Network Working Group F. Templin Internet-Draft Nokia Expires:
March 10,April 14, 2004 T. Gleeson Cisco Systems K.K. M. Talwar D. Thaler Microsoft Corporation September 10,October 15, 2003 Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) draft-ietf-ngtrans-isatap-15.txtdraft-ietf-ngtrans-isatap-16.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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 March 10,April 14, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract This document specifies an Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) that connects IPv6 hosts and routers within IPv4 sites. ISATAP treats the site's IPv4 unicast infrastructure as a Non-Broadcast, Multiple Access (NBMA) link layer for IPv6.IPv6 with no requirement for IPv4 multicast. ISATAP enables intra-siteautomatic IPv6-in-IPv4 tunneling whether globally assigned or private IPv4 addresses are used. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Basic IPv6 Operation . . . . . . . . . . . . . . . . . . . . . 4 5. Automatic Tunneling . . . . . . . . . . . . . . . . . . . . . 56 6. Neighbor Discovery . . . . . . . . . . . . . . . . . . . . . . 68 7. Address Autoconfiguration . . . . . . . . . . . . . . . . . . 912 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 912 9. Security considerations . . . . . . . . . . . . . . . . . . . 912 10. AcknowledgementsAcknowledgments . . . . . . . . . . . . . . . . . . . . . . . 1012 Normative References . . . . . . . . . . . . . . . . . . . . . 1013 Informative References . . . . . . . . . . . . . . . . . . . . 1114 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 1215 A. Major Changes . . . . . . . . . . . . . . . . . . . . . . . . 1215 B. Rationale forInterface Identifier Construction . . . . . . . 14 C. Deployment Considerations . . . . . . . . . . . . . . . . . . 15 D. Other Considerations . . . . . . .. . . . . . . . . . . . . . 1516 Intellectual Property and Copyright Statements . . . . . . . . 1718 1. Introduction This document presentsspecifies a simple approachmechanism called the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) that enables incremental deployment of IPv6 [RFC2460] within IPv4 [RFC0791] sites. ISATAP allows dual-stack nodes that do not share a link with an IPv6 router to automatically tunnel packets to the IPv6 next-hop address through IPv4, i.e., the site's IPv4 infrastructure is treated as a link layer for IPv6. SpecificThe main objectives of this document are to: 1) specify operational details for the operation of IPv6 andautomatic tunneling of IPv6 over IPv4 using ISATAP are given, including an interface identifierISATAP, 2) specify the format that embedsof IPv6 interface identifiers using an embedded IPv4 address. This format supports IPv6 address configuration and simple link-layer address mapping. Also specified isaddress, 3) specify the operation of IPv6Neighbor Discovery and deployment/securityAddress Autoconfiguration, and 4) discuss security considerations. The specification in this document is very similar to [RFC2529], with the primary distinction that ISATAP does not require IPv4 multicast support within the site. 2. Requirements The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119]. This document also makes use of internal conceptual variables to describe protocol behavior and external variables that an implementation must allow system administrators to change. The specific variable names, how their values change, and how their settings influence protocol behavior are provided to demonstrate protocol behavior. An implementation is not required to have them in the exact form described here, so long as its external behavior is consistent with that described in this document. 3. Terminology The terminology of [RFC2460][RFC2460][RFC2461][RFC2462] applies to this document. The following additional terms are defined: site: same as defined in [RFC3582], which is intended to be equivalent to "enterprise" as defined in [RFC1918]. link, on-link, off-link: same as defined in ([RFC2461], section 2.1). underlying link: a link layer that supports IPv4 (for ISATAP), and MAY also support IPv6 natively.ISATAP interface: an interface used for automatic IPv6-in-IPv4 tunneling and configured over one or more underlying links.IPv4 addresses assigned to one or more of the node's IPv4 interfaces that belong to the same site. advertising ISATAP interface: same meaning as "advertising interface"advertising interface in ([RFC2461], section 6.2.2). ISATAP address: an address with an on-link prefix assigned on an ISATAP interface and with an interface identifier constructed as specified in Section 4.1. 