One document matched: draft-ietf-16ng-ip-over-ethernet-over-802.16-00.txt




Network Working Group                                            H. Jeon
Internet-Draft                                                      ETRI
Intended status: Standards Track                               M. Riegel
Expires: June 4, 2007                                            Siemens
                                                                S. Jeong
                                                                    ETRI
                                                                Dec 2006


       Transmission of IP over Ethernet over IEEE 802.16 Networks
          draft-ietf-16ng-ip-over-ethernet-over-802.16-00.txt

Status of this Memo

   By submitting this Internet-Draft, each author represents that any
   applicable patent or other IPR claims of which he or she is aware
   have been or will be disclosed, and any of which he or she becomes
   aware will be disclosed, in accordance with Section 6 of BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on June 4, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2006).

Abstract

   This document describes the behavior of the Ethernet emulation on top
   of IEEE 802.16 to efficiently support the transmission of IPv4 as
   well as IPv6 packets over IEEE 802.16 radio links.  Due to resource
   constraints of radio transmission systems and the limitations of the
   IEEE 802.16 MAC layer for the emulation of Ethernet, the transmission



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   of IP over an emulated LAN on top of IEEE 802.16 may considerably
   benefit by adding IP specific support functions within the Ethernet
   emulation on top of IEEE 802.16.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4.  The IEEE 802.16 Link Model . . . . . . . . . . . . . . . . . .  4
     4.1.  Connection Oriented Air Interface  . . . . . . . . . . . .  4
     4.2.  Convergence Sublayers  . . . . . . . . . . . . . . . . . .  4
     4.3.  Multicast and Broadcast Support in IEEE 802.16 . . . . . .  5
     4.4.  Discovery of MAC addresses . . . . . . . . . . . . . . . .  5
   5.  The IEEE 802.16 Network Model for Ethernet . . . . . . . . . .  5
     5.1.  IEEE 802.16 Ethernet Link Model  . . . . . . . . . . . . .  5
     5.2.  Ethernet without Native Broadcast and Multicast Support  .  6
     5.3.  Default Processing of Ethernet Frames  . . . . . . . . . .  6
   6.  Deployment Scenarios for IP over Ethernet over IEEE 802.16 . .  7
     6.1.  Public Access Scenario . . . . . . . . . . . . . . . . . .  7
     6.2.  VLAN Scenario  . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Filtering and Forwarding . . . . . . . . . . . . . . . . . . .  8
     7.1.  IP Broadcast and Multicast Support . . . . . . . . . . . .  8
     7.2.  Packet Filtering . . . . . . . . . . . . . . . . . . . . .  8
     7.3.  Identification Cache Table . . . . . . . . . . . . . . . .  9
     7.4.  Address Resolution Protocol Proxy Function . . . . . . . . 10
     7.5.  Neighbor Discovery Relay Function  . . . . . . . . . . . . 10
     7.6.  Access Router Behavior . . . . . . . . . . . . . . . . . . 11
   8.  Transmission of IP over Ethernet . . . . . . . . . . . . . . . 11
     8.1.  IPv4 over Ethernet . . . . . . . . . . . . . . . . . . . . 12
       8.1.1.  Address Resolution . . . . . . . . . . . . . . . . . . 12
     8.2.  IPv6 over Ethernet . . . . . . . . . . . . . . . . . . . . 12
       8.2.1.  Router Discovery, Prefix Discovery and Parameter
               Discovery  . . . . . . . . . . . . . . . . . . . . . . 12
       8.2.2.  Address Configuration  . . . . . . . . . . . . . . . . 13
       8.2.3.  Address Resolution . . . . . . . . . . . . . . . . . . 13
     8.3.  Maximum Transmission Unit Consideration  . . . . . . . . . 13
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 13
   10. Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 14
   11. Informative References . . . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
   Intellectual Property and Copyright Statements . . . . . . . . . . 17








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1.  Introduction

   IEEE 802.16 [IEEE802.16] defines a point-to-multipoint radio
   transmission system connecting a Base Station (BS) with multiple
   Subscriber Stations (SSs).  IEEE 802.16e [IEEE802.16e] amends the
   base specification with PHY and MAC functions for supporting mobile
   terminals by adopting the same data link principles also for mobile
   networking systems.

