Individual Submission M. Hashimoto Internet-Draft Osaka University Expires: January 19, 2006 S. Ata Osaka City University H. Kitamura NEC Corporation M. Murata Osaka University July 18, 2005 IPv6 Anycast Terminology Definition draft-doi-ipv6-anycast-func-term-04 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on January 19, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract The purpose of this document is to clarify the usage of terms for IPv6 Anycast and help increase its popularity. This document discusses not only Anycasting's terminology but also its categorization and clarifies its outline. In this document, we focus on network-layer Anycast, which is defined in IPv6 specifications. M. Hashimoto, et al. Expires January 2006 [Page 1] Internet-Draft IPv6 Anycast Terminology Definition July 2005 1. Introduction In IPv6 networks, a service-oriented address can be assigned to an interface called Anycast that identifies a set of interfaces. A packet sent to an Anycast address is delivered to one of the interfaces assigned that address. This interface is the optimum one according to some anycast routing mechanisms. Since many people are interested in Anycast, it is necessary to define Anycast related terms to use them in common. This document will clarify the usage of terms for IPv6 Anycast and support documents about IPv6 Anycast. We focus on network-layer Anycast, which is defined in IPv6 specifications [ADDR-ARCH]. 2. Definition Format Definitions in this document accompany the following format. o Term to be defined. Definition: The specific definition of the term. Discussion: A brief discussion of the term, its application and other information that builds understanding. [See Also:] A list of other terms relevant to discussion of this term. This field is optional in this document. 3. Basic Terms We first define basic terms which are generally used in Anycast related documents. Fig. 1 shows the basic model of Anycasting. M. Hashimoto, et al. Expires January 2006 [Page 2] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Anycast Responder +-----+ | AR1 | (Anycast Address: AA) +-----+ (Peer Unicast Address: PUA1) Anycast Initiator Correspondent Anycast Responder +----+ +-----------+ | AI |--------------------->| AR2 = CAR | (Anycast Address: AA) +----+ Anycast +-----------+ (Peer Unicast Address: PUA2 Communication = Correspondent PUA: CPUA) Anycast Responder +-----+ | AR3 | (Anycast Address: AA) +-----+ (PUA: PUA3) Fig. 1 Basic Model of Anycasting 3.1 Addresses o Anycast Address (AA) Definition: An address used for Anycast Communication has already defined in [ANYCASTING]. Discussion: This address is a service-oriented address assigned to some interfaces. Nodes to which the same Anycast Address is assigned provide the same service. A packet sent to an Anycast address is delivered to one of the interfaces which that address is assigned to. SeeAlso: - Peer Unicast Address - Anycast Prefix o Anycast Prefix (AP) Definition: The prefix part of an Anycast Address. Discussion: Anycast Address is taken from unicast address spaces [ADDR-ARCH]. An assign method of Anycast Address is different from that of unicast address. Anycast Address is not determined by node location. We need to consider what kind of addresses should be assigned as the Anycast Address. The assignment of Anycast M. Hashimoto, et al. Expires January 2006 [Page 3] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Address depends on Anycast types (see Section 4). In Global Anycast, a prefix of the Anycast Address equals to the Anycast Prefix. SeeAlso: - Subnet Anycast - Global Anycast - Anycast Routing o Peer Unicast Address (PUA) Definition: A unicast address(es) assigned to the interface to which Anycast Address is assigned. Discussion: An Anycast Address can be resolved to a Peer Unicast Address by Anycast Address Resolving. SeeAlso: - Anycast Address - Correspondent Peer Unicast Address - Anycast Address Resolving o Correspondent Peer Unicast Address (CPUA) Definition: A Peer Unicast Address assigned to the Correspondent Anycast Responder. Discussion: SeeAlso: - Anycast Address - Peer Unicast Address - Anycast Address Resolving 3.2 Packet o Anycast Packet Definition: A packet whose destination address field is filled with an Anycast Address. Discussion: An Anycast Packet is used for Anycast Communication. When there M. Hashimoto, et al. Expires January 2006 [Page 4] Internet-Draft IPv6 Anycast Terminology Definition July 2005 are plural Anycast Responders, one of the Anycast Responders is selected to receive an Anycast Packet. 