Network Working Group H. Singh Internet-Draft W. Beebee Intended status: BCP Cisco Systems, Inc. Expires: January 15, 2009 July 14, 2008 IPv6 CPE Router Recommendations draft-wbeebee-ipv6-cpe-router-02 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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 15, 2009. Abstract This document recommends IPv6 behavior for Customer Premises Equipment (CPE) routers in Internet-enabled homes and small offices. The CPE Router may be a standalone device. The CPE Router may also be embedded in a device such as a cable modem, DSL modem, cellular phone, etc. This document describes the router portion of such a device. Singh & Beebee Expires January 15, 2009 [Page 1] Internet-Draft CPE Router Recommendations July 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3 3. Operational Behavior . . . . . . . . . . . . . . . . . . . . . 4 3.1. Conceptual Configuration Variables . . . . . . . . . . . . 4 4. Router Initialization . . . . . . . . . . . . . . . . . . . . 4 5. Basic IPv6 Provisioning . . . . . . . . . . . . . . . . . . . 5 5.1. Acquire Link-Local Address . . . . . . . . . . . . . . . . 5 5.2. Process RAs . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. Acquire IPv6 address and other configuration parameters . 6 5.3.1. Numbered Model . . . . . . . . . . . . . . . . . . . . 6 5.3.2. Unnumbered Model . . . . . . . . . . . . . . . . . . . 6 5.4. Details for DHCPv6 Address Acquisition . . . . . . . . . . 6 5.5. IPv6 Provisioning of Home Devices . . . . . . . . . . . . 7 5.5.1. LAN initialization before WAN initialization . . . . . 8 5.5.2. WAN initialization before LAN initialization . . . . . 9 5.6. IPv6 over PPP . . . . . . . . . . . . . . . . . . . . . . 9 5.6.1. Softwire support . . . . . . . . . . . . . . . . . . . 9 5.7. Stateful DHCPv6 Server . . . . . . . . . . . . . . . . . . 10 6. Cascading of Routers behind the CPE Router . . . . . . . . . . 10 7. IPv6 Data forwarding . . . . . . . . . . . . . . . . . . . . . 10 7.1. IPv6 Multicast . . . . . . . . . . . . . . . . . . . . . . 11 8. Other IPv6 Features . . . . . . . . . . . . . . . . . . . . . 12 8.1. Path MTU Discovery Support . . . . . . . . . . . . . . . . 12 8.2. Optional support for RIPv6 . . . . . . . . . . . . . . . . 13 8.3. Firewall . . . . . . . . . . . . . . . . . . . . . . . . . 13 8.3.1. Packet filters . . . . . . . . . . . . . . . . . . . . 13 9. Quality Of Service(QoS) . . . . . . . . . . . . . . . . . . . 13 10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 13.1. Normative References . . . . . . . . . . . . . . . . . . . 14 13.2. Informative References . . . . . . . . . . . . . . . . . . 14 Appendix A. CHANGE HISTORY . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Singh & Beebee Expires January 15, 2009 [Page 2] Internet-Draft CPE Router Recommendations July 2008 1. Introduction This document defines IPv6 features for a residential or small office router referred to as a CPE Router. This device also needs to support IPv4, but that work is beyond the scope of this document. Also, this document does not go into configuration details for the CPE Router. The document discusses IPv6 implications for the attached Service Provider network. The document notes that the CPE Router may be deployed in home in one of two ways. Either the Service Provider or the home user may manage this device. When the CPE Router is managed by the Service Provider, the router may need additional management and routing properties like a new MIB definition and routing protocols communicating between the CPE Router and the Service Provider network. The CPE router has one WAN interface to connect to the Service Provider and one or more LAN interfaces to the home network devices. The WAN interface is preferred to be Ethernet encapsulated but it may support other encapsulations such as PPP. Each LAN interface is Ethernet encapsulated. 