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RFC 4779

ISP IPv6 Deployment Scenarios in Broadband Access Networks

Pages: 81
Informational
Errata
Part 4 of 4 – Pages 55 to 81
First   Prev   None

Top   ToC   RFC4779 - Page 55   prevText

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
Top   ToC   RFC4779 - Page 56
   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.
Top   ToC   RFC4779 - Page 57
   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
Top   ToC   RFC4779 - Page 58
       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.
Top   ToC   RFC4779 - Page 59
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.
Top   ToC   RFC4779 - Page 60
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.
Top   ToC   RFC4779 - Page 61
   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.
Top   ToC   RFC4779 - Page 62
       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.
Top   ToC   RFC4779 - Page 63
       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.
Top   ToC   RFC4779 - Page 64
   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
Top   ToC   RFC4779 - Page 65
   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.
Top   ToC   RFC4779 - Page 66
   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
Top   ToC   RFC4779 - Page 67
   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).
Top   ToC   RFC4779 - Page 68
   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
Top   ToC   RFC4779 - Page 69
   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
Top   ToC   RFC4779 - Page 70
       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.
Top   ToC   RFC4779 - Page 71

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].
Top   ToC   RFC4779 - Page 72
   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.
Top   ToC   RFC4779 - Page 73
   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].
Top   ToC   RFC4779 - Page 74
        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.
Top   ToC   RFC4779 - Page 75
   [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.
Top   ToC   RFC4779 - Page 76
   [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.
Top   ToC   RFC4779 - Page 77
   [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.
Top   ToC   RFC4779 - Page 78
   [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.
Top   ToC   RFC4779 - Page 79

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
Top   ToC   RFC4779 - Page 80
   Jordi Palet Martinez
   Consulintel
   San Jose Artesano, 1
   Alcobendas, Madrid  E-28108
   Spain

   Phone: +34 91 151 81 99
   EMail: jordi.palet@consulintel.es
Top   ToC   RFC4779 - Page 81
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