NGTRANS Working Group F. Templin INTERNET-DRAFT Nokia T. Gleeson Cisco Systems K.K. M. Talwar D. Thaler Microsoft Corporation Expires 31 April 2003 31 October 2002 Intra-Site Automatic Tunnel Addressing Protocol (ISATAP) draft-ietf-ngtrans-isatap-06.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 for IPv6. ISATAP mechanisms use an 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 Templin, et. al. Expires 31 April 2003 [Page 1] INTERNET-DRAFT ISATAP 31 October 2002 routing table size and require no special IPv4 services (e.g., IPv4 multicast). 1. Introduction This document presents a simple approach that enables incremental deployment of IPv6 within IPv4-based sites in a manner that is com- patible 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] Templin, et. al. Expires 31 April 2003 [Page 2] INTERNET-DRAFT ISATAP 31 October 2002 - 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 encapsulation, hop limit, IPv4 header con- struction, and decapsualtion specifications in [MECH, 3], i.e., IPv6 packets are automatically encapsulated in IPv4 using 'ip-protocol-41' as the payload type number. The specifications in [MECH, 3.2, 3.4] do Templin, et. al. Expires 31 April 2003 [Page 3] INTERNET-DRAFT ISATAP 31 October 2002 not apply for ISATAP; instead: - The default link MTU SHOULD be set to the minimum IPv6 MTU of 1280 bytes [IPV6], unless specific configuration information is available. The Don't Fragment bit SHOULD NOT be set in the encapsulating IPv4 header. - IPv4 ICMP errors and ARP failures may be processed as link error notifications, as allowed by [DISC] 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- tifier 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 interface identifiers are constructed by prepending the 32-bit string '00-00-5E-FE' with an IPv4 address (see the following section for examples). Appendix B includes text explaining the rationale for this construction rule. 4.2. Stateless Autoconfiguration and Link-Local Addresses ISATAP addresses are unicast addresses [ADDR,2.5] that use 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:8108 has a prefix of '3FFE:1A05:510:1111::/64' and an ISATAP format inter- face identifier with embedded IPv4 address: '140.173.129.8'. The address is alternately written as: 3FFE:1A05:510:1111:0:5EFE:140.173.129.8 Templin, et. al. Expires 31 April 2003 [Page 4] INTERNET-DRAFT ISATAP 31 October 2002 The link-local and site-local variants (respectively) are: FE80::0:5EFE:140.173.129.8 FEC0::1111:0:5EFE:140.173.129.8 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- 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 (see section 5.2.1). In the lat- ter case, the interface will accept ISATAP packets addressed to any of the IPv4 link-layer addresses, but will choose one as its primary address, used for sourcing packets. Only this address need be repre- sented in the Potential 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 Packets received on ISATAP interfaces MUST satisfy at least one (i.e., one or both) of the following validity checks: Templin, et. al. Expires 31 April 2003 [Page 5] INTERNET-DRAFT ISATAP 31 October 2002 - 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 an "active" member of the Potential Routers List (see section 5.2), i.e., previous hop is an on-link ISATAP router actively being used by the node Packets that do not satisfy at least one of the above checks are silently discarded. 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- nation 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." 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- tions 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) in ISATAP are resolved to link-layer addresses (IPv4) by a static computation, i.e., the last four octets are treated as an IPv4 address. ISATAP nodes SHOULD perform Neighbor Unreachability Detection (NUD) as specified in [DISC, 7.3], and MUST send solicited neighbor adver- tisements as specified in [DISC, 7.2.4]. The link-layer address option used in [DISC] is not needed. Link- layer address options SHOULD NOT be sent in any Neighbor Discovery packets, and MUST be silently ignored in any received Neighbor Dis- covery packets. Templin, et. al. Expires 31 April 2003 [Page 6] INTERNET-DRAFT ISATAP 31 October 2002 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 mecha- nisms are required and specified below: 5.2.1. Conceptual Data Structures ISATAP nodes use the conceptual data structures Prefix List and Default Router List exactly as specified in [DISC,5.1]. ISATAP links add a new conceptual data structure "Potential Router List" and the following 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- local address for that interface. When a node enables an ISATAP link, it initializes the Potential Router List (PRL) for that link. Unless other information is avail- able (e.g., manual address configuration, a vendor-specific DHCP option, etc.) the following method (similar to the [SIP, 1.4.2] pro- cedure) 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 in the replies. 3. After initialization, nodes periodically repeat the above Templin, et. al. Expires 31 April 2003 [Page 7] INTERNET-DRAFT ISATAP 31 October 2002 procedure ResolveInterval to update the PRL with any IPv4 addresses added/deleted since the previous iteration. When DNS is 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- sages 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- ing 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- tisement to the address of the node which sent the Router Solicita- tion. 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. ISATAP routers MAY engage in the polling process described under Host Specification below (e.g. if Router Advertisement consistency verification [DISC,6.2.7] is desired), but this is not required. 5.2.4. Host Specification Hosts periodically poll one or more entries 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 a PRL(i) is selected for polling, the host sets its associated timer to MinRouterSolicitInterval and initiates polling following a short delay as for initial solicitations [ND,6.3.7]), and when the Templin, et. al. Expires 31 April 2003 [Page 8] INTERNET-DRAFT ISATAP 31 October 2002 associated timer expires. Polling consists of sending Router Solicitations to the ISATAP link- 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'. 