4. Basic IPv6 Operation ISATAP interfaces automatically tunnel IPv6 packets in IPv4 using the site's IPv4 infrastructure as a link layer for IPv6,layer, i.e., IPv6 treats the site's IPv4 infrastructure as a Non-Broadcast, Multiple Access (NBMA) link layer,layer with properties similar to [RFC2491]. The following ISATAP-specific considerations are notedsections specify details for basic IPv6 operation:operation on ISATAP interfaces: 4.1 Interface Identifiers and Unicast Addresses ISATAP interfaceInterface identifiers use "modified EUI-64"for ISATAP are constructed in Modified EUI-64 format ([RFC3513],as specified in ([ADDR-ARCH], section 2.5.1) and2.5.1). They are formed by appending ana 32-bit IPv4 address assigned to an underlying linkto the 32-bit string '00-00-5E-FE'. Appendix B includes non-normative rationale for this construction rule. IPv6 global and local-use ([RFC3513], sections 2.5.4, 2.5.6) ISATAP addresses are constructedleading token '0000:5EFE', then setting the universal/local ("u") bit as follows: | 64 bits | 32 bits | 32 bits |When the IPv4 address is globally unique (i.e., provider-assigned), the "u" bit is set to 1 and the leading token becomes '0200:5EFE'. When the IPv4 address is from a private allocation [RFC1918], the "u" bit is set to 0 and the leading token remains as '0000:5EFE'. Global and link-local IPv6 unicast addresses ([ADDR-ARCH], sections 2.5.4, 2.5.6) for ISATAP are constructed as follows: | 64 bits | 32 bits | 32 bits | +------------------------------+---------------+----------------+ | global/local unicastglobal/link-local prefix | 0000:5EFE000[0/2]:5EFE | IPv4 Address | +------------------------------+---------------+----------------+ (Appendix B provides additional non-normative details.) 4.2 ISATAP Interface ConfigurationManagement The IP Tunnel MIB [MIB] is used, with the following additions for ISATAP interfaces are configured over one or more underlying links that supportinterfaces: o For each IPv4 for tunneling withinaddress an ISATAP interface is configured over, a site; eachtuple consisting of the IPv4 address assignedand ifIndex for the corresponding IPv4 interface ([RFC2863], section 3.1.5) is added to ifRcvAddressTable ([MIB], section 3.1.2). o tunnelIfRemoteInetAddress in the tunnelIfEntry object ([MIB], section 4) is set to 0.0.0.0 for ISATAP interfaces. When an underlying linkIPv4 address over which an ISATAP interface is configured is removed from its IPv4 interface, the corresponding (IPv4 addres, ifIndex)-tuple MUST be removed from the ISATAP interface ifRcvAddressTable. If the IPv4 address is seenalso used as tunnelIfLocalInetAddress ([MIB], section 5) in the ISATAP interface tunnelIfEntry, the interface MUST either set tunnelIfLocalInetAddress to a link-layerdifferent IPv4 address for ISATAP.or be disabled. When a new IPv4 address is added to an IPv4 interface an ISATAP interface is configured over, a new (IPv4 address, ifIndex)-tuple MAY be added to ifRcvAddressTable and tunnelIfLocalInetAddress MAY be set to the new address. 4.3 Multicast and Anycast ISATAP interfaces recognize an IPv6 node's required addresses ([RFC3513],([ADDR-ARCH], section 2.8), including certain multicast/anycast addresses. Mechanisms2.8). The following multicast mappings are defined for packets sent on ISATAP interfaces: o When the IPv6 destination address is the 'All-Routers' ([ADDR-ARCH], section 2.7.1) or 'All_DHCP_Relay_Agents_and_Servers' ([RFC3315], section 1.2) multicast address, it is mapped to V4ADDR(i) for one or more PRL(i)'s (see: Section 6.1). The manner of selecting PRL(i)'s is up to the implementation. Other multicast mappings, and mechanisms for general-purpose multicast/anycast emulation on ISATAP interfaces (e.g., MARS [RFC2022], etc.)are outbeyond the scope of scope. 5. Automatic Tunneling The common tunneling mechanisms specified in ([MECH], sectionsthis document. 4.4 Source/Target Link Layer Address Options Source/Target Link Layer Address Options ([RFC2461], section 4.6.1) for ISATAP have the following format: +-------+-------+-------+-------+-------+-------+-------+--------+ | Type |Length | 0 | 0 | IPv4 Address | +-------+-------+-------+-------+-------+-------+-------+--------+ Type: 1 for Source Link-layer address. 2 and 3) are used,for Target Link-layer address. Length: 1 (in units of 8 octets). IPv4 Address: The 32 bit IPv4 address, in network byte order. 5. Automatic Tunneling ISATAP interfaces use the basic transition mechanisms specified in [MECH] with the following noted considerations for ISATAP:exceptions: 5.1 Tunnel MTU and Fragmentation ISATAP automatic tunnel interfaces may be configured over multiple underlying links with diverse maximum transmission units (MTUs).The specification in ([MECH], section 3.2) is not used; the specification in this section is used instead. The minimum MTU for IPv6 interfaces is 1280 bytes ([RFC2460], Section 5), but the following operational considerations apply for ISATAP interfaces:are noted: o Nearly all IPv4 nodes connect to physical links with MTUs of 1500 bytes or larger (e.g., Ethernet) o Sub-IPv4 layer encapsulations (e.g., VPN) may occur on some paths o Commonly-deployed VPN interfaces use an MTU of 1400 bytes To maximize efficiency and minimize IPv4 fragmentation for the predominant