable the ISP to control
 the subscriber access of the service and do billing for the content
 provided.  Alternative mechanisms that would support these functions
 should be investigated further.

6.4. IPv6 QoS

 The QoS configuration is particularly relevant on the router that
 represents the Layer 3 next hop for the subscriber (BRAS in the PTA
 model or the Edge Router in the LAA and Point-to-Point model) in
 order to manage resources shared amongst multiple subscribers,
 possibly with various service level agreements.
 In the DSL infrastructure, it is expected that there is already a
 level of traffic policing and shaping implemented for IPv4
 connectivity.  This is implemented throughout the NAP and is beyond
 the scope of this document.
 On the BRAS or the Edge Router, the subscriber-facing interfaces have
 to be configured to police the inbound customer traffic and shape the
 traffic outbound to the customer based on the service level
 agreements (SLAs).  Traffic classification and marking should also be

Asadullah, et al. Informational [Page 40] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 done on the router closest (at Layer 3) to the subscriber in order to
 support the various types of customer traffic (data, voice, and
 video) and to optimally use the infrastructure resources.  Each
 provider (NAP, NSP) could implement their own QoS policies and
 services so that reclassification and marking might be performed at
 the boundary between the NAP and the NSP, in order to make sure the
 traffic is properly handled by the ISP.  The same IPv4 QoS concepts
 and methodologies should be applied with IPv6 as well.
 It is important to note that when traffic is encrypted end-to-end,
 the traversed network devices will not have access to many of the
 packet fields used for classification purposes.  In these cases,
 routers will most likely place the packets in the default classes.
 The QoS design should take into consideration this scenario and try
 to use mainly IP header fields for classification purposes.

6.5. IPv6 Security Considerations

 There are limited changes that have to be done for CPEs in order to
 enhance security.  The privacy extensions for auto-configuration
 [RFC3041] should be used by the hosts.  ISPs can track the prefixes
 it assigns to subscribers relatively easily.  If, however, the ISPs
 are required by regulations to track their users at a /128 address
 level, the privacy extensions may be implemented in parallel with
 network management tools that could provide traceability of the
 hosts.  IPv6 firewall functions should be enabled on the hosts or
 CPR, if present.
 The ISP provides security against attacks that come from its own
 subscribers but it could also implement security services that
 protect its subscribers from attacks sourced from the outside of its
 network.  Such services do not apply at the access level of the
 network discussed here.
 The device that is the Layer 3 next hop for the subscribers (BRAS or
 Edge Router) should protect the network and the other subscribers
 against attacks by one of the provider customers.  For this reason,
 uRPF and ACLs should be used on all interfaces facing subscribers.
 Filtering should be implemented with regard for the operational
 requirements of IPv6 [IPv6-Security].
 The BRAS and the Edge Router should protect their processing
 resources against floods of valid customer control traffic such as:
 Router and Neighbor Solicitations, and MLD Requests.  Rate limiting
 should be implemented on all subscriber-facing interfaces.  The
 emphasis should be placed on multicast-type traffic, as it is most
 often used by the IPv6 control plane.

Asadullah, et al. Informational [Page 41] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 All other security features used with the IPv4 service should be
 similarly applied to IPv6 as well.

6.6. IPv6 Network Management

 The necessary instrumentation (such as MIB modules, NetFlow Records,
 etc.) should be available for IPv6.
 Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
 can be done over IPv4 if all managed devices have connectivity over
 both IPv4 and IPv6.  This would imply the smallest changes to the
 existing network management practices and processes.  Transport over
 IPv6 could also be implemented, and it might become necessary if IPv6
 only islands are present in the network.  The management applications
 may be running on hosts belonging to the NSP core network domain.
 Network Management Applications should handle IPv6 in a similar
 fashion to IPv4; however, they should also support features specific
 to IPv6 (such as neighbor monitoring).
 In some cases, service providers manage equipment located on
 customers' LANs.  The management of equipment at customers' LANs is
 out of scope of this memo.

7. Broadband Ethernet Networks

 This section describes the IPv6 deployment options in currently
 deployed Broadband Ethernet Access Networks.

7.1. Ethernet Access Network Elements

 In environments that support the infrastructure deploying RJ-45 or
 fiber (Fiber to the Home (FTTH) service) to subscribers, 10/100 Mbps
 Ethernet broadband services can be provided.  Such services are
 generally available in metropolitan areas in multi-tenant buildings
 where an Ethernet infrastructure can be deployed in a cost-effective
 manner.  In such environments, Metro-Ethernet services can be used to
 provide aggregation and uplink to a Service Provider.
 The following network elements are typical of an Ethernet network:
 Access Switch: It is used as a Layer 2 access device for subscribers.
 Customer Premise Router: It is used to provide Layer 3 services for
 customer premise networks.
 Aggregation Ethernet Switches: Aggregates multiple subscribers.
 Broadband Remote Access Server (BRAS)

Asadullah, et al. Informational [Page 42] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 Edge Router (ER)
 Figure 7.1 depicts all the network elements mentioned.
 Customer Premise | Network Access Provider | Network Service Provider
        CP                     NAP                        NSP
 +-----+  +------+                +------+  +--------+
 |Hosts|--|Router|              +-+ BRAS +--+ Edge   |       ISP
 +-----+  +--+---+              | |      |  | Router +===> Network
             |                  | +------+  +--------+
          +--+----+             |
          |Access +-+           |
          |Switch | |           |
          +-------+ |  +------+ |
                    +--+Agg E | |
          +-------+    |Switch+-+
 +-----+  |Access | +--+      |
 |Hosts|--+Switch +-+  +------+
 +-----+  +-------+
                                Figure 7.1
 The logical topology and design of Broadband Ethernet Networks are
 very similar to DSL Broadband Networks discussed in Section 6.
 It is worth noting that the general operation, concepts and
 recommendations described in this section apply similarly to a
 HomePNA-based network environment.  In such an environment, some of
 the network elements might be differently named.

7.2. Deploying IPv6 in IPv4 Broadband Ethernet Networks

 There are three main design approaches to providing IPv4 connectivity
 over an Ethernet infrastructure:
 A.  Point-to-Point Model: Each subscriber connects to the network
     Access switch over RJ-45 or fiber links.  Each subscriber is
     assigned a unique VLAN on the access switch.  The VLAN can be
     terminated at the BRAS or at the Edge Router.  The VLANs are
     802.1Q trunked to the Layer 3 device (BRAS or Edge Router).
     This model is presented in Section 7.2.1.

Asadullah, et al. Informational [Page 43] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 B.  PPP Terminated Aggregation (PTA) Model: PPP sessions are opened
     between each subscriber and the BRAS.  The BRAS terminates the
     PPP sessions and provides Layer 3 connectivity between the
     subscriber and the ISP.
     This model is presented in Section 7.2.2.
 C.  L2TPv2 Access Aggregation (LAA) Model: PPP sessions are opened
     between each subscriber and the ISP termination devices.  The
     BRAS tunnels the subscriber PPP sessions to the ISP by
     encapsulating them into L2TPv2 tunnels.
     This model is presented in Section 7.2.3.
 In aggregation models the BRAS terminates the subscriber VLANs and
 aggregates their connections before providing access to the ISP.
 In order to maintain the deployment concepts and business models
 proven and used with existing revenue generating IPv4 services, the
 IPv6 deployment will match the IPv4 one.  This approach is presented
 in Sections 7.2.1 - 7.2.3 that describe currently deployed IPv4 over
 Ethernet broadband access deployments.  Under certain circumstances
 where new service types or service needs justify it, IPv4 and IPv6
 network architectures could be different as described in Section
 7.2.4.

7.2.1. Point-to-Point Model

 In this scenario, the Ethernet frames from the Host or the Customer
 Premise Router are bridged over the VLAN assigned to the subscriber.
 Figure 7.2.1 describes the protocol architecture of this model.
 |   Customer Premise     |  |       NAP       |        NSP         |
 +-----+  +------+  +------+  +--------+        +----------+
 |Hosts|--+Router+--+Access+--+ Switch +--------+   Edge   |    ISP
 +-----+  +------+  |Switch|  +--------+ 802.1Q |  Router  +=>Network
                    +------+                    +----------+
                        |----------------------------|
                                Ethernet/VLANs
                               Figure 7.2.1

Asadullah, et al. Informational [Page 44] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

7.2.1.1. IPv6 Related Infrastructure Changes

 In this scenario, the Access Switch is on the customer site and the
 entire NAP is Layer 3 unaware, so no changes are needed to support
 IPv6.  The following devices have to be upgraded to dual stack: Host,
 Customer Router, and Edge Router.
 The Access switches might need upgrades to support certain IPv6-
 related features such as MLD Snooping.

