Network Working Group                                          M-K. Shin
Internet-Draft                                                      ETRI
Intended status: Informational                                  Y-H. Han
Expires: April 4, July 20, 2007                                               KUT
                                                                S-E. Kim
                                                               D. Premec
                                                          Siemens Mobile
                                                         October 1, 2006
                                                        January 16, 2007

            IPv6 Deployment Scenarios in 802.16(e) Networks

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006). (2007).


   This document provides detailed description of IPv6 deployment and
   integration methods and scenarios in wireless broadband access
   networks in coexistence with deployed IPv4 services.  In this
   document we will discuss main components of IPv6 IEEE 802.16 access
   network and its differences from IPv4 IEEE 802.16 networks and how
   IPv6 is deployed and integrated in each of the IEEE 802.16
   technologies using tunneling mechanisms and native IPv6.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Wireless Broadband Access Network Technologies -  Deploying IPv6 in IEEE 802.16 . . . . . . . . . . . . . . . . Networks . . . . . . . . . . . .  4
     2.1.  Elements of IEEE 802.16 Networks . . . . . . . . . . . . .  4
     2.2.  Deploying  Scenarios and IPv6 in IEEE 802.16 Networks Deployment  . . . . . . . . . . . . . .  5
       2.2.1.  Mobile Access Deployment Scenarios . . . . . . . . . .  6  5
       2.2.2.  Fixed/Nomadic Deployment Scenarios . . . . . . . . . . 10  9
     2.3.  IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 13 12
     2.4.  IPv6 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 14 13
     2.5.  IPv6 Security  . . . . . . . . . . . . . . . . . . . . . . 14 13
     2.6.  IPv6 Network Management  . . . . . . . . . . . . . . . . . 15 13
   3.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 16 15
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . . 17 16
   5.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18 17
   6.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 19 18
     6.1.  Normative References . . . . . . . . . . . . . . . . . . . 19 18
     6.2.  Informative References . . . . . . . . . . . . . . . . . . 19 18
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 20
   Intellectual Property and Copyright Statements . . . . . . . . . . 22 21

1.  Introduction

   Recently, broadband wireless access network is emerging for wireless
   communication for user requirements such as high quality data/voice
   service, fast mobility, wide coverage, etc.  The IEEE 802.16 Working
   Group develops standards and recommended practices to support the
   development and deployment of broadband wireless metropolitan area

   Whereas the [IEEE802.16] standard addresses fixed wireless
   applications only, the [IEEE802.16e] standard serves the needs of
   fixed, nomadic, and fully mobile networks.  It adds mobility support
   to the original standard so that mobile subscriber stations can move
   during services.  The standardization of IEEE 802.16e is completed,
   which plans to support mobility up to speeds of 70~80 mile/h that
   will enable the subscribers to carry mobile devices such as PDAs,
   phones, or laptops.  IEEE 802.16e is one of the most promising access
   technologies which would be applied to the IP-based broadband mobile

   As the deployment of wireless broadband IEEE 802.16(e) access network progresses, users
   will be connected to IPv6 networks.  While the IEEE 802.16 defines
   the encapsulation of an IPv4/IPv6 datagram in an IEEE 802.16 MAC
   payload, a complete description of IPv4/IPv6 operation and deployment
   is not present.  In this document, we will discuss main components of
   IPv6 IEEE 802.16 access network and its differences from IPv4 IEEE
   802.16 networks and how IPv6 is deployed and integrated in each of
   the IEEE 802.16 technologies using tunneling mechanisms and native

   This document extends works of [I-D.ietf-v6ops-bb-deployment-
   scenarios] and follows the structure and common terminology of the

2.  Wireless Broadband Access Network Technologies - IEEE 802.16

   This section describes the infrastructure that is based on IEEE
   802.16 networks providing wireless broadband services to the
   customer.  It also describes a way to deploy  Deploying IPv6 over in IEEE 802.16
   networks. Networks

2.1.  Elements of IEEE 802.16 Networks

   The IEEE 802.11 access network (WLAN) has driven the revolution of
   wireless communication.  However, the more people use it the more its
   limitations such as short range and lack of mobility support arose.
   Compared with such IEEE 802.11 network, IEEE 802.16 supports enhanced
   features such as wider coverage and mobility.  So it is expected that
   IEEE 802.16 network could be the next step of IEEE 802.11 network.