deployment case, LinkMTU ([RFC2461], Section 6.3.2)for theISATAP interfaceinterfaces SHOULD be set to no more than 1380 bytes (1400 minus 20 bytes for IPv4 encapsulation). LinkMTU MAY be set to larger values when a dynamic link layer (IPv4) MTU discovery mechanism is usedused, or when a static MTU assignment is used and the anticipated/measured level of fragmentation in the site's IPv4 network is deemed acceptable. When a dynamic link layer MTU discovery mechanism is not used, the ISATAP interface MUST NOT encapsulate IPv6 packets with theDon't Fragment (DF) bit MUST NOT be set in the encapsulating IPv4 header.header of packets sent on the ISATAP interface. In this case, black holes may in rare instances occur along some paths even when the tunnel interface uses the IPv6 minimum MTU of 1280 bytes. (This concern is not specific to ISATAP interfaces, but applies to all tunnels for which nested levels of sub link-layer encapsulation may occur.) 5.2 Handling IPv4 ICMP Errors ARP failures and persistent ICMPv4 errors SHOULD be processed as link-specific information indicating that a path to a neighbor has failed ([RFC2461], section 7.3.3). 5.3 Local-Use IPv6 UnicastLink-Local Addresses The specification in ([MECH], section 3.7) is not used; the specification in Section 4.1 of this document is used instead. 5.4 Ingress FilteringNeighbor Discovery over Tunnels The specification in ([MECH], section 3.9)3.8) is used. Additionally, packets received on an ISATAP interface with an ISATAP network-layer (IPv6) source address that doesnot embedused; the link-layer (IPv4) source addressspecifications in the interface identifierSection 6 and Section 7 of this document are silently discarded. 6. Neighbor Discoveryused instead. 5.5 Decapsulation/Filtering The specificationspecifications in ([MECH], section 3.8) applies only to configured tunnels. [RFC2461] providessections 3.6, 3.9 and 4.1) are used. In addition, the following guidelinesdecapsulator MUST determine the correct tunnel interface to receive each IPv4 protocol-41 packet via a table lookup for non-broadcast multiple access (NBMA) link support: "Redirect, Neighbor Unreachability Detectionthe tuple consisting of the packet's IPv4 source and next-hop determination should be implemented as described in this document. Address resolutiondestination address, and the mechanismifIndex for delivering Router Solicitations and Advertisements on NBMA links is not specified in this document."the receiving IPv4 interface. (Note that ISATAP interfaces SHOULD implement Redirect, Neighbor Unreachability Detection, and next-hop determination exactly as specified in [RFC2461]. Address resolution andmatch all IPv4 source addresses by default; if a tunnel interface with a more-specific match on the mechanismsIPv4 source address exists, it is selected to receive the packet as for delivering Router Solicitations and Advertisements are not specified by [RFC2461]; instead, theylongest-prefix-match.) Packets for which the correct tunnel interface cannot be determined are specifieddiscarded; in the following sections ofthis document. 6.1 Address Resolution and Neighbor Unreachability Detection ISATAP addresses are resolved to link-layer (IPv4) addresses by a static computation, i.e.,case, the last four octets are treated as an IPv4 address. Hosts SHOULD performdecapsulator MAY also send an initial reachability confirmation by sending Neighbor Solicitation (NS) message(s) and receiving a Neighbor Advertisement (NA)ICMPv4 Destination Unreachable message as specified in ([RFC2461],with code 3 (Port Unreachable) ([RFC1122], section 7.2). Unless otherwise specified in a future document, solicitations are sent18.104.22.168) to the target's unicast address. Hosts SHOULD additionally perform Neighbor Unreachability Detection (NUD) as specified in ([RFC2461], section 7.3). Routers MAY perform these reachability confirmation and NUD procedures, but this might not scaleIPv4 source address in all environments. All ISATAP nodesthe packet's outer header. After determining the correct tunnel interface, the decapsulator MUST send solicited neighbor advertisements ([RFC2461], section 7.2.4). 6.2 Duplicate Address Detection Duplicate Address Detection ([RFC2462], section 5.4)also verify that the packet's link-layer (IPv4) source address is not requiredcorrect for the network-layer (IPv6) source address. For ISATAP addresses, since duplicateinterfaces, the packet's link-layer source address detectionis assumed to have been already performed forcorrect if one (or more) of the IPv4 addresses from which they derive. 