   This document provides a detailed description of the Ethernet
   emulation on top of IEEE 802.16 with additional functionalities for
   efficient support of IPv4 packets as well as IPv6 packets.


2.  Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


3.  Terminology

   Description of following some terms is taken directly from
   [IEEE802.16] and [IEEE802.16e].

   Base Station (BS):  A generalized equipment set providing
      connectivity, management, and control of the subscriber station.

   Subscriber Station (SS):  A generalized equipment set providing
      connectivity between subscriber equipment and a base station.
      Within this document the term SS also represents the Mobile
      Subscriber Station introduced in IEEE 802.16e

   Service-specific Convergence Sublayer (CS):  Sublayer in the IEEE
      802.16 MAC layer which classifies external network data and
      associates them to the proper MAC service flow identifier and
      connection identifier.

   Connection Identifier (CID):  A 16 bit value that identifies a
      connection to equivalent peers in the MAC of the base station and
      subscriber station.

   Source Node:  Host which initiates an IPv6 Neighbor Discovery message
      using its own unique MAC address.  A Source Node may be co-located
      with a SS or may be behind a SS, when the SS acts as a bridge.





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   Target Node:  Host which is addressed by the target field in an IPv6
      Neighbor Discovery message.  The Target Node has its own unique
      MAC address and may be co-located with a SS or may be behind a SS,
      when the SS acts as a bridge


4.  The IEEE 802.16 Link Model

4.1.  Connection Oriented Air Interface

   The IEEE 802.16 MAC provides connections between a BS and its
   associated SSs.  Each of these connections is identified by a 16 bit
   CID number and has defined QoS capabilities.  Multiple connections
   can be established between a BS and a SS, each with its particular
   QoS class and direction.

              |         |         |                 |
           +--+--+   +--+--+   +--+--+         +--+-+-+--+
           | MAC |   | MAC |   | MAC |         |   MAC   |
           +-----+   +-----+   +-----+         +---------+
           | PHY |   | PHY |   | PHY |         |   PHY   |
           +-+-+-+   +-+-+-+   +-+-+-+         +-+-+-+-+-+
             | |       | |       | |             | | | |
             | +-------|-+-------|-+----CID#w----+ | | |
             |         |         +------CID#x------+ | |
             |         +----------------CID#y--------+ |
             +--------------------------CID#z----------+
             SS#1      SS#2      SS#3              BS

                  Figure 1. Basic IEEE 802.16 Link Model

   While uplink connections provide only unicast transmission
   capabilities from a particular SS to the BS, downlink connections can
   be used for multicast transmissions to a group of SSs as well as for
   unicast transmission from the BS to a particular SS.

4.2.  Convergence Sublayers

   The assignment of higher layer packets to particular service flows
   and the related CIDs is performed within the IEEE 802.16 convergence
   sublayer by classifying the packets according to particular header
   fields.  To enable the transmission of different kind of payloads
   over IEEE 802.16, multiple types of classification types are defined,
   each specific for one kind of upper layer protocol, like Ethernet,
   IPv4, IPv6 or even for encapsulated payload, like IPv4 over Ethernet
   or IPv6 over Ethernet.

   Optionally the convergence sublayer performs a packet header



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   suppression reducing static parts of the header to a single byte
   value.  With the application of the packet header suppression
   function there is mostly no difference in header overhead over the
   air for Ethernet encapsulated IP packets in comparison to plain IP
   packets.

4.3.  Multicast and Broadcast Support in IEEE 802.16

   Downlink connections can be shared among multiple SSs, enabling
   multicast channels with multiple SSs receiving the same information
   from the BS.  Multicast is not enabled in the uplink but must be
   realized by an entity on top the IEEE 802.16 MAC sending packets
   received on a unicast uplink downstream on a multicast channel.

4.4.  Discovery of MAC addresses

   The 48-bit unique MAC address of a SS is used during the initial
   ranging process for the identification of a SS and verified by the
   succeeding PKMv2 authentication phase.  As a result, the BS
   establishes a list of MAC addresses of all SSs connected to the BS.
   Note that there may be additional MAC addresses behind SSs when SSs
   act as bridge connecting networks behind the SSs.  The additional MAC
   addresses may be also discovered when there is a controlled link
   state for the hosts behind the SS and the SS performs authentication
   of the link, e.g. by running IEEE 802.1X on the SS.

