draft-ietf-geopriv-rfc3825bis-14.txt   draft-ietf-geopriv-rfc3825bis-15.txt 
GEOPRIV Working Group J. Polk GEOPRIV Working Group J. Polk
INTERNET-DRAFT Cisco Systems INTERNET-DRAFT Cisco Systems
Obsoletes: 3825 (if approved) J. Schnizlein Obsoletes: 3825 (if approved) J. Schnizlein
Category: Standards Track Individual Contributor Category: Standards Track Individual Contributor
Expires: May 25, 2011 M. Linsner Expires: July 4, 2011 M. Linsner
27 November 2010 Cisco Systems 14 January 2011 Cisco Systems
M. Thomson M. Thomson
Andrew Andrew
B. Aboba (ed) B. Aboba (ed)
Microsoft Corporation Microsoft Corporation
Dynamic Host Configuration Protocol Options for Dynamic Host Configuration Protocol Options for
Coordinate-based Location Configuration Information Coordinate-based Location Configuration Information
draft-ietf-geopriv-rfc3825bis-14.txt draft-ietf-geopriv-rfc3825bis-15.txt
Abstract Abstract
This document specifies Dynamic Host Configuration Protocol Options This document specifies Dynamic Host Configuration Protocol Options
(both DHCPv4 and DHCPv6) for the coordinate-based geographic location (both DHCPv4 and DHCPv6) for the coordinate-based geographic location
of the client. The Location Configuration Information (LCI) includes of the client. The Location Configuration Information (LCI) includes
Latitude, Longitude, and Altitude, with resolution or uncertainty Latitude, Longitude, and Altitude, with resolution or uncertainty
indicators for each. Separate parameters indicate the reference indicators for each. Separate parameters indicate the reference
datum for each of these values. datum for each of these values. This document obsoletes RFC 3825.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 49 skipping to change at page 1, line 49
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on May 25, 2011. This Internet-Draft will expire on July 4, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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it for publication as an RFC or to translate it into languages other it for publication as an RFC or to translate it into languages other
than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . 5
1.2 Resolution and Uncertainty . . . . . . . . . . . . . . . 5 1.2 Resolution and Uncertainty . . . . . . . . . . . . . . . 5
2. DHCP Option Format . . . . . . . . . . . . . . . . . . . . . . 6 2. DHCP Option Format . . . . . . . . . . . . . . . . . . . . . . 6
2.1 DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . 6 2.1 DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . 6
2.2 DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . 8 2.2 DHCPv4 Options . . . . . . . . . . . . . . . . . . . . . 8
2.3 Latitude and Longitude Fields . . . . . . . . . . . . . 10 2.3 Latitude and Longitude Fields . . . . . . . . . . . . . 11
2.4 Altitude . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4 Altitude . . . . . . . . . . . . . . . . . . . . . . . . 14
2.5 Datum . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.5 Datum . . . . . . . . . . . . . . . . . . . . . . . . . 16
3. Security Considerations. . . . . . . . . . . . . . . . . . . . 15 3. Security Considerations. . . . . . . . . . . . . . . . . . . . 16
4. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 16 4. IANA Considerations. . . . . . . . . . . . . . . . . . . . . . 17
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 18
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.1. Normative References . . . . . . . . . . . . . . . . . . 17 6.1. Normative References . . . . . . . . . . . . . . . . . . 18
6.2. Informational References . . . . . . . . . . . . . . . . 18 6.2. Informational References . . . . . . . . . . . . . . . . 19
Appendix A. GML Mapping . . . . . . . . . . . . . . . . . . . . . 20 Appendix A. GML Mapping . . . . . . . . . . . . . . . . . . . . . 21
A.1. GML Templates . . . . . . . . . . . . . . . . . . . . . 20 A.1. GML Templates . . . . . . . . . . . . . . . . . . . . . 21
Appendix B. Calculations of Resolution . . . . . . . . . . . . . . 23 Appendix B. Calculations of Resolution . . . . . . . . . . . . . . 24
B.1. LCI of "White House" (Example 1) . . . . . . . . . . . . 23 B.1. LCI of "White House" (Example 1) . . . . . . . . . . . . 25
B.2. LCI of "Sears Tower" (Example 2) . . . . . . . . . . . . 26 B.2. LCI of "Sears Tower" (Example 2) . . . . . . . . . . . . 27
Appendix C. Calculations of Uncertainty . . . . . . . . . . . . . 27 Appendix C. Calculations of Uncertainty . . . . . . . . . . . . . 28
C.1 LCI of "Sydney Opera House" (Example 3) . . . . . . . . 27 C.1 LCI of "Sydney Opera House" (Example 3) . . . . . . . . 28
Appendix D. Changes from RFC 3825 . . . . . . . . . . . . . . . . 31 Appendix D. Changes from RFC 3825 . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction 1. Introduction
The physical location of a network device has a range of The physical location of a network device has a range of
applications. In particular, emergency telephony applications rely applications. In particular, emergency telephony applications rely
on knowing the location of a caller in order to determine the correct on knowing the location of a caller in order to determine the correct
emergency center. emergency center.
The location of a device can be represented either in terms of The location of a device can be represented either in terms of
geospatial (or geodetic) coordinates, or as a civic address. geospatial (or geodetic) coordinates, or as a civic address.
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correspondence between shapes and uncertainty. correspondence between shapes and uncertainty.
When representing locations from sources that can quantify When representing locations from sources that can quantify
uncertainty, the goal is to find the smallest possible rectangular uncertainty, the goal is to find the smallest possible rectangular
prism that this format can describe. This is achieved by taking the prism that this format can describe. This is achieved by taking the
minimum and maximum values on each axis and ensuring that the final minimum and maximum values on each axis and ensuring that the final
encoding covers these points. This increases the region of encoding covers these points. This increases the region of
uncertainty, but ensures that the region that is described uncertainty, but ensures that the region that is described
encompasses the target location. encompasses the target location.
The DHCPv4 option format defined in this document supports both The DHCPv4 option formats defined in this document support resolution
resolution and uncertainty parameters. Version 0 of the DHCPv4 and uncertainty parameters. DHCPv4 Option 123 includes a resolution
option format includes a resolution parameter for each of the parameter for each of the dimensions of location. Since this
dimensions of location. Since this resolution parameter need not resolution parameter need not apply to all dimensions equally, a
apply to all dimensions equally, a resolution value is included for resolution value is included for each of the three location elements.
each of the three location elements. Since version 0 of the DHCPv6 DHCPv4 Option TBD as well as the DHCPv6 option format utilize an
option format is not defined, the DHCPv6 option does not support a uncertainty parameter.
resolution parameter. Version 1 of the DHCPv4 and DHCPv6 option
format utilizes an uncertainty parameter. Appendix A describes the Appendix A describes the mapping of DHCP option values to the
mapping of DHCP option values to GML. Appendix B of this document Geography Markup Language (GML). Appendix B of this document
provides examples showing the calculation of resolution values. provides examples showing the calculation of resolution values.
Appendix C provides an example demonstrating calculation of Appendix C provides an example demonstrating calculation of
uncertainty values. uncertainty values.
