draft-ietf-geopriv-dhcp-lci-option-01.txt   draft-ietf-geopriv-dhcp-lci-option-02.txt 
Internet Engineering Task Force J. Polk Internet Engineering Task Force J. Polk
Internet Draft J. Schnizlein Internet Draft J. Schnizlein
Expiration: Dec 16th, 2003 M. Linsner Expiration: Feb 21st, 2004 M. Linsner
File: draft-ietf-geopriv-dhcp-lci-option-01.txt Cisco Systems File: draft-ietf-geopriv-dhcp-lci-option-02.txt Cisco Systems
Dynamic Host Configuration Protocol Option for
Location Configuration Information for GEOPRIV Location Configuration Information for GEOPRIV
June 16th, 2003 Aug 21st, 2003
Status of this Memo Status of this Memo
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Abstract Abstract
This document specifies a Dynamic Host Configuration Protocol Option This document specifies a Dynamic Host Configuration Protocol Option
for the geographic location of the client. The Location for the geographic location of the client. The Location
Configuration Information (LCI) includes latitude, longitude, and Configuration Information (LCI) includes latitude, longitude, and
altitude, with resolution indicators for each, as well as for the altitude, with resolution indicators for each. The reference datum
datum of the location. for these values is also included.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Rationale . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 Rationale . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Changes from version -00 . . . . . . . . . . . . . . . . 4 1.4 Changes from version -00 . . . . . . . . . . . . . . . . 4
2. Location Configuration Information (LCI) Elements . . . . . . 4 2. Location Configuration Information (LCI) Elements . . . . . . 5
2.1 Elements of the Location Configuration Information . . . 5 2.1 Elements of the Location Configuration Information . . . 6
3. Purpose of Resolution Value per La/Lo/Alt Element . . . . . . 7 3. Purpose of Resolution Value per La/Lo/Alt Elements . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8. Author Information . . . . . . . . . . . . . . . . . . . . . 9
Appendix Calculations of Imprecision possible with the DHC LCI . 10 Appendix Calculations of Imprecision possible with the DHC LCI . 10
A.1 LCI of "White House" (Example 1) . . . . . . . . . . . . 10 A.1 LCI of "White House" (Example 1) . . . . . . . . . . . . 10
A.2 LCI of "Sears Tower" (Example 2) . . . . . . . . . . . . 12 A.2 LCI of "Sears Tower" (Example 2) . . . . . . . . . . . . 13
9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8. Author Information . . . . . . . . . . . . . . . . . . . . . 14
9. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
This document specifies a Dynamic Host Configuration Protocol [1] This document specifies a Dynamic Host Configuration Protocol [1]
Option for the geographic location of the client, to be provided by Option for the geographic location of the client, to be provided by
the server. the server.
The DHCP server is assumed to have determined the location from the The DHCP server is assumed to have determined the location from the
Circuit-ID Relay Agent Information Option (RAIO) defined (as SubOpt Circuit-ID Relay Agent Information Option (RAIO) defined (as SubOpt
1) in [2]. In order to translate the circuit (switch port 1) in [2]. In order to translate the circuit (switch port
identifier) into a location, the DHCP server is assumed to have identifier) into a location, the DHCP server is assumed to have
access to a service that maps from circuit-ID to the location at access to a service that maps from circuit-ID to the location at
which the circuit connected to that port terminates in the building; which the circuit connected to that port terminates in the building;
for example, the location of the wall jack. for example, the location of the wall jack.
The Location Configuration Information (LCI) format presented here An important feature of this specification is that location
could be considered a subset of the information which would be information is completely under control of the end device rather
included in a GEOPRIV Location Object. This LCI is part of the than stored in an outside service for retrieval by the end device.
generation of location by the GEOPRIV origin. Storage outside the end device during times of emergency can cause
unnecessary delay, or failure during communication.