2. Terminology and Abbreviations Host - this is a personal computer or any other network device in a home that connects to the Internet via the CPE Router. LAN interface(s) - a set of network interfaces on the CPE Router that are used to connect hosts in the home. This set of ports could be switched, bridged, or routed. WLAN interface - an optional wireless access point interface on the CPE Router used to connect wireless hosts in the home in either managed or ad-hoc modes. WAN interface - a single network interface on the CPE Router that is used to connect the router to the access network of the Service Provider. GRE tunnel - Generic Routing Encapsulation tunnel. SLAAC - StateLess Address Auto Configuration. IPTV - Internet Protocol TeleVision. Singh & Beebee Expires January 15, 2009 [Page 3] Internet-Draft CPE Router Recommendations July 2008 3. Operational Behavior The CPE Router is a gateway to the Internet for a home. The router is also intended to provide home networking functionality. The CPE Router may have a console or web interface for configuration. This document defines the core set of features that are supported by the CPE Router, however individual implementations may include value- added features such as WLAN capability. The core set of IPv6 features for the CPE Router includes provisioning the CPE Router for IPv6, IPv6 data forwarding including IPv6 multicast, CPE Router provisioning hosts on its LAN interface(s), firewall, and QoS behavior. An IPv6 firewall is discussed briefly in the Firewall section where the section refers the draft-ietf-v6ops-cpe-simple-security [I-D.ietf-v6ops-cpe-simple-security] for more details. 3.1. Conceptual Configuration Variables The CPE Router maintains such a list of conceptual optional configuration variables. 1. Loopback interface enable. 2. PPPOE enable. 3. Softwire enable 4. RIPv6 enable. 5. If DHCPv6 fails, the CPE Router may initiate PPPOE or L2TPv2 Softwire tunnel. 4. Router Initialization Before the CPE Router is initialized, the device must have IPv6 enabled. The CPE Router should support the ability to disable its IPv6 stack. The CPE Router also has the ability to block or forward IPv6 traffic to and from the router's LAN interface(s). [RFC2669] includes a MIB definition to block the IPv4 or IPv6 Ethertype in the upstream or downstream interface(s) of a device such as the CPE Router. Some portion of this MIB may need to be modified for use with the CPE Router. The CPE Router supports at least one of two modes of initialization: either the LAN interface(s) become operational first or the WAN interface becomes operational first. More details have been provided Singh & Beebee Expires January 15, 2009 [Page 4] Internet-Draft CPE Router Recommendations July 2008 in the Basic IPv6 Provisioning section. 5. Basic IPv6 Provisioning The CPE Router needs to support two WAN interface models, one of which will be active on the CPE Router at any given time. In one model called as the numbered model the WAN interface of the CPE Router must acquire a global IPv6 address. In another model called as the unnumbered model, the WAN interface only acquires a link-local address. Further, in this unnumbered model, the CPE router enables an optional Loopback network interface, facing the Service Provider upstream, which initiates stateless DHCPv6 for IA_PD option and other IPv6 configuration. On completing DHCPv6, the Loopback interface will be assigned an IPv6 address sub-delegated from the IA_PD. In the numbered model, we recommend the CPE Router WAN interface acquire its global IPv6 address using stateful DHCPv6 for administrative control of the router. DHCPv6 IA_PD option can be used as described in [RFC3633]. Any of stateful DHCPv6, stateless autoconfiguration, or manual configuration may be supported by the CPE router for IPv6 address configuration of the WAN interface. Manual configuration is beyond the scope of this document. The CPE Router acquires its IPv6 addresses from the Service Provider along with any other IPv6 configuration any time the WAN interface is connected to the Service Provider network. Thereafter the CPE Router provisions its LAN interface(s) for IPv6 router functionality including provisioning global IPv6 addresses on the LAN interface(s). Even if LAN interface(s) have been operational and provisioned earlier, the global IPv6 configuration of LAN interface(s) is still required. More details for provisioning the CPE Router are given in the following sections. 