HTTP/1.1 200 OK Date: Tue, 09 Apr 2002 03:51:36 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Fri, 01 Sep 1995 22:00:00 GMT ETag: "2f532a-3e89-30478260" Accept-Ranges: bytes Content-Length: 16009 Connection: close Content-Type: text/plain INTERNET-DRAFT Y. Rekhter, Cisco August 30, 1995 P. Lothberg, STUPI.AB Expires in six months R. Hinden, Ipsilon Networks S. Deering, Xerox PARC J. Postel, ISI Editors An IPv6 Provider-Based Unicast Address Format Status of this Memo This document is an Internet Draft. 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. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a ``working draft'' or ``work in progress.'' Please check the 1id-abstracts.txt listing contained in the internet- drafts Shadow Directories on nic.ddn.mil, nnsc.nsf.net, nic.nordu.net, ftp.nisc.sri.com, or munnari.oz.au to learn the current status of any Internet Draft. 1.0 Introduction This document defines an IPv6 provider-based unicast address format for use in the Internet. The address format defined in this document is consistent with the "IPv6 Addressing Architecture" [ARCH] and the "An Architecture for IPv6 Unicast Address Allocation" [ALLOC], and is intended to facilitate scalable Internet routing. The unicast address format defined in this document doesn't preclude the use of other unicast address formats. draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 1] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 2.0 Overview of the IPv6 Address IPv6 addresses are 128-bit identifiers for interfaces and sets of interfaces. There are three types of addresses: Unicast, Anycast, and Multicast. This document defines a specific type of Unicast address. In this document, fields in addresses are given specific names, for example "subscriber". When this name is used with the term "ID" (for "identifier") after the name (e.g., "subscriber ID"), it refers to the contents of the named field. When it is used with the term "prefix" (e.g. "subscriber prefix") it refers to all of the address up to and including this field. The specific type of an IPv6 address is indicated by the leading bits in the address. The variable-length field comprising these leading bits is called the Format Prefix (FP). This document defines an address format for the 010 (binary) Format Prefix for Provider-Based Unicast addresses. The same address format could be used for other Format Prefixes, as long as these Format Prefixes also identify IPv6 unicast addresses. Only the "010" Format Prefix is defined here. 3.0 IPv6 Provider-Based Unicast Address Format This document defines an address format for the IPv6 provider-based unicast address assignment. It is expected that this address format will be widely used for IPv6 nodes connected to the Internet. The address format defined in this document conforms to the "Architecture for IPv6 Unicast Address Allocation" [ALLOC]. Specifically, the format is designed to support aggregation of network layer reachability information at multiple levels of routing hierarchy. For addresses of the format described in this document the address administration is organized into a three level hierarchy -- registry, provider, and subscriber. The address format defined here allows flexible address allocation at each level of the address administration hierarchy in such a way as to support a wide spectrum of demands for address allocation. This document assumes that the Internet routing system doesn't make any assumptions about the specific structure and semantics of an IPv6 address, except for the structure and semantics of the Format Prefix part of the address, and the use of the "longest prefix match" algorithm (on arbitrary bit boundaries) for making a forwarding decision. draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 2] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 The address format defined in this document is intended to facilitate scalable Internet-wide routing that does not impose any constraints on connectivity among the providers, as well as among the providers and subscribers. 3.1 Provider-Based Unicast Address Structure For the purpose of address allocation, the address format defined in this document consists of the following parts: Format Prefix, Registry ID, Provider ID, Subscriber ID, and an Intra-Subscriber part. The Intra-Subscriber part definition is the responsibility of the subscriber and is not defined in this document. The provider-based unicast address format is as follows: | 3 | 5 bits | 16 bits | 8 | 24 bits | 8 | 64 bits | +---+----------+----------+---+------------+---+----------------+ |010|RegistryID|ProviderID|RES|SubscriberID|RES|Intra-Subscriber| +---+----------+----------+---+------------+---+----------------+ The following sections specify each part of the IPv6 Provider-Based Unicast address format. In general other allocation strategies are possible within this framework, but the ones described in this document will be used to assign IPv6 provider-based addresses. The fields identified as "RES" are reserved and must be set to zero (0). They are intended to allow for the fields on either side to grow into that space if needed for future growth. 