7.2.1.2. Addressing

 The Hosts or the Customer Routers have the Edge Router as their Layer
 3 next hop.  If there is no Customer Router all the hosts on the
 subscriber site belong to the same /64 subnet that is statically
 configured on the Edge Router for that subscriber VLAN.  The hosts
 can use stateless auto-configuration or stateful DHCPv6-based
 configuration to acquire an address via the Edge Router.
 However, as manual configuration for each customer is a provisioning
 challenge, implementations are encouraged to develop mechanism(s)
 that automatically map the VLAN (or some other customer-specific
 information) to an IPv6 subnet prefix, and advertise the customer-
 specific prefix to all the customers with minimal configuration.
 If a Customer Router is present:
 A.  It is statically configured with an address on the /64 subnet
     between itself and the Edge Router, and with /64 prefixes on the
     interfaces connecting the hosts on the customer site.  This is
     not a desired provisioning method, being expensive and difficult
     to manage.
 B.  It can use its link-local address to communicate with the ER.  It
     can also dynamically acquire, through stateless auto-
     configuration, the address for the link between itself and the
     ER.  This step is followed by a request via DHCP-PD for a prefix
     shorter than /64 that in turn is divided in /64s and assigned to
     its interfaces connecting the hosts on the customer site.
 The Edge Router has a /64 prefix configured for each subscriber VLAN.
 Each VLAN should be enabled to relay DHCPv6 requests from the
 subscribers to DHCPv6 servers in the ISP network.  The VLANs
 providing access for subscribers that use DHCP-PD have to be enabled
 to support the feature.  The uplink to the ISP network is configured
 with a /64 prefix as well.

Asadullah, et al. Informational [Page 45] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The prefixes used for subscriber links and the ones delegated via
 DHCP-PD should be planned in a manner that allows as much
 summarization as possible at the Edge Router.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

7.2.1.3. Routing

 The CPE devices are configured with a default route that points to
 the Edge Router.  No routing protocols are needed on these devices,
 which generally have limited resources.
 The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
 The connected prefixes have to be redistributed.  If DHCP-PD is used,
 with every delegated prefix a static route is installed by the Edge
 Router.  For this reason, the static routes must also be
 redistributed.  Prefix summarization should be done at the Edge
 Router.

7.2.2. PPP Terminated Aggregation (PTA) Model

 The PTA architecture relies on PPP-based protocols (PPPoE).  The PPP
 sessions are initiated by Customer Premise Equipment and are
 terminated at the BRAS.  The BRAS authorizes the session,
 authenticates the subscriber, and provides an IP address on behalf of
 the ISP.  The BRAS then does Layer 3 routing of the subscriber
 traffic to the NSP Edge Router.
 When the NSP is also the NAP, the BRAS and NSP Edge Router could be
 the same piece of equipment and provide the above mentioned
 functionality.
 The PPPoE logical diagram in an Ethernet Broadband Network is shown
 in Fig 7.2.2.1.

Asadullah, et al. Informational [Page 46] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 |     Customer Premise      | |       NAP       | |      NSP       |
                                                      +-----------+
                                                      |    AAA    |
                                              +-------+   Radius  |
                                              |       |   TACACS  |
                                              |       +-----------+
 +-----+ +-------+ +--------+ +--------+ +----+-----+ +-----------+
 |Hosts|-+Router +-+A Switch+-+ Switch +-+   BRAS   +-+    Edge   |  C
 +-----+ +-------+ +--------+ +--------+ +----------+ |   Router  +=>O
      |----------------  PPP ----------------|        |           |  R
                                                      +-----------+  E
                             Figure 7.2.2.1
 The PPP sessions are initiated by the Customer Premise Equipment
 (Host or Router).  The BRAS authenticates the subscriber against a
 local or remote database.  Once the session is established, the BRAS
 provides an address and maybe a DNS server to the user; this
 information is acquired from the subscriber profile or a DHCP server.
 This model allows for multiple PPPoE sessions to be supported over
 the same VLAN, thus allowing the subscriber to connect to multiple
 services at the same time.  The hosts can initiate the PPPoE sessions
 as well.  It is important to remember that the PPPoE encapsulation
 reduces the IP MTU available for the customer traffic.

7.2.2.1. IPv6 Related Infrastructure Changes

 In this scenario, the BRAS is Layer 3 aware and has to be upgraded to
 support IPv6.  Since the BRAS terminates the PPP sessions, it has to
 support PPPoE with IPv6.  The following devices have to be upgraded
 to dual stack: Host, Customer Router (if present), BRAS and Edge
 Router.

7.2.2.2. Addressing

 The BRAS terminates the PPP sessions and provides the subscriber with
 an IPv6 address from the defined pool for that profile.  The
 subscriber profile for authorization and authentication can be
 located on the BRAS, or on an AAA server.  The Hosts or the Customer
 Routers have the BRAS as their Layer 3 next hop.
 The PPP session can be initiated by a host or by a Customer Router.
 In the latter case, once the session is established with the BRAS,
 DHCP-PD can be used to acquire prefixes for the Customer Router
 interfaces.  The BRAS has to be enabled to support DHCP-PD and to
 relay the DHCPv6 requests of the hosts on the subscriber sites.

Asadullah, et al. Informational [Page 47] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The BRAS has a /64 prefix configured on the link facing the Edge
 router.  The Edge Router links are also configured with /64 prefixes
 to provide connectivity to the rest of the ISP network.
 The prefixes used for subscribers and the ones delegated via DHCP-PD
 should be planned in a manner that allows maximum summarization at
 the BRAS.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

7.2.2.3. Routing

 The CPE devices are configured with a default route that points to
 the BRAS router.  No routing protocols are needed on these devices,
 which generally have limited resources.
 The BRAS runs an IGP to the Edge Router: OSPFv3 or IS-IS.  Since the
 addresses assigned to the PPP sessions are represented as connected
 host routes, connected prefixes have to be redistributed.  If DHCP-PD
 is used, with every delegated prefix a static route is installed by
 the BRAS.  For this reason, the static routes must also be
 redistributed.  Prefix summarization should be done at the BRAS.
 The Edge Router is running the IGP used in the ISP network: OSPFv3 or
 IS-IS.  A separation between the routing domains of the ISP and the
 Access Provider is recommended if they are managed independently.
 Controlled redistribution will be needed between the Access Provider
 IGP and the ISP IGP.

7.2.3. L2TPv2 Access Aggregation (LAA) Model

 In the LAA model, the BRAS forwards the CPE initiated session to the
 ISP over an L2TPv2 tunnel established between the BRAS and the Edge
 Router.  In this case, the authentication, authorization, and
 subscriber configuration are performed by the ISP itself.

Asadullah, et al. Informational [Page 48] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 | Customer Premise   | |         NAP          | |       NSP       |
                                                     +-----------+
                                                     |    AAA    |
                                              +------+   Radius  |
                                              |      |   TACACS  |
                                              |      +-----+-----+
                                              |            |
 +-----+ +-------+ +--------+ +--------+ +----+-----+ +-----------+
 |Hosts|-+Router +-+A Switch+-+ Switch +-+   BRAS   +-+    Edge   |  C
 +-----+ +-------+ +--------+ +--------+ +----------+ |   Router  +=>O
                                                      |           |  R
                                                      +-----------+  E
             |-----------------------------------------------|
                                     PPP
                                              |--------------|
                                                   L2TPv2
                              Figure 7.2.3.1

7.2.3.1. IPv6 Related Infrastructure Changes

 In this scenario, the BRAS is Layer 3 aware and has to be upgraded to
 support IPv6.  The PPP sessions initiated by the subscriber are
 forwarded over the L2TPv2 tunnel to the aggregation point in the ISP
 network.  The BRAS (LAC) can aggregate IPv6 PPP sessions and tunnel
 them to the LNS using L2TPv2.  The L2TPv2 tunnel between the LAC and
 LNS could run over IPv6 or IPv4.  These capabilities have to be
 supported on the BRAS.  The following devices have to be upgraded to
 dual stack: Host, Customer Router (if present), BRAS and Edge Router.

7.2.3.2. Addressing

 The Edge Router terminates the PPP sessions and provides the
 subscriber with an IPv6 address from the defined pool for that
 profile.  The subscriber profile for authorization and authentication
 can be located on the Edge Router or on an AAA server.  The Hosts or
 the Customer Routers have the Edge Router as their Layer 3 next hop.
 The PPP session can be initiated by a host or by a Customer Router.
 In the latter case, once the session is established with the Edge
 Router and an IPv6 address is assigned to the Customer Router by the
 Edge Router, DHCP-PD can be used to acquire prefixes for the Customer
 Router other interfaces.  The Edge Router has to be enabled to
 support DHCP-PD and to relay the DHCPv6 requests of the hosts on the
 subscriber sites.  The uplink to the ISP network is configured with a
 /64 prefix as well.

Asadullah, et al. Informational [Page 49] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The BRAS has a /64 prefix configured on the link to the Edge Router.
 The Edge Router links are also configured with /64 prefixes to
 provide connectivity to the rest of the ISP network.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.
 The address assignment and prefix summarization issues discussed in
 Section 6.2.3.2 are relevant in the same way for this media access
 type as well.

7.2.3.3. Routing

 The CPE devices are configured with a default route that points to
 the Edge Router that terminates the PPP sessions.  No routing
 protocols are needed on these devices, which have limited resources.
 The BRAS runs an IPv6 IGP to the Edge Router: OSPFv3 or IS-IS.
 Different processes should be used if the NAP and the NSP are managed
 by different organizations.  In this case, controlled redistribution
 should be enabled between the two domains.
 The Edge Router is running the IPv6 IGP used in the ISP network:
 OSPFv3 or IS-IS.