5.1. Acquire Link-Local Address If an interface of the CPE Router is configured for IPv6, when the interface initializes itself, as per [RFC4862], the CPE Router must create a link-local address for the interface. We recommend the CPE Router use the EUI-64 identifier as a link-local address for each of its interfaces. Refer to EUI-64 details in [RFC4291]. Further, as per section 5.4 of [RFC4862], since the CPE Router supports link- layer multicast on all of its interfaces draft-ietf-6man-node-req-bis [I-D.ietf-6man-node-req-bis], it must perform Duplicate Address Detection (DAD) on all unicast addresses unless a layer 2-specific document specifies that DupAddrDetectTransmits is zero for that linktype. If the CPE Router detects a duplicate address assigned to an interface, the CPE Router must not send IPv6 packets from the interface. Singh & Beebee Expires January 15, 2009 [Page 5] Internet-Draft CPE Router Recommendations July 2008 5.2. Process RAs The CPE Router must process incoming RAs received on the WAN interface as specified in section 6.3 of [RFC4861]. The CPE Router locates routers that reside on the attached WAN link from the received RAs. 5.3. Acquire IPv6 address and other configuration parameters The CPE Router must process RAs received on the WAN interface. As per [RFC4861] if the M bit is set in the RA, the WAN interface must perform stateful DHCPv6- if the O bit is set in the RA, the WAN interface acquires other configuration information using stateless DHCPv6 [RFC3736]. If the A bit in the RA is clear or the RA does not include any Prefix Information Option (PIO), the WAN interface must not perform SLAAC. IPv6 deployments that configure RA to not include any PIO are discussed in draft-ietf-6man-ipv6-subnet-model [I-D.ietf-6man-ipv6-subnet-model]. If SLAAC is used to acquire a global IPv6 address, then subsequently, the WAN interface must initiate stateless DHCPv6 to obtain other parameters like Domain Name Server(s) IPv6 addresses and IA_PD DHCPv6 option. 5.3.1. Numbered Model As instructed by the RA message, the WAN interface acquires global IPv6 address using SLAAC or stateful DHCPv6. 5.3.2. Unnumbered Model When the CPE router is configured for Unnumbered model, after the WAN and Loopback interfaces have acquired a link-local address, the Loopback interface initiates SLAAC or stateful DHCPv6 to obtain IA_PD option and other configuration information. On receiving the DHCPv6 REPLY with IA_PD option, the CPE Router sub-delegates one global IPv6 address from the IA_PD option to the Loopback interface. At any instance in time of the CPE Router operation, the router does not forward any traffic between its WAN and LAN interface(s) if the router has not completed IPv6 provisioning process that involves the acquisition of a global IPv6 address by the WAN or loopback interface and the acquisition of a global or Unique Local Address (ULA) by the LAN interface(s). 5.4. Details for DHCPv6 Address Acquisition If the WAN interface uses stateful DHCPv6, the interface sends a DHCPv6 Solicit message as described in section 17.1.1 of [RFC3315]. The Solicit message must include an IA_NA option as specified by Singh & Beebee Expires January 15, 2009 [Page 6] Internet-Draft CPE Router Recommendations July 2008 [RFC3315]. If the WAN interfaces uses stateless DHCPv6, the WAN interface sends an Information Request. Both the DHCPv6 SOLICIT and Information Request also include other option like an IA_PD option as specified by [RFC3633], a Reconfigure Accept option to inform the server that client is willing to accept Reconfigure message from server, and the Options Request option that includes the DNS Recursive Name server option as specified in [RFC3646]. The Solicit may also include the Rapid Commit option if the CPE Router is willing to accept a 2-message DHCPv6 exchange with the server. When the CPE Router processes a DHCPv6 response from the server, if the response message (e.g. ADVERTISE or REPLY) received does not include an IA_PD option, or Reconfigure Accept option, then the CPE Router has failed DHCPv6 address acquisition. For stateful DHCPv6, the response message must also include an IA_NA option or stateful DHCPv6 address acquisition has failed. If stateful DHCPv6 succeeds, the CPE Router must perform DAD with the IPv6 address acquired from DHCPv6. If the CPE Router detects a duplicate, the CPE Router must send a DHCPv6 Decline message to the DHCPv6 server. The CPE Router may support the Reconfigure Key Authentication Protocol, as described in section 21.5 of [RFC3315]. The CPE Router may also support prefix sub-delegation. Prefix sub-delegation involves DHCPv6 server support with IA_PD on the CPE router and the ability to provision the server from a DHCPv6 REPLY with IA_PD option received on the WAN interface. 