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 is pro- cesses in the same manner described in [DISC,6.3.4]. The host addi- tionally resets the timer associated with the V4ADDR_PRL(i) embedded in the network-layer source address in the Router Advertisement. The timer is reset to either 0.5 * (the minimum value in the router life- time or valid lifetime of any on-link prefixes advertised) or Min- RouterSolicitInterval; 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- TAP is implemented) and also supports IPv6 natively, then ISATAP MAY be enabled if the native IPv6 layer does not receive Router Adver- tisements (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 SHOULD discontinue the 'Router Polling Process' process specified in section 5.2.4 and allow exist- ing ISATAP address configurations to expire as specified in [DISC,5.3][AUTO,5.5.4]. Any ISATAP addresses added to the DNS for this host should also be removed. In this way, ISATAP use will gradu- ally diminish as IPv6 routers are widely deployed throughout the site. Routers MAY configure an interface 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. The IPv4 address(es) configured on a router's ISATAP interface(s) SHOULD be added (either automatically or manually) to the site's address records for ISATAP router interfaces (see section 5.2.1). Templin, et. al. Expires 31 April 2003 [Page 9] INTERNET-DRAFT ISATAP 31 October 2002 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 ([5.2.4]) bounds control traffic for large numbers of nodes even in worst-case scenarios. - ISATAP nodes periodically refresh the entries on the PRL, typically by polling the DNS. Responsible site administration can reduce the control traffic. At a minimum, administrators SHOULD ensure that the site's address records for ISATAP router interfaces (see section 5.2.1) are well maintained. 7. IANA considerations Appendix B offers one possible specification for managing the IEEE OUI assigned to IANA for EUI-64 interface identifier construction. This specification is made freely available to IANA for any purpose they may find useful. 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 Templin, et. al. Expires 31 April 2003 [Page 10] INTERNET-DRAFT ISATAP 31 October 2002 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 elimi- nated 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-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, 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, 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. The authors wish to acknowledge 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 Templin, et. al. Expires 31 April 2003 [Page 11] INTERNET-DRAFT ISATAP 31 October 2002 the authors' attention on September 20, 2002. Finally, the authors recognize that ideas similar to those in this document may have already been presented by others and wish to acknowledge 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/tutori- als/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. Templin, et. al. Expires 31 April 2003 [Page 12] INTERNET-DRAFT ISATAP 31 October 2002 [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. [VET] Nguyen, Quang, "Virtual Ethernet: A New Approach to IPv6 Transition", http://irl.cs.ucla.edu/vet/report.ps, MS Project Report, Spring 1998. Authors Addresses Fred L. Templin Nokia 313 Fairchild Drive Mountain View, CA, USA Phone: (650)-625-2331 Email: ftemplin@iprg.nokia.com Tim Gleeson Cisco Systems K.K. Shinjuku Mitsu Building 2-1-1 Nishishinjuku, Shinjuku-ku Tokyo 163-0409, JAPAN email: tgleeson@cisco.com Mohit Talwar Microsoft Corporation Templin, et. al. Expires 31 April 2003 [Page 13] INTERNET-DRAFT ISATAP 31 October 2002 One Microsoft Way Redmond, WA 98052-6399 Phone: +1 425 705 3131 EMail: mohitt@microsoft.com Dave Thaler Microsoft Corporation One Microsoft Way Redmond, WA 98052-6399 Phone: +1 425 703 8835 EMail: dthaler@microsoft.com APPENDIX A: Major Changes changes from version 05 to version 06: - Addressed operational issues identified in 05 based on discussion between co-authors - Clarified ambiguous text per comments from Hannu Flinck; Jason Goldschmidt changes from version 04 to version 05: - Moved historical text in section 4.1 to Appendix B in response to comments from Pekka Savola - Identified operational issues for anticipated deployment scenarios - Included SRI IPR statement and contact information - Included reference to Quang Nguyen work 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 Templin, et. al. Expires 31 April 2003 [Page 14] INTERNET-DRAFT ISATAP 31 October 2002 - 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 prefixes 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. APPENDIX B: Rationale for Interface Identifier Construction Rules ISATAP specifies an [EUI64]-format address construction for the Orga- nizationally-Unique Identifier (OUI) owned by the Internet Assigned Numbers Authority [IANA]. This format (given below) is used to con- struct both native [EUI64] addresses for general use and modified EUI-64 format interface identifiers for use in IPv6 unicast addresses: Templin, et. al. Expires 31 April 2003 [Page 15] INTERNET-DRAFT ISATAP 31 October 2002 |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 identi- fiers (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 indi- cate an IPv4 address is embedded. Thus, when the first four octets of a [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 "ISATAP format" and the next four octets embed an IPv4 address encoded in network byte order. INTELLECTUAL PROPERTY SRI International has notified the IETF of IPR considerations for Templin, et. al. Expires 31 April 2003 [Page 16] INTERNET-DRAFT ISATAP 31 October 2002 some aspects of this specification. For more information consult the online list of claimed rights. Templin, et. al. Expires 31 April 2003 [Page 17]