   The mechanism of transporting IP traffic over IEEE 802.16 networks is
   outlined in [IEEE802.16], but [IEEE802.16].  [IEEE802.16] only specifies the
   convergence sublayers and the ability to transport IP over the air
   interface.  The details of IPv6 (and IPv4) operations over IEEE
   802.16 are being discussed now. now in 16ng WG.

   Here are some of the key elements of an IEEE 802.16 network:

   o  MS: Mobile Station.  A station network.  The
   terminologies in the mobile service intended this document "SS(MS)", "BS", and "AR" are to be used while
   interpreted as described in motion [I-D.ietf-16ng-ps-goals].

   o  Subscriber Station (SS): An end-user equipment that provides
      connectivity to the 802.16 networks.  It can be either fixed/
      nomadic or during halts at unspecified points.  A mobile station equipment.  In mobile environment, SS represents
      the Mobile Subscriber Station (MS) is always a subscriber station (SS) which must
      provide mobility function. introduced in IEEE 802.16e

   o  BS:  Base Station. Station (BS): A generalized equipment set sets providing
      connectivity, management, and control of MS connections.  There is a
      unidirectional mapping between BS and MS medium access control
      (MAC) peers for the purpose of transporting a service flow's
      traffic.  A connection is identified by a connection identifier
      (CID).  All traffic is carried on subscriber
      station and the connection.  Sometimes there
      can be alternative IEEE 802.16 network deployment where a BS is
      integrated with an access router, composing one box in view of
      implementation. networks.

   o  AR:  Access Router.  A generalized equipment set providing IP
      connectivity between BS and IP based network. Router (AR): An AR entity that performs
      first hop an IP routing function
      to all MS. provide IP connectivity for subscriber station (SS or MS).

   Figure 1 illustrates the key elements of IEEE 802.16(e) networks. typical mobile 802.16

          Customer |     Access Provider    | Service Provider
          Premise  |                        | (Backend Network)

       +-----+            +----+     +----+   +--------+
       | MSs SSs |--(802.16)--| BS |-----|    |   | Edge   |   ISP
       +-----+            +----+     | AR |---| Router |==>Network
                                  +--|    |   | (ER)   |
                                  |  +----+   +--------+
       +-----+            +----+  |                |  +------+
       | MSs SSs |--(802.16)--| BS |--+                +--|AAA   |
       +-----+            +----+                      |Server|

             Figure 1: Key Elements of IEEE 802.16(e) Networks

2.2.  Deploying  Scenarios and IPv6 in IEEE 802.16 Networks Deployment

   [IEEE802.16] specifies two modes for sharing the wireless medium:
   point-to-multipoint (PMP) and mesh (optional).  This document only
   focuses on PMP mode.

   Some of the factors that hinder deployment of native IPv6 core
   protocols are introduced by [I-D.jee-16ng-problem-statement].  The
   summary of them is as follows:

   1.  Lacking of Facility for IPv6 Native Multicasting

   IEEE 802.16 PMP mode is a connection oriented technology without bi-
   directional native multicast support.  IPv6 neighbor discovery
   [RFC2461] supports various functions for the interaction between
   nodes attached on the same subnet, such as on-link determination and
   address resolution.  It is designed with no dependence on a specific
   link layer technology, but requires that the link layer technology
   support native multicast.  This lacking of facility for IPv6 native
   multicast results in inappropriateness to apply the standard neighbor
   discover protocol specially regarding, address resolution, router
   discovery, stateless auto-configuration and duplicated address

   2.  Impact on IPv6 Subnet Model

   IEEE 802.16 is different from existing wireless access technologies
   such as IEEE 802.11 or 3G, and, while IEEE 802.16 defines the
   encapsulation of an IP datagram in an IEEE 802.16 MAC payload, a
   complete description of IPv6 operation is not present.  IEEE 802.16
   can rather benefit from IETF input and specification to support IPv6
   operation.  Especially, BS should look at the classifiers and decide
   where to send the packet, since IEEE 802.16 connection always ends at
   BS, while IPv6 connection terminates at a default router.  This
   operation and limitation may be dependent on the given subnet model

