NGTRANS Working Group F. Templin INTERNET-DRAFT SRI International T. Gleeson Cisco Systems K.K. M. Talwar D. Thaler Microsoft Corporation Expires
30 July18 October 2002 30 January18 April 2002 Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) draft-ietf-ngtrans-isatap-03.txtdraft-ietf-ngtrans-isatap-04.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. Abstract This document specifies the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) that connects IPv6 hosts and routers (nodes) within IPv4 sites. ISATAP is a transition mechanism that enables incremental deployment of IPv6 by treating the site's IPv4 infrastructure as a Non-Broadcast Multiple Access (NBMA) link layer.layer for IPv6. ISATAP mechanisms use a newan IPv6 interface identifier format that embeds an IPv4 address - this enables automatic IPv6-in-IPv4 tunneling within a site, whether the site uses globally assigned or private IPv4 addresses. The new interface identifier format can be used with both local and global unicast IPv6 prefixes - this enables IPv6 routing both locally and globally. ISATAP mechanisms introduce no impact on routing table size and require no special IPv4 services (e.g., IPv4 multicast). 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. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved.1. Introduction This document presents a simple, scalable approach that enables incremental deployment of IPv6 within IPv4-based sites in a manner that is compatible with inter-domain transition mechanisms, e.g., [6TO4]. We refer to this approach as the Intra-Site Automatic Tunnel Addressing Protocol, or ISATAP (pronounced: "ice-a-tap"). ISATAP allows dual-stack nodes that do not share a common 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 an NBMA link layer. This document specifies details for the transmission of IPv6 packets over ISATAP links (i.e., automatic IPv6-in-IPv4 tunneling), including a new EUI-64 [EUI64] based interface identifier [ADDR][AGGR] format that embeds an IPv4 address. This format supports configuration of global, site-local and link-local addresses as specified in [AUTO] as well as simple link-layer address mapping. Simple validity checks for received packets are given. Also specified in this document is the operation of IPv6 Neighbor Discovery for ISATAP, as permitted for NBMA links by [DISC]. The document finally presents deployment and security considerations for ISATAP. 2. Applicability Statement ISATAP provides the following features: - treats site's IPv4 infrastructure as an NBMA link layer using automatic IPv6-in-IPv4 tunneling (i.e., no configured tunnel state) - enables incremental deployment of IPv6 hosts within IPv4 sites with no aggregation scaling issues at border gateways - requires no special IPv4 services within the site (e.g., multicast) - supports both stateless address autoconfiguration and manual configuration - supports networks that use non-globally unique IPv4 addresses (e.g., when private address allocations [PRIVATE] are used), but does not allow the virtual ISATAP link to span a Network Address Translator [NAT] - compatible with other NGTRANS mechanisms (e.g., [6TO4]) 3. Terminology The terminology of [IPv6] applies to this document. The following additional terms are defined: link: same definition as [AUTO][DISC]. underlying link: a link layer that supports IPv4 (for ISATAP), and MAY also support IPv6 natively. ISATAP link: one or more underlying links used for IPv4 tunneling. The IPv4 network layer addresses of the underlying links are used as link-layer addresses on the ISATAP link. ISATAP interface: a node's attachment to an ISATAP link. ISATAP prefix: a prefix used to configure an address on the ISATAP interface. This prefix is administratively assigned to the ISATAP link and MUST NOT be duplicated on native IPv6 links. ISATAP address: an IPv6 address with an ISATAP prefix and an ISATAP format interface identifier constructed as specified in section 4. ISATAP router: an IPv6 node that has an ISATAP interface over which it forwards packets not explicitly addressed to itself. ISATAP host: any node that has an ISATAP interface and is not an ISATAP router. 