7.2.4. Hybrid Model for IPv4 and IPv6 Service

 It was recommended throughout this section that the IPv6 service
 implementation should map the existing IPv4 one.  This approach
 simplifies manageability and minimizes training needed for personnel
 operating the network.  In certain circumstances, such mapping is not
 feasible.  This typically becomes the case when a Service Provider
 plans to expand its service offering with the new IPv6 deployed
 infrastructure.  If this new service is not well supported in a
 network design such as the one used for IPv4, then a different design
 might be used for IPv6.
 An example of such circumstances is that of a provider using an LAA
 design for its IPv4 services.  In this case, all the PPP sessions are
 bundled and tunneled across the entire NAP infrastructure, which is
 made of multiple BRAS routers, aggregation routers, etc.  The end
 point of these tunnels is the ISP Edge Router.  If the SP decides to
 offer multicast services over such a design, it will face the problem
 of NAP resources being over-utilized.  The multicast traffic can be
 replicated only at the end of the tunnels by the Edge Router, and the
 copies for all the subscribers are carried over the entire NAP.

Asadullah, et al. Informational [Page 50] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 A Modified Point-to-Point (see Section 7.2.4.2) or a PTA model is
 more suitable to support multicast services because the packet
 replication can be done closer to the destination at the BRAS.  Such
 a topology saves NAP resources.
 In this sense, IPv6 deployments can be viewed as an opportunity to
 build an infrastructure that can better support the expansion of
 services.  In this case, an SP using the LAA design for its IPv4
 services might choose a modified Point-to-Point or PTA design for
 IPv6.

7.2.4.1. IPv4 in LAA Model and IPv6 in PTA Model

 The coexistence of the two PPP-based models, PTA and LAA, is
 relatively straightforward.  It is a straightforward overlap of the
 two deployment models.  The PPP sessions are terminated on different
 network devices for the IPv4 and IPv6 services.  The PPP sessions for
 the existing IPv4 service deployed in an LAA model are terminated on
 the Edge Router.  The PPP sessions for the new IPv6 service deployed
 in a PTA model are terminated on the BRAS.
 The logical design for IPv6 and IPv4 in this hybrid model is
 presented in Figure 7.2.4.1.
 IPv6          |--------------------------|
                          PPP                    +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----+-----+
                                         |             |
 +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
 |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
 +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                 +-----------+
 IPv4          |----------------------------------------|
                                 PPP
                                          |------------|
                                              L2TPv2
                          Figure 7.2.4.1

Asadullah, et al. Informational [Page 51] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

7.2.4.2. IPv4 in LAA Model and IPv6 in Modified Point-to-Point Model

 The coexistence of the modified Point-to-Point and the LAA models
 implies a few specific changes.
 For the IPv4 service in LAA model, the VLANs are terminated on the
 BRAS, and PPP sessions are terminated on the Edge Router (LNS).  For
 the IPv6 service in the Point-to-Point model, the VLANs are
 terminated at the Edge Router as described in Section 6.2.1.  In this
 hybrid model, the Point-to-Point link could be terminated on the
 BRAS, a NAP-owned device.  The IPv6 traffic is then routed through
 the NAP network to the NSP.  In order to have this hybrid model, the
 BRAS has to be upgraded to a dual-stack router.  The functionalities
 of the Edge Router, as described in Section 6.2.1, are now
 implemented on the BRAS.
 The logical design for IPv6 and IPv4 in this hybrid model is in
 Figure 7.2.4.2.
 IPv6              |----------------|
                         Ethernet
                                                 +-----------+
                                                 |    AAA    |
                                         +-------+   Radius  |
                                         |       |   TACACS  |
                                         |       +-----+-----+
                                         |             |
 +-----+  +-------+      +--------+ +----+-----+ +-----+-----+
 |Hosts|--+Router +------+ Switch +-+  BRAS    +-+   Edge    |
 +-----+  +-------+      +--------+ +----------+ |  Router   +=>Core
                                                 +-----------+
 IPv4          |----------------------------------------|
                                 PPP
                                           |------------|
                                               L2TPv2
                               Figure 7.2.4.2

7.3. IPv6 Multicast

 The typical multicast services offered for residential and very small
 businesses are video/audio streaming where the subscriber joins a
 multicast group and receives the content.  This type of service model
 is well supported through PIM-SSM, which is very simple and easy to
 manage.  PIM-SSM has to be enabled throughout the ISP network.  MLDv2
 is required for PIM-SSM support.  Vendors can choose to implement
 features that allow routers to map MLDv1 group joins to predefined
 sources.

Asadullah, et al. Informational [Page 52] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 Subscribers might use a set-top box that is responsible for the
 control piece of the multicast service (does group joins/leaves).
 The subscriber hosts can also join desired multicast groups as long
 as they are enabled to support MLDv1 or MLDv2.  If a CPR is used,
 then it has to be enabled to support MLDv1 and MLDv2 in order to
 process the requests of the hosts.  It has to be enabled to support
 PIM-SSM in order to send PIM joins/leaves up to its Layer 3 next hop
 whether it is the BRAS or the Edge Router.  When enabling this
 functionality on a CPR, its limited resources should be taken into
 consideration.  Another option would be for the CPR to support MLD
 proxy routing.  MLD snooping or similar Layer 2 multicast-related
 protocols could be enabled on the NAP switches.
 The router that is the Layer 3 next hop for the subscriber (BRAS in
 the PTA model or the Edge Router in the LAA and Point-to-Point model)
 has to be enabled to support MLDv1 and MLDv2 in order to process the
 requests coming from subscribers without CPRs.  It has to be enabled
 for PIM-SSM in order to receive joins/leaves from customer routers
 and send joins/leaves to the next hop towards the multicast source
 (Edge Router or the NSP core).
 MLD authentication, authorization, and accounting are usually
 configured on the edge router in order to enable the ISP to control
 the subscriber access of the service and do billing for the content
 provided.  Alternative mechanisms that would support these functions
 should be investigated further.
 Please refer to section 6.3 for more IPv6 multicast details.

7.4. IPv6 QoS

 The QoS configuration is particularly relevant on the router that
 represents the Layer 3 next hop for the subscriber (BRAS in the PTA
 model or the Edge Router in the LAA and Point-to-Point model) in
 order to manage resources shared amongst multiple subscribers,
 possibly with various service level agreements.
 On the BRAS or the Edge Router, the subscriber-facing interfaces have
 to be configured to police the inbound customer traffic and shape the
 traffic outbound to the customer based on the SLAs.  Traffic
 classification and marking should also be done on the router closest
 (at Layer 3) to the subscriber in order to support the various types
 of customer traffic: data, voice, video, and to optimally use the
 network resources.  This infrastructure offers a very good
 opportunity to leverage the QoS capabilities of Layer 2 devices.
 Diffserv-based QoS used for IPv4 should be expanded to IPv6.

Asadullah, et al. Informational [Page 53] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 Each provider (NAP, NSP) could implement their own QoS policies and
 services so that reclassification and marking might be performed at
 the boundary between the NAP and the NSP, in order to make sure the
 traffic is properly handled by the ISP.  The same IPv4 QoS concepts
 and methodologies should be applied for the IPv6 as well.
 It is important to note that when traffic is encrypted end-to-end,
 the traversed network devices will not have access to many of the
 packet fields used for classification purposes.  In these cases,
 routers will most likely place the packets in the default classes.
 The QoS design should take into consideration this scenario and try
 to use mainly IP header fields for classification purposes.

7.5. IPv6 Security Considerations

 There are limited changes that have to be done for CPEs in order to
 enhance security.  The privacy extensions [RFC3041] for auto-
 configuration should be used by the hosts with the same
 considerations for host traceability as discussed in Section 6.5.
 IPv6 firewall functions should be enabled on the hosts or Customer
 Premise Router, if present.
 The ISP provides security against attacks that come from its own
 subscribers, but it could also implement security services that
 protect its subscribers from attacks sourced from outside its
 network.  Such services do not apply at the access level of the
 network discussed here.
 If any Layer 2 filters for Ethertypes are in place, the NAP must
 permit the IPv6 Ethertype (0X86DD).
 The device that is the Layer 3 next hop for the subscribers (BRAS
 Edge Router) should protect the network and the other subscribers
 against attacks by one of the provider customers.  For this reason
 uRPF and ACLs should be used on all interfaces facing subscribers.
 Filtering should be implemented with regard for the operational
 requirements of IPv6 [IPv6-Security].
 The BRAS and the Edge Router should protect their processing
 resources against floods of valid customer control traffic such as:
 Router and Neighbor Solicitations, and MLD Requests.  Rate limiting
 should be implemented on all subscriber-facing interfaces.  The
 emphasis should be placed on multicast-type traffic, as it is most
 often used by the IPv6 control plane.
 All other security features used with the IPv4 service should be
 similarly applied to IPv6 as well.

Asadullah, et al. Informational [Page 54] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

7.6. IPv6 Network Management

 The necessary instrumentation (such as MIB modules, NetFlow Records,
 etc.) should be available for IPv6.
 Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
 can be done over IPv4 if all managed devices have connectivity over
 both IPv4 and IPv6.  This would imply the smallest changes to the
 existing network management practices and processes.  Transport over
 IPv6 could also be implemented and it might become necessary if IPv6
 only islands are present in the network.  The management applications
 may be running on hosts belonging to the NSP core network domain.
 Network Management Applications should handle IPv6 in a similar
 fashion to IPv4; however, they should also support features specific
 to IPv6 such as neighbor monitoring.
 In some cases, service providers manage equipment located on
 customers' LANs.

8. Wireless LAN

 This section provides a detailed description of IPv6 deployment and
 integration methods in currently deployed wireless LAN (WLAN)
 infrastructure.