   3.  Multiple Convergence Sublayers (CS)

   There are operational complexity problems of IP over 802.16 caused by
   the existence of multiple convergence sublayers [I-D.iab-link-
   encaps].  We should consider which type of Convergence Sublayer (CS)
   can be efficiently used on each subnet models and scenarios.  IEEE
   802.16 CS delivers and classifies various kinds of higher layer PDUs
   such as ATM, IPv4 packet and IPv6 packets over radio channel.  For
   this purpose, IEEE 802.16 introduces the Connection Identifier (CID).
   Generally, CS performs the following functions in terms of IP packet
   transmission: 1) Receipt of protocol data units (PDUs) from the
   higher layer, 2) Performing classification and CID mapping of the
   PDUs, 3) Delivering the PDUs to the appropriate MAC SAP, 4) Receipt
   of PDUs from the peer MAC SAP, and 5) Forwarding the PDUs to the
   corresponding AR.  The specification of IEEE 802.16 defines several
   CSs for carrying IP packets, but does not provide a detailed
   description of how to carry them.  The several CSs are generally
   classified into two types of CS: IPv6 CS and Ethernet CS.

   In addition, due to the problems caused by the existence of multiple
   convergence sublayers [I-D.iab-link-encaps], the mobile access
   scenarios need solutions about how roaming will work when forced to
   move from one CS to another.  Note that, at this phase this issue is
   the out of scope of this draft.  It should be also discussed in 16ng
   WG. deployment of native IPv6 core
   protocols are already introduced by [I-D.ietf-16ng-ps-goals].

   There are two different deployment scenarios: fixed and mobile
   access. access
   deployment scenarios.  A fixed access scenario substitudes for
   existing wired-based access technologies such as digital subscriber
   line (xDSL) and cable network.  This fixed access scenario can
   provide nomadic access within the radio coverages, which is called
   Hot-zone model.  A mobile access scenario is for new paradigm for
   voice, data and video over mobile network.  This scenario can provide
   high speed data rate equalivent to wire-based Internet as well as
   mobility function equivalent to cellular system.  The mobile access
   scenario can be classified into two different IPv6 sunbet link models:
   shared IPv6 prefix link model and point-to-point link model.

2.2.1.  Mobile Access Deployment Scenarios

   Unlike IEEE 802.11, IEEE 802.16 BS can offer mobility function as
   well as fixed communication.  [IEEE802.16e] has been standardized to
   provide mobility features on IEEE 802.16 environments.  This use case
   will be implemented only with the licensed spectrum.  IEEE 802.16
   BS might be deployed with a proprietary backend managed by an
   All original IPv6 functionalities [RFC2461], [RFC2462] will not
   survive.  Some architectural characteristics of IEEE 802.16 networks
   may affect the detailed operations of NDP [RFC2461]. [RFC2461], [RFC2462].

   There are two possible IPv6 subnet link models for mobile access deployment
   scenarios: shared IPv6 prefix link model and point-to-
   point point-to-point link
   model [I-D.madanapalli-16ng-subnet-model-analysis]. [I-D.ietf-16ng-ipv6-link-model-analysis].  There is alwayes a
   default access router in the scenarios.  There exist multiple hosts
   behind an MS (networks behind an MS may exist).  The mobile access
   deployment models, Mobile WiMax and WiBro, fall within this
   deployment model.

   1.  Shared IPv6 Prefix Link Model

   This link model represents IEEE 802.16 mobile access network
   deployment where a subnet consists of only single interface of AR and
   multiple MSs.  Therefore, all MSs and corresponding interface of AR
   share the same IPv6 prefix as shown in Figure 2.  IPv6 prefix will be
   different from the interface of AR.

     | MS1 |<-(16)-+
     +-----+       |
     +-----+       |    +-----+     +-----+    +--------+
     | MS2 |<-(16)-+----| BS1 |--+->| AR  |----| Edge   |    ISP
     +-----+            +-----+  |  +-----+    | Router +==>Network
                                 |             +--------+
     +-----+            +-----+  |
     | MS3 |<-(16)-+----| BS2 |--+
     +-----+       |    +-----+
     +-----+       |
     | MS4 |<-(16)-+