5.5. IPv6 Provisioning of Home Devices The CPE Router may include a stateful DHCPv6 server to assign addresses to home devices connected via the LAN interface(s) of the CPE Router. However, we recommend that the CPE Router use SLAAC for home devices. If the LAN interface(s) are switched or bridged ports, then the CPE Router assigns a single global IPv6 address to a conceptual virtual interface serving all the LAN interface(s). If each LAN interface is a routed port, then the CPE router will assign a global IPv6 address and unique subnet to each LAN interface. In either case, when the CPE Router needs to assign a single IPv6 address to LAN interface(s) or multiple IPv6 addresses, the CPE Router redistributes the addresses and subnets from the prefix received in IA_PD option by the WAN interface. If the IA_PD changes, the CPE Router must reconfigure the LAN interface(s) with new IPv6 addresses derived from the new IA_PD and then also renumber the IPv6 ND RA configuration on the LAN interface(s). This document recommends the RA sent out by LAN Interface(S) to be Singh & Beebee Expires January 15, 2009 [Page 7] Internet-Draft CPE Router Recommendations July 2008 configured for stateless autoconfiguration so that the prefix advertised in the RA is derived from the IA_PD assigned to the CPE Router by the Service Provider; the O-bit is also set so that the CPE Router can pass Domain Name Server(s) IPv6 address(es) to home devices. The CPE Router obtained the Domain Name Server(s) in OPTION_DNS_SERVERS option from the DHCPv6 server when the CPE Router WAN interface completed DHCPv6. 5.5.1. LAN initialization before WAN initialization On power up, the LAN interface(s) of the CPE Router may become operational before the WAN interface. This mode is appropriate for manual user configuration of the CPE Router. After any LAN interface has acquired a link-local address, the address can be used for user configuration via the network. The interface can assign itself a Unique Local Address automatically through the pseudo-random number generation algorithm described in [RFC4193]. Note that the ULA needs to have a larger subnet than a /64 if multiple routers are cascaded behind the CPE router and prefix sub-delegation is used (see the Cascading of Routers behind the CPE Router section below). Once the IPv6 address configuration of the LAN interface(s) is complete with a ULA, as per [RFC4862], the CPE Router sends Router Advertisements (RA) to devices in the home. Hosts receiving the RA from LAN interface(s) will process the RA and perform IPv6 address acquisition. After all the LAN interface(s) have become operational, if the WAN interface is connected to the Service Provider network, then the WAN interface provisions itself and may acquire an IA_PD. If an IA_PD is acquired, it may be sub-delegated to any cascaded routers or used for SLAAC provisioning of hosts in the home. Based on the IA_PD, the CPE Router configures global address(es) on the LAN interface(s) and sends an RA containing the global address and unique local prefixes out the LAN interface(s). After this process, every LAN interface has a link-local unicast address, a ULA, and a global unicast address (GUA). Therefore, the interface has to apply source address selection to determine which address to use as a source for outgoing packets. Since the GUA has a larger scope than the link- local address, or the ULA (rule #2 of [RFC3484]), the GUA will be used as a source address of outgoing packets that are not subject to rule #1. If a user desires to keep CPE Router configuration traffic local to the home network, the user can do the following: Use the ULA of the CPE Router as the destination of the configuration traffic. Use access control lists (ACL)s to block any ULA sourced packet from being sent out the WAN interface. Rule #1 of [RFC3484] and the ACLs ensure that the traffic does not Singh & Beebee Expires January 15, 2009 [Page 8] Internet-Draft CPE Router Recommendations July 2008 escape the home network. After the WAN interface initializes, then the LAN interface(s) can acquire global unicast addresses. 