8.1. WLAN Deployment Scenarios

 WLAN enables subscribers to connect to the Internet from various
 locations without the restriction of staying indoors.  WLAN is
 standardized by IEEE 802.11a/b/g.
 Figure 8.1 describes the current WLAN architecture.
     Customer |             Access Provider        | Service Provider
     Premise  |                                    |
   +------+         +--+ +--------------+ +----------+ +------+
   |WLAN  |  ----   |  | |Access Router/| | Provider | |Edge  |
   |Host/ |-(WLAN)--|AP|-|Layer 2 Switch|-| Network  |-|Router|=>SP
   |Router|  ----   |  | |              | |          | |      |Network
   +------+         +--+ +--------------+ +----------+ +------+
                                                         |
                                                      +------+
                                                      |AAA   |
                                                      |Server|
                                                      +------+
                               Figure 8.1

Asadullah, et al. Informational [Page 55] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The host should have a wireless Network Interface Card (NIC) in order
 to connect to a WLAN network.  WLAN is a flat broadcast network and
 works in a similar fashion as Ethernet.  When a host initiates a
 connection, it is authenticated by the AAA server located at the SP
 network.  All the authentication parameters (username, password,
 etc.) are forwarded by the Access Point (AP) to the AAA server.  The
 AAA server authenticates the host; once successfully authenticated,
 the host can send data packets.  The AP is located near the host and
 acts as a bridge.  The AP forwards all the packets coming to/from
 host to the Edge Router.  The underlying connection between the AP
 and Edge Router could be based on any access layer technology such as
 HFC/Cable, FTTH, xDSL, etc.
 WLANs operate within limited areas known as WiFi Hot Spots.  While
 users are present in the area covered by the WLAN range, they can be
 connected to the Internet given they have a wireless NIC and required
 configuration settings in their devices (notebook PCs, PDAs, etc.).
 Once the user initiates the connection, the IP address is assigned by
 the SP using DHCPv4.  In most of the cases, SP assigns a limited
 number of public IP addresses to its customers.  When the user
 disconnects the connection and moves to a new WiFi hot spot, the
 above-mentioned process of authentication, address assignment, and
 accessing the Internet is repeated.
 There are IPv4 deployments where customers can use WLAN routers to
 connect over wireless to their service provider.  These deployment
 types do not fit in the typical Hot Spot concept, but rather they
 serve fixed customers.  For this reason, this section discusses the
 WLAN router options as well.  In this case, the ISP provides a public
 IP address and the WLAN Router assigns private addresses [RFC1918] to
 all WLAN users.  The WLAN Router provides NAT functionality while
 WLAN users access the Internet.
 While deploying IPv6 in the above-mentioned WLAN architecture, there
 are three possible scenarios as discussed below.
 A. Layer 2 NAP with Layer 3 termination at NSP Edge Router
 B. Layer 3 aware NAP with Layer 3 termination at Access Router
 C. PPP-Based Model

8.1.1. Layer 2 NAP with Layer 3 termination at NSP Edge Router

 When a Layer 2 switch is present between AP and Edge Router, the AP
 and Layer 2 switch continues to work as a bridge, forwarding IPv4 and
 IPv6 packets from WLAN Host/Router to Edge Router and vice versa.

Asadullah, et al. Informational [Page 56] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 When initiating the connection, the WLAN Host is authenticated by the
 AAA server located at the SP network.  All the parameters related to
 authentication (username, password, etc.) are forwarded by the AP to
 the AAA server.  The AAA server authenticates the WLAN Hosts, and
 once the WLAN Host is authenticated and associated successfully with
 the WLAN AP, it acquires an IPv6 address.  Note that the initiation
 and authentication process is the same as used in IPv4.
 Figure 8.1.1 describes the WLAN architecture when a Layer 2 Switch is
 located between AP and Edge Router.
     Customer |             Access Provider        | Service Provider
     Premise  |                                    |
   +------+         +--+ +--------------+ +----------+ +------+
   |WLAN  |  ----   |  | |              | | Provider | |Edge  |
   |Host/ |-(WLAN)--|AP|-|Layer 2 Switch|-| Network  |-|Router|=>SP
   |Router|  ----   |  | |              | |          | |      |Network
   +------+         +--+ +--------------+ +----------+ +------+
                                                         |
                                                      +------+
                                                      |AAA   |
                                                      |Server|
                                                      +------+
                               Figure 8.1.1

8.1.1.1. IPv6 Related Infrastructure Changes

 IPv6 will be deployed in this scenario by upgrading the following
 devices to dual stack: WLAN Host, WLAN Router (if present), and Edge
 Router.

8.1.1.2. Addressing

 When a customer WLAN Router is not present, the WLAN Host has two
 possible options to get an IPv6 address via the Edge Router.
 A.  The WLAN Host can get the IPv6 address from an Edge Router using
     stateless auto-configuration [RFC2462].  All hosts on the WLAN
     belong to the same /64 subnet that is statically configured on
     the Edge Router.  The IPv6 WLAN Host may use stateless DHCPv6 for
     obtaining other information of interest such as DNS, etc.
 B.  The IPv6 WLAN Host can use DHCPv6 [RFC3315] to get an IPv6
     address from the DHCPv6 server.  In this case, the DHCPv6 server
     would be located in the SP core network, and the Edge Router
     would simply act as a DHCP Relay Agent.  This option is similar

Asadullah, et al. Informational [Page 57] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

     to what is done today in case of DHCPv4.  It is important to note
     that host implementation of stateful auto-configuration is rather
     limited at this time, and this should be considered if choosing
     this address assignment option.
 When a customer WLAN Router is present, the WLAN Host has two
 possible options as well for acquiring IPv6 address.
 A.  The WLAN Router may be assigned a prefix between /48 and /64
     [RFC3177] depending on the SP policy and customer requirements.
     If the WLAN Router has multiple networks connected to its
     interfaces, the network administrator will have to configure the
     /64 prefixes to the WLAN Router interfaces connecting the WLAN
     Hosts on the customer site.  The WLAN Hosts connected to these
     interfaces can automatically configure themselves using stateless
     auto-configuration.
 B.  The WLAN Router can use its link-local address to communicate
     with the ER.  It can also dynamically acquire through stateless
     auto-configuration the address for the link between itself and
     the ER.  This step is followed by a request via DHCP-PD for a
     prefix shorter than /64 that, in turn, is divided in /64s and
     assigned to its interfaces connecting the hosts on the customer
     site.
 In this option, the WLAN Router would act as a requesting router and
 the Edge Router would act as a delegating router.  Once the prefix is
 received by the WLAN Router, it assigns /64 prefixes to each of its
 interfaces connecting the WLAN Hosts on the customer site.  The WLAN
 Hosts connected to these interfaces can automatically configure
 themselves using stateless auto-configuration.  The uplink to the ISP
 network is configured with a /64 prefix as well.
 Usually it is easier for the SPs to stay with the DHCP-PD and
 stateless auto-configuration model and point the clients to a central
 server for DNS/domain information, proxy configurations, etc.  Using
 this model, the SP could change prefixes on the fly, and the WLAN
 Router would simply pull the newest prefix based on the valid/
 preferred lifetime.
 The prefixes used for subscriber links and the ones delegated via
 DHCP-PD should be planned in a manner that allows maximum
 summarization at the Edge Router.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

Asadullah, et al. Informational [Page 58] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

8.1.1.3. Routing

 The WLAN Host/Router is configured with a default route that points
 to the Edge Router.  No routing protocols are needed on these
 devices, which generally have limited resources.
 The Edge Router runs the IGP used in the SP network such as OSPFv3 or
 IS-IS for IPv6.  The connected prefixes have to be redistributed.
 Prefix summarization should be done at the Edge Router.  When DHCP-PD
 is used, the IGP has to redistribute the static routes installed
 during the process of prefix delegation.

8.1.2. Layer 3 Aware NAP with Layer 3 Termination at Access Router

 When an Access Router is present between the AP and Edge Router, the
 AP continues to work as a bridge, bridging IPv4 and IPv6 packets from
 WLAN Host/Router to Access Router and vice versa.  The Access Router
 could be part of the SP network or owned by a separate Access
 Provider.
 When the WLAN Host initiates the connection, the AAA authentication
 and association process with WLAN AP will be similar, as explained in
 Section 8.1.1.
 Figure 8.1.2 describes the WLAN architecture when the Access Router
 is located between the AP and Edge Router.
     Customer |             Access Provider        | Service Provider
     Premise  |                                    |
   +------+         +--+ +--------------+ +----------+ +------+
   |WLAN  |  ----   |  | |              | | Provider | |Edge  |
   |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
   |Router|  ----   |  | |              | |          | |      |Network
   +------+         +--+ +--------------+ +----------+ +------+
                                                         |
                                                      +------+
                                                      |AAA   |
                                                      |Server|
                                                      +------+
                                Figure 8.1.2

8.1.2.1. IPv6 Related Infrastructure Changes

 IPv6 is deployed in this scenario by upgrading the following devices
 to dual stack: WLAN Host, WLAN Router (if present), Access Router,
 and Edge Router.