An important feature of this document is it places location
information completely under control of the end device rather than
storing this Location Configuration Information in an outside
service for retrieval by the end device. Storage outside the end
device during times of emergency can cause unnecessary delay, or
failure during communication.
Another important feature of this LCI is its inclusion of a Another important feature of this LCI is its inclusion of a
resolution parameter for each of the dimensions of location. The resolution parameter for each of the dimensions of location. The
GEOPRIV working group has a stated requirement [3] to enable GEOPRIV working group has a stated requirement [3] to enable
decreasing the precision of a location element. Because this decreasing the precision of a location element. Because this
resolution parameter need not apply to all dimensions equally, a resolution parameter need not apply to all dimensions equally, a
resolution value is included for each of the 3 location elements. resolution value is included for each of the 3 location elements.
This resolution method provides a natural ability for the device to This resolution method provides a natural ability for the device to
hide from the center point of the bounding area as this resolution hide from the center point of the bounding area as this resolution
method is determined via the inherent affects of binary mathematics, method is determined via the inherent effects of binary
using the power of 2. representation.
Resolution does not define how Geographic Privacy policy should relate to precision.
The resulting location information using this resolution method is a The resulting location information using this resolution method is a
small fixed length Configuration Information that can be easily small fixed length Configuration Information that can be easily
carried in protocols, such as DHCP, which have limited packet size carried in protocols, such as DHCP, which have limited packet size
because this LCI is only 16 bytes long. because this LCI is only 18 bytes long.
Finally, in the appendix this document provides some arithmetic Finally, in the appendix this document provides some arithmetic
examples of just how the imprecision can be introduced in any or all examples of just how the imprecision can be introduced in any or all
of the La/Lo/Alt values without the IP device needing to be of the La/Lo/Alt values without the IP device needing to be
preprogrammed with bogus location information, and just how preprogrammed with bogus location information, and just how
imprecise the La/Lo/Alt values can be. imprecise the La/Lo/Alt values can be.
This document does not cover any policy regarding the use of this This document does not cover any policy regarding the use of this
other than a few as potential suggestions to convey the meaning other than a few as potential suggestions to convey the meaning
intended by the document. intended by the document.
skipping to change at page 4, line 14 skipping to change at page 4, line 13
location of the radio access point used during host configuration, location of the radio access point used during host configuration,
but will need some more exotic mechanisms, maybe GPS, or maybe a but will need some more exotic mechanisms, maybe GPS, or maybe a
future DHCP option, which includes a list of geo-locations like that future DHCP option, which includes a list of geo-locations like that
defined here, which has the locations of the radio access points defined here, which has the locations of the radio access points
that are close to the client. that are close to the client.
1.3 Rationale 1.3 Rationale
Within the LCI described here, Latitude and Longitude are Within the LCI described here, Latitude and Longitude are
represented in fixed-point 2s-complement binary degrees, for the represented in fixed-point 2s-complement binary degrees, for the
economy of a smaller option size compared to the string encoding of economy of a smaller option size compared to a string encoding of
digits in [5]. The integer parts of these fields are 9 bits long to digits in [5]. The integer parts of these fields are 9 bits long to
accommodate +/- 180 degrees. The fractional part is 25 bits long, accommodate +/- 180 degrees. The fractional part is 25 bits long,
better than the precision of 7 decimal digits. Each parameter is 40 better than the precision of 7 decimal digits. Each parameter is 40
bits total, in length. bits total, in length.
Altitude is represented in measurement units (MU) indicated by the Altitude is determined by the Altitude Type (AT) indicated by the
MU field, which is 4 bits long. Two measurement units are defined AT field, which is 4 bits long. Two Altitude Types are defined
here, meters (code=1) and floors (code=2), both of which are 2s- here, meters (code=1) and floors (code=2), both of which are 2s-
complement fixed-point with 8 bits of fraction. Additional complement fixed-point with 8 bits of fraction. Additional
measurement units MAY be assigned by IANA. The floor of a building Altitude Types MAY be assigned by IANA. The "floors" Altitude Type
is often the relevant location information, and not necessarily is provided because altitude in meters may not be known within a
computable from meters of altitude. building, and a floor indication may be more useful.