Since the PIDF-LO format [RFC4119][RFC5491] is used to conveying Since the Presence Information Data Format Location Object (PIDF-LO)
location and the associated uncertainty within an emergency call [RFC4119][RFC5491] is used to conveying location and the associated
[Convey], a mechanism is needed to convert the information contained uncertainty within an emergency call [Convey], a mechanism is needed
within the DHCPv4 and DHCPv6 options to PIDF-LO. This document to convert the information contained within the DHCPv4 and DHCPv6
describes the following conversions: options to PIDF-LO. This document describes the following
conversions:
version 0 to PIDF-LO DHCPv4 Option 123 to PIDF-LO
version 1 to PIDF-LO DHCPv4 Option TBD and DHCPv6 option to PIDF-LO
PIDF-LO to version 1 PIDF-LO to DHCP Option TBD and DHCPv6 option
Conversion to PIDF-LO does not increase uncertainty; conversion from Conversion to PIDF-LO does not increase uncertainty; conversion from
PIDF-LO to version 1 increases uncertainty by less than a factor of 2 PIDF-LO to DHCPv4 Option TBD and the DHCPv6 option increases
in each dimension. Since it is not possible to translate an uncertainty by less than a factor of 2 in each dimension. Since it
arbitrary PIDF-LO to version 0 with a bounded increase in is not possible to translate an arbitrary PIDF-LO to DHCP Option 123
uncertainty, the conversion to version 0 is not specified. with a bounded increase in uncertainty, the conversion is not
specified.
2. DHCP Option Format 2. DHCP Option Format
This section defines the format for the DHCPv4 and DHCPv6 options. This section defines the format for the DHCPv4 and DHCPv6 options.
These options utilize a similar format, differing primarily in the These options utilize a similar format, differing primarily in the
option code. option code.
2.1. DHCPv6 Option 2.1. DHCPv6 Option
The DHCPv6 [RFC3315] option format is as follows: The DHCPv6 [RFC3315] option format is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code (TBD) | OptLen (16) | | Option Code (TBD) | OptLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LatUnc | Latitude + | LatUnc | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Lat (cont'd) | LongUnc | Longitude + | Lat (cont'd) | LongUnc | Longitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude (cont'd) | AType | AltUnc | Altitude + | Longitude (cont'd) | AType | AltUnc | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Altitude (cont'd) |Ver| Res |Datum| | Altitude (cont'd) |Ver| Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: GEOCONF_GEODETIC (16 bits). Code: DHCP Option Code TBD (16 bits).
OptLen: Option Length (16). This option has a fixed length, so OptLen: Option Length. For version 1, the option length is 16.
that the value of this octet will always be 16.
LatUnc: 6 bits. When the Ver field = 1, this field represents LatUnc: 6 bits. When the Ver field = 1, this field represents
latitude uncertainty. The contents of this field is latitude uncertainty. The contents of this field is
undefined for other values of the Ver field. undefined for other values of the Ver field.
Latitude: a 34 bit fixed point value consisting of 9 bits of Latitude: a 34 bit fixed point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as
described in Section 2.3. described in Section 2.3.
LongUnc: 6 bits. When the Ver field = 1, this field represents LongUnc: 6 bits. When the Ver field = 1, this field represents
longitude uncertainty. The contents of this field is longitude uncertainty. The contents of this field is
undefined for other values of the Ver field. undefined for other values of the Ver field.
Longitude: a 34 bit fixed point value consisting of 9 bits of Longitude: a 34 bit fixed point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as integer and 25 bits of fraction, interpreted as
described in Section 2.3. described in Section 2.3.
AType: Altitude Type (4 bits). AType: Altitude Type (4 bits), defined in Section 2.4.
AltUnc: 6 bits. When the Ver field = 1, this field represents AltUnc: 6 bits. When the Ver field = 1, this field represents
altitude uncertainty. The contents of this field is altitude uncertainty. The contents of this field is
undefined for other values of the Ver field. undefined for other values of the Ver field.
Altitude: A 30 bit value defined by the AType field. Altitude: A 30 bit value defined by the AType field, described in
Section 2.4.
Ver: The Ver field is two bits, providing for four potential Ver: The Ver field is two bits, providing for four potential
versions. This specification defines the behavior of versions. This specification defines the behavior of
version 1. The Ver field is always located at the same version 1. The Ver field is always located at the same
offset from the beginning of the option, regardless of offset from the beginning of the option, regardless of
the version in use. the version in use. DHCPv6 clients implementing this
specification MUST support receiving version 1
responses. DHCPv6 servers implementing this
specification MUST send version 1 responses.
Res: The Res field which is 3 bits, is reserved. These bits Res: The Res field which is 3 bits, is reserved. These bits
have been used by [IEEE-802.11y], but are not defined have been used by [IEEE-802.11y], but are not defined
within this specification. within this specification.
Datum: 3 bits. The Map Datum used for the coordinates given in Datum: 3 bits. The Map Datum used for the coordinates given in
this Option. this Option.
2.2. DHCPv4 Option 2.2. DHCPv4 Options
The DHCPv4 option format is as follows: 2.2.1. DHCPv4 Option 123
The format of DHCPv4 Option 123 is as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code 123 | Length | LatUnc | Latitude + | Code 123 | Length | LaRes | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude (cont'd) | LongUnc | + | Latitude (cont'd) | LoRes | +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude | | Longitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude + | AType | AltRes | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Alt.(cont'd) |Ver| Res |Datum| | Alt.(cont'd) | Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: 8 bits. The code for the DHCPv4 option (123). Code: 8 bits. The code for the DHCPv4 option (123).
Length: 8 bits. The length of the DHCPv4 option, in octets. Length: 8 bits. The length of the DHCPv4 option, in octets.
For versions 0 and 1, the option length is 16. The option length is 16.
LatUnc: 6 bits. When the Ver field = 0, this field represents LaRes: 6 bits. This field represents latitude resolution.
latitude resolution. When the Ver field = 1,
this field represents latitude uncertainty.
Latitude: a 34 bit fixed point value consisting of 9 bits of Latitude: a 34 bit fixed point value consisting of 9 bits of
signed integer and 25 bits of fraction, interpreted signed integer and 25 bits of fraction, interpreted
as described in Section 2.3. as described in Section 2.3.
LongUnc: 6 bits. When the Ver field = 0, this field represents LoRes: 6 bits. This field represents longitude resolution.
longitude resolution. When the Ver field = 1,
this field represents longitude uncertainty.
Longitude: a 34 bit fixed point value consisting of 9 bits of Longitude: a 34 bit fixed point value consisting of 9 bits of
signed integer and 25 bits of fraction, interpreted signed integer and 25 bits of fraction, interpreted
as described in Section 2.3. as described in Section 2.3.
AType: Altitude Type (4 bits). AType: Altitude Type (4 bits), defined in Section 2.4.
AltUnc: 6 bits. When the Ver field = 0, this field represents AltRes: 6 bits. This field represents altitude resolution.
altitude resolution. When the Ver field = 1,
this field represents altitude uncertainty.
Altitude: A 30 bit value defined by the AType field. Altitude: A 30 bit value defined by the AType field, described in
Section 2.4.
Res: The Res field which is 5 bits, is reserved. These bits
have been used by IEEE 802.11y [IEEE-802.11y], but are
not defined within this specification.
Datum: 3 bits. The Map Datum used for the coordinates given in
this Option.
2.2.2. DHCPv4 Option TBD
The format of DHCPv4 option TBD is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code TBD | Length | LatUnc | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude (cont'd) | LongUnc | +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Alt.(cont'd) |Ver| Res |Datum|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: 8 bits. The code for the DHCPv4 option (TBD).
Length: 8 bits. The length of the DHCPv4 option, in octets.
For version 1, the option length is 16.
LatUnc: 6 bits. When the Ver field = 1, this field represents
latitude uncertainty. The contents of this field is
undefined for other values of the Ver field.
Latitude: a 34 bit fixed point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as
described in Section 2.3.
LongUnc: 6 bits. When the Ver field = 1, this field represents
longitude uncertainty. The contents of this field is
undefined for other values of the Ver field.
Longitude: a 34 bit fixed point value consisting of 9 bits of
integer and 25 bits of fraction, interpreted as
described in Section 2.3.