Asadullah, et al. Informational [Page 59] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

8.1.2.2. Addressing

 There are three possible options in this scenario for IPv6 address
 assignment:
 A.  The Edge Router interface facing towards the Access Router is
     statically configured with a /64 prefix.  The Access Router
     receives/ configures a /64 prefix on its interface facing towards
     the Edge Router through stateless auto-configuration.  The
     network administrator will have to configure the /64 prefixes to
     the Access Router interface facing toward the customer premise.
     The WLAN Host/Router connected to this interface can
     automatically configure itself using stateless auto-
     configuration.
 B.  This option uses DHCPv6 [RFC3315] for IPv6 prefix assignments to
     the WLAN Host/Router.  There is no use of DHCP PD or stateless
     auto-configuration in this option.  The DHCPv6 server can be
     located on the Access Router, the Edge Router, or somewhere in
     the SP network.  In this case, depending on where the DHCPv6
     server is located, the Access Router or the Edge Router would
     relay the DHCPv6 requests.
 C.  It can use its link-local address to communicate with the ER.  It
     can also dynamically acquire through stateless auto-configuration
     the address for the link between itself and the ER.  This step is
     followed by a request via DHCP-PD for a prefix shorter than /64
     that, in turn, is divided in /64s and assigned to its interfaces
     connecting the hosts on the customer site.
     In this option, the Access Router would act as a requesting
     router, and the Edge Router would act as a delegating router.
     Once the prefix is received by the Access Router, it assigns /64
     prefixes to each of its interfaces connecting the WLAN Host/
     Router on the customer site.  The WLAN Host/Router connected to
     these interfaces can automatically configure itself using
     stateless auto-configuration.  The uplink to the ISP network is
     configured with a /64 prefix as well.
 It is easier for the SPs to stay with the DHCP PD and stateless auto-
 configuration model and point the clients to a central server for
 DNS/domain information, proxy configurations, and others.  Using this
 model, the provider could change prefixes on the fly, and the Access
 Router would simply pull the newest prefix based on the valid/
 preferred lifetime.

Asadullah, et al. Informational [Page 60] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 As mentioned before, the prefixes used for subscriber links and the
 ones delegated via DHCP-PD should be planned in a manner that allows
 the maximum summarization possible at the Edge Router.  Other
 information of interest to the host, such as DNS, is provided through
 stateful [RFC3315] and stateless [RFC3736] DHCPv6.

8.1.2.3. Routing

 The WLAN Host/Router is configured with a default route that points
 to the Access Router.  No routing protocols are needed on these
 devices, which generally have limited resources.
 If the Access Router is owned by an Access Provider, then the Access
 Router can have a default route, pointing towards the SP Edge Router.
 The Edge Router runs the IGP used in the SP network such as OSPFv3 or
 IS-IS for IPv6.  The connected prefixes have to be redistributed.  If
 DHCP-PD is used, with every delegated prefix a static route is
 installed by the Edge Router.  For this reason the static routes must
 be redistributed.  Prefix summarization should be done at the Edge
 Router.
 If the Access Router is owned by the SP, then the Access Router will
 also run IPv6 IGP, and will be part of the SP IPv6 routing domain
 (OSPFv3 or IS-IS).  The connected prefixes have to be redistributed.
 If DHCP-PD is used, with every delegated prefix a static route is
 installed by the Access Router.  For this reason, the static routes
 must be redistributed.  Prefix summarization should be done at the
 Access Router.

8.1.3. PPP-Based Model

 PPP Terminated Aggregation (PTA) and L2TPv2 Access Aggregation (LAA)
 models, as discussed in Sections 6.2.2 and 6.2.3, respectively, can
 also be deployed in IPv6 WLAN environment.

8.1.3.1. PTA Model in IPv6 WLAN Environment

 While deploying the PTA model in IPv6 WLAN environment, the Access
 Router is Layer 3 aware and it has to be upgraded to support IPv6.
 Since the Access Router terminates the PPP sessions initiated by the
 WLAN Host/Router, it has to support PPPoE with IPv6.
 Figure 8.1.3.1 describes the PTA Model in IPv6 WLAN environment.

Asadullah, et al. Informational [Page 61] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

     Customer |             Access Provider        | Service Provider
     Premise  |                                    |
   +------+         +--+ +--------------+ +----------+ +------+
   |WLAN  |  ----   |  | |              | | Provider | |Edge  |
   |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
   |Router|  ----   |  | |              | |          | |      |Network
   +------+         +--+ +--------------+ +----------+ +------+
                                                         |
     |---------------------------|                    +------+
                 PPP                                  |AAA   |
                                                      |Server|
                                                      +------+
                              Figure 8.1.3.1

8.1.3.1.1. IPv6 Related Infrastructure Changes

 IPv6 is deployed in this scenario by upgrading the following devices
 to dual stack: WLAN Host, WLAN Router (if present), Access Router,
 and Edge Router.

8.1.3.1.2. Addressing

 The addressing techniques described in Section 6.2.2.2 apply to the
 IPv6 WLAN PTA scenario as well.

8.1.3.1.3. Routing

 The routing techniques described in Section 6.2.2.3 apply to the IPv6
 WLAN PTA scenario as well.

8.1.3.2. LAA Model in IPv6 WLAN Environment

 While deploying the LAA model in IPv6 WLAN environment, the Access
 Router is Layer 3 aware and has to be upgraded to support IPv6.  The
 PPP sessions initiated by the WLAN Host/Router are forwarded over the
 L2TPv2 tunnel to the aggregation point in the SP network.  The Access
 Router must have the capability to support L2TPv2 for IPv6.
 Figure 8.1.3.2 describes the LAA Model in IPv6 WLAN environment.

Asadullah, et al. Informational [Page 62] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

     Customer |             Access Provider        | Service Provider
     Premise  |                                    |
   +------+         +--+ +--------------+ +----------+ +------+
   |WLAN  |  ----   |  | |              | | Provider | |Edge  |
   |Host/ |-(WLAN)--|AP|-|Access Router |-| Network  |-|Router|=>SP
   |Router|  ----   |  | |              | |          | |      |Network
   +------+         +--+ +--------------+ +----------+ +------+
                                                         |
     |-------------------------------------------------- |
                             PPP                         |
                                  |--------------------- |
                                             L2TPv2      |
                                                      +------+
                                                      |AAA   |
                                                      |Server|
                                                      +------+
                              Figure 8.1.3.2

8.1.3.2.1. IPv6 Related Infrastructure Changes

 IPv6 is deployed in this scenario by upgrading the following devices
 to dual stack: WLAN Host, WLAN Router (if present), Access Router,
 and Edge Router.

8.1.3.2.2. Addressing

 The addressing techniques described in Section 6.2.3.2 apply to the
 IPv6 WLAN LAA scenario as well.

8.1.3.2.3. Routing

 The routing techniques described in Section 6.2.3.3 apply to the IPv6
 WLAN LAA scenario as well.

8.2. IPv6 Multicast

 The typical multicast services offered are video/audio streaming
 where the IPv6 WLAN Host joins a multicast group and receives the
 content.  This type of service model is well supported through PIM-
 SSM, which is enabled throughout the SP network.  MLDv2 is required
 for PIM-SSM support.  Vendors can choose to implement features that
 allow routers to map MLDv1 group joins to predefined sources.

Asadullah, et al. Informational [Page 63] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 It is important to note that in the shared wireless environments,
 multicast can have a significant bandwidth impact.  For this reason,
 the bandwidth allocated to multicast traffic should be limited and
 fixed, based on the overall capacity of the wireless specification
 used in 802.11a, 802.11b, or 802.11g.
 The IPv6 WLAN Hosts can also join desired multicast groups as long as
 they are enabled to support MLDv1 or MLDv2.  If WLAN/Access Routers
 are used, then they have to be enabled to support MLDv1 and MLDv2 in
 order to process the requests of the IPv6 WLAN Hosts.  The WLAN/
 Access Router also needs to be enabled to support PIM-SSM in order to
 send PIM joins up to the Edge Router.  When enabling this
 functionality on a WLAN/Access Router, its limited resources should
 be taken into consideration.  Another option would be for the WLAN/
 Access Router to support MLD proxy routing.
 The Edge Router has to be enabled to support MLDv1 and MLDv2 in order
 to process the requests coming from the IPv6 WLAN Host or WLAN/Access
 Router (if present).  The Edge Router has also needs to be enabled
 for PIM-SSM in order to receive joins from IPv6 WLAN Hosts or WLAN/
 Access Router (if present), and send joins towards the SP core.
 MLD authentication, authorization, and accounting are usually
 configured on the Edge Router in order to enable the SP to do billing
 for the content services provided.  Further investigation should be
 made in finding alternative mechanisms that would support these
 functions.
 Concerns have been raised in the past related to running IPv6
 multicast over WLAN links.  Potentially these are the same kind of
 issues when running any Layer 3 protocol over a WLAN link that has a
 high loss-to-signal ratio, where certain frames that are multicast
 based are dropped when settings are not adjusted properly.  For
 instance, this behavior is similar to an IGMP host membership report,
 when done on a WLAN link with a high loss-to-signal ratio and high
 interference.
 This problem is inherited by WLAN that can impact both IPv4 and IPv6
 multicast packets; it is not specific to IPv6 multicast.
 While deploying WLAN (IPv4 or IPv6), one should adjust their
 broadcast/multicast settings if they are in danger of dropping
 application dependent frames.  These problems are usually caused when
 the AP is placed too far (not following the distance limitations),
 high interference, etc.  These issues may impact a real multicast
 application such as streaming video or basic operation of IPv6 if the
 frames were dropped.  Basic IPv6 communications uses functions such
 as Duplicate Address Detection (DAD), Router and Neighbor

Asadullah, et al. Informational [Page 64] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 Solicitations (RS, NS), Router and Neighbor Advertisement (RA, NA),
 etc., which could be impacted by the above mentioned issues as these
 frames are Layer 2 Ethernet multicast frames.
 Please refer to Section 6.3 for more IPv6 multicast details.