4. Transmission of IPv6 Packets on ISATAP Links ISATAP links transmit IPv6 packets via automatic tunneling using the site's IPv4 infrastructure as an NBMA link layer. Automatic tunneling for ISATAP uses the same mechanisms specified in [MECH,3.1-3.6], i.e., IPv6 packets are automatically encapsulated in IPv4 using 'ip- protocol-41''ip-protocol-41' as the payload type number. Specific considerations for ISATAP links are given below: 4.1. ISATAP Interface Identifier Construction IPv6 unicast addresses [ADDR][AGGR] include a 64-bit interface iden- tifieridentifier field in "modified EUI-64 format", based on the IEEE EUI-64 [EUI64] specification. (Modified EUI-64 format inverts the sense of the 'u/l' bit from its specification in [EUI64], i.e., 'u/l' = 0 indicates local-use.) ISATAP specifies an [EUI64]-format address con- structionconstruction for the Organizationally-Unique Identifier (OUI) owned by the Internet Assigned Numbers Authority [IANA]. This format (given below) is used to construct both native [EUI64] addresses for general use and modified EUI-64 format interface identifiers for use in IPv6 unicast addresses: |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' and 'g' bits (3 octets) TYPE Type field; specifies interpretation 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 embedded IPv4 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 (hence, other interpreta- tions 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 identif- iersidentifiers (e.g., an IANA EUI-48 format multicast address such as: '01-00- 5E-01-02-03''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 indicateindicating an IPv4 address is embedded. Thus, when the first four octets of a [ADDR]- compatiblean [ADDR]-compatible IPv6 interface identifier are: '00-00-5E-FE' (note: the 'u/l' bit MUST be 0) the interface identifier is said to be in "ISA- TAP"ISATAP format" and the next four octets embed an IPv4 address encoded in network byte order (least significant octet first).order. Addresses con- figuredconfigured on thean ISATAP interface MUST use the ISATAP interface iden- tifieridentifier format. 4.2. Stateless Autoconfiguration and Link-Local Addresses ISATAP addresses are IPv6 unicast addresses [ADDR,2.5] that usewith ISATAP format interface identifiers as follows: | 64 bits | 32 bits | 32 bits | +------------------------------+---------------+----------------+ | link-local, site-local or | 0000:5EFE | IPv4 Address | | global unicast prefix | | of ISATAP link | +------------------------------+---------------+----------------+ Link-local, site-local, and global ISATAP addresses can be created exactly as specified in [ADDR], (e.g., by auto-configuration [AUTO] or manual configuration). For example, the IPv6 address: 3FFE:1a05:510:1111:0:5EFE:8CAD:81083FFE:1A05:510:1111:0:5EFE:8CAD:8108 has a prefix of '3FFE:1a05:510:1111::/64''3FFE:1A05:510:1111::/64' and an ISATAP format inter- faceinterface identifier with embedded IPv4 address: '188.8.131.52'. The address is alternately written as: 3FFE:1a05:510:1111:0:5EFE:184.108.40.206FFE:1A05:510:1111:0:5EFE:220.127.116.11 The link-local and site-local variants (respectively) are: FE80::0:5EFE:18.104.22.168 FEC0::1111:0:5EFE:22.214.171.124 4.3. ISATAP Link/Interface Configuration A node configures an ISATAP link over one or more underlying IPv4 links, i.e., the ISATAP link MAY be configured over one or more link-layer (IPv4) addresses. Each link-layer address 'V4ADDR_LINK' is used to configure a link-local address 'FE80::0:5EFE:V4ADDR_LINK' on an ISATAP interface. ISATAP interfaces MAY be assigned one per link- layerlink-layer address, or as a single interface for multiple link-layer addresses. In the former case, the address of each ISATAP interface SHOULD be added to the Potential Routers List.List (see section 5.2.1). In the latter case, the inter- faceinterface will accept ISATAP packets addressed to any of the IPv4 link- layerlink-layer addresses, but will choose one as its primary address, used for sourcing packets. Only this address need be represented in the Poten- tialPotential Routers List. 4.4. Sending Rules and Address Mapping The IPv6 next-hop address for packets sent on an ISATAP link MUST be an ISATAP address. Packets that do not satisfy this constraint MUST be discarded and an ICMP destination unreachable indication with code 3 (Address Unreachable) [ICMPv6] MUST be returned. No other sending rules are necessary. The procedure for mapping unicast addresses into link-layer addresses is to simply treat the last four octets of the ISATAP address as an IPv4 address (in network byte order). No multicast address mappings are specified. 