                  Figure 2: Shared IPv6 Prefix Link Model

   2.  Point-to-Point Link Model

   This link model represents IEEE 802.16 mobile access network
   deployment where a subnet consists of only single AR, BS and MS.
   That is, each connection to a mobile node is treated as a single
   link.  Each link between the MS and the AR is allocated a separate,
   unique prefix or unique set of prefixes by the AR.  The point-to-
   point link model follows the recommendations of [RFC3314].

      | MS1 |<-(16)---------+
      +-----+               |
      +-----+            +-----+     +-----+    +--------+
      | MS2 |<-(16)------| BS1 |--+->| AR  |----| Edge   |    ISP
      +-----+            +-----+  |  +-----+    | Router +==>Network
                                  |             +--------+
      +-----+            +-----+  |
      | MS3 |<-(16)------| BS2 |--+
      +-----+            +-----+
      +-----+               |
      | MS4 |<-(16)---------+

                    Figure 3: Point-to-Point Link Model  IPv6 Related Infrastructure Changes

   IPv6 will be deployed in this scenario by upgrading the following
   devices to dual-stack: MS, BS, AR and ER.  In this scenario, IEEE 802.16
   BSs have only MAC and PHY layers without router function and operates
   as a bridge.  The BS does not need to support IPv6.  However, if IPv4
   stack is loaded to them for management and configuration purpose, it
   is expected that BS should be upgraded by implementing IPv6 stack,
   too.  Addressing

   IPv6 MS has two possible options to get an IPv6 address.  These
   options will be equally applied to the other scenario below (Section

   1.  IPv6 MS can get the IPv6 address from an access router using
   stateless auto-configuration.  In this case, router discovery and DAD
   operation should be properly operated over IEEE 802.16 link.

   2.  IPv6 MS can use DHCPv6 to get an IPv6 address from the DHCPv6
   server.  In this case, the DHCPv6 server would be located in the
   service provider core network and the AR should provide DHCPv6 relay
   agent.  This option is similar to what we do today in case of DHCPv4.

   In this scenario, a router and multiple BSs form an IPv6 subnet and a
   single prefix is allocated to all the attached MSs.  All MSs attached
   to same AR can be on same IPv6 link.

   As for the prefix assignment, in case of shared IPv6 prefix link
   model, one or more IPv6 prefixes are assigned to the link and hence
   shared by all the nodes that are attached to the link.  In point-to-
   point link model, the AR assigns a unique prefix or set of unique
   prefixes for each MS.  Prefix delegation can be required if networks
   can exist behind MS.  IPv6 Transport

   In a subnet, there are always two underlying links: one is the IEEE
   802.16 wireless link between MS and BS, and the other is a wired link
   between BS and AR.  The IPv6 packet should be classified by IPv6
   source/destination addresses, etc.  BS generates the flow based on
   the classification.  It also decides where to send the packet or just
   forward the packet to the ACR, since IEEE 802.16 connection always
   ends at BS while IPv6 connection terminates at the AR.  This
   operation may be dependent on IPv6 subnet models.

   If stateless auto-configuration is used to get an IPv6 address,
   router discovery and DAD operation should be properly operated over
   IEEE 802.16 link.  In case of shared IPv6 prefix link model, the DAD
   [RFC2461] does not adapt well to the 802.16 air interface as there is
   no native multicast support and when supported consumes air bandwidth
   as well as it would have adverse effect on MSs that were in the
   dormant mode. support.  An optimization, called Relay DAD, may
   be required to perform DAD.  However, in case of point-to-point link
   model, DAD is easy since each connection to a MN is treated as a
   unique IPv6 link.

   Note that in this scenario IPv6 CS may be more appropriate than
   Ethernet CS to transport IPv6 packets, since there are some overhead
   of Ethernet CS (e.g., Ethernet header) under mobile access
   environments .
   environments.  However PHS (Packet Header Compression), if deployed,
   mitigates much of this overhead.

   Simple or complex network equipments may constitute the underlying
   wired network between the AR and the ER.  If the IP aware equipments
   between the AR and the ER do not support IPv6, the service providers
   can deploy IPv6-in-IPv4 tunneling mechanisms to transport IPv6
   packets between the AR and the ER.