AType: Altitude Type (4 bits), defined in Section 2.4.
AltUnc: 6 bits. When the Ver field = 1, this field represents
altitude uncertainty. The contents of this field is
undefined for other values of the Ver field.
Altitude: A 30 bit value defined by the AType field, described in
Section 2.4.
Ver: The Ver field is two bits, providing for four potential Ver: The Ver field is two bits, providing for four potential
versions. This specification defines the behavior of versions. This specification defines the behavior of
version 0 (originally specified in [RFC3825]) as well as
version 1. The Ver field is always located at the same version 1. The Ver field is always located at the same
offset from the beginning of the option, regardless of offset from the beginning of the option, regardless of
the version in use. the version in use.
Res: The Res field which is 3 bits, is reserved. These bits Res: The Res field which is 3 bits, is reserved. These bits
have been used by [IEEE-802.11y], but are not defined have been used by [IEEE-802.11y], but are not defined
within this specification. within this specification.
Datum: 3 bits. The Map Datum used for the coordinates given in Datum: 3 bits. The Map Datum used for the coordinates given in
this Option. this Option.
2.2.1. Version Support 2.2.3. Option Support
2.2.1.1. Client Version Support 2.2.3.1. Client Support
DHCPv6 clients implementing this specification MUST support receiving DHCPv4 clients implementing this specification MUST support receiving
version 1 responses. DHCPv4 clients implementing this specification DHCPv4 Option TBD (version 1), and MAY support receiving DHCPv4
MUST support receiving responses of versions 0 and 1. It is required Option 123 (originally defined in RFC 3825 [RFC3825]).
that DHCPv4 client implementations support version 1 so the
versioning capability added by this document does not cause errors
interpreting the Latitude, Longitude and Altitude values. Since this
specification utilizes the same DHCPv4 option code as [RFC3825], the
option format does not provide a means for the DHCPv4 client to
indicate the highest version that it supports to the DHCPv4 server.
Moving forward, DHCPv4 and DHCPv6 clients not understanding a datum DHCPv4 clients request the DHCPv4 server to send Option 123, Option
value MUST assume a World Geodesic System 1984 (WGS84) [WGS84] datum TBD or both via inclusion of the Parameter Request List option. As
(EPSG [EPSG] 4326 or 4979, depending on whether there is an Altitude noted in Section 9.8 of RFC 2132 [RFC2132]:
value present) and proceed accordingly. Assuming that a less
accurate location value is better than none, this ensures that some
(perhaps less accurate) location is available to the client.
2.2.1.2. Server Version Selection This option is used by a DHCP client to request values for
specified configuration parameters. The list of requested
parameters is specified as n octets, where each octet is a valid
DHCP option code as defined in this document.
DHCPv6 servers implementing this specification MUST send version 1 The client MAY list the options in order of preference. The DHCP
responses. A DHCPv4 server implementing this specification MUST server is not required to return the options in the requested
support sending version 1 responses and SHOULD support sending order, but MUST try to insert the requested options in the order
version 0 responses. A DHCPv4 server that provides location requested by the client.
information cannot provide options with both version 0 and version 1
formats in the same response. This is not useful since receiving two
copies of the same Option (either in the same response or a separate
response) causes a DHCPv4 client to replace the information in the
old Option with the information in the new Option.
A DHCPv4 server uses configuration to determine which version to send When DHCPv4 and DHCPv6 clients implementing this specification do not
in a response. For example, where a mixture of version 0 and version understand a datum value, they MUST assume a World Geodesic System
1 clients are expected, the DHCPv4 server could be configured to send 1984 (WGS84) [WGS84] datum (EPSG [EPSG] 4326 or 4979, depending on
version 0 or version 1 depending on configuration (possibly making whether there is an Altitude value present) and proceed accordingly.
the choice based on information such as the client MAC address). Assuming that a less accurate location value is better than none,
Where few version 0 clients are expected, the DHCPv4 server could be this ensures that some (perhaps less accurate) location is available
configured to send only version 1 responses. Version 0 options will to the client.
provide resolution, while version 1 options will provide an area of
uncertainty.
An RFC 3825 DHCPv4 client that receives a version 1 option defined in 2.2.3.2. Server Option Selection
this document will either reject the Option, or will not understand
the additions to the Datum field and will misinterpret the LongUnc,
LatUnc, and AltUnc values. If the RFC 3825 DHCPv4 client does not
reject the option and utilizes the location data it will most likely
assume a datum. Assuming one of the RFC 3825 datums causes correct
interpretation of Latitude/Longitude/Altitude values. The values for
LongUnc/LatUnc/AltUnc are mistakenly interpreted as representing
significant digits. The resultant location value will be in error up
to a full degree of latitude and longitude, and a full increment of
altitude.
This results in a version 0-only DHCPv4 client either not obtaining A DHCPv4 server implementing this specification MUST support sending
location information (with no ability to indicate to the server that Option TBD version 1 and SHOULD support sending Option 123 in
version 1 was unsupported), or misinterpreting the option. responses.
Therefore, if it is not known whether all DHCPv4 clients support
version 1, and it is not possible for the DHCPv4 server to A DHCPv4 server that provides location information SHOULD honor the
distinguish between version 0 and version 1 DHCPv4 clients by some Parameter Request List included by the DHCPv4 client in order to
means, by default the DHCPv4 server SHOULD send a version 0 response. decide whether to send Option 123, Option TBD or both in the
Response.
2.3. Latitude and Longitude Fields 2.3. Latitude and Longitude Fields
The Latitude and Longitude values in this specification are encoded The Latitude and Longitude values in this specification are encoded
as 34 bit, twos complement, fixed point values with 9 integer bits as 34 bit, twos complement, fixed point values with 9 integer bits
and 25 fractional bits. The exact meaning of these values is and 25 fractional bits. The exact meaning of these values is
determined by the datum; the description in this section applies to determined by the datum; the description in this section applies to
the datums defined in this document. This document uses the same the datums defined in this document. This document uses the same
definition for all datums it specifies. definition for all datums it specifies.
skipping to change at page 11, line 16 skipping to change at page 11, line 48
of the Prime Meridian (Greenwich) and negative (2s complement) of the Prime Meridian (Greenwich) and negative (2s complement)
longitudes are west of the Prime Meridian. longitudes are west of the Prime Meridian.
When encoding, Latitude and Longitude values are rounded to the When encoding, Latitude and Longitude values are rounded to the
nearest 34-bit binary representation. This imprecision is considered nearest 34-bit binary representation. This imprecision is considered
acceptable for the purposes to which this form is intended to be acceptable for the purposes to which this form is intended to be
applied and is ignored when decoding. applied and is ignored when decoding.
2.3.1. Latitude and Longitude Resolution 2.3.1. Latitude and Longitude Resolution
The Latitude (LatUnc), Longitude (LongUnc) and Altitude (AltUnc) The Latitude (LaRes), Longitude (LoRes) and Altitude (AltRes)
Uncertainty fields are encoded as 6 bit, unsigned integer values. In Resolution fields are encoded as 6 bit, unsigned integer values. In
the version 0 DHCPv4 Option, the LatUnc, LongUnc and AltUnc fields the DHCPv4 Option 123, the LaRes, LoRes and AltRes fields are used to
are used to encode the number of bits of resolution. The resolution encode the number of bits of resolution. The resolution sub-fields
sub-fields accommodate the desire to easily adjust the precision of a accommodate the desire to easily adjust the precision of a reported
reported location. Contents beyond the claimed resolution MAY be location. Contents beyond the claimed resolution MAY be randomized
randomized to obscure greater precision that might be available. to obscure greater precision that might be available.