4.5. Validity Checks for Received Packets ISATAP interfaces MUST silently discard any received packets that do not satisfy ONE OFat least one of the following validity checks: - the network-layer (IPv6) source address has a prefix configured on the ISATAP interface and an ISATAP-format interface identifier that embeds the link-layer (IPv4) source address, i.e., source is on-link - the link-layer (IPv4) source address is in the Potential Routers List (see section 5.2),5.2.1), i.e., previous hop is an on-link ISATAP router 5. Neighbor Discovery for ISATAP Links Section 3.2 of [DISC] ("Supported Link Types") provides the following guidelines for non-broadcast multiple access (NBMA) link support: "Redirect, Neighbor Unreachability Detection and next-hop determi- nationdetermination should be implemented as described in this document. Address resolution and the mechanism for delivering Router Solicitations and Advertisements on NBMA links is not specified in this docu- ment."document." ISATAP links SHOULD implement Redirect, Neighbor Unreachability Detection, and next-hop determination exactly as specified in [DISC]. Address resolution and the mechanisms for delivering Router Solicita- tionsSolicitations and Advertisements for ISATAP links are not specified by [DISC]; instead, they are specified in this document. (Note that these mechanisms MAY potentially apply to other types of NBMA links in the future.) 5.1. Address Resolution Protocol addresses (IPv6) inon ISATAP links are resolved to link-layer addresses (IPv4) by a static computation, i.e., the last four octets are treated as an IPv4 address. Thus the functions and conceptual data structures used by [DISC] for the purpose of address resolution are not required. The conceptual "neighbor cache" described in [DISC] is still needed for other functions, such as neighbor unreachability detection, but it is not used for address resolution. The link-layer address option used in [DISC] is not needed. Implemen- tations SHOULD NOT send link-layerLink-layer address options SHOULD NOT be sent in any Neighbor Discovery packets, and MUST be silently ignore any such optionsignored in any received Neighbor Discovery packets which are received.packets. 5.2. Router and Prefix Discovery Since the site's IPv4 infrastructure is treated as an NBMA link layer, unsolicited Router Advertisements do not provide sufficient means for router discovery on ISATAP links. Thus, alternate mechan- ismsmechanisms are required and specified below: 5.2.1. Conceptual Data Structures ISATAP nodes use the conceptual data structures Prefix List and Default Router List conceptual data structuresexactly as specified in [DISC,5.1]. ISATAP links add a new conceptual data structure "Potential Router List" and the fol- lowingfollowing new configuration variable: ResolveInterval Time between name service resolutions. Default and suggested minimum: 1hr A Potential Router List (PRL) is associated with every ISATAP link. The PRL provides context for router discovery and a trust basis for router validation (see security considerations). Each entry in the PRL has an IPv4 address and an associated timer used for polling. The IPv4 address represents a router's ISATAP interface (likely to be an "advertising interface"), and is used to construct the ISATAP link- locallink-local address for that interface. When thea node enables an ISATAP link, it initializes the Potential Router List (PRL) for that link. Unless other information is available (e.g., manual address configuration, a vendor-specific DHCP option, etc.) the following method (similar to the [SIP, 1.4.2] procedure) SHOULD be used: 1. The site administrator maintains address records for ISATAP router interfaces, and makes these available in the site's name service. Nodes attempt to find one or more addresses for the PRL by querying the name service. 2. There are no mandatory rules on the selection of domain name to be used within a site for this purpose, but administrators are encouraged to use the "isatap.domainname" convention (e.g., isatap.example.com), as specified in [RFC2219]. Nodes can construct this domain name by prepending the label "isatap" to their parent domain name, which is established by other means. Nodes then query this domain name for address records (e.g., DNS 'A' resource records), and initialize the PRL with the IPv4 addresses discovered through name service lookups forin the Well- Known Service name "ISATAP" (see "IANA Considerations"). Nodesreplies. 3. After initialization, nodes periodically repeat this process afterthe above procedure every ResolveInterval seconds to detect additions/deletions for the PRL. Initialization ofupdate the PRL through staticwith any IPv4 address assignments and/or an alternate name for lookups is a supported configuration option, butaddresses added/deleted since the method described aboveprevious iteration. When DNS is preferred.used, nodes MUST follow the procedures in [RFC1035] regarding cache invalidation when the DNS time-to-live expires. 