   The service providers are deploying tunneling mechanisms to transport
   IPv6 over their existing IPv4 networks as well as deploying native
   IPv6 where possible.  Native IPv6 should be preferred over tunneling
   mechanisms as native IPv6 deployment option might be more scalable
   and provide required service performance.  Tunneling mechanisms
   should only be used when native IPv6 deployment is not an option.
   This can be equally applied to other scenario below (Section 2.2.2).  Routing

   In general, the MS is configured with a default route that points to
   the the AR.  Therefore, no routing protocols are needed on the MS.
   The MS just sends to the AR by default route.

   The AR can configure multiple link to ER for network reliability.
   The AR should support IPv6 routing protocol such as OSPFv3 [RFC2740]
   or IS-IS for IPv6 when connected to the ER with multiple links.

   The ER runs the IGP such as OSPFv3 or IS-IS for IPv6 in the service
   provider network.  The routing information of the ER can be
   redistributed to the AR.  Prefix summarization should be done at the
   ER.  Mobility

   As for mobility management, the movement between BSs is handled by
   Mobile IPv6 [RFC3775], if it requires a subnet change.  Also, in
   certain cases (e.g., fast handover [I-D.ietf-mipshop-fmipv6-
   rfc4068bis]) the link mobility information must be available for
   facilitating layer 3 handoff procedure.

   Mobile IPv6 defines that movement detection uses Neighbor
   Unreachability Detection to detect when the default router is no
   longer bi-directionally reachable, in which case the mobile node must
   discover a new default router.  Periodic Router Advertisements for
   reachability and movement detection may be unnecessary because IEEE
   802.16 MAC provides the reachability by its Ranging procedure and the
   movement detection by the Handoff procedure.

   IEEE 802.16 defines L2 triggers whether refresh of an IP address is
   required during the handoff.  Though a handoff has occurred, an
   additional router discovery procedure is not required in case of
   intra-subnet handoff.  Also, faster handoff may be occurred by the L2
   trigger in case of inter-subnet handoff.

   Also, IEEE 802.16g which is under-developed defines L2 triggers for
   link status such as link-up, link-down, handoff-start.  These L2
   triggers may make Mobile IPv6 procedure more efficient and faster.
   In addition, Mobile IPv6 Fast Handover assumes the support from link-
   layer technology, but the particular link-layer information being
   available, as well as the timing of its availability (before, during
   or after a handover has occurred), differs according to the
   particular link-layer technology in use.  This issue is also being
   discussed in [I-D.ietf-mipshop-fh80216e].

   In addition, due to the problems caused by the existence of multiple
   convergence sublayers [I-D.iab-link-encaps], the mobile access
   scenarios need solutions about how roaming will work when forced to
   move from one CS to another.  Note that, at this phase this issue is
   the out of scope of this draft.  It should be also discussed in 16ng

2.2.2.  Fixed/Nomadic Deployment Scenarios

   The IEEE 802.16 access networks can provide plain Ethernet
   connectivity end-to-end.  Wireless DSL deployment model is an example
   of a fixed/nomadic IPv6 deployment of IEEE 802.16.  Many wireless
   Internet service providers (Wireless ISPs) have planned to use IEEE
   802.16 for the purpose of high quality broadband wireless service.  A
   company can use IEEE 802.16 to build up mobile office.  Wireless
   Internet spreading through a campus or a cafe can be also implemented
   with it.  The distinct point of this use case is that it can use
   unlicensed (2.4 & 5 GHz) band as well as licensed (2.6 & 3.5GHz)
   band.  By using the unlicensed band, an IEEE 802.16 BS might be used
   just as a wireless switch/hub which a user purchases to build a
   private wireless network in his/her home or laboratory.

   Under fixed access model, the IEEE 802.16 BS will be deployed using
   an IP backbone rather than a proprietary backend like cellular
   systems.  Thus, many IPv6 functionalities such as [RFC2461],
   [RFC2462] will be preserved when adopting IPv6 to IEEE 802.16

   This scenario also represents IEEE 802.16 network deployment where a
   subnet consists of multiple MSs and multiple interface of the
   multiple BSs.  Multiple access routers can exist.  There exist
   multiple hosts behind an SS (networks behind an MS SS may exist).  When
   802.16 access networks are widely deployed like WLAN, this case
   should be also considered.  Hot-zone deployment model falls within
   this case.