Each of these 3 variables is preceded by an accuracy sub-field of 6 GPS systems today can use WGS84 for horizontal and vertical datums,
[9] defines WGS84 as a three-dimensional datum. For other datum
values that do not include a vertical component, both the horizontal
and vertical datum of reference will be specified in the IANA
record.
Each of these 3 elements is preceded by an accuracy sub-field of 6
bits, indicating the number of bits of resolution. This resolution bits, indicating the number of bits of resolution. This resolution
sub-field accommodates the GEOPRIV requirement [3] to easily adjust sub-field accommodates the GEOPRIV requirement [3] to easily adjust
the precision of a reported location. Contents beyond the claimed the precision of a reported location. Contents beyond the claimed
resolution MAY be randomized to obscure greater precision that might resolution MAY be randomized to obscure greater precision that might
be available. be available.
1.4 Changes from version -00 1.4 Changes from version -00
Here is a list of changes to version -01 from -00: Here is a list of changes to version -01 from -00:
- inadvertently left out the Acknowledgements section; corrected - inadvertently left out the Acknowledgements section; corrected
that error that error
- added the NAD83 Datum to the list in section 2.1, and to the list - added the NAD83 Datum to the list in section 2.1, and to the list
put forth for IANA registration put forth for IANA registration
Here is a list of changes to version -02 from -01:
- changed Measurement Unit to Altitude Type to relieve some
confusion regarding the use of Floors in this field
- added some text explaining GPS uses of WGS 84
- Clarified the text to eliminate ˘pairing÷ of datum, but requiring
both horizontal and vertical where the reference datum is not 3-D,
as it is in WGS 84.
- added a line to each *Res description section that it isn't to be
used to provide or enforce policy by the domain (which is
contradictory to Geopriv requirements of a single point of policy
injection)
- Split the Datum NAD83 into two different datum registries: One
adding a vertical datum (NVAD88) for land (not near Tidal water),
and added a new NAD83 datum pair (currently #5) to include NAD83
when used on the water/sea/ocean - with a vertical datum of MLLW
- Deleted all text regarding policy (through the use of the *Res
field values) not being injected at two places (Geopriv
requirements state this should only occur at one location)
- augmented the IANA section to include the Horizontal and Vertical
Datum pairings for #s 1, 2 & 3
- Deleted the all references to datums ED50 and ED87 because Carl
Reed established that neither has a "well known" vertical datum to
pair either with
2. DHC Location Configuration Information Elements 2. DHC Location Configuration Information Elements
DHCP is a binary Protocol; GEOPRIV is text-based. Most coordinate DHCP is a binary Protocol; GEOPRIV is text-based. Since most
systems translate fairly easily between binary-based and text-based coordinate systems translate fairly easily between binary-based and
location output (i.e. even emergency services within the US). The text-based location output (even emergency services within the US),
authors believe translation/conversion is a non-issue with DHCP's translation/conversion is a non-issue with DHCP's binary format.
binary format.
This binary format provides a fortunate benefit in a mechanism for This binary format provides a fortunate benefit in a mechanism for
making a true/correct location coordinate imprecise. It further making a true/correct location coordinate imprecise. It further
provides the capability to have this binary representation be provides the capability to have this binary representation be
deterministically imprecise. deterministically imprecise.
The proposed LCI format is: The proposed LCI format is:
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 TBD | 16 | LaRes | Latitude + | Code TBD | 16 | LaRes | Latitude +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Latitude (cont'd) | LoRes | + | Latitude (cont'd) | LoRes | +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Longitude | | Longitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MU | AltRes | Altitude | | AT | AltRes | Altitude |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Alt (cont'd) | Datum | | Alt (cont'd) | Datum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.1 Elements of the Location Configuration Information 2.1 Elements of the Location Configuration Information
Code TBD: The code for this DHCP option is TBD by IANA. Code TBD: The code for this DHCP option is TBD by IANA.