5.2.2. Validation of Router Advertisement Messages A node MUST silently discard any received Router Advertisement mes- sagesmessages that do not satisfy the validity checks in [DISC,6.1.2] as well as the following additional validity check for ISATAP: - the network-layer (IPv6) source address is derived from an IPv4 address in the PRL 5.2.3. Router Specification Advertising ISATAP interfaces of routers behave the same as advertis- ingadvertising interfaces described in [DISC,6.2]. However, periodic unsolicited multicast Router Advertisements are not required, thus the "interval timer" associated with advertising interfaces is not used for that purpose. When an ISATAP router receives a valid Router Solicitation on an advertising ISATAP interface, it replies with a unicast Router Adver- tisementAdvertisement to the address of the node which sent the Router Solicita- tion.Solicitation. The source address of the Router Advertisement is a link-local unicast address associated with the interface. This MAY be the same as the destination address of the Router Solicitation. By default,ISATAP routers will not receive Router Advertisements from other ISATAP routers. Thus,MAY engage in the polling process described under Host Specification below (e.g. if Router Advertisement consistency verification [DISC,6.2.7] is not supported by default. Routers MAY OPTIONALLY engage in the exchange of router advertisements with other members of the PRL to enabledesired), but this function.is not required. 5.2.4. Host Specification Hosts periodically poll each entry in the PRL ("PRL(i)") by sending unicast Router Solicitation messages using the IPv4 address ("V4ADDR_PRL(i)") and associated timer in the entry. Hosts add the following variable to support the polling process: MinRouterSolicitInterval Minimum time between sending Router Solicitations to any router. Default and suggested minimum: 15min When PRL(i) is first added to the list, the host sets its associated timer to MinRouterSolicitInterval. Entries are polled when they are created (following a short delay as for initial solicitations [ND,6.3.7]), and when the associated timer expires. Polling consists of sending Router Solicitations to the ISATAP link- locallink-local address constructed from the entry's IPv4 address, i.e., they are sent to 'FE80::0:5EFE:V4ADDR_PRL(i)' instead of 'All-Routers mul- ticast'.multicast'. They are otherwise sent in the same manner described in [DISC,6.3.7]. When the host receives a valid Router Advertisement (i.e., one that satisfies the validity checks in sections 4.5 and 5.2.2) it processes them in the same manner described in [DISC,6.3.4]. The host addition- allyadditionally resets the timer associated with the PRL entry that matches the network-layer source address in the Router Advertisement. The timer is reset to either 0.5 * (the minimum value in the router lifetime or valid lifetime of any on-link prefixes advertised) or MinRouterSoli- citInterval;MinRouterSolicitInterval; whichever is longer. 6. ISATAP Deployment Considerations 6.1. Host And Router Deployment Considerations For hosts, if an underlying link supports both IPv4 (over which ISA- TAPISATAP is implemented) and also supports IPv6 natively, then ISATAP MAY be enabled if the native IPv6 layer does not receive Router Adver- tisementsAdvertisements (i.e., does not have connection with an IPv6 router). After a non-link-local address has been configured and a default router acquired on the native link, the host MAYSHOULD discontinue the 'Router Polling Process' process specified in section 5.2.4 and allow exist- ingexisting ISATAP address configurations to expire as specified in [DISC,5.3][AUTO,5.5.4]. In this way, ISATAP use will gradually dimin- ishdiminish as IPv6 routers are widely deployed throughout the site. Routers MAY configure a native link to simultaneously support both native IPv6, and also ISATAP (over IPv4). Routing will operate as usual between these two domains. Note that the prefixes used on the ISATAP and native IPv6 interfaces will be distinct. When an ISATAP router is configured, theThe IPv4 address used for itsaddress(es) configured on a router's ISATAP interfaceinterface(s) SHOULD be added (either automatically or manually) to the site's name serviceaddress records for the "ISATAP" Well-Known Ser- vice name (e.g., by adding an A record in DNS), so it will be added to theISATAP Potential Router list of all nodes on the link.router interfaces (see section 5.2.1). 