8.3. IPv6 QoS

 Today, QoS is done outside of the WiFi domain, but it is nevertheless
 important to the overall deployment.
 The QoS configuration is particularly relevant on the Edge Router in
 order to manage resources shared amongst multiple subscribers
 possibly with various service level agreements (SLAs).  However, the
 WLAN Host/Router and Access Router could also be configured for QoS.
 This includes support for appropriate classification criteria, which
 would need to be implemented for IPv6 unicast and multicast traffic.
 On the Edge Router, the subscriber-facing interfaces have to be
 configured to police the inbound customer traffic and shape the
 traffic outbound to the customer, based on the SLA.  Traffic
 classification and marking should also be done on the Edge Router in
 order to support the various types of customer traffic: data, voice,
 and video.  The same IPv4 QoS concepts and methodologies should be
 applied for the IPv6 as well.
 It is important to note that when traffic is encrypted end-to-end,
 the traversed network devices will not have access to many of the
 packet fields used for classification purposes.  In these cases,
 routers will most likely place the packets in the default classes.
 The QoS design should take into consideration this scenario and try
 to use mainly IP header fields for classification purposes.

8.4. IPv6 Security Considerations

 There are limited changes that have to be done for WLAN the Host/
 Router in order to enhance security.  The privacy extensions
 [RFC3041] for auto-configuration should be used by the hosts with the
 same consideration for host traceability as described in Section 6.5.
 IPv6 firewall functions should be enabled on the WLAN Host/Router, if
 present.
 The ISP provides security against attacks that come from its own
 subscribers, but it could also implement security services that
 protect its subscribers from attacks sourced from outside its
 network.  Such services do not apply at the access level of the
 network discussed here.

Asadullah, et al. Informational [Page 65] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 If the host authentication at hotspots is done using a web-based
 authentication system, then the level of security would depend on the
 particular implementation.  User credentials should never be sent as
 clear text via HTTP.  Secure HTTP (HTTPS) should be used between the
 web browser and authentication server.  The authentication server
 could use RADIUS and LDAP services at the back end.
 Authentication is an important aspect of securing WLAN networks prior
 to implementing Layer 3 security policies.  For example, this would
 help avoid threats to the ND or stateless auto-configuration
 processes. 802.1x [IEEE8021X] provides the means to secure the
 network access; however, the many types of EAP (PEAP, EAP-TLS, EAP-
 TTLS, EAP-FAST, and LEAP) and the capabilities of the hosts to
 support some of the features might make it difficult to implement a
 comprehensive and consistent policy.
 The 802.11i [IEEE80211i] amendment has many components, the most
 obvious of which are the two new data-confidentiality protocols,
 Temporal Key Integrity Protocol (TKIP) and Counter-Mode/CBC-MAC
 Protocol (CCMP). 802.11i also uses 802.1X's key-distribution system
 to control access to the network.  Because 802.11 handles unicast and
 broadcast traffic differently, each traffic type has different
 security concerns.  With several data-confidentiality protocols and
 the key distribution, 802.11i includes a negotiation process for
 selecting the correct confidentiality protocol and key system for
 each traffic type.  Other features introduced include key caching and
 pre-authentication.
 The 802.11i amendment is a step forward in wireless security.  The
 amendment adds stronger encryption, authentication, and key
 management strategies that could make wireless data and systems more
 secure.
 If any Layer 2 filters for Ethertypes are in place, the NAP must
 permit the IPv6 Ethertype (0X86DD).
 The device that is the Layer 3 next hop for the subscribers (Access
 or Edge Router) should protect the network and the other subscribers
 against attacks by one of the provider customers.  For this reason
 uRPF and ACLs should be used on all interfaces facing subscribers.
 Filtering should be implemented with regard for the operational
 requirements of IPv6 [IPv6-Security].
 The Access and the Edge Router should protect their processing
 resources against floods of valid customer control traffic such as:
 RS, NS, and MLD Requests.  Rate limiting should be implemented on all

Asadullah, et al. Informational [Page 66] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 subscriber-facing interfaces.  The emphasis should be placed on
 multicast-type traffic, as it is most often used by the IPv6 control
 plane.

8.5. IPv6 Network Management

 The necessary instrumentation (such as MIB modules, NetFlow Records,
 etc) should be available for IPv6.
 Usually, NSPs manage the edge routers by SNMP.  The SNMP transport
 can be done over IPv4 if all managed devices have connectivity over
 both IPv4 and IPv6.  This would imply the smallest changes to the
 existing network management practices and processes.  Transport over
 IPv6 could also be implemented and it might become necessary if IPv6
 only islands are present in the network.  The management applications
 may be running on hosts belonging to the NSP core network domain.
 Network Management Applications should handle IPv6 in a similar
 fashion to IPv4; however, they should also support features specific
 to IPv6 (such as neighbor monitoring).
 In some cases, service providers manage equipment located on
 customers' LANs.

9. Broadband Power Line Communications (PLC)

 This section describes the IPv6 deployment in Power Line
 Communications (PLC) Access Networks.  There may be other choices,
 but it seems that this is the best model to follow.  Lessons learnt
 from cable, Ethernet, and even WLAN access networks may be applicable
 also.
 Power Line Communications are also often called Broadband Power Line
 (BPL) and sometimes even Power Line Telecommunications (PLT).
 PLC/BPL can be used for providing, with today's technology, up to
 200Mbps (total, upstream+downstream) by means of the power grid.  The
 coverage is often the last half mile (typical distance from the
 medium-to-low voltage transformer to the customer premise meter) and,
 of course, as an in-home network (which is out of the scope of this
 document).
 The bandwidth in a given PLC/BPL segment is shared among all the
 customers connected to that segment (often the customers connected to
 the same medium-to-low voltage transformer).  The number of customers
 can vary depending on different factors, such as distances and even
 countries (from a few customers, just 5-6, up to 100-150).

Asadullah, et al. Informational [Page 67] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 PLC/BPL could also be used in the medium voltage network (often
 configured as Metropolitan Area Networks), but this is also out of
 the scope of this document, as it will be part of the core network,
 not the access one.

9.1. PLC/BPL Access Network Elements

 This section describes the different elements commonly used in PLC/
 BPL access networks.
 Head End (HE): Router that connects the PLC/BPL access network (the
 power grid), located at the medium-to-low voltage transformer, to the
 core network.  The HE PLC/BPL interface appears to each customer as a
 single virtual interface, all of them sharing the same physical
 media.
 Repeater (RPT): A device that may be required in some circumstances
 to improve the signal on the PLC/BPL.  This may be the case if there
 are many customers in the same segment or building.  It is often a
 bridge, but it could also be a router if, for example, there is a lot
 of peer-to-peer traffic in a building and due to the master-slave
 nature of the PLC/BPL technology, is required to improve the
 performance within that segment.  For simplicity within this
 document, the RPT will always be considered a transparent Layer 2
 bridge, so it may or may not be present (from the Layer 3 point of
 view).
 Customer Premise Equipment (CPE): Modem (internal to the host),
 modem/bridge (BCPE), router (RCPE), or any combination among those
 (i.e., modem+bridge/router), located at the customer premise.
 Edge Router (ER)
 Figure 9.1 depicts all the network elements indicated above.
 Customer Premise | Network Access Provider | Network Service Provider
  +-----+  +------+  +-----+        +------+   +--------+
  |Hosts|--| RCPE |--| RPT |--------+ Head +---+ Edge   |    ISP
  +-----+  +------+  +-----+        | End  |   | Router +=>Network
                                    +--+---+   +--------+
  +-----+  +------+  +-----+           |
  |Hosts|--| BCPE |--| RPT |-----------+
  +-----+  +------+  +-----+
                                  Figure 9.1

Asadullah, et al. Informational [Page 68] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 The logical topology and design of PLC/BPL is very similar to
 Ethernet Broadband Networks as discussed in Section 7.  IP
 connectivity is typically provided in a Point-to-Point model, as
 described in Section 7.2.1

9.2. Deploying IPv6 in IPv4 PLC/BPL

 The most simplistic and efficient model, considering the nature of
 the PLC/BPL networks, is to see the network as a point-to-point, one
 to each customer.  Even if several customers share the same physical
 media, the traffic is not visible among them because each one uses
 different channels, which are, in addition, encrypted by means of
 3DES.
 In order to maintain the deployment concepts and business models
 proven and used with existing revenue-generating IPv4 services, the
 IPv6 deployment will match the IPv4 one.  Under certain circumstances
 where new service types or service needs justify it, IPv4 and IPv6
 network architectures could be different.  Both approaches are very
 similar to those already described for the Ethernet case.

9.2.1. IPv6 Related Infrastructure Changes

 In this scenario, only the RPT is Layer 3 unaware, but the other
 devices have to be upgraded to dual stack Hosts, RCPE, Head End, and
 Edge Router.