16: The length of this option is 16 bytes. 16: The length of this option is 16 bytes.
LaRes: Latitude resolution. 6 bits indicating the valid number LaRes: Latitude resolution. 6 bits indicating the number
of valid bits in the fixed-point value of Latitude. of valid bits in the fixed-point value of Latitude.
This value is the number of high-order Latitude bits that should be This value is the number of high-order Latitude bits that should be
considered valid. Any bits entered to the right of this limit should considered valid. Any bits entered to the right of this limit
not be considered valid and might be purposely false, or zeroed by should not be considered valid and might be purposely false, or
the sending device (meaning the Geopriv target towards the zeroed by the sending.
requestor).
The examples below in section 4.0, are to illustrate that a smaller The examples below in section 4.0, are to illustrate that a smaller
value in the resolution field increases the area within which the value in the resolution field increases the area within which the
device is located (without deception). device is located (without deception).
LaRes does not define how Geographic Privacy policy should relate to
precision.
Values of resolution above decimal 34 are Undefined and reserved Values of resolution above decimal 34 are Undefined and reserved
because that is the largest number of bits in the Latitude field. because that is the largest number of bits in the Latitude field.
Latitude: a 34 bit fixed point value consisting of 9 bits of integer Latitude: a 34 bit fixed point value consisting of 9 bits of integer
and 25 bits of fraction. Latitude SHOULD be normalized to within +/- and 25 bits of fraction. Latitude SHOULD be normalized to
90 degrees. Geo-location formats provide for positive numbers to be within +/- 90 degrees. Geo-location formats provide for
north of the equator and negative numbers to be south of the positive numbers to be north of the equator and negative
equator. numbers to be south of the equator.
A value of 2 in the LaRes field indicates a precision of no greater A value of 2 in the LaRes field indicates a precision of no greater
than 1/6th that of the globe (detailed in the first example in than 1/6th that of the globe (detailed in the first example in
section 4.0). A value of 34 in the LaRes field indicates a precision section 4.0). A value of 34 in the LaRes field indicates a
within 3.11 mm in Latitude. precision of about 3.11 mm in Latitude.
LoRes: Longitude resolution. 6 bits indicating the number of LoRes: Longitude resolution. 6 bits indicating the number of
valid bits in the fixed-point value of Longitude. valid bits in the fixed-point value of Longitude.
This value is the number of high-order Longitude bits that should be This value is the number of high-order Longitude bits that should be
considered valid. Any bits entered to the right of this limit should considered valid. Any bits entered to the right of this limit
not be considered valid and might be purposely false, or zeroed by should not be considered valid and might be purposely false, or
the sending device (meaning the GEOPRIV target towards the zeroed by the sending.
requestor).
LoRes does not define how Geographic Privacy policy should relate to
precision.
Values above decimal 34 are undefined and reserved. Values above decimal 34 are undefined and reserved.
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. Longitude SHOULD be normalized to integer and 25 bits of fraction. Longitude SHOULD be
within +/- 180 degrees. Geo-location formats provide for positive normalized to within +/- 180 degrees. Geo-location
numbers to be east of the prime meridian and negative (2s formats provide for positive numbers to be east of the
complement) numbers to be west of the prime meridian. prime meridian and negative (2s complement) numbers to be
west of the prime meridian.
Entering a value of 2 in the LoRes field will result in the Entering a value of 2 in the LoRes field will result in the
precision of no greater than 1/6th that of the globe (see first precision of no greater than 1/6th that of the globe (see first
example in section 4.0 for more here). A value of 34 in the LoRes example in section 4.0 for more here). A value of 34 in the LoRes
field indicates a precision within 2.42 mm in longitude (at the field indicates a precision of about 2.42 mm in longitude (at the
equator). Because lines of longitude converge at the poles, the equator). Because lines of longitude converge at the poles, the
distance is smaller (resolution greater) for locations away from the distance is smaller (resolution greater) for locations away from the
equator. equator.
