Internet Draft P. Francis <draft-francis-ipngwg-site-def-00.txt> TAHOE Networks Apr. 1,2001 IPv6 Site Definition 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. 1 Introduction A key concept in IPv6 is that of the site. Unfortunately, there is no rigorous definition of a site. Rather, a site is only loosely and informally defined as "a region of topology that belongs to a single organization and is located within a single geographic location" [1]. This document rectifies this situation. It gives a rigorous definition of site, based on the basic loose definition so far provided. One of the primary advantages of the definition chosen is that it allows routers to autoconfigure site boundaries. 1.1 Conventions used in this document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [2]. 2 Problem The definition of a site is currently too loose. The phrase "single geographic location" is too ambiguous. Network managers may not Francis Expires Sept. 1, 2001 Page 1 IPv6 Site Definition Apr. 1, 2001 know if a given network topology constitutes a single site or multiple sites. For instance, there can be little disagreement that the following network topology is a single site: ISP | | R R R R | | | | --------- ---------- | | R------------------------------R East Wing West Wing In this topology, separate networks in the east and west wings of a single building are connected by a point-to-point link (only routers, not hosts, are shown). A router in the west wing is attached to an ISP. The following network topology, on the other hand, is clearly not a single site: ISP | | R R R R | | | | --------- ---------- | | R------------------------------R LA Branch NY Branch Here, the separate networks are on opposite U.S. coasts, clearly too far apart to be a single site. It is not clear, however, whether the following topology is a single site or two sites: ISP | | R R R R | | | | --------- ---------- | | R------------------------------R Left Bank Right Bank Francis Expires Sept. 1, 2001 Page 2 IPv6 Site Definition Apr. 1, 2001 In this network, the two halves are close together, but not that close together. It is critical that site administrators be able to determine what is and isn't a site. 3 Site Definition The only way to unambiguously define site and still stay in the spirit of the current understood definition is to nail down the geographical boundaries of a site. There are a number of ways to do this. One could, for instance, specify only the area that a site may cover, for instance one square kilometer, but not specify the shape of the site. If the site covered a multi-story building, then each story could contribute to the square footage. The problem with this approach is that it does not lend itself to easy autoconfiguration of site boundaries. This is because the shape of the site is left unspecified. Autoconfiguration is one of the key benefits of IPv6, so an approach that supports autoconfiguration of site boundaries is preferable. This draft proposes the following rigorous definition of a site: A site is defined as the set of routers that fit inside a hexagonal shape with a distance of one kilometer between opposite corners. Any hosts sharing a link with a router in a given site are considered part of the site. The hexagonal shape is chosen because it can be tiled while still approximating a circle. The administrator is free to decide exactly where to lay the hexagons. However, they MUST not overlap, and every router MUST be within the boundary of one and only one hexagon. All stories of a multi-story building are considered to be in the site covered by the hexagon. Since a site must be internally connected (that is, a path from any router in the site must only go through routers in the site), a given tiling may cause some sites to be partitioned. In these cases, either a different tiling must be chosen, or additional links must be added to connect the site internally. 4 Site Boundary Autoconfiguration A site can be completely defined with three parameters: the longitude and latitude of the center of the site, and the number of degrees west of north of a corner. We call this the site bearing. Given these three parameters, any router can decide if it is a given site or not. To autoconfigure a site, one router in the site MUST be configured with the site bearing. In addition, every router MUST be configured with its own longitude and latitude (position). Francis Expires Sept. 1, 2001 Page 3 IPv6 Site Definition Apr. 1, 2001 Fortunately, this can be done automatically with GPS equipment. (They may be other benefits to routers knowing their position, but these are outside the scope of this document.) The router configured with the bearing of the site includes it in its router advertisements. It also includes its own position in its router advertisements. Every router, upon receiving a router advertisement, determines if it is the site or not, and if its neighbor is in the site or not. If it is, it in turns includes the site bearing and its location in its advertisements. If not, it includes only its location. In this way, every router will know what site it is in and what site its neighbors are in. Thusly, site boundaries are autoconfigured. 5 Security Considerations While there may be new failure modes introduced by autoconfigured site boundaries, there are no new security considerations resulting from this work. 6 Copyright The following copyright notice is copied from RFC 2026 [Bradner, 1996], Section 10.4, and describes the applicable copyright for this document. 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The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use other technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication 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 Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 8 References 1 "IPv6 Scoped Address Architecture ", draft-ietf-ipngwg-scoping- arch-02.txt 2 S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Francis Expires Sept. 1, 2001 Page 5