3.3 Node o Anycast Initiator (AI) Definition: A node that sends an Anycast Packet and initiates Anycast Communication. Discussion: Any node can become an Anycast Initiator. A node that wants a particular service sends an Anycast Packet and becomes an Anycast Initiator. We prefer to use "Initiator" instead of "Client" because it is not appropriate to call Anycast Communication client-server type communication. Anycast is basically used for a one-shot type communication. SeeAlso: - Anycast Communication - Anycast Responder - Correspondent Anycast Responder o Anycast Responder(s) (AR) Definition: A node that can respond to an Anycast packet. Discussion: Anycast Responder has an interface(s) assigned to an Anycast Address. Only one Anycast Responder (Correspondent Anycast Responder) receives an Anycast Packet sent from an Anycast Initiator. SeeAlso: - Anycast Initiator - Correspondent Anycast Responder - Anycast Group Membership o Correspondent Anycast Responder (CAR) Definition: A node that actually receives an Anycast Packet issued from an Anycast Initiator. Discussion: When an Anycast Initiator sends an Anycast Packet, one of the M. Hashimoto, et al. Expires January 2006 [Page 5] Internet-Draft IPv6 Anycast Terminology Definition July 2005 nodes in the Anycast Group Membership is selected based on the Anycast Responder Selection Criteria. The selected node is called the Correspondent Anycast Responder. Even when using the same Anycast Responder Selection Criteria, the Correspondent Anycast Responder can be changed by Anycast Initiators' locations, network conditions, etc. SeeAlso: - Anycast Responder Selection - Anycast Group Membership - Anycast Communication - Anycast Responder - Anycast Initiator o Home Anycast Responder (HAR) Definition: An Anycast Responder that can receive Anycast Packets even by unicast routing. Discussion: A Home Anycast Responder is a special Anycast Responder. Home Anycast Responder's Peer Unicast Address equals its Anycast Address. SeeAlso: - Anycast Responder - Home Anycast Responder Link - Peer Unicast Address - Anycast Routing o Anycast Router Definition: A router node that can deal with Anycast Routing Protocols. Discussion: SeeAlso: - Anycast Routing - Anycast Routing Table - Anycast Routing Protocol - Anycast Communication Path 3.4 Link o Anycast Responder Link(s) (ARL) M. Hashimoto, et al. Expires January 2006 [Page 6] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Definition: The links to which one or more Anycast Responders belong. Discussion: SeeAlso: - Anycast Responder - Home Anycast Responder Link o Home Anycast Responder Link (HARL) Definition: A link to which a Home Anycast Responder belongs. Discussion: SeeAlso: - Home Anycast Responder - Anycast Responder Link o Anycast Initiator Link(s) (AIL) Definition: The links to which an Anycast Initiator belongs. Discussion: SeeAlso: - Anycast Responder - Home Anycast Responder Link 3.5 Communication o Anycast Communication Definition: Communication initiated by an Anycast Initiator using an Anycast Packet. Discussion: Anycast Communication is one-way communication from an Anycast Initiator to a Correspondent Anycast Responder. SeeAlso: - Global Anycast - Anycast Routing - Anycast Communication Path M. Hashimoto, et al. Expires January 2006 [Page 7] Internet-Draft IPv6 Anycast Terminology Definition July 2005 o Anycast Communication Path (ACP) Definition: A path where an Anycast packet passes in Anycast communication. Discussion: SeeAlso: - Global Anycast - Anycast Routing - Anycast Communication 4. Categorization of Anycast Anycast is roughly classified into two types (Subnet Anycast and Global Anycast) according to locations where Anycast Responders exist. o Subnet Anycast (SA) Definition: An Anycast which use an address whose lower bits are defined by Anycast intrinsically. | n bits | 128-n bits | +----------------------------------------+------------------------+ | subnet prefix (= segments' prefix) | anycast intrinsic part | +----------------------------------------+------------------------+ Fig. 2 Anycast Address for Subnet Anycast Discussion: An Anycast Address which is used in Subnet Anycast is based on the Anycast Responder's unicast address prefix. In typical case, all Anycast Responders are located on the same segment. Routers forward this type of packets only by unicast routing information. Some special routing mechanisms are not required. Because a prefix of the address is depend on unicast address. In Subnet Anycast, Anycast Packets can reach the last hop router by unicast routing. When the last hop router receives the Anycast Packets, the Anycast Responder is determined by the Neighbor Cache [ND] of the last hop router. (i.e., Anycast Responder Selection is up to the last hop router.) Fig. 2 shows Anycast Address format for Subnet Anycast and Fig. 3 shows Subnet Anycast. SeeAlso: - Anycast Responder Selection - Anycast Prefix - Anycast Routing M. Hashimoto, et al. Expires January 2006 [Page 8] Internet-Draft IPv6 Anycast Terminology Definition July 2005 - Global Anycast +----------+ | Anycast Responders | | | +-----+ | | Router +----| AR1 | Anycast | | +-----+ | +-----+ Initiator | |------| R |----+ +----+ | | +-----+ | +-----+ | AI |------| Internet | +----| AR2 | +----+ | | | +-----+ | | | | | | +-----+ | | +----| AR3 | | | | +-----+ +----------+ | Fig. 3 Subnet Anycast o Global Anycast (GA) Definition: An Anycast which use an address whose whole bits are defined by Anycast. | 128 bits | +-----------------------------------------------------------------+ | Anycast Address | +-----------------------------------------------------------------+ Fig. 4 Anycast Address for Global Anycast Discussion: Unicast routing is useless for this type of addresses. Because unicast address is not used for this address at all. Some special Anycast Routing mechanisms are necessary to achieve Global Anycast communications. Fig. 4 shows Anycast Address format for Global Anycast and Fig. 5 shows Global Anycast. In special cases, Subnet Anycast and Global Anycast are combined. In such cases, an Anycast Packet is delivered to the last hop router by Anycast Routing, which then delivers the Anycast Packet according to its Neighbor Cache. An Anycast in this case is shown in Fig. 6. SeeAlso: - Anycast Responder Selection - Anycast Prefix - Anycast Routing - Anycast Communication Path - Subnet Anycast M. Hashimoto, et al. Expires January 2006 [Page 9] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Anycast Responders +----------+ | +-----+ | | Routers +----| AR1 | | | +-----+ | +-----+ | |------| R |----+ | | +-----+ | | | Anycast | | Initiator | | +-----+ | +----+ | |---------| R |----+ | AI |------| Internet | +-----+ | +-----+ +----+ | | +----| AR2 | | | | +-----+ | | | | | | +-----+ | | |------| R |----+ | | +-----+ | +-----+ | | +----| AR3 | +----------+ | +-----+ Fig. 5 Global Anycast +----------+ Anycast Responders | | | +-----+ | | Routers +----| AR1 | | | +-----+ | +-----+ Anycast | |------| R |----+ Initiator | | +-----+ | +-----+ +----+ | | +----| AR2 | | AI |------| Internet | | +-----+ +----+ | | | | | | +-----+ | | |---------| R |----+ | | +-----+ | +-----+ | | +----| AR3 | +----------+ | +-----+ Fig. 6 Global Anycast plus Subnet Anycast 5. Anycast Routing This section defines terms related to Anycast Routing. o Anycast Routing Definition: M. Hashimoto, et al. Expires January 2006 [Page 10] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Routing for Anycast Communication. Discussion: An Anycast Packet is delivered from an Anycast Initiator to an Anycast Responder via Anycast Routing. SeeAlso: - Anycast Router - Anycast Routing Table - Anycast Routing Protocol o Anycast Routing Table Definition: A routing table for Anycast Routing. Discussion: All Anycast Routers have Anycast Routing Tables. An Anycast Initiator may also have an Anycast Routing Table. SeeAlso: - Anycast Routing - Anycast Router - Anycast Routing Protocol - Peer Unicast Address - Anycast Address Resolving o Anycast Routing Protocol Definition: A routing protocol for anycasting. Discussion: SeeAlso: - Anycast Routing - Anycast Router - Anycast Routing Table o Anycast Address Resolving (AAR) Definition: To resolve an Anycast Address to the Peer Unicast Address. Discussion: By considering Anycast a service discovery mechanism [AARP], after an Anycast Responder is