Altitude: A 30 bit value defined by the AT field
AltRes: Altitude resolution. 6 bits indicating the number of valid AltRes: Altitude resolution. 6 bits indicating the number of valid
bits in the altitude. Values above 30 (decimal) are bits in the altitude. Values above 30 (decimal) are
undefined and reserved. undefined and reserved.
MU: Measurement unit for altitude. Codes defined are: AltRes does not define how Geographic Privacy policy should relate
to precision.
AT: Altitude Type for altitude. Codes defined are:
1: Meters - in 2s-complement fixed-point 22-bit integer part with 1: Meters - in 2s-complement fixed-point 22-bit integer part with
8-bit fraction 8-bit fraction
If MU = 1, an AltRes value 0 would indicate unknown altitude. The If AT = 1, an AltRes value 0.0 would indicate unknown altitude.
most precise Altitude would have an AltRes value of 30. The most precise Altitude would have an AltRes value of 30. Many
values of AltRes would obscure any variation due to vertical datum
differences.
2: Floors - in 2s-complement fixed-point 22-bit integer part with 2: Floors - in 2s-complement fixed-point 22-bit integer part with
8-bit fraction 8-bit fraction
MU = 2 for Floors enables representing altitude in a form more AT = 2 for Floors enables representing altitude in a form more
relevant in buildings which have different floor-to-floor relevant in buildings which have different floor-to-floor
dimensions. An altitude coded as MU=2, AltRes = 30, and Altitude = dimensions. An altitude coded as AT=2, AltRes = 30, and Altitude =
0, represents the ground level outside as well as the ground floor 0.0 is meaningful even outside a building, and represents ground
within a building). This encoding is useful where the precise level at the given latitude and longitude. Inside a building, 0.0
altitude is less important than the location at ground level. represents the floor level associated with ground level at the main
entrance. This document defines a number; one must arrive at the
number by counting floors from the floor defined to be 0.0.
Any additional Geopriv Measurement Unit(s) to be defined for use via The values represented by this AT will be of local significance.
Since buildings and floors can vary due to lack of common control,
the values chosen to represent the characteristics of an individual
building will be derived and agreed upon by the operator of the
building and the intended users of the data. Attempting to
standardize this type of function is beyond the scope this document.
Sub-floors can be represented by non-integer values. Example: a
mezzanine between floor 1 and floor 2 could be represented as a
value=1.1. Example: (2) mezzanines between floor 4 and floor 5
could be represented as values=4.1 and 4.2 respectively.
Floors located below ground level could be represented by negative
values.
Larger values represent floors that are above (higher in altitude)
floors with lower values.
The AltRes field SHOULD be set to maximum precision when AT = 2
(floors) when a floor value is included in the DHCP Reply, or
the AT = 0 to denote the floor isn't known.
Any additional Geopriv Altitude Types(s) to be defined for use via
this DHC Option MUST be done through a Standards Track RFC. this DHC Option MUST be done through a Standards Track RFC.
Datum: The Map Datum used for the coordinates given in this Option Datum: The Map Datum used for the coordinates given in this Option
The Datum byte has 255 possibilities, of which 4 are to be The datum must include both a horizontal and a vertical reference.
Since the WGS 84 reference datum is three-dimensional, it includes
both. For any additional datum parameters, the datum codepoint must
specify both horizontal datum and vertical datum references.