   BS can construct link local address of each SS from adding prefix
   "FE80::/64" to last 24 bits of MAC address corresponding to the each
   SS and also derive solicited-node MAC address of each SS from prefix
   "33-33-FF" and last 24 bits of each SS's MAC address.


5.  The IEEE 802.16 Network Model for Ethernet

5.1.  IEEE 802.16 Ethernet Link Model

   According to [I-D.ietf-ipv6-2461bis], an IP Link is defined as a
   communication facility or medium over which nodes can communicate at
   the link layer, i.e. the layer immediately below IP.  IEEE 802.16
   provides point-to-point connections between SSs and the BS without
   enabling any direct SS to SS connectivity.  Ethernet is realized on
   top of IEEE 802.16 by implementing bridging between all SSs with IEEE
   802.16 providing the links between the hosts and the bridge behind
   the BS like the twisted pair wires used in today's switched Ethernet.







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          ------------------------ IP Link ------------------------

          |         |                 |                 |         |
         ETH       ETH               ETH               ETH       ETH
          |         |                 |                 |         |
          |         |       +---------+---------+       |         |
          |         |       |      Bridge       |       |         |
          |         |       +--+-+---------+-+--+       |         |
          |         |          | |         | |          |         |
       +--+--+   +--+--+    +--+-+--+   +--+-+--+    +--+--+   +--+--+
       | MAC |   | MAC |    |  MAC  |   |  MAC  |    | MAC |   | MAC |
       +-----+   +-----+    +-------+   +-------+    +-----+   +-----+
       | PHY |   | PHY |    |  PHY  |   |  PHY  |    | PHY |   | PHY |
       +-+-+-+   +-+-+-+    +-+-+-+-+   +-+-+-+-+    +-+-+-+   +-+-+-+
         | |       | |        | | |       | | |        | |       | |
         | +-------|-+--CID#u-+ | |       | | +-CID#x--+-|-------+ |
         |         +----CID#v---+ |       | +---CID#y----+         |
         +--------------CID#w-----+       +-----CID#z--------------+

         SS#1      SS#2       BS#1         BS#2       SS#3      SS#4

             Figure 2. IEEE 802.16 IP over Ethernet Link Model

   It is possible to control the size and coverage of IP links by
   segmenting the Ethernet and grouping particular links into VLANs.
   Such segmentation is mostly done between BSs, but it is also possible
   to extend the segmentation over IEEE802.16 links when multiple hosts
   are attached to a bridge at the SS.

5.2.  Ethernet without Native Broadcast and Multicast Support

   Ethernet is emulated on top of IEEE 802.16 without making use of MBS
   as defined in 6.3.23 of [IEEE802.16e] to allow full control over the
   reaction of SSs to broadcast messages.  Instead of using MBS,
   broadcast and multicast messages are transferred in a unicast manner.

5.3.  Default Processing of Ethernet Frames

   The BS SHALL forward all the radio connections belonging to one SS to
   a port of a bridge between all ports on the radio side and the
   interfaces towards the network side.  If the SS functions as a bridge
   then it SHALL support a bridging between all its LAN ports and the
   airlink.

   When performing Learning Process specified in [IEEE802.1D], the
   bridge or the SS that performs bridging function shall learn all
   source MAC addresses originating from a port.  This enables the
   bridge or the SS to construct Dynamic Filtering Entries if the same



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   MAC addresses are not already listed as Static Filtering Entries.
   The information in the Dynamic Filtering Entry shall be automatically
   unlearned after BRIDGETIMEOUT seconds have expired without any
   traffic from that MAC address.  The dynamic information on all
   learned MAC to port associations and static information in Static
   Filtering Entries constitute the Filtering Database.  Bridge decides
   to which ports of the bridge a frame should be forwarded by querying
   the Filtering Database.