In the version 0 DHCPv4 Option, the LatUnc value encodes the number In the DHCPv4 Option 123, the LaRes value encodes the number of high-
of high-order latitude bits that should be considered valid. Any order latitude bits that should be considered valid. Any bits
bits entered to the right of this limit should not be considered entered to the right of this limit should not be considered valid and
valid and might be purposely false, or zeroed by the sender. The might be purposely false, or zeroed by the sender. The examples in
examples in Appendix B illustrate that a smaller value in the Appendix B illustrate that a smaller value in the resolution field
resolution field increases the area within which the device is increases the area within which the device is located. A value of 2
located. A value of 2 in the LatUnc field indicates a precision of in the LaRes field indicates a precision of no greater than 1/6th
no greater than 1/6th that of the globe (see the first example of that of the globe (see the first example of Appendix B). A value of
Appendix B). A value of 34 in the LatUnc field indicates a precision 34 in the LaRes field indicates a precision of about 3.11 mm in
of about 3.11 mm in latitude at the equator. latitude at the equator.
In the version 0 DHCPv4 Option, the LongUnc value encodes the number In the DHCPv4 Option 123, the LoRes value encodes the number of high-
of high-order longitude bits that should be considered valid. Any order longitude bits that should be considered valid. Any bits
bits entered to the right of this limit should not be considered entered to the right of this limit should not be considered valid and
valid and might be purposely false, or zeroed by the sender. A value might be purposely false, or zeroed by the sender. A value of 2 in
of 2 in the LongUnc field indicates precision of no greater than the LoRes field indicates precision of no greater than 1/6th that of
1/6th that of the globe (see the first example of Appendix B). A the globe (see the first example of Appendix B). A value of 34 in
value of 34 in the LongUnc field indicates a precision of about 2.42 the LoRes field indicates a precision of about 2.42 mm in Longitude
mm in Longitude (at the equator). Because lines of longitude (at the equator). Because lines of longitude converge at the poles,
converge at the poles, the distance is smaller (better precision) for the distance is smaller (better precision) for locations away from
locations away from the equator. the equator.
2.3.2. Latitude and Longitude Uncertainty 2.3.2. Latitude and Longitude Uncertainty
In the DHCPv6 option and the version 1 DHCPv4 option, the Latitude In the DHCPv6 option and the DHCPv4 Option TBD, the Latitude and
and Longitude Uncertainty fields (LatUnc and LongUnc) quantify the Longitude Uncertainty fields (LatUnc and LongUnc) quantify the amount
amount of uncertainty in each of the Latitude and Longitude values of uncertainty in each of the Latitude and Longitude values
respectively. A value of 0 is reserved to indicate that the respectively. A value of 0 is reserved to indicate that the
uncertainty is unknown; values greater than 34 are reserved. uncertainty is unknown; values greater than 34 are reserved.
A point within the region of uncertainty is selected to be the A point within the region of uncertainty is selected to be the
encoded point; the centroid of the region is often an appropriate encoded point; the centroid of the region is often an appropriate
choice. The value for uncertainty is taken as the distance from the choice. The value for uncertainty is taken as the distance from the
selected point to the furthest extreme of the region of uncertainty selected point to the furthest extreme of the region of uncertainty
on that axis. This is demonstrated in the figure below, which shows on that axis. This is demonstrated in the figure below, which shows
a two-dimensional polygon that is projected on each axis. In the a two-dimensional polygon that is projected on each axis. In the
figure, "X" marks the point that is selected; the ranges marked with figure, "X" marks the point that is selected; the ranges marked with
skipping to change at page 13, line 29 skipping to change at page 14, line 18
x = 8 - ceil( log2( uncertainty ) ) x = 8 - ceil( log2( uncertainty ) )
Note that the result of encoding this value increases the range of Note that the result of encoding this value increases the range of
uncertainty to the next available power of two; subsequent repeated uncertainty to the next available power of two; subsequent repeated
encodings and decodings do not change the value. Only increasing encodings and decodings do not change the value. Only increasing
uncertainty means that the associated confidence does not have to uncertainty means that the associated confidence does not have to
decrease. decrease.
2.4. Altitude 2.4. Altitude
The Altitude value is expressed as a 30 bit, fixed point, twos How the Altitude value is interpreted depends on the Altitude Type
complement integer with 22 integer bits and 8 fractional bits. How
the Altitude value is interpreted depends on the Altitude Type
(AType) value and the selected datum. Three Altitude Type values are (AType) value and the selected datum. Three Altitude Type values are
defined in this document: unknown (0), meters (1) and floors (2). defined in this document: unknown (0), meters (1) and floors (2).
2.4.1. No Known Altitude (AType = 0) 2.4.1. No Known Altitude (AType = 0)
In some cases, the altitude of the location might not be provided. In some cases, the altitude of the location might not be provided.
An Altitude Type value of zero indicates that the altitude is not An Altitude Type value of zero indicates that the altitude is not
given to the client. In this case, the Altitude and Altitude given to the client. In this case, the Altitude and Altitude
Uncertainty fields can contain any value and MUST be ignored. Uncertainty fields can contain any value and MUST be ignored.
2.4.2. Altitude in Meters (AType = 1) 2.4.2. Altitude in Meters (AType = 1)
If the Altitude Type has a value of one, Altitude is measured in If the Altitude Type has a value of one, Altitude is measured in
meters, in relation to the zero set by the vertical datum. meters, in relation to the zero set by the vertical datum. For AType
= 1, the Altitude value is expressed as a 30 bit, fixed point, twos
complement integer with 22 integer bits and 8 fractional bits.
2.4.3. Altitude in Floors (AType = 2) 2.4.3. Altitude in Floors (AType = 2)
A value of two for Altitude Type indicates that the Altitude value is A value of two for Altitude Type indicates that the Altitude value is
measured in floors. This value is relevant only in relation to a measured in floors. Since altitude in meters may not be known within
building; the value is relative to the ground level of the building. a building, a floor indication may be more useful. For AType = 2,
the Altitude value is expressed as a 30 bit, fixed point, twos
complement integer with 22 integer bits and 8 fractional bits.
In this definition, numbering starts at ground level, which is floor This value is relevant only in relation to a building; the value is
0 regardless of local convention. relative to the ground level of the building. Floors located below
ground level are represented by negative values. In some buildings
it might not be clear which floor is at ground level or an
intermediate floor might be hard to identify as such. Determining
what floor is at ground level and what constitutes a sub-floor as
opposed to an naturally numbered floor is left to local
interpretation.
Larger values represent floors that are farther away from floor 0
such that:
- if positive, the floor value is farther above the ground floor.
- if negative, the floor value is farther below the ground floor.
Non-integer values can be used to represent intermediate or sub- Non-integer values can be used to represent intermediate or sub-
floors, such as mezzanine levels. For instance, a mezzanine between floors, such as mezzanine levels. Example: a mezzanine between floor
floors 4 and 5 could be represented as 4.1. 1 and floor 2 could be represented as a value of 1.25. Example:
mezzanines between floor 4 and floor 5 could be represented as values
of 4.5 and 4.75.
2.4.4. Altitude Resolution 2.4.4. Altitude Resolution
In the version 0 DHCPv4 Option, the Altitude Uncertainty (AltUnc) In the DHCPv4 Option 123, the Altitude Resolution (AltRes) value
value encodes the number of high-order altitude bits that should be encodes the number of high-order altitude bits that should be
considered valid. Values above 30 (decimal) are undefined and considered valid. Values above 30 (decimal) are undefined and
reserved. reserved.