6.2. Site Administration Considerations The following considerations are noted for sites that deploy ISATAP: - ISATAP links are administratively defined by a set of router interfaces, and set of nodes which have those interface addresses in their potential router lists. Thus, ISATAP links are defined by administrative (not physical) boundaries. - ISATAP hosts and routers can be deployed in an ad-hoc and independent fashion. In particular, ISATAP hosts can be deployed with little/no advanced knowledge of existing ISATAP routers, and ISATAP routers can deployed with no reconfiguration requirements for hosts. - ISATAP nodes periodically send Router Solicitations to all entries in the Potential Router List. Worst-case control traffic is on the order of (M x N), where 'M' is the number of routers in the Potential Router List and 'N' is the total number of nodes on the ISATAP link. The MinRouterSolicitInterval of 15min([5.2.4]) bounds control traffic for large numbers of nodes even in worst-case scenarios. - StrategicISATAP nodes periodically refresh the entries on the PRL, typically by polling the DNS. Responsible site administration, along with robust host and routerprotocol implementations, can provide significant reductions in control traffic. At a minimum, siteadministrators SHOULD ensure that name servicethe site's address records for the "ISATAP" Well-Known Service nameISATAP router interfaces (see section 5.2.1) are well maintained, and represent valid ISATAP routers.maintained. 7. IANA considerations We propose that IANA adopt the interface identifier construction specified in section 4.1 for the existing IANA IEEE OUI registration ('00-00-5E'). Additionally, we request that the name "ISATAP" be reserved in the IANA "Protocol and Service Names" assigned numbers document.8. Security considerations Site administrators are advised that, in addition to possible attacks against IPv6, security attacks against IPv4 MUST also be considered. Many security considerations in [6OVER4,9] apply also to ISATAP. Responsible IPv4 site security management is strongly encouraged. In particular, border gateways SHOULD implement filtering to detect spoofed IPv4 source addresses at a minimum; ip-protocol-41 filtering SHOULD also be implemented. If IPv4 source address filtering is not correctly implemented, the validity checks in section 4.7 will not be effective in preventing IPv6 source address spoofing. If filtering for ip-protocol-41 is not correctly implemented, IPv6 source address spoofing is clearly possible, but this can be elim- inatedeliminated if both IPv4 source address filtering, and the validity checks in section 4.7 are implemented. [DISC,6.1.2] implies that nodes trust Router Advertisements they receive from on-link routers, as indicated by a value of 255 in the IPv6 'hop-limit' field. Since this field is not decremented when ip- protocol-41ip-protocol-41 packets traverse multiple IPv4 hops [MECH,3.3], ISATAP links require a different trust model. In particular, ONLY those Router Advertisements received from a member of the Potential Routers List are trusted; all others are silently discarded (see section 5.2.2). This trust model is predicated on IPv4 source address filter- ing,filtering, as described above. The ISATAP address format does not support privacy extensions for stateless address autoconfiguration [PRIVACY]. However, since the ISATAP interface identifier is derived from the node's IPv4 address, ISATAP addresses do not have the same level of privacy concerns as IPv6 addresses that use an interface identifier derived from the MAC address. Acknowledgements Some of the ideas presented in this draft were derived from work at SRI with internal funds and contractual support. Government sponsors who supported the work include Monica Farah-Stapleton and Russell Langan from U.S. Army CECOM ASEO, and Dr. Allen Moshfegh from U.S. Office of Naval Research. Within SRI, Dr. Mike Frankel, J. Peter Mar- cotullio,Marcotullio, Lou Rodriguez, and Dr. Ambatipudi Sastry supported the work and helped foster early interest. The following peer reviewers are acknowledged for taking the time to review a pre-release of this document and provide input: Jim Bound, Rich Draves, Cyndi Jung, Ambatipudi Sastry, Aaron Schrader, Ole Troan, Vlad Yasevich. The authors acknowledge members of the NGTRANS community who have made significant contributions to this effort, including Rich Draves, Alain Durand, Nathan