   When performing bridging, any packets destined for one of the
   addresses in the Filtering Database SHALL be forwarded directly to
   that port, if appropriate for the particular scenario, and all
   packets received from a port, for which the packet's destination MAC
   address is also an entry for that port in the Filtering Database,
   SHALL be silently discarded.


6.  Deployment Scenarios for IP over Ethernet over IEEE 802.16

   Figure 3 and 4 show possible deployment scenarios in case of IP over
   Ethernet over IEEE 802.16.  In both figures, the AR is connected to a
   bridge, which is connected to all BSs.  The bridge supports Static
   Filtering Entries and Standard Learned Bridging, as specified in
   Section 5.3.  Multiple ARs can exist on a link, and a subnet (IP
   Link) consists of multiple hosts usually being co-located with a SS
   acting as bridge.  The network behind a SS can support various access
   network technologies, e.g. 802.3, 802.11 or 802.15.

6.1.  Public Access Scenario

   Figure 3 depicts an IEEE 802.16 network deployment scenario without
   direct host-to-host communication.  In the general public access
   case, direct communication between nodes is restricted because of
   security and accounting issues.  In this scenario, the bridge SHALL
   forward all packets received from any radio side port to a network
   side port.  Peer-to-peer communication is not supported by the bridge
   and all packets originated from a SS should be delivered to an AR.


               +-----+    +-----+      +-------+
               | SS  |----| BS1 |------|       |       +------+
               +-----+    +-----+      |       |-------|  AR  |
                                       |Bridge |       +------+
      +-----+  +-----+    +-----+      |       |
      |Hosts|--| SS  |----| BS2 |------|       |
      +-----+  +-----+    +-----+      +-------+





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     Figure 3. Network Model without direct host-to-host communication

6.2.  VLAN Scenario

   Figure 4 shows the VLAN scenario.  Particular SSs grouped into a VLAN
   can directly communicate with each other when this model is enabled
   for the VLAN.  Otherwise, direct communication is prohibited and the
   VLAN shows the same behavior as the public access scenario.  The
   bridge has been extended to support VLAN capability and configurable
   direct host-to-host communication.


               +-----+    +-----+      +-------+
               | SS  |----| BS1 |------|       |       +------+
               +-----+    +-----+      |Bridge |-------|  AR  |
                                       |(VLAN) |       +------+
      +-----+  +-----+    +-----+      |       |
      |Hosts|--| SS  |----| BS2 |------|       |
      +-----+  +-----+    +-----+      +-------+


      Figure 4. Network Model with direct host-to-host communication


7.  Filtering and Forwarding

7.1.  IP Broadcast and Multicast Support

   IP broadcast and multicast data are replicated and then transferred
   in a unicast manner without using native MBS support as explained in
   Section 5.2.

   Unicast 802.16 transport connections are extended to a bridge by any
   tunneling mechanism such as GRE tunnel between BSs and the bridge.
   As a result, point-to-point connections have been established between
   a bridge and each SSs.

   IP Broadcast and multicast data shall be carried to the intended SSs
   via the tunnels and unicast 802.16 transport connections.

7.2.  Packet Filtering

   The bridge SHALL have the ability to enable or disable any filtering
   functionality defined herein.  If a packet is filtered it SHALL be
   silently discarded.  The filtering functionality is based on the
   information in the Identification Cache Table (ICT) defined in
   Section 7.3.




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   The bridge SHALL support filtering of all packets received from a
   network side port to a destination MAC address or Multicast IP
   address not existing in the ICT or expired address.

   The bridge SHALL support filtering of all packets received from a
   network side port to a broadcast or all-nodes multicast MAC address.

   If filtering is enabled the bridge SHALL permit all Address
   Resolution Protocol messages to pass to the ARP Proxy Agent and all
   Neighbor Discovery messages to pass to the Neighbor Discovery (ND)
   Relay Agent for additional processing as specified in following
   section.

7.3.  Identification Cache Table

   The bridge establishes and maintains information about each SS by the
   mean of an Identification Cache Table (ICT), which is an extension of
   the Filtering Database.  Note that the bridge in this document
   supports IGMP/MLD Snooping [RFC4541].