The Datum byte has 255 possibilities, of which 3 are to be
registered with IANA by this document (all derived from registered with IANA by this document (all derived from
specification in [8]): specification in [8]):
1: WGS 84 (Geographical 3D) - World Geodesic System 1984, CRS 1: WGS 84 (Geographical 3D) - World Geodesic System 1984, CRS
Code 4327, Prime Meridian Name: Greenwich Code 4327, Prime Meridian Name: Greenwich
2: ED50 - European Datum 1950(77), CRS Code 4154, Prime Meridian 2: NAD83 - North American Datum 1983, CRS Code 4269, Prime
Name: Greenwich Meridian Name: Greenwich; The associated vertical
datum is the North American Vertical Datum of 1988
(NAVD88)
3: ED87 - European Datum 1987, CRS Code 4231, Prime Meridian This datum pair would be used when referencing
Name: Greenwich locations on land, not near tidal water (which would
use Datum = 3 below)
4: NAD83 - North American Datum 1983, CRS Code 4269, Prime 3: NAD83 - North American Datum 1983, CRS Code 4269, Prime
Meridian Name: Greenwich Meridian Name: Greenwich; The associated vertical
datum is Mean Lower Low Water (MLLW)
This datum pair would be used when referencing
locations on water/sea/ocean
Any additional Geopriv datum(s) to be defined for use via this DHC Any additional Geopriv datum(s) to be defined for use via this DHC
Option MUST be done through a Standards Track RFC. Option MUST be done through a Standards Track RFC.
3. Purpose of Resolution Value per La/Lo/Alt Element 3. Purpose of Resolution Value per La/Lo/Alt Element
GEOPRIV specified [3] the requirement that any location expressed GEOPRIV specified the requirement [3] that any location expressed
from or proxied on behalf of a device through the GEOPRIV Protocol from or proxied on behalf of a device through the GEOPRIV Protocol
can have the accuracy or precision of that device's location can have the accuracy or precision of that device's location
limited. The owner of the device, or the domain of the device limited. The owner of the device, or the domain of the device
determines the policy for divulging how precise the location is for determines the policy for divulging how precise the location is for
any/all given requesters of that device's location. any/all given requesters of that device's location.
One aspect within the GEOPRIV WG is the precision of a device's As stated in section 2.1, these resolution fields are not intended
ability to present its location coordinates might have a domain to specify policy towards the endpoint. However, the *Res fields
policy override the individual policy in the sense of maximum can provide a quite useful feature by providing to the endpoint the
resolution possible. In other words, a user of a device might not maximum precision of location in the DHCP Reply.
mind providing a quite precise location return to a location
request, but the local domain might not want that level of precision
by its policy. In this case, the resolution value provided in the
DHCP Reply can set this maximum precision value, perhaps allowing
the user of the Target device to make the values more imprecise
based on who is requesting their location. The document does not go
further down this thought for good reason.
4. Security Considerations 4. Security Considerations
Where critical decisions might be based on the value of this Where critical decisions might be based on the value of this
GeoLoc option, DHCP authentication in [7] SHOULD be used to GeoLoc option, DHCP authentication in [7] SHOULD be used to
protect the integrity of the DHCP options. protect the integrity of the DHCP options.
Since there is no privacy protection for DHCP messages, an
eavesdropper who can monitor the link between the DHCP server and
requesting client can discover this LCI.
5. IANA Considerations 5. IANA Considerations
The DHCP option code for the GeoLoc option is TBD. The DHCP option code for the GeoLoc option is TBD.