If the Altitutde Type value is one (AType = 1), an AltUnc value 0.0 If the Altitude Type value is one (AType = 1), an AltRes value 0.0
would indicate unknown Altitude. The most precise altitude would would indicate unknown Altitude. The most precise altitude would
have an AltUnc value of 30. Many values of AltUnc would obscure any have an AltRes value of 30. Many values of AltRes would obscure any
variation due to vertical datum differences. variation due to vertical datum differences.
The AltUnc field SHOULD be set to maximum precision when AType = 2 The AltRes field SHOULD be set to maximum precision when AType = 2
(floors) when a floor value is included in the DHCP Reply, or when (floors) when a floor value is included in the DHCP Reply, or when
AType = 0, to denote that the floor isn't known. An altitude coded AType = 0, to denote that the floor isn't known. An altitude coded
as AType = 2, AltRes = 30, and Altitude = 0.0 is meaningful even as AType = 2, AltRes = 30, and Altitude = 0.0 is meaningful even
outside a building, and represents ground level at the given latitude outside a building, and represents ground level at the given latitude
and longitude. and longitude.
2.4.5. Altitude Uncertainty 2.4.5. Altitude Uncertainty
In the DHCPv6 option or the version 1 DHCPv4 option, the AltUnc value In the DHCPv6 option or the DHCPv4 Option TBD, the AltUnc value
quantifies the amount of uncertainty in the Altitude value. As with quantifies the amount of uncertainty in the Altitude value. As with
LatUnc and LongUnc, a value of 0 for AltUnc is reserved to indicate LatUnc and LongUnc, a value of 0 for AltUnc is reserved to indicate
that Altitude Uncertainty is not known; values above 30 are also that Altitude Uncertainty is not known; values above 30 are also
reserved. Altitude Uncertainty only applies to Altitude Type 1. reserved. Altitude Uncertainty only applies to Altitude Type 1.
The amount of Altitude Uncertainty can be determined by the following The amount of Altitude Uncertainty can be determined by the following
formula, where x is the encoded integer value: formula, where x is the encoded integer value:
Uncertainty = 2 ^ ( 21 - x ) Uncertainty = 2 ^ ( 21 - x )
skipping to change at page 16, line 11 skipping to change at page 17, line 12
Geopriv requirements (including security requirements) are discussed Geopriv requirements (including security requirements) are discussed
in "Geopriv Requirements" [RFC3693]. A threat analysis is provided in "Geopriv Requirements" [RFC3693]. A threat analysis is provided
in "Threat Analysis of the Geopriv Protocol" [RFC3694]. in "Threat Analysis of the Geopriv Protocol" [RFC3694].
Since there is no privacy protection for DHCP messages, an Since there is no privacy protection for DHCP messages, an
eavesdropper who can monitor the link between the DHCP server and eavesdropper who can monitor the link between the DHCP server and
requesting client can discover this LCI. requesting client can discover this LCI.
To minimize the unintended exposure of location information, the LCI To minimize the unintended exposure of location information, the LCI
option SHOULD be returned by DHCP servers only when the DHCP client option SHOULD be returned by DHCP servers only when the DHCP client
has included this option in its 'parameter request list' (section 3.5 has included this option in its 'parameter request list' (Section 3.5
[RFC2131]). [RFC2131], Section 9.8 [RFC2132]).
Where critical decisions might be based on the value of this option, Where critical decisions might be based on the value of this option,
DHCP authentication as defined in "Authentication for DHCP Messages" DHCP authentication as defined in "Authentication for DHCP Messages"
[RFC3118] and "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)" [RFC3118] and "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)"
[RFC3315] SHOULD be used to protect the integrity of the DHCP [RFC3315] SHOULD be used to protect the integrity of the DHCP
options. options.
Link layer confidentiality and integrity protection may also be Link layer confidentiality and integrity protection may also be
employed to reduce the risk of location disclosure and tampering. employed to reduce the risk of location disclosure and tampering.
4. IANA Considerations 4. IANA Considerations
IANA has assigned a DHCPv4 option code of 123 for the GeoConf option IANA has assigned a DHCPv4 option code of 123 for the GeoConf option.
defined in this document. Assignment of a DHCPv6 option code is Assignment of an additional DHCPv4 option code as well as a DHCPv6
requested. option code is requested.
The GeoConf Option defines two fields for which IANA maintains a IANA maintains registries for the Altitude Type (AType), Datum and
registry: The Altitude Type (AType) field and the Datum field (see Version fields. New values for each of these registries are assigned
Section 2). The datum indicator MUST include specification of both through "Standards Actions" [RFC5226].
horizontal and vertical datum. New values for the Altitude Type
(AType) and Datum fields are assigned through "Standards Action" Each AType registry entry MUST define the way that the 30 bit
[RFC5226]. New Altitude Types MUST define the way that the 30 bit
altitude values and the associated 6 bit uncertainty are interpreted. altitude values and the associated 6 bit uncertainty are interpreted.
New datums MUST define the way that the 34 bit values and the
respective 6 bit uncertainties are interpreted. The initial values Each Datum registry entry MUST include specification of both
of the Altitude registry are as follows: horizontal and vertical datum, and MUST define the way that the 34
bit values and the respective 6 bit uncertainties are interpreted.
The initial AType registry is:
AType = 0 No known altitude. AType = 0 No known altitude.
AType = 1 meters of altitude defined by the vertical datum AType = 1 meters of altitude defined by the vertical datum
specified. specified.
AType = 2 building floors of altitude. AType = 2 building floors of altitude.
The initial Datum registry is:
Datum = 1 denotes the vertical datum WGS 84 as defined by the EPSG Datum = 1 denotes the vertical datum WGS 84 as defined by the EPSG
as their CRS Code 4327; CRS Code 4327 also specifies WGS 84 as their CRS Code 4327; CRS Code 4327 also specifies WGS 84
as the vertical datum. as the vertical datum.
Datum = 2 denotes the vertical datum NAD83 as defined by the EPSG as Datum = 2 denotes the vertical datum NAD83 as defined by the EPSG as
their CRS Code 4269; North American Vertical Datum of 1988 their CRS Code 4269; North American Vertical Datum of 1988
(NAVD88) is the associated vertical datum for NAD83. (NAVD88) is the associated vertical datum for NAD83.
Datum = 3 denotes the vertical datum NAD83 as defined by the EPSG as Datum = 3 denotes the vertical datum NAD83 as defined by the EPSG as
their CRS Code 4269; Mean Lower Low Water (MLLW) is the their CRS Code 4269; Mean Lower Low Water (MLLW) is the
associated vertical datum for NAD83. associated vertical datum for NAD83.
This document defines the Ver field for the DHCPv4 and DHCPv6 The initial Version registry is:
options. New values for the Ver field are assigned through
"Standards Action" [RFC5226]. Initial values are as follows:
0: DHCPv4 Implementations conforming to [RFC3825] 1: Implementations utilizing uncertainty parameters
1: Implementations of this specification (for both DHCPv4 and DHCPv6) (for both DHCPv4 and DHCPv6).
5. Acknowledgments 5. Acknowledgments
The authors would like to thank Randall Gellens, Patrik Falstrom, The authors would like to thank Randall Gellens, Patrik Falstrom,
Ralph Droms, Ted Hardie, Jon Peterson, Robert Sparks and Nadine Ralph Droms, Ted Hardie, Jon Peterson, Robert Sparks, Ralph Droms and
Abbott for their inputs and constructive comments regarding this Nadine Abbott for their inputs and constructive comments regarding
document. Additionally, the authors would like to thank Greg Troxel this document. Additionally, the authors would like to thank Greg
for the education on vertical datums, as well as Carl Reed. Thanks Troxel for the education on vertical datums, as well as Carl Reed.
to Richard Barnes for his contribution on GML mapping for resolution. Thanks to Richard Barnes for his contribution on GML mapping for
resolution.