3.2 Registry ID With the growth of the Internet and its increasing globalization, much thought has been given to the evolution of the Network Layer address space allocation and assignment process. RFC 1466, "Guidelines for Management of IP Address Space", proposes a plan that defines distributed allocation and assignment of the IPv4 address space. As the Internet transitions to IPv6, the plan for distributed allocation and assignment of the IPv4 address space established in RFC1466 forms a base for the distributed allocation and assignment of the IPv6 address space. The Internet Assigned Number Authority (IANA) is the principal registry for the IPv6 address space. The IANA may allocate blocks of IPv6 addresses and delegate the assignment of those blocks to qualified Regional Registries. The IANA will serve as the default registry in cases where no delegated registration authority has been identified. draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 3] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 The Registry ID of the IPv6 provider-based unicast address format is intended to facilitate a broad geographic address allocation and facilitate the operations of the distributed Regional Registries. The Registry ID immediately follows the format prefix part of an IPv6 address. At present there are three Regional Registries: INTERNIC, RIPE NCC, and APNIC. In addition, address allocation could be done directly by the IANA. Corresponding to this division of address allocation, this document defines the following Registry IDs: Regional Registry Value (binary) -------------------- -------------- Multi-Regional (IANA) 10000 RIPE NCC 01000 INTERNIC 11000 APNIC 10100 All other values of the Registry ID are reserved by the IANA. Use of the Multi-regional Registry ID permits flexibility in address assignments which are outside of the geographical regions already allocated. The IANA will be responsible for managing address space registration under the Multi-Regional Registry ID. It is expected that the IANA, and any designated Regional Registries, allocate addresses in conformance with this overall scheme. Where there are qualifying Regional Registries established, primary responsibility for allocation from within that block will be delegated to that registry. A Regional Registry may have more than one block of addresses allocated to it (as a result the Registry would have multiple Registry IDs associated with it). 3.3 Provider ID The Provider ID is initially assigned 16 bits. At some time in the future it may be allowed to grow (to the right) into the "RES" field if additional providers are needed in a particular registry. The 16-bit Provider ID provides for 65,535 providers per Registry ID without any expansion of the Provider ID, or 2,031,585 providers within this format prefix. The value of the Provider ID associated with an address block a registry draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 4] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 allocates to a particular provider uniquely identifies this provider within the registry. Provider ID's should be allocated from right to left as shown in following table: Provider Provider ID Value (binary) --------- -------------------------- Provider 1 0000 0000 0000 0001 Provider 2 0000 0000 0000 0010 Provider 3 0000 0000 0000 0011 Provider 4 0000 0000 0000 0100 Provider 5 0000 0000 0000 0101 : : : : Provider 65,535 1111 1111 1111 1111 This document assumes that some subscribers may decide to acquire their addresses space directly from a registry, thus making their addresses independent of the provider(s) they are directly attached. 