6.3 Router and Prefix Discovery Thefollowing sections describe mechanisms to supportare true: o the router and prefix discovery process ([RFC2461], section 6): 6.3.1 Conceptual Data Structuresnetwork-layer source address is an ISATAP nodes useaddress that embeds the conceptual data structures Prefix List and Default Router List exactly aslink-layer source address in ([RFC2461], section 5.1). ISATAP adds a new conceptual data structure "Potential Router List" (PRL)its interface identifier. o the network-layer source address is an IPv6 neighbor within the same site as the receiving ISATAP interface, and the following new configuration variable: PrlRefreshInterval Timelink-layer source address matches the link layer address in seconds between successive refreshmentsthe neighbor cache. o the link-layer source address is a member of the PRL after initialization. ItPotential Router List for the site (see: Section 6.1). Packets for which the link-layer source address is incorrect are discarded, and an ICMPv6 Destination Unreachable message ([ICMPV6], section 3.1) SHOULD be no less than 3,600 seconds. The designated valuesent to the IPv6 source in the inner header of all 1's (0xffffffff) represents infinity. Default: 3,600 seconds A PRL is associatedthe encapsulated packet (subject to rate limiting as in [ICMPV6], section 2.4, paragraph f). 6. Neighbor Discovery ISATAP interfaces use the neighbor discovery mechanisms specified in [RFC2461] with everythe following exceptions: 6.1 Conceptual Model Of A Host To the list of Conceptual Data Structures ([RFC2461], section 5.1), ISATAP interface and supportsinterfaces add: Potential Router List A set of entries about potential routers for the site; used to support the mechanisms specified in Section 22.214.171.124.2.3. Each entry in the PRL("PRL(i)") has an associated timer ("TIMER(i)"), and an IPv4 address ("V4ADDR(i)") that represents a site borderrouter's advertising ISATAP interface. When a node enables an ISATAP interface, it initializes6.2 Router and Prefix Discovery 6.2.1 Message Validation 126.96.36.199 Validation of Router Solicitation Messages To the PRL with IPv4 addresses. The addresses MAY be discovered via a DHCPv4 [RFC2131] option for ISATAP, manual configuration, or an unspecified alternate method (e.g., DHCPv4 vendor-specific option, etc.). When no other mechanisms are available, a DNS fully-qualified domain name (FQDN) [RFC1035] established by an out-of-band method (e.g., DHCPv4, manual configuration, etc.) MAY be used. The FQDN is resolved into IPv4 addresseslist of validity checks for Router Soliciation messages ([RFC2461], section 6.1.1), ISATAP interfaces add: o If the PRL through a static host file, a site-specific name service, queryingmessage includes a DNS server withinSource Link Layer Address Option, the site, ormessage also includes an unspecified alternate method. There are no mandatory rules for the selection of a FQDN, but manual configuration MUST be supported. When DNS is used, client resolvers use the IPv4 transport. After initialization, nodes periodically refresh the PRL (i.e., using one or more of the methods described above) after PrlRefreshInterval. 6.3.2IP authentication Header. 188.8.131.52 Validation of Router AdvertisementsAdvertisement Messages The specification inTo the list of validity checks for Router Advertisement messages ([RFC2461], section 6.1.2) is used. 6.3.3 Router Specification Routers with advertising6.1.1), ISATAP interfaces behaveadd: o IP Source Address is an ISATAP link-local address that embeds V4ADDR(i) for some PRL(i). o If the same as described in ([RFC2461], section 6.2).message includes a Source Link Layer Address Option, the message also includes an IP authentication Header. 6.2.2 Router Specification As permitted by ([RFC2461], section 6.2.6), advertising ISATAP interfaces SHOULD sendunicast RARouter Advertisement messages to athe soliciting host's unicastaddress when the solicitation's source address is not the unspecified address. 184.108.40.206.3 Host Specification Hosts behave220.127.116.11 Host Variables To the same as described inlist of host variables ([RFC2461], section 6.3) with the following additional considerations for ISATAP: 18.104.22.168 Soliciting Router Advertisements Hosts solicit Router Advertisements (RAs) by sending Router Solicitations (RSs) to advertising6.3.2), ISATAP interfaces add: PrlRefreshInterval Time in seconds between successive refreshments of the PRL.PRL after initialization. It SHOULD be no less than 3600 seconds. The mannerdesignated value of selecting PRL(i)'s for solicitation is up to the implementation. Hosts add the following variable to support the solicitation process:all 1's (0xffffffff) represents infinity. Default: 3600 seconds MinRouterSolicitInterval Minimum time in seconds between successive solicitations of the same advertising ISATAP interface. It SHOULD be no less than 900 seconds. The designated value of alll 1's (0xffffffff) represents infinity. Default: 900 seconds RS messages use a link-local unicast address from22.214.171.124 Interface Initialization The host joins the all-nodes multicast address on ISATAP interfaceinterfaces, as for multicast-capable interfaces ([RFC2461], section 6.3.3). Additionally, the IPv6 source address. 