6. References 6. References
6.1. Normative References 6.1. Normative References
[EPSG] European Petroleum Survey Group, http://www.epsg.org/ and [EPSG] European Petroleum Survey Group, http://www.epsg.org/ and
http://www.epsg-registry.org/ http://www.epsg-registry.org/
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997. March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC2132, March 1997.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC [RFC3046] Patrick, M., "DHCP Relay Agent Information Option", RFC
3046, January 2001. 3046, January 2001.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001. Messages", RFC 3118, June 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C. and
M. Carney, "Dynamic Host Configuration Protocol for IPv6 M. Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003. (DHCPv6)", RFC 3315, July 2003.
skipping to change at page 20, line 36 skipping to change at page 21, line 36
that covers three dimensional coordinates. By necessity, locations that covers three dimensional coordinates. By necessity, locations
described in these datums can be represented by two dimensional described in these datums can be represented by two dimensional
shapes only; that is, either a two dimensional point or a polygon. shapes only; that is, either a two dimensional point or a polygon.
If the Altitude Type is 2 (floors), then this value can be If the Altitude Type is 2 (floors), then this value can be
represented using a civic address object [RFC5139] that is presented represented using a civic address object [RFC5139] that is presented
alongside the geodetic object. alongside the geodetic object.
This Appendix describes how the location value encoded in DHCP format This Appendix describes how the location value encoded in DHCP format
for geodetic location can be expressed in GML. The mapping is valid for geodetic location can be expressed in GML. The mapping is valid
for the DHCPv6 option as well as versions 0 and 1 of the DHCPv4 for the DHCPv6 option as well as both of the DHCPv4 options, and for
option, and for the currently-defined datum values (1, 2, and 3). the currently-defined datum values (1, 2, and 3). Further version or
Further version or datum definitions should provide similar mappings. datum definitions should provide similar mappings.
These shapes can be mapped to GML by first computing the bounds that These shapes can be mapped to GML by first computing the bounds that
are described using the coordinate and uncertainty fields, then are described using the coordinate and uncertainty fields, then
encoding the result in a GML Polygon or Prism shape. encoding the result in a GML Polygon or Prism shape.
A.1. GML Templates A.1. GML Templates
If Altitude is provided in meters (Altitude Type 1) and the datum If Altitude is provided in meters (AType 1) and the datum value is
value is WGS84 (value 1), then the proper GML shape is a Prism, with WGS84 (value 1), then the proper GML shape is a Prism, with the
the following form (where $value$ indicates a value computed from the following form (where $value$ indicates a value computed from the
DHCP option as described below): DHCP option as described below):
<gs:Prism srsName="urn:ogc:def:crs:EPSG::4979" <gs:Prism srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gs="http://www.opengis.net/pidflo/1.0" xmlns:gs="http://www.opengis.net/pidflo/1.0"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gs:base> <gs:base>
<gml:Polygon> <gml:Polygon>
<gml:exterior> <gml:exterior>
<gml:LinearRing> <gml:LinearRing>
<gml:posList> <gml:posList>
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this uses a three-dimensional CRS; otherwise, it uses a two- this uses a three-dimensional CRS; otherwise, it uses a two-
dimensional CRS. dimensional CRS.
<gml:Point srsName="$CRS-URN$" <gml:Point srsName="$CRS-URN$"
xmlns:gml="http://www.opengis.net/gml"> xmlns:gml="http://www.opengis.net/gml">
<gml:pos>$Latitude$ $Longitude$ $[Altitude]$</gml:pos> <gml:pos>$Latitude$ $Longitude$ $[Altitude]$</gml:pos>
</gml:Point> </gml:Point>
A.1.1. Finding Low and High Values using Uncertainty Fields A.1.1. Finding Low and High Values using Uncertainty Fields
The uncertainty fields (LatUnc, LongUnc, AltUnc) indicate the bounds For the DHCPv4 Option 123, resolution fields are used (LaRes, LoRes,
of the location region described by a DHCP location object. For AltRes), indicating how many bits of a value contain information.
version 0 of the DHCPv4 option, the uncertainty fields represent Any bits beyond those indicated can be either zero or one.
resolution, indicating how many bits of a value contain information.
Any bits beyond those indicated can be either zero or one. For the For the DHCPv6 option and DHCPv4 Option TBD, the LatUnc, LongUnc and
DHCPv6 option and version 1 of the DHCPv4 option, the LatUnc, LongUnc AltUnc fields indicate uncertainty distances, denoting the bounds of
and AltUnc fields indicate uncertainty distances. the location region described by the DHCP location object.
The two sections below describe how to compute the Latitude, The two sections below describe how to compute the Latitude,
Longitude, and Altitude bounds (e.g., $lowLatitude$, $highAltitude$) Longitude, and Altitude bounds (e.g., $lowLatitude$, $highAltitude$)
in the templates above. The first section describes how these bounds in the templates above. The first section describes how these bounds
are computed in the "resolution encoding" (version 0), while the are computed in the "resolution encoding" (DHCPv4 Option 123), while
second section addresses the "uncertainty encoding" (version 1). the second section addresses the "uncertainty encoding" (DHCPv6
Option and DHCPv4 Option TBD).
A.1.1.1. Resolution Encoding A.1.1.1. Resolution Encoding
Given a number of resolution bits (i.e., the value of a resolution Given a number of resolution bits (i.e., the value of a resolution
field), if all bits beyond those bits are set to zero, this gives the field), if all bits beyond those bits are set to zero, this gives the
lowest possible value. The highest possible value can be found lowest possible value. The highest possible value can be found
setting all bits to one. setting all bits to one.
If the encoded value of Latitude/Longitude and resolution (LatUnc, If the encoded value of Latitude/Longitude and resolution (LaRes,
LongUnc) are treated as 34-bit unsigned integers, the following can LoRes) are treated as 34-bit unsigned integers, the following can be
be used (where ">>" is a bitwise right shift, "&" is a bitwise AND, used (where ">>" is a bitwise right shift, "&" is a bitwise AND, "~"
"~" is a bitwise negation, and "|" is a bitwise OR). is a bitwise negation, and "|" is a bitwise OR).
mask = 0x3ffffffff >> resolution mask = 0x3ffffffff >> resolution
lowvalue = value & ~mask lowvalue = value & ~mask
highvalue = value | mask + 1 highvalue = value | mask + 1
Once these values are determined, the corresponding floating point Once these values are determined, the corresponding floating point
numbers can be computed by dividing the values by 2^25 (since there numbers can be computed by dividing the values by 2^25 (since there
are 25 bits of fraction in the fixed-point representation). are 25 bits of fraction in the fixed-point representation).
Alternatively, the lowest possible value can be found by using Alternatively, the lowest possible value can be found by using
resolution to determine the size of the range. This method has the resolution to determine the size of the range. This method has the
advantage that it operates on the decoded floating point values. It advantage that it operates on the decoded floating point values. It
is equivalent to the first mechanism, to a possible error of 2^-25 is equivalent to the first mechanism, to a possible error of 2^-25
(2^-8 for altitude). (2^-8 for altitude).
scale = 2 ^ ( 9 - resolution ) scale = 2 ^ ( 9 - resolution )
lowvalue = floor( value / scale ) * scale lowvalue = floor( value / scale ) * scale
highvalue = lowvalue + scale highvalue = lowvalue + scale
Altitude resolution (AltUnc for v0) uses the same process with Altitude resolution (AltRes) uses the same process with different
different constants. There are 22 whole bits in the Altitude constants. There are 22 whole bits in the Altitude encoding (instead
encoding (instead of 9) and 30 bits in total (instead of 34). of 9) and 30 bits in total (instead of 34).