3.4 Subscriber ID The Subscriber ID is initially assigned 24 bits. At some time in the future it may be allowed to grow (to the left) into the "RES" field if additional subscribers are needed in a particular provider. The 24-bit Subscriber ID provides for 16,777,215 subscribers per Provider ID without any expansion of the Provider ID, or approximately 34 trillion subscribers within this format prefix. The structure and assignment strategy of Subscriber ID's is specified by each provider. A (direct) provider may decide to group its subscribers into regions. This grouping may be useful when the (direct) provider is attached to another (indirect) provider at multiple points, as it allows the direct provider to exert a certain degree of control over the coupling between the attachment points and flow of the traffic destined to a particular subscriber (see Section 5.3.1 of [ALLOC]). To accommodate such a grouping the (direct) provider may allocate some small number of high-order bits of the Subscriber ID as a Subscriber- Region ID. The purpose of a Subscriber-Region ID is to identify a group of subscribers that are within a close topological proximity to each other (from the providers point of view), and thus could be reachable through a particular attachment point between the (direct) provider and other (indirect) provider(s). draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 5] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 3.5 Intra-Subscriber Part This document leaves the organization of Intra-Subscriber portion of the address up to individual subscribers. The provider-based unicast address format described in this document leaves 64 bits for the local portion of the address. The editors of this document recommended that subscribers use IPv6 auto-configuration capabilities [AUTO] to generate addresses using 48 bit IEEE-802 MAC addresses as Interface IDs. In this case 16 bits is left for the Subnet ID. This should sufficient (e.g., 65,535 subnets) for all but the largest of subscribers. This is shown as follows: | 64 bits | 16 bits | 48 bits | +--------------------------------+-----------+------------------+ | Subscriber Prefix | Subnet ID | Interface ID | +--------------------------------+-----------+------------------+ Subscribers who need additional subnets (and who desire to continue to use 48 bit IEEE-802 MAC addresses for Interface ID's) can be accommodated by allowing the Subnet ID can grow to the left into the "RES" field. Alternatively, an extremely large subscriber could be assigned its own Provider ID which would give it 48 bits of address space to create its own local address hierarchy. 4.0 National Registries A Regional Registry may allocate blocks of address space to several National Registries. The National Registry then becomes the entity that allocates address space to individual providers within the country served by the National Registry. To create National Registries the Regional Registry may add a layer of hierarchy in the Provider ID field to create National Registries. The resulting Provider Prefix is a follows: | | | 16 bits | | 3 | 5 bits | n bits | 16-n bits | +---+----------+---------------------+-------------+ |010|RegistryID|National-Registry ID | Provider ID | +---+----------+---------------------+-------------+ This document assumes that within each regional registry there will be a relatively small number of national registries. The size of the National-Registry ID should be related to the number of countries in the region administrated by the regional registry and the number providers draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 6] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 expected to be in each country. National Registries who need additional providers can be supported by allowing the Provider ID to grow to the right into the "RES" field. draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 7] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 6.0 Acknowledgments The editors would like to express our thanks to Jim Bound (DEC), Scott Bradner (Harvard), Brian Carpenter (CERN), Geoff Huston (AANET), and Tony Li (cisco) for their review and constructive comments. 6.0 References [ALLOC] Rekhter, Y., Li, T., "An Architecture for IPv6 Unicast Address Allocation", Internet Draft. [ARCH] Hinden, R., "IP Version 6 Addressing Architecture" Internet Draft. [AUTO] Thompson, S., "IPv6 Stateless Address Autoconfiguration", Internet Draft. 7.0 Security Considerations Security issues are not discussed in this memo. 8.0 Editors' Addresses Yakov Rekhter Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134-1706 USA Phone: +1 914 528-0090 email: yakov@cisco.com Peter Lothberg STUPI.AB Box 9129 S-102 72 Stockholm Sweden Phone:+46 8 6699720 email: roll@Stupi.SE draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 8] INTERNET-DRAFT Provider-Based Unicast Address Format August 30, 1995 Robert M. Hinden Ipsilon Networks, Inc. 2465 Latham Street, Suite 100 Mt. View, CA 94040 USA phone: +1 415 528 4604 email: hinden@ipsilon.com Stephen E. Deering Xerox Palo Alto Research Center 3333 Coyote Hill Road Palo Alto, CA 94304 USA phone: +1 415 812 4839 fax: +1 415 812 4471 email: deering@parc.xerox.com Jon Postel Information Sciences Institute 4676 Admiralty Way Marina del Rey, CA 90292-6695 USA phone: +1 310 822 1511 fax: +1 310 823 6714 email: postel@isi.edu draft-ietf-ipngwg-unicast-addr-fmt-02.txt [Page 9]