5.5.2. WAN initialization before LAN initialization On power up, the WAN interface of the CPE Router may become operational before the LAN interface(s). This mode is appropriate for Service Provider configuration of the CPE Router. After the IPv6 address configuration for WAN interface is completed, the CPE Router configures IPv6 address for LAN interface(s). Once IPv6 address configuration of the LAN interface(s) is complete, as per [RFC4862], the CPE Router sends Router Advertisements (RA) to devices in the home. Hosts receiving the RA from LAN interface(s) will process the RA and perform IPv6 address acquisition. 5.6. IPv6 over PPP In some deployments IPv6 over PPP is preferred to connect the home to the Service Provider. For such a deployment, another configuration variable on the CPE Router enables optional IPv6 over PPP support. After IPv6CP negotiates IPv6 over PPP and the WAN interface acquires an IA_PD option via stateless DHCPv6, the CPE Router assigns global address(es) to its LAN interface(s) and sub-delegates the IA_PD to hosts connected to the LAN interface(s). IPv6 over PPP follows [RFC5072]. As per [RFC5072], the CPE router does not initiate any DAD for unicast IPv6 addresses since DupAddrDetectTransmits variable from [RFC4862] is zero for IPv6 over PPP. If the Service Provider deployment supports dual-stack PPP support, then the CPE Router WAN interface may initiate one PPP logical channel and support NCP IPv4 and IPv6 control protocols over one PPP logical channel. [RFC4241] describes such behavior. The IPv4 and IPv6 NCP's are independent of each other and start and terminate independently. 5.6.1. Softwire support If the CPE Router is deployed in a deployment where the home includes IPv6 hosts but the Service Provider network does not support IPv6, an optional softwire feature must be enabled on the CPE Router. The softwire draft-ietf-softwire-hs-framework-l2tpv2 [I-D.ietf-softwire-hs-framework-l2tpv2] initiates L2TPv2 tunnel from the CPE Router to tunnel IPv6 data from the home over an IPv4 network. The feature is enabled before any IPv6 host in the home is connected to the CPE Router or the WAN interface of the CPE Router is Singh & Beebee Expires January 15, 2009 [Page 9] Internet-Draft CPE Router Recommendations July 2008 operational. If the CPE Router supports the Softwire feature, then the CPE Router must support the deployment scenario of Router CPE as Softwire Initiator described in section 3.1.2 of draft-ietf-softwire-hs-framework-l2tpv2 [I-D.ietf-softwire-hs-framework-l2tpv2]. IPV6CP negotiates IPv6 over PPP which also provides the capability for the Service Provider to assign the 64-bit Interface-Identifier to the WAN interface of the CPE Router. After the WAN interface has acquired an IA_PD option, global addresses from the IA_PD are assigned to the LAN interface(s) and the IA_PD is also sub-delegated to clients connected to the LAN interface(s). 5.7. Stateful DHCPv6 Server The CPE Router may support a stateful DHCPv6 server to serve clients on the CPE Router LAN interface(s). If the CPE Router needs to support a stateful DHCPv6 server, then more details will be added to this section specifying the minimal functionality that the stateful DHCPv6 server needs to support. 6. Cascading of Routers behind the CPE Router To support cascading routers behind the CPE Router this document recommends using prefix sub-delegation of the prefix obtained either via IA_PD from WAN interface or a ULA from the LAN interface. The network interface of the downstream router may obtain an IA_PD either via stateful DHCPv6 or stateless DHCPv6. If the CPE router supports cascading of routers through automatic prefix sub-delegation, the CPE router must support a DHCPv6 server or DHCPv6 relay agent. If an IA_PD is used, the Service Provider or user needs to allocate an IA_PD or ULA prefix short enough to be sub-delegated and subsequently used for SLAAC. Therefore, a prefix length shorter than /64 is needed. 7. IPv6 Data forwarding Each of the WAN and LAN interface(s) of the CPE Router must have its own L2 (e.g. MAC) address. The CPE Router supports ND protocol on both the WAN interface and LAN interface(s) to advertise itself as a router to neighbors in the Service Provider and home networks. The CPE Router forwards packets between the Service Provider and the home network. To do this, the CPE Router needs to look up the destination address of the packet in the routing table and decide which route to use to forward the packet. The CPE Router routing table will be initialized during CPE Router initialization. The Singh & Beebee Expires January 15, 2009 [Page 10] Internet-Draft CPE Router