9.2.2. Addressing

 The Hosts or the RCPEs have the HE as their Layer 3 next hop.
 If there is no RCPE, but instead a BCPE, all the hosts on the
 subscriber site belong to the same /64 subnet that is statically
 configured on the HE.  The hosts can use stateless auto-configuration
 or stateful DHCPv6-based configuration to acquire an address via the
 HE.
 If an RCPE is present:
 A.  It is statically configured with an address on the /64 subnet
     between itself and the HE, and with /64 prefixes on the
     interfaces connecting the hosts on the customer site.  This is
     not a desired provisioning method, being expensive and difficult
     to manage.
 B.  It can use its link-local address to communicate with the HE.  It
     can also dynamically acquire through stateless auto-configuration
     the address for the link between itself and the HE.  This step is

Asadullah, et al. Informational [Page 69] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

     followed by a request via DHCP-PD for a prefix shorter than /64
     (typically /48 [RFC3177]) that, in turn, is divided in /64s and
     assigned to its interfaces connecting the hosts on the customer
     site.  This should be the preferred provisioning method, being
     cheaper and easier to manage.
 The Edge Router needs to have a prefix, considering that each
 customer in general will receive a /48 prefix, and that each HE will
 accommodate customers.  Consequently, each HE will require n x /48
 prefixes.
 It could be possible to use a kind of Hierarchical Prefix Delegation
 to automatically provision the required prefixes and fully auto-
 configure the HEs, and consequently reduce the network setup,
 operation, and maintenance cost.
 The prefixes used for subscriber links and the ones delegated via
 DHCP-PD should be planned in a manner that allows as much
 summarization as possible at the Edge Router.
 Other information of interest to the host, such as DNS, is provided
 through stateful [RFC3315] and stateless [RFC3736] DHCPv6.

9.2.3. Routing

 If no routers are used on the customer premise, the HE can simply be
 configured with a default route that points to the Edge Router.  If a
 router is used on the customer premise (RCPE), then the HE could also
 run an IGP (such as OSPFv3, IS-IS or even RIPng) to the ER.  The
 connected prefixes should be redistributed.  If DHCP-PD is used, with
 every delegated prefix a static route is installed by the HE.  For
 this reason, the static routes must also be redistributed.  Prefix
 summarization should be done at the HE.
 The RCPE requires only a default route pointing to the HE.  No
 routing protocols are needed on these devices, which generally have
 limited resources.
 The Edge Router runs the IPv6 IGP used in the NSP: OSPFv3 or IS-IS.
 The connected prefixes have to be redistributed, as well as any
 routing protocols (other than the ones used on the ER) that might be
 used between the HE and the ER.

Asadullah, et al. Informational [Page 70] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

9.3. IPv6 Multicast

 The considerations regarding IPv6 Multicast for Ethernet are also
 applicable here, in general, assuming the nature of PLC/BPL is a
 shared media.  If a lot of Multicast is expected, it may be worth
 considering using RPT which are Layer 3 aware.  In that case, one
 extra layer of Hierarchical DHCP-PD could be considered, in order to
 facilitate the deployment, operation, and maintenance of the network.

9.4. IPv6 QoS

 The considerations introduced for QoS in Ethernet are also applicable
 here.  PLC/BPL networks support QoS, which basically is the same
 whether the transport is IPv4 or IPv6.  It is necessary to understand
 that there are specific network characteristics, such as the
 variability that may be introduced by electrical noise, towards which
 the PLC/BPL network will automatically self-adapt.

9.5. IPv6 Security Considerations

 There are no differences in terms of security considerations if
 compared with the Ethernet case.

9.6. IPv6 Network Management

 The issues related to IPv6 Network Management in PLC networks should
 be similar to those discussed for Broadband Ethernet Networks in
 Section 7.6.  Note that there may be a need to define MIB modules for
 PLC networks and interfaces, but this is not necessarily related to
 IPv6 management.

10. Gap Analysis

 Several aspects of deploying IPv6 over SP Broadband networks were
 highlighted in this document, aspects that require additional work in
 order to facilitate native deployments, as summarized below:
 A.  As mentioned in section 5, changes will need to be made to the
     DOCSIS specification in order for SPs to deploy native IPv6 over
     cable networks.  The CM and CMTS will both need to support IPv6
     natively in order to forward IPv6 unicast and multicast traffic.
     This is required for IPv6 Neighbor Discovery to work over DOCSIS
     cable networks.  Additional classifiers need to be added to the
     DOCSIS specification in order to classify IPv6 traffic at the CM
     and CMTS in order to provide QoS.  These issues are addressed in
     a recent proposal made to Cable Labs for DOCSIS 3.0
     [DOCSIS3.0-Reqs].

Asadullah, et al. Informational [Page 71] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 B.  Section 6 stated that current RBE-based IPv4 deployment might not
     be the best approach for IPv6, where the addressing space
     available gives the SP the opportunity to separate the users on
     different subnets.  The differences between IPv4 RBE and IPv6 RBE
     were highlighted in Section 6.  If, however, support and reason
     are found for a deployment similar to IPv4 RBE, then the
     environment becomes NBMA and the new feature should observe
     RFC2491 recommendations.
 C.  Section 6 discussed the constraints imposed on an LAA-based IPv6
     deployment by the fact that it is expected that the subscribers
     keep their assigned prefix, regardless of LNS.  A deployment
     approach was proposed that would maintain the addressing schemes
     contiguous and offers prefix summarization opportunities.  The
     topic could be further investigated for other solutions or
     improvements.
 D.  Sections 6 and 7 pointed out the limitations (previously
     documented in [IPv6-Multicast]) in deploying inter-domain ASM;
     however, SSM-based services seem more likely at this time.  For
     such SSM-based services of content delivery (video or audio),
     mechanisms are needed to facilitate the billing and management of
     listeners.  The currently available feature of MLD AAA is
     suggested; however, other methods or mechanisms might be
     developed and proposed.
 E.  In relation to Section 8, concerns have been raised related to
     running IPv6 multicast over WLAN links.  Potentially, these are
     the same kind of issues when running any Layer 3 protocol over a
     WLAN link that has a high loss-to-signal ratio; certain frames
     that are multicast based are dropped when settings are not
     adjusted properly.  For instance this behavior is similar to an
     IGMP host membership report, when done on a WLAN link with high
     loss-to-signal ratio and high interference.  This problem is
     inherited by WLAN that can impact both IPv4 and IPv6 multicast
     packets; it is not specific to IPv6 multicast.
 F.  The privacy extensions were mentioned as a popular means to
     provide some form of host security.  ISPs can track relatively
     easily the prefixes assigned to subscribers.  If, however, the
     ISPs are required by regulations to track their users at host
     address level, the privacy extensions [RFC3041] can be
     implemented only in parallel with network management tools that
     could provide traceability of the hosts.  Mechanisms should be
     defined to implement this aspect of user management.

Asadullah, et al. Informational [Page 72] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 G.  Tunnels are an effective way to avoid deployment dependencies on
     the IPv6 support on platforms that are out of the SP control
     (GWRs or CPEs) or over technologies that did not standardize the
     IPv6 support yet (cable).  They can be used in the following
     ways:
      i.  Tunnels directly to the CPE or GWR with public or private
          IPv4 addresses.
      ii. Tunnels directly to hosts with public or private IPv4
          addresses.  Recommendations on the exact tunneling
          mechanisms that can/should be used for last-mile access need
          to be investigated further and should be addressed by the
          IETF Softwire Working Group.
 H.  Through its larger address space, IPv6 allows SPs to assign
     fixed, globally routable prefixes to the links connecting each
     subscriber.
     This approach changes the provisioning methodologies that were
     used for IPv4.  Static configuration of the IPv6 addresses for
     all these links on the Edge Routers or Access Routers might not
     be a scalable option.  New provisioning mechanisms or features
     might need to be developed in order to deal with this issue, such
     as automatic mapping of VLAN IDs/PVCs (or other customer-specific
     information) to IPv6 prefixes.
 I.  New deployment models are emerging for the Layer 2 portion of the
     NAP where individual VLANs are not dedicated to each subscriber.
     This approach allows Layer 2 switches to aggregate more then 4096
     users.  MAC Forced Forwarding [RFC4562] is an example of such an
     implementation, where a broadcast domain is turned into an NBMA-
     like environment by forwarding the frames based on both Source
     and Destination MAC addresses.  Since these models are being
     adopted by the field, the implications of deploying IPv6 in such
     environments need to be further investigated.
 J.  The deployment of IPv6 in continuously evolving access service
     models raises some issues that may need further investigation.
     Examples of such topics are [AUTO-CONFIG]:
      i.  Network Service Selection & Authentication (NSSA) mechanisms
          working in association with stateless auto-configuration.
          As an example, NSSA relevant information, such as ISP
          preference, passwords, or profile ID, can be sent by hosts
          with the RS [RFC4191].

Asadullah, et al. Informational [Page 73] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

      ii. Providing additional information in Router Advertisements to
          help access nodes with prefix selection in multi-ISP/
          multi-homed environments.
 Solutions to some of these topics range from making a media access
 capable of supporting native IPv6 (cable) to improving operational
 aspects of native IPv6 deployments.

11. Security Considerations

 Please refer to the individual "IPv6 Security Considerations"
 technology sections for details.

12. Acknowledgements

 We would like to thank Brian Carpenter, Patrick Grossetete, Toerless
 Eckert, Madhu Sudan, Shannon McFarland, Benoit Lourdelet, and Fred
 Baker for their valuable comments.  The authors would like to
 acknowledge the structure and information guidance provided by the
 work of Mickles, et al., on "Transition Scenarios for ISP Networks"
 [ISP-CASES].