            +-----+                        +-----+    +-----+    ISP 1
            | SS1 |<-(16)+              +->| AR1 |----| ER1 |===>Network
            +-----+      |              |  +-----+    +-----+
            +-----+      |     +-----+  |
            | SS2 |<-(16)+-----| BS1 |--|
            +-----+            +-----+  |  +-----+    +-----+    ISP 2
                                        +->| AR2 |----| ER2 |===>Network
 +-----+    +-----+            +-----+  |  +-----+    +-----+
 |Hosts|<-->|SS/GW|<-(16)------| BS2 |--+
 +-----+    +-----+            +-----+
    This network
 behind MS SS may exist

                Figure 4: Fixed/Nomadic Deployment Scenario

   While Figure 3 4 illustrates a generic deployment scenario, the
   following Figure 4 5 shows in more detail how an existing DSL ISP would
   integrate the 802.16 access network into its existing infrastructure.

 +-----+                        +---+      +-----+    +-----+    ISP 1
 | SS1 |<-(16)+                 |   |  +-->|BRAS |----| ER1 |===>Network
 +-----+      |                 |  b|  |   +-----+    +-----+
 +-----+      |     +-----+     |E r|  |
 | SS2 |<-(16)+-----| BS1 |-----|t i|  |
 +-----+            +-----+     |h d|--+
                                |  g|  |   +-----+    +-----+    ISP 2
 +-----+            +-----+     |  e|  +-->|BRAS |----| ER2 |===>Network
 | SS3 |<-(16)------| BS2 |-----|   |  |   +-----+    +-----+
 +-----+            +-----+     +---+  |
 +-----+            +-----+            |
 | TE  |<-(DSL)-----|DSLAM|------------+
 +-----+            +-----+

      Figure 5: Integration of 802.16 access into DSL infrastructure

   In this approach the 802.16 BS is acting as a DSLAM (Digital
   Subscriber Line Access Multiplexer).  On the network side, the BS is
   connected to an Ethernet bridge which can be separate equipment or
   integrated into BRAS (Broadband Remote Access Server).  IPv6 Related Infrastructure Changes

   IPv6 will be deployed in this scenario by upgrading the following
   devices to dual-stack: MS, BS, AR and ER.  In this scenario, IEEE 802.16
   BSs have only MAC and PHY layers without router function and operates
   as a bridge.  The BS does not need to support IPv6.  However, if IPv4
   stack is loaded to them for management and configuration purpose, it
   is expected that BS should be upgraded by implementing IPv6 stack,

   The BRAS in Figure 4 5 is providing the functionality of the AR.  The
   Ethernet bridge is necessary for protecting the BRAS from 802.16 link
   layer peculiarities.  The Ethernet bridge relays all traffic received
   through BS to its network side port(s) connected to BRAS.  Any
   traffic received from BRAS is relayed to appropriate BS.  Since
   802.16 MAC layer has no native support for multicast (and broadcast)
   in the uplink direction, the Ethernet bridge will emulate Ethernet
   level implement multicast
   (and broadcast) by relaying the multicast frame received from the MS
   to all of its ports.  The Ethernet bridge may also provide some IPv6
   specific functions to increase link efficiency of the 802.16 radio
   link (see Section  Addressing

   One or more IPv6 prefixes can be shared to all the attached MSs.
   Prefix delegation can be required since if networks can exist behind SS.  IPv6 Transport

   Note that in this scenario Ethernet CS may be more appropriate than
   IPv6 CS to transport IPv6 packets, since the scenario need to support
   plain Ethernet connectivity end-to-end.  However, the IPv6 CS can
   also be supported.  Every  The MS and the BS has will consider the Ethernet type MAC
   address.  If connections
   between the MS is using peer IP CS, then the BS needs to take care of
   the Ethernet header.  In the upstream direction, CSs at the MS and BS will need to
   generate an appropriate Ethernet header and prepend it form a point to the IP
   datagram. point
   link.  In the downstream direction, the BS will use the
   destination address from the Ethernet header to identify the MS and
   then it will strip the Ethernet header before relaying the IP
   datagram over the 802.16 MAC connection. CS case, an Ethernet bridge may provide
   implementation of authoritative address cache and Relay DAD.
   Authoritative address cache is a mapping between the IPv6 address and
   the MAC addresses of all attached MSs.