Recommendations July 2008 routing table is filled by directly connected, static, and routing protocol routes. The CPE Router consumes any packet destined to its WAN or LAN interface. The CPE Router forwards other packets destined to hosts attached to CPE Router LAN interface(s). Any packet that is not routable by the CPE Router must be dropped. The CPE Router must support the ND protocol specified by [RFC4861]. Proxy Neighbor Advertisements as described in Section 7.2.8 of [RFC4861] are not applicable to the CPE Router. Also note, as per section 6.2.8 of [RFC4861] the link-local address on a router should rarely change, if ever. As per [RFC2460], the CPE Router decrements the Hop Limit by 1 for any packet it forwards. The packet is discarded if Hop Limit is decremented to zero and the CPE Router also sends an ICMP Time Exceeded message to the source of the packet. 7.1. IPv6 Multicast The CPE Router needs to support multicast clients in the home. These clients are connected to the CPE Router LAN interface(s). Therefore the CPE Router must implement IPv6 multicast MLDv2 router functionality as per [RFC3810] on each of the LAN interface(s). Further, the IPv6 multicast router also maintains a conceptual Multicast Client Database for each LAN interface which maintains multicast client reception state for connected hosts. The CPE Router builds the Multicast Client Database from MLD Reports messages arriving at the LAN interface(s) from hosts in the home. In the CPE Router downstream direction the device needs to forward multicast data to LAN interface(s). In order to do that, the CPE Router needs to support being a MLDv2 multicast Listener, defined in [RFC3810], on the WAN interface. The CPE Router learns IPv6 multicast group membership information received on LAN interface(s) and proxies the information on the WAN interface to the next upstream multicast router. Multicast downstream packets arriving at the WAN interface are forwarded to the respective LAN interface based on information the CPE Router learned from LAN interface MLDv1/v2 Reports. The CPE Router also merges all multicast connected client information from all the LAN interface(s) in a conceptual IPv6 multicast Group Membership Database. The WAN interface follows section 4.2 of [RFC3810] to maintain the multicast reception interface state. Therefore, if an entry in the IPv6 multicast Group Membership Database changes, the CPE Router reports the change with an unsolicited MLDv2 Report. Likewise, if the CPE Router WAN interface is queried by an upstream multicast router, the CPE Router will Singh & Beebee Expires January 15, 2009 [Page 11] Internet-Draft CPE Router Recommendations July 2008 respond with information from the Group Membership Database. The format of records in the Group Membership Database is specified in section 7.2 of [RFC3810]. A record will exist per LAN interface and per multicast address joined. Querier Election rules as described in section 7.6.2 of [RFC3810] do not apply to the CPE Router since the home network has only one router. Therefore, the CPE Router must always act as an MLD querier on its LAN interface(s). The CPE Router maintains a conceptual Multicast Forwarding Information Base (MFIB). To forward any multicast packet, the CPE Router will lookup the multicast group and output interface list in the MFIB. The CPE Router transmits IPv6 multicast packets out an interface if and only if at least one receiving host is joined to the corresponding group on the interface. Entries in the MFIB are added and updated via the Multicast Client Database and the Group Membership Database. Consistent with the above model, the CPE Router may not implement the router portion of MLDv2 for the WAN interface. Likewise, the LAN interfaces on the CPE router may not implement an MLDv2 Multicast Listener. However, if a user at home wants to create a new multicast group and send multicast data to other nodes on the Service Provider network, then the WAN interface of the CPE Router will need to implement the router portion of MLDv2 and the LAN interface will need to implement MLDv2 Multicast Listener. Furthermore, in this case, the router implementation described above should be extended to handle multicast traffic flowing in the upstream direction. 