A.1.1.2. Uncertainty Encoding A.1.1.2. Uncertainty Encoding
In the uncertainty encoding, the uncertainty fields (LongUnc/LatUnc In the uncertainty encoding, the uncertainty fields (LongUnc/LatUnc)
in version 1) directly represent the logarithms of uncertainty directly represent the logarithms of uncertainty distances. So the
distances. So the low and high bounds are computed by first low and high bounds are computed by first computing the uncertainty
computing the uncertainty distances, then adding and subtracting distances, then adding and subtracting these from the value provided.
these from the value provided. If "uncertainty" is the unsigned If "uncertainty" is the unsigned integer value of the uncertainty
integer value of the uncertainty field and "value" is the value of field and "value" is the value of the coordinate field:
the coordinate field:
distance = 2 ^ (8 - uncertainty) distance = 2 ^ (8 - uncertainty)
lowvalue = value - distance lowvalue = value - distance
highvalue = value + distance highvalue = value + distance
Altitude uncertainty (AltUnc in version 1) uses the same process with Altitude uncertainty (AltUnc in version 1) uses the same process with
different constants: different constants:
distance = 2 ^ (21 - uncertainty) distance = 2 ^ (21 - uncertainty)
lowvalue = value - distance lowvalue = value - distance
Appendix B. Calculations of Resolution Appendix B. Calculations of Resolution
The following examples for two different locations demonstrate how The following examples for two different locations demonstrate how
the Resolution values for Latitude, Longitude, and Altitude (used in the Resolution values for Latitude, Longitude, and Altitude (used in
the version 0 DHCPv4 option) can be calculated. In both examples, DHCPv4 Option 123) can be calculated. In both examples, the geo-
the geo-location values were derived from maps using the WGS84 map location values were derived from maps using the WGS84 map datum,
datum, therefore in these examples, the Datum field would have a therefore in these examples, the Datum field would have a value = 1
value = 1 (00000001, or 0x01). (00000001, or 0x01).
B.1. Location Configuration Information of "White House" (Example 1) B.1. Location Configuration Information of "White House" (Example 1)
The grounds of the White House in Washington D.C. (1600 Pennsylvania The grounds of the White House in Washington D.C. (1600 Pennsylvania
Ave. NW, Washington, DC 20006) can be found between 38.895375 and Ave. NW, Washington, DC 20006) can be found between 38.895375 and
38.898653 degrees North and 77.037911 and 77.035116 degrees West. In 38.898653 degrees North and 77.037911 and 77.035116 degrees West. In
this example, we assume that we are standing on the sidewalk on the this example, we assume that we are standing on the sidewalk on the
north side of the White House, between driveways. Since we are not north side of the White House, between driveways. Since we are not
inside a structure, we assume an Altitude value of 15 meters, inside a structure, we assume an Altitude value of 15 meters,
interpolated from the US Geological survey map, Washington Washington interpolated from the US Geological survey map, Washington Washington
West quadrangle. West quadrangle.
The address was NOT picked for any political reason and can easily be The address was NOT picked for any political reason and can easily be
found on the Internet or mapping software, but was picked as an found on the Internet or mapping software, but was picked as an
easily identifiable location on our planet. easily identifiable location on our planet.
In this example, the requirement of emergency responders in North In this example, the requirement of emergency responders in North
America via their NENA Model Legislation [NENA] could be met by a America via their NENA Model Legislation [NENA] could be met by a
LatUnc value of 21 and a LongUnc value of 20. This would yield a LaRes value of 21 and a LoRes value of 20. This would yield a geo-
geo-location that is Latitude 38.8984375 north to Latitude 38.8988616 location that is Latitude 38.8984375 north to Latitude 38.8988616
north and Longitude -77.0371094 to Longitude -77.0375977. This is an north and Longitude -77.0371094 to Longitude -77.0375977. This is an
area of approximately 89 feet by 75 feet or 6669 square feet, which area of approximately 89 feet by 75 feet or 6669 square feet, which
is very close to the 7000 square feet requested by NENA. In this is very close to the 7000 square feet requested by NENA. In this
example, a service provider could enforce that a device send a example, a service provider could enforce that a device send a
Location Configuration Information with this minimum amount of Location Configuration Information with this minimum amount of
resolution for this particular location when calling emergency resolution for this particular location when calling emergency
services. services.
An approximate representation of this location might be provided using An approximate representation of this location might be provided using
the version 0 encoding as follows: the DHCPv4 Option 123 encoding as follows:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code (123) | OptLen (16) | LatUnc | Latitude . | Code (123) | OptLen (16) | LaRes | Latitude .
|0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|0 0 0 1 0 0 1 1 0 1. |0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|0 0 0 1 0 0 1 1 0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) | LongUnc | . . Latitude (cont'd) | LoRes | .
.1 1 0 0 1 0 1 1 1 0 0 1 1 0 0 0 0 1 1 0 0 0 1 1|0 1 0 0 0 1|1 1. .1 1 0 0 1 0 1 1 1 0 0 1 1 0 0 0 0 1 1 0 0 0 1 1|0 1 0 0 0 1|1 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Longitude (cont'd) | . Longitude (cont'd) |
.0 1 1 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0 0| .0 1 1 0 0 1 0 1 1 1 1 0 1 1 0 1 0 1 0 0 0 0 1 0 1 1 0 0 0 1 0 0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude . | AType | AltRes | Altitude .
|0 0 0 1|0 1 0 0 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1. |0 0 0 1|0 1 0 0 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Alt (cont'd) |Ver| Res |Datum| . Alt (cont'd) | Res |Datum|
.0 0 0 0 0 0 0 0|0 0|0 0 0|0 0 1| .0 0 0 0 0 0 0 0|0 0 0 0 0|0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In hexadecimal, this is 7B10484D CB986347 65ED42C4 1440000F 0001. In hexadecimal, this is 7B10484D CB986347 65ED42C4 1440000F 0001.
Decoding Location Configuration Information with Resolution Decoding Location Configuration Information with Resolution
Decoding this option gives a latitude of 38.897647 (to 7 decimal Decoding this option gives a latitude of 38.897647 (to 7 decimal
places) with 18 bits of resolution; a longitude of -77.0366000 with places) with 18 bits of resolution; a longitude of -77.0366000 with
17 bits of resolution; an altitude type of meters with a value of 15 17 bits of resolution; an altitude type of meters with a value of 15
and 17 bits of resolution; version 0 (resolution) and the WGS84 and 17 bits of resolution; version 0 (resolution) and the WGS84
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Latitude = 0001010011110000011111011101010001 Latitude = 0001010011110000011111011101010001
Longitude 87.63602 degrees West (or -87.63602 degrees) Longitude 87.63602 degrees West (or -87.63602 degrees)
Using 2s complement, 34 bit fixed point, 25 bit fraction Using 2s complement, 34 bit fixed point, 25 bit fraction
Longitude = 0xf50ba5b97, Longitude = 0xf50ba5b97,
Longitude = 1101010000101110100101101110010111 Longitude = 1101010000101110100101101110010111
Altitude 103 Altitude 103
In this example, we are inside a structure, therefore we will assume In this example, we are inside a structure, therefore we will assume
an Altitude value of 103 to indicate the floor we are on. The an Altitude value of 103 to indicate the floor we are on. The
Altitude Type value is 2, indicating floors. The AltUnc field would Altitude Type value is 2, indicating floors. The AltRes field would
indicate that all bits in the Altitude field are true, as we want to indicate that all bits in the Altitude field are true, as we want to
accurately represent the floor of the structure where we are located. accurately represent the floor of the structure where we are located.