126.96.36.199 Router Advertisement Processing RAs received from a member ofhost provisions the ISATAP interface's PRL (i.e., RAswith anIPv4 addresses it discovers via manual configuration, a DNS fully-qualified domain name (FQDN) [RFC1035], a DHCPv4 option for ISATAP IPv6 source address that embeds V4ADDR(i)[ISDHCP], a DHCPv4 vendor-specific option, or an unspecified alternate method. (Support for some PRL(i))manual configuration is REQUIRED; other methods are processedOPTIONAL.) When FQDNs are used, the host establishes the FQDN via manual configuration or an unspecified alternate method. (Support for manual configuration is REQUIRED; other methods are OPTIONAL.) The host resolves the FQDN into IPv4 addresses through lookup in a static host file, a site-specific name service, querying the site's DNS service, or an unspecified alternate method. When DNS is used, client resolvers use the IPv4 transport. After the host provisions the ISATAP interface's PRL with IPv4 addresses, it sets PrlRefreshIntervalTimer to PrlRefreshInterval seconds. The host re-initializes the PRL (i.e., as specified above) when PrlRefreshIntervalTimer expires, or when an asynchronous re-initialization event occurs. When the host re-initializes the PRL, it resets PrlRefreshIntervalTimer to PrlRefreshInterval seconds. 188.8.131.52 Processing Received Router Advertisements Router Advertisements (RAs) are processed exactly as specified in ([RFC2461], section 6.3.4).6.3.4) except that, if the MTU option is present, the option's value SHOULD be stored in a per-neighbor cache entry for the source of the RA; it MUST NOT be copied into LinkMTU for the ISATAP interface. Additionally, hosts reset TIMER(i) to schedule the next solicitation event (see: Section 184.108.40.206).220.127.116.11). Let "MIN_LIFETIME" be the minimum value in the Router Lifetime or the lifetime(s) encoded in options included in the RA message. Then, TIMER(i) is reset as follows: TIMER(i) = MAX((0.5 * MIN_LIFETIME), MinRouterSolicitInterval) RAs received from a router other than a member of18.104.22.168 Sending Router Solicitations To the PRL are processed as specified in ([RFC2461], section 6.3.4) except that any RA contentslist of events after which RSs may be sent ([RFC2461], section 6.2.3) that would alter6.3.2), ISATAP link parameters are silently ignored. In particular, non-zero values in theinterfaces add: o TIMER(i) for some PRL(i) expires. Additionally, hosts MAY send Router Lifetime, M and O flags, Cur Hop Limit, Reachable Time, and Retrans Timer as well as prefix options with the L and/or A bits set are ignored. If the MTU option is present, the option's value SHOULD be stored in a per-neighbor cache entrySolicitations to an ISATAP link-local address that embeds V4ADDR(i) for some PRL(i) instead of the sourceAll-Routers multicast address. 6.3 Address Resolution and Neighbor Unreachability Detection 6.3.1 Message Validation 22.214.171.124 Validation of Neighbor Solicitations To the RA; it MUST NOT be copied into LinkMTUlist of validity checks for theNeighbor Solicitation (NS) messages ([RFC2461], section 7.1.1), ISATAP link. 7.interfaces add: o If the message includes a Source Link Layer Address Autoconfiguration Hosts invoke stateless address autoconfiguration underOption, the conditions specified in ([RFC2462], sections 5.5). Hosts invoke stateful address autoconfiguration undermessage also includes an IP authentication Header. 126.96.36.199 Validation of Neighbor Solicitations To the conditions specifiedlist of validity checks for Neighbor Advertisement (NA) messages ([RFC2461], section 7.1.2), ISATAP interfaces add: o If the message includes a Target Link Layer Address Option, the message also includes an IP authentication Header. 6.3.2 Address Resolution The specification in ([RFC2462],([RFC2461], section 5.5). When DHCPv6 [RFC3315]7.2) is used, hosts sendused. NS and NA messages toMAY omit the "All_DHCP_Relay_Agents_and_Servers" multicastsource/target link layer address ([RFC3315], sections 1.2 and 1.3). Sending implementations mapoption when the "All_DHCP_Relay_Agents_and_Servers" multicast address to a link-layer (IPv4) address by selecting V4ADDR(i)source/target is an ISATAP address. ISATAP addresses for some PRL(i). When the site supports the DHCPv6 service,which the server/relay function MUSTneighbor's link-layer address cannot otherwise be deployed equally on each router that is a member of the PRL. 8. IANA Considerations The IANA is advised to specify construction rules for IEEE EUI-64 addresses formeddetermined (i.e., from the Organizationally Unique Identifier (OUI) "00-00-5E"neighbor cache or a link layer address option in a received packet) are resolved to link-layer addresses by a static computation, i.e., the IANA "ethernet-numbers" registry. The non-normative text in Appendix B is offeredlast four octets are treated as an example specification. 