discovered, the Anycast Initiator uses the server's Peer Unicast Address for continuous M. Hashimoto, et al. Expires January 2006 [Page 11] Internet-Draft IPv6 Anycast Terminology Definition July 2005 communication. SeeAlso: - Anycast Address - Peer Unicast Address 6. Anycast Responder Selection o Anycast Responder Selection (ARS) Definition: The selection of a Correspondent Anycast Responder from an Anycast Group Membership. Discussion: SeeAlso: - Anycast Responder Selection Criteria - Anycast Group Membership - Correspondent Anycast Responder - Candidate(s) for Correspondent Anycast Responder o Anycast Responder Selection Criteria (ARSC) Definition: The selection criteria of a Correspondent Anycast Responder from Anycast Group Membership. Discussion: SeeAlso: - Anycast Responder Selection - Anycast Group Membership - Correspondent Anycast Responder - Candidate(s) for Correspondent Anycast Responder o Anycast Group Membership (AGM) Definition: A set of nodes that have interfaces with the same Anycast Address. Discussion: A node can join the Anycast Group Membership to become an Anycast Responder, and an Anycast Responder can quit the Anycast Group Membership. SeeAlso: M. Hashimoto, et al. Expires January 2006 [Page 12] Internet-Draft IPv6 Anycast Terminology Definition July 2005 - Anycast Responder - Anycast Responder Selection o Anycast Initiator's Scope (AIS) Definition: A zone where an Anycast Packet, which one Anycast Initiator sends, can reach. Discussion: In other words, a zone Candidate(s) for Correspondent Anycast Responder exist(s). SeeAlso: - Candidates for Correspondent Anycast Responder - Anycast Responder's Service Zone - Anycast Group Membership o Anycast Responder's Service Zone (ARSZ) Definition: A zone where an Anycast Responder can respond to an Anycast Packet issued by an Anycast Initiator. Discussion: SeeAlso: - Candidates for Correspondent Anycast Responder - Anycast Initiator's Scope - Anycast Group Membership o Candidates for Correspondent Anycast Responder (CCAR) Definition: Anycast Responder(s) that can receive an Anycast Packet from one Anycast Initiator. Discussion: SeeAlso: - Anycast Responder - Anycast Group Membership - Anycast Initiator's Scope - Anycast Responder's Service Zone 7. Security Considerations This paper does not address any Anycast security issues. M. Hashimoto, et al. Expires January 2006 [Page 13] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Anycast security descriptions are shown in [ANALYSIS]. 8. References [ANYCASTING] Partridge, C., and Mendez, T., and Milliken, T., "Host Anycasting Service," RFC1546, November 1993 [ADDR-ARCH] Hinden, R., and Deering, S., "IP Version 6 Addressing Architecture," RFC3513, April 2003. [ANALYSIS] Hagino, J., and Ettikan, K., "An Analysis of IPv6 Anycast," , June 2003 "work in progress." [SUBNET] Johnson, D., and Deering, S., "Researved IPv6 Subnet Anycast Addresses," RFC2526, March 1999. [ADDR-AUTO] Thomson, S., Narten, T., "IPv6 Stateless Address Autoconfiguration," RFC2462, December 1998. [ND] Narten, T., Nordmark, E., and Simpson, W., "Neighbor Discovery for IP Version 6 (IPv6)," RFC 2461, December 1998. [AARP] Ata, S., Kitamura, H., and Murata, M., "A Protocol for Anycast Address Resolving," , June 2002. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. M. Hashimoto, et al. Expires January 2006 [Page 14] Internet-Draft IPv6 Anycast Terminology Definition July 2005 9. Authors' Addresses Masakazu Hashimoto Osaka University 1-5 Yamadaoka, Suita-shi Osaka 565-0871 Japan Phone: +81-6-6879-4542 Fax: +81-6-6879-4544 Email: msk-hasi@ist.osaka-u.ac.jp Shingo Ata Osaka City University 3-3-138, Sugimoto, Sumiyoshi-ku Osaka 558-8585 Japan Phone: +81-6-6605-2191 Fax: +81-6-6690-5382 EMail: ata@info.eng.osaka-cu.ac.jp Hiroshi Kitamura NEC Corporation (Igarashi Building 4F) 11-5, Shibaura 2-Chome Minato-ku, Tokyo 108-8557 Japan Phone: +81-3-5476-1071 Fax: +81-3-5476-1005 EMail: kitamura@da.jp.nec.com Masayuki Murata Osaka University 1-5 Yamadaoka, Suita-shi Osaka 565-0871 Japan Phone: +81-6-6879-4543 Fax: +81-6-6879-4544 EMail: murata@ist.osaka-u.ac.jp M. Hashimoto, et al. Expires January 2006 [Page 15] Internet-Draft IPv6 Anycast Terminology Definition July 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. M. Hashimoto, et al. Expires January 2006 [Page 16]