8. Other IPv6 Features 8.1. Path MTU Discovery Support GRE tunnels, such as IPv6 to IPv4 tunnels (which may be terminated on the CPE Router), can modify the default Ethernet MTU of 1500 bytes. Also, in the future, Ethernet Jumbo frames (9000+ bytes) may also be supported. Since the MTU can vary, a newly initiated TCP stream must detect the largest packet that can be sent to the destination without fragmentation. This can be detected using Path MTU Discovery [RFC1981]. Packets which are too large to be forwarded along the path from source to destination may generate an ICMPv6 Packet Too Big message. The CPE Router must route back to the source any ICMPv6 Packet Too Big messages generated anywhere on this path. Singh & Beebee Expires January 15, 2009 [Page 12] Internet-Draft CPE Router Recommendations July 2008 8.2. Optional support for RIPv6 The CPE Router may support RIPv6 routing protocol [RFC2080] so that RIPv6 operates between the CPE Router and the Service Provider network. RIPv6 has scaling and security implications for the Service Provider network where one Service Provider router may terminate several tens of thousands of CPE routers. However, RIPv6 does provide one solution from the CPE Router to the Service Provider network for prefix route injection. 8.3. Firewall The CPE Router must support an IPv6 Firewall feature. The firewall may include features like access-control lists. The firewall may support interpretation or recognition of most IPv6 extension header information including inspecting fragmentation header. The firewall needs to support stateful and stateless Packet Filters as follows. 8.3.1. Packet filters The CPE Router needs to support packet filtering based on IP headers, extended headers, UDP and TCP ports etc. There are numerous filters mentioned (section 3.2) in draft-ietf-v6ops-cpe-simple-security [I-D.ietf-v6ops-cpe-simple-security], like some that allow IKE, IPSec packets while another filter may block Teredo packets. 9. Quality Of Service(QoS) The CPE router MAY support differentiated services [RFC2474]. 10. Security Considerations Security considerations of a CPE router are covered by draft-ietf-v6ops-cpe-simple-security [I-D.ietf-v6ops-cpe-simple-security]. 11. IANA Considerations None. 12. Acknowledgements Thanks (in alphabetical order) to Bernie Volz, Carlos Pignataro, Mark Townsley, Mikael Abrahamsson, Ole Troan, Remi Denis-Courmont, and Singh & Beebee Expires January 15, 2009 [Page 13] Internet-Draft CPE Router Recommendations July 2008 Shin Miyakawa for their input on the document. 13. References 13.1. Normative References [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September 2007. 13.2. Informative References [I-D.ietf-6man-ipv6-subnet-model] Singh, H., Beebee, W., and E. Nordmark, "IPv6 Subnet Model: the Relationship between Links and Subnet Prefixes", draft-ietf-6man-ipv6-subnet-model-01 (work in progress), July 2008. [I-D.ietf-6man-node-req-bis] Loughney, J., "IPv6 Node Requirements RFC 4294-bis", draft-ietf-6man-node-req-bis-01 (work in progress), February 2008. [I-D.ietf-softwire-hs-framework-l2tpv2] Storer, B., Pignataro, C., Santos, M., Stevant, B., and J. Tremblay, "Softwire Hub & Spoke Deployment Framework with L2TPv2", draft-ietf-softwire-hs-framework-l2tpv2-09 (work in progress), July 2008. [I-D.ietf-v6ops-cpe-simple-security] Woodyatt, J., "Recommended Simple Security Capabilities in Customer Premises Equipment for Providing Residential IPv6 Internet Service", draft-ietf-v6ops-cpe-simple-security-02 (work in progress), February 2008. [RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989. [RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery for IP version 6", RFC 1981, August 1996. [RFC2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080, January 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. Singh & Beebee Expires January 15, 2009 [Page 14] Internet-Draft CPE Router Recommendations July 2008 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998. [RFC2669] St. Johns, M., "DOCSIS Cable Device MIB Cable Device Management Information Base for DOCSIS compliant Cable Modems and Cable Modem Termination Systems", RFC 2669, August 1999. [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. [RFC3484] Draves, R., "Default Address Selection for Internet Protocol version 6 (IPv6)", RFC 3484, February 2003. [RFC3633] Troan, O. and R. Droms, "IPv6 Prefix Options for Dynamic Host Configuration Protocol (DHCP) version 6", RFC 3633, December 2003. [RFC3646] Droms, R., "DNS