Internet DRAFT - draft-francis-ipngwg-site-def
draft-francis-ipngwg-site-def
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.
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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
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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
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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).
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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.
Copyright (C) The Internet Society XXX 0, 0000. All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
7 Intellectual Property
The following notice is copied from RFC 2026 [Bradner, 1996],
Section 10.4, and describes the position of the IETF concerning
intellectual property claims made against this document.
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.
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