This document calls for the IANA registration of the following: This document calls for the IANA registration of the following:
MU = 1 is meters of Altitude from mean low tide. Semantics are AT = 1 is meters of Altitude defined by the vertical datum
included in this document (section 2.1) specified. Semantics are included in this document (section
2.1)
MU = 2 is building Floors of Altitude. Semantics are included in AT = 2 is building Floors of Altitude. Semantics are included in
this document (section 2.1) this document (section 2.1)
Datum = 1 is denoting WGS 84 (Geographical 3D) as defined by the Datum = 1 is denoting the vertical datum WGS 84 as defined by the
EPSG as their CRS Code 4327 EPSG as their CRS Code 4327; CRS Code 4327 also specifies
WGS 84 as the vertical datum
Datum = 2 is denoting ED50(77) as defined by the EPSG as their CRS Datum = 2 is denoting the vertical datum NAD83 as defined by the
Code 4154 EPSG as their CRS Code 4269; North American Vertical Datum
of 1988 (NAVD88) is the associated vertical datum for NAD83
Datum = 3 is denoting ED87 as defined by the EPSG as their CRS Code The semantics of this datum pair (#2) is presented in
4231 section 2.1 above
Datum = 4 is denoting NAD83 as defined by the EPSG as their CRS Code Datum = 3 is denoting the vertical datum NAD83 as defined by the
4269 EPSG as their CRS Code 4269; Mean Lower Low Water (MLLW) is
the associated vertical datum for NAD83
The semantics of this datum pair (#3) is presented in
section 2.1 above
6. Acknowledgements 6. Acknowledgements
The authors would like to thank Patrik Falstrom, Ralph Droms, Ted The authors would like to thank Patrik Falstrom, Ralph Droms, Ted
Hardie and Nadine Abbott for their inputs and constructive comments Hardie, Jon Peterson and Nadine Abbott for their inputs and
regarding this document, as well as the patience of the WG chairs. constructive comments regarding this document. Additionally, the
authors would like to thank Greg Troxel for the education on
7. References vertical datums, and to Carl Reed.
[1] Droms R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997
[2] Patrick M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001
[3] Cuellar J., Morris J., Mulligan D., "GEOPRIV Requirements",
[4] Bradner S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997
[5] Farrell C., Schulze M., Pleitner S. and Baldoni D., "DNS
Encoding of Geographical Location", RFC 1712, November 1994.
[6] National Emergency Number Association (NENA) www.nena.org
NENA Technical Information Document on Model Legislation
Enhanced 911 for Multi-Line Telephone Systems
(http://www.nena.org/9%2D1%2D1techstandards/TechInfoDocs/
MLTS_ModLeg_Nov200.PDF)
[7] Droms R., "Authentication for DHCP Messages", RFC 3118, June
2001
[8] European Petroleum Survey Group, http://www.epsg.org/ and
http://www.ihsenergy.com/epsg/geodetic2.html
8. Author Information
James M. Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082 USA
jmpolk@cisco.com
John Schnizlein
Cisco Systems
9123 Loughran Road
Fort Washington, MD 20744 USA
john.schnizlein@cisco.com
Marc Linsner
Cisco Systems
Marco Island, FL 34145 USA
marc.linsner@cisco.com
Appendix: Calculations of Imprecision possible with the DHC LCI Appendix: Calculations of Imprecision possible with the DHC LCI
The following examples for two different locations demonstrate The following examples for two different locations demonstrate
how the Resolution values for Latitude, Longitude and Altitude how the Resolution values for Latitude, Longitude and Altitude
can be used. In both examples the geo-location values were derived can be used. In both examples the geo-location values were derived
from maps using the WGS84 map datum, therefore in these examples, from maps using the WGS84 map datum, therefore in these examples,
the datum field would have a value = 1 (00000001, or 0x01). the datum field would have a value = 1 (00000001, or 0x01).
A.1 Location Configuration Information of "White House" (Example 1) A.1 Location Configuration Information of "White House" (Example 1)
skipping to change at page 10, line 44 skipping to change at page 11, line 24
Longitude = 0xf65ecf031, Longitude = 0xf65ecf031,
Longitude = 1101100101111011001111000000110001 Longitude = 1101100101111011001111000000110001
Altitude 15 Altitude 15
In this example we are not inside a structure, therefore we will In this example we are not inside a structure, therefore we will
assume an altitude value of 15 meters, interpolated from the US assume an altitude value of 15 meters, interpolated from the US
Geological survey map, Washington West quadrangle. Geological survey map, Washington West quadrangle.