Configuration options for Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646, December 2003. [RFC3736] Droms, R., "Stateless Dynamic Host Configuration Protocol (DHCP) Service for IPv6", RFC 3736, April 2004. [RFC3769] Miyakawa, S. and R. Droms, "Requirements for IPv6 Prefix Delegation", RFC 3769, June 2004. [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast Addresses", RFC 4193, October 2005. [RFC4241] Shirasaki, Y., Miyakawa, S., Yamasaki, T., and A. Takenouchi, "A Model of IPv6/IPv4 Dual Stack Internet Access Service", RFC 4241, December 2005. [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006. [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, "Internet Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605, August 2006. Singh & Beebee Expires January 15, 2009 [Page 15] Internet-Draft CPE Router Recommendations July 2008 [RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless Address Autoconfiguration", RFC 4862, September 2007. [RFC5072] S.Varada, Haskin, D., and E. Allen, "IP Version 6 over PPP", RFC 5072, September 2007. Appendix A. CHANGE HISTORY [NOTE TO RFC EDITOR: PLEASE REMOVE THIS SECTION UPON PUBLICATION.] Changes in draft-wbeebee-ipv6-cpe-router-02.txt since -01.txt are: o Added a new section called Conceptual Configuration Variables to list optional configuration variables. o Removed the following sentence from the LAN initialization before WAN initialization section. "Note that if the home does not cascade CPE routers, then ULA's are not needed for the LAN interfaces, since link-local addresses are sufficient for configuration." o Removed the following sentence from IPv6 Data Forwarding Section. "Each protocol that the CPE Router can forward packets for must have a separate routing table." o Removed the following sentence from IPv6 Data Forwarding Section because once it was explained what the sentence is describing, reviewers said the facts are obvious for a router. "Before forwarding a packet in any direction from CPE router, the CPE Router will perform a MAC rewrite operation that rewrites the source L2 address of the packet with CPE Router's WAN or LAN interface MAC address." o Reworded the QoS section and added a reference to [RFC2474]. o Changed hyphenated 6-to-4 text in the Path MTU Discovery Support section to IPv6 to IPv4. o Added a new IPv6 over PPP section. o Added a new Softwires section. o Added one new sentence at the end of second paragraph of the IPv6 Provisioning of Home Devices for renumbering behavior for the CPE Router network interfaces. Changes in draft-wbeebee-ipv6-cpe-router-01.txt since -00.txt are: Singh & Beebee Expires January 15, 2009 [Page 16] Internet-Draft CPE Router Recommendations July 2008 o Added to Abstract to explain better what is the scope of the CPE Router document. o In Introduction section, changed WAN port from only Ethernet encapsulation to also support other encapsulation types like PPP. o Added another router initialization mode of LAN first before WAN to Router Initialization section. o Split up Acquire IPv6 address and other configuration parameters section into two sub-sections to support no global IPV6 address assigned to WAN interface. Added details as to how WAN interface works without a global IPv6 address. o IPv6 Provisioning of Home Devices section was split up into two sections called LAN initialization before WAN initialization and WAN initialization before LAN initialization. Details have been provided for workings of the CPE Router in such initialization modes. o New section called Cascading of Routers behind the CPE Router was added. o Text of draft between sections 4-5 has a lot of shuffling around to accomodate new initialization modes and two different kind of WAN interface address support. Authors' Addresses Hemant Singh Cisco Systems, Inc. 1414 Massachusetts Ave. Boxborough, MA 01719 USA Phone: +1 978 936 1622 Email: shemant@cisco.com URI: http://www.cisco.com/ Singh & Beebee Expires January 15, 2009 [Page 17] Internet-Draft CPE Router Recommendations July 2008 Wes Beebee Cisco Systems, Inc. 1414 Massachusetts Ave. Boxborough, MA 01719 USA Phone: +1 978 936 2030 Email: wbeebee@cisco.com URI: http://www.cisco.com/ Singh & Beebee Expires January 15, 2009 [Page 18] Internet-Draft CPE Router Recommendations July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). 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