Lutchansky, Art Shelest, Margaret Wasserman, and Brian Zill. Finally, the authors recognize that ideas similar to those in this document may have already been presented by others and wish to ack- nowledgeacknowledge any other such contributions. Normative References [ADDR] Hinden, R., and S. Deering, "IP Version 6 Addressing Architecture", RFC 2373, July 1998. (Pending approval of "addr-arch-v3"). [AGGR] Hinden., R, O'Dell, M., and Deering, S., "An IPv6 Aggregatable Global Unicast Address Format", RFC 2374, July 1998. [AUTO] Thomson, S., and T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 2462, December 1998. [DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 2461, December 1998. [EUI64] IEEE, "Guidelines for 64-bit Global Identifier (EUI-64) Registration Authority", http://standards.ieee.org/regauth/oui/tutorials/EUI64.html, March 1997. [ICMPv6] Conta, A. and S. Deering, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC 2463, December 1998. [IPV4] Postel, J., "Internet Protocol", RFC 791. [IPV6] Deering, S., and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460. [MECH] Gilligan, R., and E. Nordmark, "Transition Mechanisms for IPv6 Hosts and Routers", RFC 2893, August 2000. [NAT] Egevang, K., and P. Francis, "The IP Network Address Translator (NAT)", RFC 1631, May 1994. [PRIVATE] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., and E. Lear, "Address Allocation for Private Internets", RFC 1918, February 1996. [SIP] Handley, M., Schulzrinne, H., Schooler, E., and J. Rosenberg, "SIP: Session Initiation Protocol", RFC 2543, March 1999. Informative References [6OVER4] Carpenter, B. and C. Jung, "Transmission of IPv6 over IPv4 Domains without Explicit Tunnels", RFC 2529. [6TO4] Carpenter, B., and K. Moore, "Connection of IPv6 Domains via IPv4 Clouds", RFC 3056, February 2001. [IANA] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, USC/Information Sciences Institute, October 1994. [PRIVACY] Narten, T., R. Draves, "Privacy Extensions for Stateless Address Autoconfiguration in IPv6", RFC 3041, January 2001. [RFC1035] Mockapetris, P., "Domain Names - Implementation and Specification", RFC 1035, November 1987. [RFC2219] Hamilton, M., and R. Wright, "Use of DNS Aliases for Network Services", RFC 2219 (BCP), October 1997. Authors Addresses Fred L. Templin SRI International 333 Ravenswood Ave. Menlo Park, CA 94025, USA Phone: (650)-859-3144 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 Phone: +1 425 705 3131 EMail: email@example.com Dave Thaler Microsoft Corporation One Microsoft Way Redmond, WA 98052-6399 Phone: +1 425 703 8835 EMail: firstname.lastname@example.org APPENDIX A: Major Changes changes from version 03 to version 04: - Re-wrote section on Potential Router List initialization to reference existing precedence in other documents - several minor wording changes based on feedback from the community changes from version 02 to version 03: - Added contributing co-authors - RSs are now sent to unicast addresses rather than all-routers-multicast - Brought draft into better alignment with other IPv6 standards-track documents - Added applicability statement changes from version 01 to version 02: - Cleaned up text and tightened up terminology. Changed "IPv6 destination address" to "IPv6 next-hop address" under "sending rules". Changed definition of ISATAP prefix to include link and site-local. Changed language in sections 4 and 5 changes from version 00 to version 01: - Revised draft to require different /64 prefixs for ISATAP addresses and native IPv6 addresses. Thus, a node's ISATAP interface is assigned a /64 prefix that is distinct from the prefixes assigned to any other interfaces attached to the node - be they physical or logical interfaces. This approach eliminates ISATAP-specific sending rules presented in earlier draft versions. - Changed sense of 'u/l' bit in the ISATAP address interface identifier to indicate "local scope", since ISATAP interface identifiers are unique only within the scope of the ISATAP prefix. (See section 4.) changes from personal draft to version 00: - Title change to provide higher-level description of field of use addressed by this draft. Removed other extraneous text. - Major new section on automatic discovery of off-link IPv6 routers when IPv6-IPv4 compatibility addresses are used. Intellectual Property The IETF has been notified of intellectual property rights claimed in regard to some or all of the specification contained in this docu- ment.document. For more information consult the online list of claimed rights.