   The bridge builds its authoritative address cache by parsing the IPv6
   Neighbor Discovery messages used during address configuration (DAD).
   Relay DAD means that the Neighbor Solicitation message used in DAD
   process will be relayed only to the MS which already has configured
   the solicited address as its own address (if such MS exist at all).  Routing

   In this scenario, IPv6 multi-homing considerations exist.  For
   example, if there exist two routers to support MSs, default router
   must be selected.

   The Edge Router runs the IGP used in the SP network such as OSPFv3
   [RFC2740] or IS-IS for IPv6.  The connected prefixes have to be
   redistributed.  Prefix summarization should be done at the Edge
   Router.  Mobility

   No mobility functions are supported in fixed access scenario.
   However, mobility can support in the radio coverage without any
   mobility protocol like WLAN technology.  Therefore, a user can access
   Internet nomadically in the coverage.

2.3.  IPv6 Multicast

   In IEEE 802.16 air link, downlink connections can be shared among
   multiple MSs, enabling multicast channels with multiple MSs receiving
   the same information from the BS.  MBS may be used to efficiently
   implement multicast.  However, it is not clear how to do this, as
   currently CID is assigned by BS, but in MBS it should be done at an
   AR and it's network scope.  For MBS how this mapping will happen is
   not clear, so MBS discussions have been postponed in WiMax for now.
   Note that it should be intensively researched later, since MBS will
   be one of the killer services in IEEE 802.16 networks.

   In order to support multicast services in IEEE 802.16, Multicast
   Listener Discovery (MLD) [RFC2710] must be supported between the MS
   and AR.  Also, the inter-working with IP multicast protocols and
   Multicast and Broadcast Service (MBS) should be considered.

   MBS defines Multicast and Broadcast Services, but actually, MBS seems
   to be a broadcast service, not multicasting.  MBS adheres to
   broadcast services, while traditional IP multicast schemes define
   multicast routing using a shared tree or source-specific tree to
   deliver packets efficiently.

   In IEEE 802.16 networks, two types of access to MBS may be supported:
   single-BS access and multi-BS access.  Therefore, these two types of
   services may be roughly mapped into Source-Specific Multicast.

2.4.  IPv6 QoS

   In IEEE 802.16 networks, a connection is unidirectional and has a QoS
   specification.  The QoS has different semantics with IP QoS (e.g.,
   diffserv).  Mapping CID to Service Flow IDentifier (SFID) defines QoS
   parameters of the service flow associated with that connection.  In
   order to interwork with IP QoS, IP QoS (e.g., diffserv, or flow label
   for IPv6) mapping to IEEE 802.16 link specifics should be provided.

2.5.  IPv6 Security

   When initiating the connection, an MS is authenticated by the AAA
   server located at its service provider network.  All the parameters
   related to authentication (username, password and etc.) are forwarded
   by the BS to the AAA server.  The AAA server authenticates the MSs
   and once authenticated.  When an MS is once authenticated and
   associated successfully with BS, IPv6 address will be acquired by the
   MS with stateless autoconfiguration or DHCPv6.  Note the initiation
   and authentication process is the same as used in IPv4.

   IPsec is a fundamental part of IPv6.  Unlike IPv4, IPsec for IPv6 may
   be used within the global end-to-end architecture.  But, we don't
   have PKIs across organizations and IPsec isn't integrated with IEEE
   802.16 network mobility management.

   IEEE 802.16 network threats may be different from IPv6 and IPv6
   transition threat models [I-D.ietf-v6ops-security-overview].  It
   should be also discussed.

2.6.  IPv6 Network Management

   For IPv6 network management, the necessary instrumentation (such as
   MIBs, NetFlow Records, etc) should be available.

   Upon entering the network, an MS is assigned three management
   connections in each direction.  These three connections reflect the
   three different QoS requirements used by different management levels.
   The first of these is the basic connection, which is used for the
   transfer of short, time-critical MAC management messages and radio
   link control (RLC) messages.  The primary management connection is
   used to transfer longer, more delay-tolerant messages such as those
   used for authentication and connection setup.  The secondary
   management connection is used for the transfer of standards-based
   management messages such as Dynamic Host Configuration Protocol
   (DHCP), Trivial File Transfer Protocol (TFTP), and Simple Network
   Management Protocol (SNMP).