   For IPv4 over Ethernet, ICT contains MAC address and Port Map, which
   constitute a filtering entry in Filtering Database, tunnel ID,
   lifetime, and one or more unicast and multicast IPv4 addresses.  The
   unicast IPv4 addresses can be learned by examining the source address
   of packets or DHCP Response message.  The multicast IPv4 address can
   be added and removed by snooping IGMP Membership Report and Leave
   Group messages from SS.

   For IPv6 over Ethernet, ICT includes one or more unicast IPv6
   addresses with associated Valid Flags and multicast IPv6 address in
   addition to MAC address, Port Map, tunnel ID, and lifetime in ICT for
   IPv4 over Ethernet.  In case of stateful address configuration, the
   unicast IPv6 addresses can be learned by examining the source address
   of packets or DHCP message.  In stateless address autoconfiguration,
   the unicast IPv6 address is learned by extracting the Target field in
   the Neighbor Solicitation (NS) message for Duplicate Address
   Detection (DAD), if the tentative IPv6 address does not exist yet as
   a valid IPv6 address in the ICT.  In this case, the Valid Flag is set
   to indicate the tentative IPv6 address has become valid.  Otherwise,
   the IPv6 address in the Target field in a DAD NS message is stored as
   IPv6 address with Valid Flag is not set to identify the Source Node
   when the bridge relays the Neighbor Advertisement message from Target
   Node.  The multicast IPv6 address can be added and removed by
   snooping MLD Report and Done messages from SS.

   The tunnel ID identifies tunnels between bridge and BSs which
   construct the point-to-point connection between bridge and SS with
   IEEE 802.16 unicast connection.  GRE key can be one of the tunnel ID.



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   The lifetime is similar to Ageing Time in [IEEE802.1D].  It has
   elapsed since the corresponding entry was added and it is refreshed
   by continuous traffic from the MAC address.  The default value of the
   lifetime is set by management.

   The ARP Proxy Agent and the ND Relay Agent functions are based on
   information contained in the ICT.  Figure 5 and Figure 6 show the ICT
   for IPv4 over Ethernet and IPv6 over Ethernet.


             +---------+--------+-------+------+-------+---------+
             |   MAC   |  Port  |Tunnel | Life |Unicast|Multicast|
             | address |  MAP   |  ID   | time |address| address |
             +---------+--------+-------+------+-------+---------+
             |         |        |       |      |       |         |
             +---------+--------+-------+------+-------+---------+


           Figure 5. ICT on Bridge in case of IPv4 over Ethernet



             +-------+------+------+-----+---------+-----+----------+
             |  MAC  | Port |Tunnel|Life | Unicast |Valid| Multicast|
             |address| MAP  |  ID  |time | address |Flag | address  |
             +-------+------+------+-----+---------+-----+----------+
             |       |      |      |     |         |     |          |
             +-------+------+------+-----+---------+-----+----------+


           Figure 6. ICT on Bridge in case of IPv6 over Ethernet

7.4.  Address Resolution Protocol Proxy Function

   In the case of IPv4 over Ethernet, ARP requests can be responded by
   the ARP Proxy Agent of the bridge. (refer to Section 8.1.1 for more
   detail)

   However, a proxy function in IPv6 over Ethernet is subjected to
   restriction because of security issues.  Support of SeND [RFC3971]
   has been adopted in the IPv6 over Ethernet case.

7.5.  Neighbor Discovery Relay Function

   In the case of IPv6 over Ethernet, the AR sends periodically Router
   Advertisement and the Router Advertisement messages can be relayed by
   the ND Relay Agent of the bridge.  The ND Relay Agent unicasts the
   Router Advertisement via all the already established a point-to-point



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   connections between bridge and SSs.

   When the bridge receives Neighbor Solicitation for DAD, the ND Relay
   Agent of the bridge performs the same operation as the Relay DAD.
   The ND Relay Agent looks up in the ICT to detect whether a tentative
   address in the Neighbor Solicitation message is in use or not.  If
   the tentative address is not in use, the ND Relay Agent discards the
   Neighbor Solicitation.  Otherwise, the Neighbor Solicitation message
   is relayed only to the addressed Target Node.