13. References

13.1. Normative References

 [RFC1918]         Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot,
                   G., and E. Lear, "Address Allocation for Private
                   Internets", BCP 5, RFC 1918, February 1996.
 [RFC2080]         Malkin, G. and R. Minnear, "RIPng for IPv6",
                   RFC 2080, January 1997.
 [RFC2364]         Gross, G., Kaycee, M., Lin, A., Malis, A., and J.
                   Stephens, "PPP Over AAL5", RFC 2364, July 1998.
 [RFC2461]         Narten, T., Nordmark, E., and W. Simpson, "Neighbor
                   Discovery for IP Version 6 (IPv6)", RFC 2461,
                   December 1998.
 [RFC2462]         Thomson, S. and T. Narten, "IPv6 Stateless Address
                   Autoconfiguration", RFC 2462, December 1998.
 [RFC2473]         Conta, A. and S. Deering, "Generic Packet Tunneling
                   in IPv6 Specification", RFC 2473, December 1998.

Asadullah, et al. Informational [Page 74] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 [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.
 [RFC2529]         Carpenter, B. and C. Jung, "Transmission of IPv6
                   over IPv4 Domains without Explicit Tunnels",
                   RFC 2529, March 1999.
 [RFC2661]         Townsley, W., Valencia, A., Rubens, A., Pall, G.,
                   Zorn, G., and B. Palter, "Layer Two Tunneling
                   Protocol "L2TP"", RFC 2661, August 1999.
 [RFC2740]         Coltun, R., Ferguson, D., and J. Moy, "OSPF for
                   IPv6", RFC 2740, December 1999.
 [RFC2784]         Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
                   Traina, "Generic Routing Encapsulation (GRE)",
                   RFC 2784, March 2000.
 [RFC3041]         Narten, T. and R. Draves, "Privacy Extensions for
                   Stateless Address Autoconfiguration in IPv6",
                   RFC 3041, January 2001.
 [RFC3053]         Durand, A., Fasano, P., Guardini, I., and D. Lento,
                   "IPv6 Tunnel Broker", RFC 3053, January 2001.
 [RFC3056]         Carpenter, B. and K. Moore, "Connection of IPv6
                   Domains via IPv4 Clouds", RFC 3056, February 2001.
 [RFC3177]         IAB and IESG, "IAB/IESG Recommendations on IPv6
                   Address Allocations to Sites", RFC 3177,
                   September 2001.
 [RFC3180]         Meyer, D. and P. Lothberg, "GLOP Addressing in
                   233/8", BCP 53, RFC 3180, September 2001.
 [RFC3315]         Droms, R., Bound, J., Volz, B., Lemon, T., Perkins,
                   C., and M. Carney, "Dynamic Host Configuration
                   Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003.
 [RFC3618]         Fenner, B. and D. Meyer, "Multicast Source
                   Discovery Protocol (MSDP)", RFC 3618, October 2003.
 [RFC3704]         Baker, F. and P. Savola, "Ingress Filtering for
                   Multihomed Networks", BCP 84, RFC 3704, March 2004.

Asadullah, et al. Informational [Page 75] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 [RFC3736]         Droms, R., "Stateless Dynamic Host Configuration
                   Protocol (DHCP) Service for IPv6", RFC 3736,
                   April 2004.
 [RFC3904]         Huitema, C., Austein, R., Satapati, S., and R. van
                   der Pol, "Evaluation of IPv6 Transition Mechanisms
                   for Unmanaged Networks", RFC 3904, September 2004.
 [RFC3931]         Lau, J., Townsley, M., and I. Goyret, "Layer Two
                   Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931,
                   March 2005.
 [RFC4001]         Daniele, M., Haberman, B., Routhier, S., and J.
                   Schoenwaelder, "Textual Conventions for Internet
                   Network Addresses", RFC 4001, February 2005.
 [RFC4029]         Lind, M., Ksinant, V., Park, S., Baudot, A., and P.
                   Savola, "Scenarios and Analysis for Introducing
                   IPv6 into ISP Networks", RFC 4029, March 2005.
 [RFC4191]         Draves, R. and D. Thaler, "Default Router
                   Preferences and More-Specific Routes", RFC 4191,
                   November 2005.
 [RFC4213]         Nordmark, E. and R. Gilligan, "Basic Transition
                   Mechanisms for IPv6 Hosts and Routers", RFC 4213,
                   October 2005.
 [RFC4214]         Templin, F., Gleeson, T., Talwar, M., and D.
                   Thaler, "Intra-Site Automatic Tunnel Addressing
                   Protocol (ISATAP)", RFC 4214, October 2005.
 [RFC4380]         Huitema, C., "Teredo: Tunneling IPv6 over UDP
                   through Network Address Translations (NATs)",
                   RFC 4380, February 2006.

13.2. Informative References

 [6PE]             De Clercq, J., Ooms, D., Prevost, S., and F. Le
                   Faucheur, "Connecting IPv6 Islands across IPv4
                   Clouds with BGP", Work in Progress, December 2006.
 [AUTO-CONFIG]     Wen, H., Zhu, X., Jiang, Y., and R. Yan, "The
                   deployment of IPv6 stateless auto-configuration in
                   access network", 8th International Conference on
                   Telecommunications, ConTEL 2005, June 2005.

Asadullah, et al. Informational [Page 76] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 [BSR]             Bhaskar, N., Gall, A., Lingard, J., and S. Venaas,
                   "Bootstrap Router (BSR) Mechanism for PIM", Work
                   in Progress, June 2006.
 [DOCSIS3.0-OSSI]  CableLabs, CL., "DOCSIS 3.0 OSSI Specification(CM-
                   SP-OSSIv3.0-D02-060504)", May 2006.
 [DOCSIS3.0-Reqs]  Droms, R., Durand, A., Kharbanda, D., and J-F.
                   Mule, "DOCSIS 3.0 Requirements for IPv6 Support",
                   Work in Progress, March 2006.
 [DynamicTunnel]   Palet, J., Diaz, M., and P. Savola, "Analysis of
                   IPv6 Tunnel End-point Discovery Mechanisms", Work
                   in Progress, January 2005.
 [IEEE80211i]      IEEE, "IEEE Standards for Information Technology:
                   Part 11: Wireless LAN Medium Access Control (MAC)
                   and Physical Layer (PHY) specifications, Amendment
                   6: Medium Access Control (MAC) Security
                   Enhancements", July 2004.
 [IEEE8021X]       IEEE, "IEEE Standards for Local and Metropolitan
                   Area Networks: Port based Network Access Control,
                   IEEE Std 802.1X-2001", June 2001.
 [IPv6-Multicast]  Savola, P., "IPv6 Multicast Deployment Issues",
                   Work in Progress, April 2004.
 [IPv6-Security]   Convery, S. and D. Miller, "IPv6 and IPv4 Threat
                   Comparison and Best-Practice Evaluation",
                   March 2004.
 [ISISv6]          Hopps, C., "Routing IPv6 with IS-IS", Work
                   in Progress, October 2005.
 [ISP-CASES]       Mickles, C., "Transition Scenarios for ISP
                   Networks", Work in Progress, September 2002.
 [Protocol41]      Palet, J., Olvera, C., and D. Fernandez,
                   "Forwarding Protocol 41 in NAT Boxes", Work
                   in Progress, October 2003.
 [RF-Interface]    CableLabs, CL., "DOCSIS 2.0(CM-SP-RFIv2.0-I10-
                   051209)", December 2005.
 [RFC4562]         Melsen, T. and S. Blake, "MAC-Forced Forwarding: A
                   Method for Subscriber Separation on an Ethernet
                   Access Network", RFC 4562, June 2006.

Asadullah, et al. Informational [Page 77] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 [Softwire]        Dawkins, S., Ed., "Softwire Problem Statement",
                   Work in Progress, May 2006.
 [v6tc]            Palet, J., Nielsent, K., Parent, F., Durand, A.,
                   Suryanarayanan, R., and P. Savola, "Goals for
                   Tunneling Configuration", Work in Progress,
                   August 2005.

Asadullah, et al. Informational [Page 78] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

Authors' Addresses

 Salman Asadullah
 Cisco Systems
 170 West Tasman Drive
 San Jose, CA  95134
 USA
 Phone: 408 526 8982
 EMail: sasad@cisco.com
 Adeel Ahmed
 Cisco Systems
 2200 East President George Bush Turnpike
 Richardson, TX  75082
 USA
 Phone: 469 255 4122
 EMail: adahmed@cisco.com
 Ciprian Popoviciu
 Cisco Systems
 7025-6 Kit Creek Road
 Research Triangle Park, NC  27709
 USA
 Phone: 919 392 3723
 EMail: cpopovic@cisco.com
 Pekka Savola
 CSC - Scientific Computing Ltd.
 Espoo
 Finland
 EMail: psavola@funet.fi

Asadullah, et al. Informational [Page 79] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

 Jordi Palet Martinez
 Consulintel
 San Jose Artesano, 1
 Alcobendas, Madrid  E-28108
 Spain
 Phone: +34 91 151 81 99
 EMail: jordi.palet@consulintel.es

Asadullah, et al. Informational [Page 80] RFC 4779 ISP IPv6 Deployment Scenarios in BB January 2007

Full Copyright Statement

 Copyright (C) The IETF Trust (2007).
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 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
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Acknowledgement

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Asadullah, et al. Informational [Page 81]

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