   IPv6 based IEEE 802.16 network can be managed by IPv4 or IPv6 when
   network elements are implemented dual stak.  For example, network
   management system (NMS) can send SNMP message by IPv4 with IPv6
   related object identifier.  Also, an NMS can use IPv6 for SNMP
   request and response including IPv4 related OID.

3.  IANA Considerations

   This document requests no action by IANA.

4.  Security Considerations

   Please refer to Section 2.5 "IPv6 Security" technology sections for

5.   Acknowledgements

   This work extends v6ops works on [I-D.ietf-v6ops-bb-deployment-
   scenarios].  We thank all the authors of the document.  Special
   thanks are due to Maximilian Riegel, Jonne Soininen, Brian E
   Carpenter, Jim Bound, David Johnston, Basavaraj Patil, Byoung-Jo Kim
   and Jung-Mo Moon for extensive review of this document.

6.  References

6.1.  Normative References

   [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.

   [RFC2710]  Deering, S., Fenner, W., and B. Haberman, "Multicast
              Listener Discovery (MLD) for IPv6", RFC 2710,
              October 1999.

   [RFC2740]  Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6",
              RFC 2740, December 1999.

6.2.  Informative References

   [RFC3314]  Wasserman, M., "Recommendations for IPv6 in Third
              Generation Partnership Project (3GPP) Standards",
              RFC 3314, September 2002.

   [RFC3775]  Johnson, D., Perkins, C., and J. Arkko, "Mobility Support
              in IPv6", RFC 3775, June 2004.


              Jee, J., "16ng "IP over 802.16 Problem Statement",
              draft-jee-16ng-problem-statement-02 Statement and Goals",
              draft-ietf-16ng-ps-goals-00 (work in progress),
              October 2005.

   [I-D.madanapalli-16ng-subnet-model-analysis] 2006.

              Madanapalli, S., "Analysis of IPv6 Link Models for 802.16
              based Networks",
              draft-ietf-16ng-ipv6-link-model-analysis-02 (work in
              progress), September 2006. January 2007.

              Koodli, R., "Fast Handovers for Mobile IPv6",
              draft-ietf-mipshop-fmipv6-rfc4068bis-00 (work in
              progress), May 2006.

              Jang, H., "Mobile IPv6 Fast Handovers over IEEE 802.16e
              Networks", draft-ietf-mipshop-fh80216e-00 draft-ietf-mipshop-fh80216e-01 (work in
              progress), April 2006. January 2007.

              Davies, E., "IPv6 Transition/Co-existence Security
              Considerations", draft-ietf-v6ops-security-overview-05 draft-ietf-v6ops-security-overview-06
              (work in progress), September October 2006.

              Asadullah, S., "ISP IPv6 Deployment Scenarios in Broadband
              Access Networks",
              draft-ietf-v6ops-bb-deployment-scenarios-05 (work in
              progress), June 2006.

              Aboba, B., "Multiple Encapsulation Methods Considered
              Harmful", draft-iab-link-encaps-02 draft-iab-link-encaps-05 (work in progress),
              October 2006.

              "IEEE 802.16-2004, IEEE standard for Local and
              metropolitan area networks, Part 16: Air Interface for
              fixed broadband wireless access systems", October 2004.

              "IEEE Std. for Local and metropolitan area networks Part
              16: Air Interface for Fixed and Mobile Broadband Wireless
              Access Systems Amendment 2: Physical and Medium Access
              Control Layers for Combined Fixed and Mobile Operation in
              Licensed Bands and Corrigendum 1", February 2006.

Authors' Addresses

   Myung-Ki Shin
   161 Gajeong-dong Yuseng-gu
   Daejeon, 305-350

   Phone: +82 42 860 4847

   Youn-Hee Han
   Gajeon-Ri 307 Byeongcheon-Myeon
   Cheonan-Si Chungnam Province, 330-708


   Sang-Eon Kim
   17 Woomyeon-dong, Seocho-gu
   Seoul, 137-791


   Domagoj Premec
   Siemens Mobile
   Heinzelova 70a
   10010 Zagreb


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