   When the bridge receives the DAD Neighbor Advertisement message from
   the Target Node, the ND Relay Agent of the bridge identifies the
   corresponding Source Node by the ICT and then unicasts the DAD
   Neighbor Advertisement message via the established point-to-point
   connection to the corresponding Source Node.

7.6.  Access Router Behavior

   The assignment of a common prefix to all SSs means locating them "on-
   link" in terms of IP packet transfer.  According to
   [I-D.ietf-ipv6-2461bis], an IP node performs a longest prefix match
   against the prefix list in order to decide whether the destination of
   the IP packet is on-link or not.  Therefore, SSs sharing a prefix can
   be said to be on-link IP nodes.

   In the Public Access scenario, all unicast packets originated from a
   SS should be delivered to an AR even though the SS sends packets to
   on-link SSs.  Therefore, it is necessary for the AR to relay the on-
   link packets.

   The AR SHALL have packet-relay functionality.  The AR relays packets
   destined for IP broadcast address and link-local scoped multicast
   addresses to incoming interface again.  When relaying, AR does not
   decrease the value of TTL or Hop Limit.

   When the AR relays packets destined for on-link host, the packet may
   be forwarded onto the incoming interface.  It should be prevented
   that the AR transmits a Redirect message to sender when direct
   communication between on-link SSs occurs.

   In the case of the VLAN scenario, direct communication between SSs
   may be enabled for all SSs belonging to a particular VLAN.  In this
   case, no special handling is required.


8.  Transmission of IP over Ethernet





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8.1.  IPv4 over Ethernet

   [RFC0894] defines the transmission of IP packets over Ethernet
   networks.  It contains the specification of the encapsulation of the
   IP packets into Ethernet frames as well as rules for mapping of IP
   addresses onto Ethernet MAC addresses.  The use of ARP [RFC0826] is
   recommended for dynamic address resolution.

8.1.1.  Address Resolution

   The bridge SHALL support an ARP Proxy.  The bridge SHALL have the
   ability to enable or disable the ARP Proxy.

   If the ARP Proxy is disabled, the ARP Proxy Agent shall pass all ARP
   packets without discrimination or modification using bridging.  The
   ARP Proxy Agent shall pass all ARP Response packets without
   discrimination or modification using bridging.

   If the ARP Proxy is enabled, upon receiving an ARP Request from an
   radio side interface, the ARP Proxy Agent shall unicast an ARP
   Response back to the interface provided that the target address
   matches an entry in the ICT.  Otherwise, the ARP Proxy Agent shall
   flood the ARP Request to all network side interfaces, that are in a
   forwarding state.

   The ARP Proxy Agent shall silently discard any received self-ARP
   Requests.  Those are requests for a target IP address, that when
   queried in the ICT results in a response MAC equal to the Request's
   source MAC address.

   The ARP Proxy Agent shall issue a gratuitous ARP on the network side
   interfaces for any new addition to the ICT.  An unsolicited broadcast
   ARP Response constitutes a gratuitous ARP.

8.2.  IPv6 over Ethernet

   The transmission of IPv6 Packets over Ethernet Networks is defined by
   [RFC2464] providing the frame format for encapsulation of IPv6
   packets into Ethernet frames.

8.2.1.  Router Discovery, Prefix Discovery and Parameter Discovery

   Router Discovery, Prefix Discovery and Parameter Discovery procedures
   are achieved by receiving Router Advertisement (RA) messages.  The RA
   is forwarded by using all-nodes IP multicast transmission.

   This document assumes a point-to-point connection between each SS and
   bridge.  The ND Relay Agent of the bridge unicast the RA from AR via



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   the point-to-point connection.

   Note that the RA has a long lifetime and minimum packet size which
   can be sent in IEEE 802.16 to the SSs being in sleep-mode during the
   periodic wakeup-time.

8.2.2.  Address Configuration

8.2.2.1.  Stateful Address Autoconfiguration

   When the'M' flag in the received RA is set, a SS should perform
   stateful address configuration according to [RFC3315].  In this case,
   an AR supports DHCPv6 server or relay function.

8.2.2.2.  Stateless Address Autoconfiguration

   The global IPv6 addresses is derived based on prefix and EUI-64-
   derived interface identifier and then confirmed through Duplicate
   Address Detection (DAD) as specified in [RFC2462].