9. Security considerations ISATAP site border routers MUST implement IPv6 andIPv4 ingress filtering and in particular MUST discard any packets originating from outside of the site that use an IP address from the site as the sourceaddress. Additionally, site border routers MUST implement ip-protocol-41 filteringHosts SHOULD perform an initial reachability confirmation by not allowing packets for that protocol insending NS message(s) and out ofreceiving a NA message; NS messages are sent to the site. Finally, site border routers MUST NOT forward any packets with local-use source or destination addresses outside oftarget's unicast address. Routers MAY perform an initial reachability confirmation, but this might not scale in all environments. As specified in ([RFC2461], section 7.2.4), all nodes MUST send solicited neighbor advertisements on ISATAP interfaces. 6.3.3 Neighbor Unreachability Detection Hosts SHOULD perform Neighbor Unreachability Detection as specified in ([RFC2461], section 7.3). Routers MAY perform neighbor unreachability detection, but this might not scale in all environments. 6.4 Redirect Function To the site ([RFC3513],list of validity checks for Redirect messages (([RFC2461], section 2.5.6). Even8.1), ISATAP interfaces add: o If the message includes a Target Link Layer Address Option, the message also includes an IP authentication Header. 7. Address Autoconfiguration ISATAP interfaces use the address autoconfiguration mechanisms specified in [RFC2462] with the following exceptions: 7.1 Address Lifetime Expiry The specification in ([RFC2462], section 5.5.4) is used, except that an ISATAP address also becomes deprecated when the IPv4 and IPv6 ingress filtering, reflection attacks can originateaddress embedded in its interface identifier is removed from compromised nodes withinan IPv4 interface over which the ISATAP interface is configured. (This deprecation rule applies to all ISATAP addresses, including link-local addresses.) 7.2 Stateful Address Autoconfiguration When the site uses DHCPv6 [RFC3315] as the stateful address autoconfiguration mechanism, the server/relay function MUST be deployed equally on each router that spoof IPv6 source addresses. Security mechanismsis a member of the PRL. 8. IANA Considerations The IANA is advised to specify construction rules for reflection attack mitigation SHOULD be usedIEEE EUI-64 addresses formed from the Organizationally Unique Identifier (OUI) "00-00-5E" in routers with advertising ISATAP interfaces. At a minimum,the IANA "ethernet-numbers" registry. The non-normative text in Appendix B is offered as an example specification. 9. Security considerations The security considerations in [RFC2461][RFC2462][MECH] apply. Additionally, site border routers SHOULD log potential source address spoofing cases. Siteadministrators maintain a listMUST ensure that lists of IPv4 addresses representing the advertising ISATAP interfaces and make them available via one or moreof PRL members are well maintained. 10. Acknowledgments Most of the mechanisms describedbasic ideas in Section 6.3.1. The list can include IPv4 anycast address(es) but administratorsthis document are advised to consider operational implications of anycast (e.g., see: [RFC1546]). ISATAP addresses donot support privacy extensions for stateless address autoconfiguration [RFC3041]. 10. Acknowledgementsoriginal; the authors acknowledge the original architects of those ideas. Portions of this work were derived fromsponsored through SRI International internal fundsprojects and government contracts. Government sponsors include Monica Farah-Stapleton and Russell Langan (U.S. Army CECOM ASEO), and Dr. Allen Moshfegh (U.S. Office of Naval Research). SRI International sponsors include Dr. Mike Frankel, J. Peter Marcotullio, Lou Rodriguez, and Dr. Ambatipudi Sastry. The following are acknowledged for providing peer review input: Jim Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader, Ole Troan, Vlad Yasevich. The following additional individualsare acknowledged for their significant contributions: Rich Draves,Alain Durand, Hannu Flinck, Jason Goldschmidt, Nathan Lutchansky, Karen Nielsen, Mohan Parthasarathy, Chirayu Patel, Art Shelest, Pekka Savola, Margaret Wasserman, Brian Zill. The authors alsoacknowledge the work of Quang Nguyen [VET] under the guidance of Dr. Lixia Zhang that proposed very similar ideas to those that appear in this document. This work was first brought to the authors' attention on September 20, 2002. Normative Referencesauthors' attention on September 20, 2002. Normative References [ADDR-ARCH] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", draft-ietf-ipv6-addr-arch-v4-00 (work in progress), October 2003. [ICMPV6] Conta, A. and S. Deering, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", draft-ietf-ipngwg-icmp-v3 (work in progress), November 2001. [MECH] Gilligan, R. and E. Nordmark, "Basic Transition Mechanisms for IPv6 Hosts and Routers", draft-ietf-v6ops-mech-v2-00 (work in progress), February 2003. [MIB] Thaler, D., "IP Tunnel MIB", draft-thaler-inet-tunnel-mib (work in progress), September 2003. [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [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. [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. [RFC3513] Hinden, R. and S. Deering, "InternetInformative References [ISDHCP] Templin, F., "Dynamic Host Configuration Protocol Version 6 (IPv6)(DHCPv4) Option for the Intra-Site Automatic Tunnel Addressing Architecture", RFC 3513, AprilProtocol (ISATAP)", draft-templin-isatap-dhcp (work in progress), October 2003. Informative References[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. [RFC1546] Partridge, C., Mendez, T. and W. Milliken, "Host Anycasting Service",[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1546, November 1993.1122, October 1989. [RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G. and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC2022] Armitage, G., "Support for Multicast over UNI 3.0/3.1 based ATM Networks", RFC 2022, November 1996. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997.[RFC2491] Armitage, G., Schulter, P., Jork, M. and G. Harter, "IPv6 over Non-Broadcast Multiple Access (NBMA) networks", RFC 2491, January 1999. [RFC2529] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels", RFC 2529, March 1999. [RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing", BCP 38, RFC 2827, May 2000. [RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB", RFC 2863, June 2000. [RFC3041] Narten, T. and R. Draves, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 3041, January 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. [RFC3582] Abley, J., Black, B. and V. Gill, "Goals for IPv6 Site-Multihoming Architectures", RFC 3582, August 2003. [VET] Nguyen, Q., "http://irl.cs.ucla.edu/vet/report.ps", spring 1998. Authors' Addresses Fred L. Templin Nokia 313 Fairchild Drive Mountain View, CA 94110 US Phone: +1 650 625 2331 EMail: email@example.com Tim Gleeson Cisco Systems K.K. Shinjuku Mitsu Building 2-1-1 Nishishinjuku, Shinjuku-ku Tokyo 163-0409 Japan EMail: firstname.lastname@example.org Mohit Talwar Microsoft Corporation One Microsoft Way Redmond, WA> 98052-6399 US Phone: +1 425 705 3131 EMail: email@example.com Dave Thaler Microsoft Corporation One Microsoft Way Redmond, WA 98052-6399 US Phone: +1 425 703 8835 EMail: firstname.lastname@example.org Appendix A. Major Changes changes from version 14 to version 15: o several editorial changes o revised Security; IANA considerations o revised Section 188.8.131.52 o added new section on ingress filtering o revised stateful autoconfiguration and moved to new section o removed overly-restrictive text at end of Section 184.108.40.206 changes from version 13 to version 14: o removed applicability statement; applicability TBD by v6ops o updated deployment/site admin sections; moved to appendices o new text on "L" bit in prefix options in section 220.127.116.11 o removed extraneous text in Security Considerations o fixed "layering bug" in section 18.104.22.168 o revised "ISATAP address" definition o updated references for RFC 3315; 3513Major changes from earlier versions to version 13: o Revised ISATAP interface/link terminology o Returned to using symbolic reference names o Revised MTU section; moved non-normative MTU text to separate document o Added multicast/anycast subsection o Revised PRL initialization o Updated neighbor discovery, security consideration sections o Rearranged/revised sections 5, 6, 7 o Added stateful autoconfiguration mechanism16: o Normative references to RFC 2491, RFC 2462dropped "underlying link" from terminology. o Moved non-normative MTU text to appendix Cspecified multicast mappings. o clarifiedspecified layer address resolution, Neighbor Unreachability Detectionoption format. o specified MTU/MRU requirements o Addressed operational issues identified in 05 based on discussion between co-authors o Clarified ambiguous text per comments from Hannu Flinck; Jason Goldschmidt o Moved historical text in section 4.1 to Appendix B in response to comments from Pekka Savolasetting of "u" bit in interface id's. o Identified operational issues for anticipated deployment scenariosremoved obsoleted appendix sections. o Included referencere-organized major sections to Quang Nguyen workmatch normative references. o revised neighbor discovery, address autoconfiguration, security considerations sections. Added new subsections on interface management, decapsulation/filtering, address lifetime expiry. Appendix B. Rationale forInterface Identifier Construction ISATAP specifiesThis section provides an EUI64-format address constructionexample specification for constructing EUI64 addresses from the Organizationally-Unique Identifier (OUI) owned by the Internet Assigned Numbers Authority (IANA). This format (given below) isIt can be used to construct both native EUI64 addresses for general use andmodified EUI-64 format interface identifiers for IPv6 unicast addresses:addresses ([ADDR-ARCH], section 2.5.1) and "native" EUI64 addresses for future use: |0 2|2 3|3 3|4 6| |0 3|4 1|2 9|0 3| +------------------------+--------+--------+------------------------+ | OUI ("00-00-5E"+u+g) | TYPE | TSE | TSD | +------------------------+--------+--------+------------------------+ Where the fields are: OUI IANA's OUI: 00-00-5E with 'u'"u" and 'g'"g" bits (3 octets) TYPE Type field; specifies use of (TSE, TSD) (1 octet) TSE Type-Specific Extension (1 octet) TSD Type-Specific Data (3 octets) And the following interpretations are specified based on TYPE: TYPE (TSE, TSD) Interpretation ---- ------------------------- 0x00-0xFD RESERVED for future IANA use 0xFE (TSE, TSD) together contain an embeddedIPv4 address 0xFF TSD is interpreted based on TSE as follows: TSE TSD Interpretation --- ------------------ 0x00-0xFD RESERVED for future IANA use 0xFE TSD contains 24-bit EUI-48 intf id 0xFF RESERVED by IEEE/RAC Thus, if TYPE=0xFE, TSE is an extension of TSD. If TYPE=0xFF, TSE is an extension of TYPE. Other values for TYPE (thus, other interpretations of TSE, TSD) are reserved for future IANA use. The above specification is compatible with all aspects of EUI64, including support for encapsulating legacy EUI-48 interface identifiers (e.g., an IANA EUI-48 format multicast address such as: '01-00-5E-01-02-03' is encapsulated as: '01-00-5E-FF-FE-01-02-03'). But, the specification also provides a special TYPE (0xFE) to indicate an IPv4 address is embedded. Thus, when the first four octets of an IPv6 interface identifier are: '00-00-5E-FE' (note: the 'u/l' bit MUST be 0) the interface identifier is said to be in "ISATAP format" and the next four octets embed an IPv4 address encoded in network byte order. Appendix C. Deployment Considerations Hosts can enable ISATAP, e.g., when native IPv6 service is unavailable. When native IPv6 service is acquired, hosts can discontinue the ISATAP router solicitation process (Section 6.3.4) and/or allow associated state to expire (see: [RFC2461], section 5.3 and [RFC2462], section 5.5.4). In this case, any associated addresses added to the DNS should also be removed. Routers can configure both native IPv6 and ISATAP interfaces over the same physical link. The prefixes used on each interface will be distinct, and normal IPv6 routing between the interfaces can occur. Routers can obtain IPv6 prefix delegations from a server via0x00-0xFD RESERVED for future IANA use 0xFE TSD contains 24-bit EUI-48 intf id 0xFF RESERVED by IEEE/RAC Using this example specification, if TYPE=0xFE, then TSE is an ISATAP interfaceextension of TSD. If TYPE=0xFF, then TSE is an extension of TYPE. (Other values for TYPE, and advertise the delegated prefix(es) onother IPv6 interface(s). Responsible administration can reduce control traffic overhead associated with router and prefix discovery. Appendix D. Other Considerations The Potential Router List (PRL) containsinterpretations of TSE, TSD are reserved for future IANA use.) When TYPE='0xFE' the EUI64 address embeds an IPv4 address, encoded in network byte order. For Modified EUI64 format interface identifiers in IPv6 unicast addresses of advertising ISATAP interfaces on site border routers,([ADDR-ARCH], Appendix A) using IANA's OUI, when TYPE=0xFE and the specification mandates that nodes only accept Router Advertisement (RA) parameters that alter the ISATAP link (e.g., default router list, on-link prefix list, LinkMTU, etc.) if they are sent byIPv4 address is a member of the PRL. However, the specification allows any node onglobally unique (i.e., provider-assigned) unicast address, the ISATAP link"u" bit is set to send "other" parameters in RAs and also allows any node on the ISATAP link1 to act as a (non-default) IPv6 router, e.g., ifindicate universal scope. When TYPE=0xFE and the nodeIPv4 address is configured asfrom a router for its other IPv6 links. These aspects of the specification allow useful functionality, includingprivate allocation, the ability for ISATAP nodes other than PRL members"u" bit is set to serve as routers for "stub" IPv6 networks, the ability for ISATAP nodes0 to send IPv6 packets with non-ISATAP source addresses (e.g., RFC 3401 privacy addresses), etc. But, allowing this functionality prevents ISATAP nodes from perform effective ingress filtering for IPv6 source addresses in packets they receive. Instead,indicate local scope. Thus, when the nodes must trust that: 1) site border routers are performing ingress filtering, and 2) malicious nodes are effectively denied access tofirst four octets of the link. Additionally,interface identifier in an IPv6 unicast address are either: '02-00-5E-FE' or: '00-00-5E-FE', the specification expects that thatnext four octets embed an IPv4 addresses are uniquely assigned withinaddress and the ISATAP site.interface identifier is said to be in "ISATAP format". Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. 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