AltUnc = 30, 0x1e, 011110 AltRes = 30, 0x1e, 011110
AType = 2, 0x02, 000010 AType = 2, 0x02, 000010
Altitude = 103, 0x00006700, 000000000000000110011100000000 Altitude = 103, 0x00006700, 000000000000000110011100000000
For the accuracy of the Latitude and Longitude, the best information For the accuracy of the Latitude and Longitude, the best information
available to us was supplied by a generic mapping service that shows available to us was supplied by a generic mapping service that shows
a single geo-loc for all of the Sears Tower. Therefore we are going a single geo-loc for all of the Sears Tower. Therefore we are going
to show LatUnc as value 18 (0x12 or 010010) and LongUnc as value 18 to show LaRes as value 18 (0x12 or 010010) and LoRes as value 18
(0x12 or 010010). This would be describing a geo-location area that (0x12 or 010010). This would be describing a geo-location area that
is Latitude 41.8769531 to Latitude 41.8789062 and extends from is Latitude 41.8769531 to Latitude 41.8789062 and extends from
-87.6367188 degrees to -87.6347657 degrees Longitude. This is an -87.6367188 degrees to -87.6347657 degrees Longitude. This is an
area of approximately 373412 square feet (713.3 ft. x 523.5 ft.). area of approximately 373412 square feet (713.3 ft. x 523.5 ft.).
Appendix C. Calculations of Uncertainty Appendix C. Calculations of Uncertainty
The following example demonstrates how uncertainty values for The following example demonstrates how uncertainty values for
Latitude, Longitude, and Altitude (LatUnc, LongUnc and AltUnc Latitude, Longitude, and Altitude (LatUnc, LongUnc and AltUnc
used in the DHCPv6 Option as well as the version 1 DHCPv4 option) used in the DHCPv6 option as well as DHCPv4 Option TBD)
can be calculated. can be calculated.
C.1. Location Configuration Information of "Sydney Opera House" C.1. Location Configuration Information of "Sydney Opera House"
(Example 3) (Example 3)
This section describes an example of encoding and decoding the This section describes an example of encoding and decoding the
geodetic DHCP Option. The textual results are expressed in GML geodetic DHCP Option. The textual results are expressed in GML
[OGC.GML-3.1.1] form, suitable for inclusion in PIDF-LO [RFC4119]. [OGC.GML-3.1.1] form, suitable for inclusion in PIDF-LO [RFC4119].
These examples all assume a datum of WGS84 (datum = 1) and an These examples all assume a datum of WGS84 (datum = 1) and an
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The result of this equation is also 18, or 010010 in binary. The result of this equation is also 18, or 010010 in binary.
Altitude Uncertainty (AltUnc) uses the formula from Section 2.4.4: Altitude Uncertainty (AltUnc) uses the formula from Section 2.4.4:
x = 21 - ceil( log2( 33.7 - 0 ) ) x = 21 - ceil( log2( 33.7 - 0 ) )
The result of this equation is 15, which is encoded as 001111 in The result of this equation is 15, which is encoded as 001111 in
binary. binary.
Adding an Altitude Type of 1 (meters) and a Datum of 1 (WGS84), this Adding an Altitude Type of 1 (meters) and a Datum of 1 (WGS84), this
gives the following DHCPv4 form: gives the following DHCPv4 Option TBD form:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code (123) | OptLen (16) | LatUnc | Latitude . | Code (TBD) | OptLen (16) | LatUnc | Latitude .
|0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|1 1 1 0 1 1 1 1 0 0. |0 1 1 1 1 0 1 1|0 0 0 1 0 0 0 0|0 1 0 0 1 0|1 1 1 0 1 1 1 1 0 0.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) | LongUnc | . . Latitude (cont'd) | LongUnc | .
.0 1 0 0 1 0 0 1 0 0 1 1 0 1 1 0 0 0 0 0 1 1 0 1|0 1 0 0 1 0|0 1. .0 1 0 0 1 0 0 1 0 0 1 1 0 1 1 0 0 0 0 0 1 1 0 1|0 1 0 0 1 0|0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Longitude (cont'd) | . Longitude (cont'd) |
.0 0 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 1 1 1 0 1 1 0 0 0 0 1 1| .0 0 1 0 1 1 1 0 0 1 1 0 1 1 1 0 0 0 1 0 1 1 1 0 1 1 0 0 0 0 1 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude . | AType | AltUnc | Altitude .
|0 0 0 1|0 0 1 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1. |0 0 0 1|0 0 1 1 1 1|0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1.
skipping to change at page 31, line 7 skipping to change at page 32, line 7
</gs:Prism> </gs:Prism>
Note that this representation is only appropriate if the uncertainty Note that this representation is only appropriate if the uncertainty
is sufficiently small. [GeoShape] recommends that distances between is sufficiently small. [GeoShape] recommends that distances between
polygon vertices be kept short. A GML representation like this one polygon vertices be kept short. A GML representation like this one
is only appropriate where uncertainty is less than 1 degree (an is only appropriate where uncertainty is less than 1 degree (an
encoded value of 9 or greater). encoded value of 9 or greater).
Appendix D. Changes from RFC 3825 Appendix D. Changes from RFC 3825
This section lists the major changes between [RFC3825] and this This section lists the major changes between RFC 3825 and this
document. Minor changes, including style, grammar, spelling and document. Minor changes, including style, grammar, spelling and
editorial changes are not mentioned here. editorial changes are not mentioned here.
o Section 1 now includes clarifications on wired and wireless uses. o Section 1 now includes clarifications on wired and wireless uses.
o The former Sections 1.2 and 1.3 have been removed. Section 1.2 o The former Sections 1.2 and 1.3 have been removed. Section 1.2
now defines the concepts of uncertainty and resolution, as well now defines the concepts of uncertainty and resolution, as well
as conversion between the DHCP option format and PIDF-LO. as conversion between the DHCP option format and PIDF-LO.
o A DHCPv6 option is now defined (Section 2.1) as well o A DHCPv6 option is now defined (Section 2.1) as well
as a DHCPv4 option (Section 2.2). as DHCPv4 options (Section 2.2).
o The former Datum field has been split into three fields: o The former Datum field has been split into three fields:
Ver, Res and Datum. These fields are used in both the Ver, Res and Datum. These fields are used in both the
DHCPv4 and DHCPv6 options. DHCPv4 and DHCPv6 options.
o Section 2.2.1 has been added, describing Version support. o Section 2.2.3 has been added, describing Option support.
o Section 2.3 has been added, describing the Latitude and o Section 2.3 has been added, describing the Latitude and
Longitude fields. Longitude fields.
o Section 2.3.1 has been added, covering Latitude and Longitude o Section 2.3.1 has been added, covering Latitude and Longitude
resolution. resolution.
o Section 2.3.2 has been added, covering Latitude and Longitude o Section 2.3.2 has been added, covering Latitude and Longitude
uncertainty. uncertainty.
o Section 2.4 has been added, covering values of the Altitude o Section 2.4 has been added, covering values of the Altitude
field (Sections 2.4.1, 2.4.2 and 2.4.3), Altitude resolution field (Sections 2.4.1, 2.4.2 and 2.4.3), Altitude resolution
(Section 2.4.4), and Altitude uncertainty (Section 2.4.5). (Section 2.4.4), and Altitude uncertainty (Section 2.4.5).
o Section 2.5 has been added, covering the Datum field. o Section 2.5 has been added, covering the Datum field.
skipping to change at page 32, line 40 skipping to change at page 33, line 40
AU AU
EMail: martin.thomson@andrew.com EMail: martin.thomson@andrew.com
Bernard Aboba Bernard Aboba
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 USA Redmond, WA 98052 USA
USA USA
EMail: bernarda@microsoft.com EMail: bernard_aboba@hotmail.com
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