   For DAD, the Source Node sends Neighbor Solicitation to the
   solicited-node MAC address corresponding to the generated global IPv6
   address for DAD.  The Neighbor Solicitation is passed to the ND Relay
   Agent when arriving at the bridge.

8.2.3.  Address Resolution

   The Source Node sends Neighbor Solicitation to the solicited-node
   address corresponding to the target address for address resolution.

   Upon receiving the Neighbor Solicitation, the bridge retrieves the
   port corresponding to the solicited-node MAC address in its ICT and
   then forwards the Neighbor Solicitation via that port.

   Finally the Target Node responds to the Neighbor Solicitation.

8.3.  Maximum Transmission Unit Consideration

   When stacked VLAN headers are transferred over GRE tunnels, the sizes
   of the VLAN headers and the GRE header need to be considered in
   setting the value of MTU of the transport path.


9.  Security Considerations

   [RFC3971] specifies security mechanisms for ND Protocol and defines
   means for securing ND Protocol messages.  This document aims to fully
   support security mechanisms specified in [RFC3971].



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10.  Acknowledgement

   We would like to express special thanks to David Johnston and Dave
   Thaler for their inputs to this work.


11.  Informative References

   [I-D.ietf-ipv6-2461bis]
              Narten, T., "Neighbor Discovery for IP version 6 (IPv6)",
              draft-ietf-ipv6-2461bis-09 (work in progress),
              October 2006.

   [I-D.jee-16ng-ps-goals]
              Jee, J., "IP over 802.16 Problem Statements and Goals",
              draft-jee-16ng-ps-goals-00 (work in progress),
              February 2006.

   [IEEE802.16]
              IEEE Std 802.16-2004, "IEEE Standard for Local and
              metropolitan area networks,  Part 16: Air Interface for
              Fixed Broadband Wireless Access Systems", October 2004.

   [IEEE802.16e]
              IEEE P802.16e-2005, "IEEE Standard for Local and
              metropolitan area networks, Amendment for Physical and
              Medium Access  Control Layers for Combined Fixed and
              Mobile Operation in Licensed Bands", December 2005.

   [IEEE802.1D]
              IEEE Std 802.1D-2004, "IEEE Standard for Local and
              metropolitan area networks,  Media Access Control (MAC)
              Bridges", June 2004.

   [RFC0826]  Plummer, D., "Ethernet Address Resolution Protocol: Or
              converting network protocol addresses to 48.bit Ethernet
              address for transmission on Ethernet hardware", STD 37,
              RFC 826, November 1982.

   [RFC0894]  Hornig, C., "Standard for the transmission of IP datagrams
              over Ethernet networks", STD 41, RFC 894, April 1984.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2460]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", RFC 2460, December 1998.




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   [RFC2461]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
              Discovery for IP Version 6 (IPv6)", RFC 2461,
              December 1998.

   [RFC2464]  Crawford, M., "Transmission of IPv6 Packets over Ethernet
              Networks", RFC 2464, December 1998.

   [RFC3041]  Narten, T. and R. Draves, "Privacy Extensions for
              Stateless Address Autoconfiguration in IPv6", RFC 3041,
              January 2001.

   [RFC3971]  Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
              Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC4541]  Christensen, M., Kimball, K., and F. Solensky,
              "Considerations for Internet Group Management Protocol
              (IGMP) and Multicast Listener Discovery (MLD) Snooping
              Switches", RFC 4541, May 2006.


Authors' Addresses

   Hongseok Jeon
   Electronics Telecommunications Research Institute
   161 Gajeong-dong, Yuseong-gu
   Daejeon,   305-350
   KOREA

   Phone: +82-42-860-3892
   Email: jeonhs@etri.re.kr


   Max Riegel
   Siemens
   St-Martin-Str 76
   Munich,   81541
   Germany

   Phone: +49-89-636-75194
   Email: maximilian.riegel@siemens.com











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   Sangjin Jeong
   Electronics Telecommunications Research Institute
   161 Gajeong-dong, Yuseong-gu
   Daejeon,   305-350
   KOREA

   Phone: +82-42-860-1877
   Email: sjjeong@gmail.com











































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