AltRes = 30, 0x1e, 011110 AltRes = 30, 0x1e, 011110
MU = 1, 0x01, 000001 AT = 1, 0x01, 000001
Altitude = 15, 0x0F00, 00000000000000000000000001111100000000 Altitude = 15, 0x0F00, 00000000000000000000000001111100000000
If: LaRes is expressed as value 2 (0x02 or 000010) and LoRes is If: LaRes is expressed as value 2 (0x02 or 000010) and LoRes is
expressed as value 2 (0x02 or 000010), then it would describe a expressed as value 2 (0x02 or 000010), then it would describe a
geo-location region that is north of the equator and extends geo-location region that is north of the equator and extends
from -1 degree (west of the meridian) to -128 degrees. This from -1 degree (west of the meridian) to -128 degrees. This
would include the area from approximately 600km south of would include the area from approximately 600km south of
Saltpond, Ghana, due north to the North Pole and approximately Saltpond, Ghana, due north to the North Pole and approximately
4400km south-southwest of Los Angeles, CA due north to the North 4400km south-southwest of Los Angeles, CA due north to the North
Pole. This would cover an area of about one-sixth of the globe, Pole. This would cover an area of about one-sixth of the globe,
skipping to change at page 11, line 20 skipping to change at page 11, line 52
CN. and from the Amazons of northern Brazil to approximately CN. and from the Amazons of northern Brazil to approximately
4400km south-southwest of Los Angeles, CA. This area would 4400km south-southwest of Los Angeles, CA. This area would
include North America, Central America, and parts of Venezuela include North America, Central America, and parts of Venezuela
and Columbia, except portions of Alaska and northern and eastern and Columbia, except portions of Alaska and northern and eastern
Canada, approximately 10 million square nm. Canada, approximately 10 million square nm.
If: LaRes is expressed as value 5 (0x05 or 000101) and LoRes is If: LaRes is expressed as value 5 (0x05 or 000101) and LoRes is
expressed as value 5 (0x05 or 000101), then it would describe a expressed as value 5 (0x05 or 000101), then it would describe a
geo-location area that is latitude 32 north of the equator to geo-location area that is latitude 32 north of the equator to
latitude 48 and extends from -64 degrees to -80 degrees latitude 48 and extends from -64 degrees to -80 degrees
longitude. This is approximately an east-west boundary of a time longitude. This is approximately an east-west boundary of a
zone, an area of approximately 700,000 square nm. time zone, an area of approximately 700,000 square nm.
If: LaRes is expressed as value 9 (0x09 or 001001) and LoRes is If: LaRes is expressed as value 9 (0x09 or 001001) and LoRes is
expressed as value 9 (0x09 or 001001), which includes all the expressed as value 9 (0x09 or 001001), which includes all the
integer bits, then it would describe a geo-location area that is integer bits, then it would describe a geo-location area that is
latitude 38 north of the equator to latitude 39 and extends from latitude 38 north of the equator to latitude 39 and extends from
-77 degrees to -78 degrees longitude. This is an area of -77 degrees to -78 degrees longitude. This is an area of
approximately 9600 square km (111.3km x 86.5km). approximately 9600 square km (111.3km x 86.5km).
If: LaRes is expressed as value 18 (0x12 or 010010) and LoRes is If: LaRes is expressed as value 18 (0x12 or 010010) and LoRes is
expressed as value 18 (0x12 or 010010), then it would describe a expressed as value 18 (0x12 or 010010), then it would describe a
skipping to change at page 12, line 12 skipping to change at page 12, line 45
geo-location area that is latitude 38.8986797 north to latitude geo-location area that is latitude 38.8986797 north to latitude
38.8986802 and extends from -77.0372300 degrees to -77.0372296 38.8986802 and extends from -77.0372300 degrees to -77.0372296
degrees longitude. This is an area of approximately 19.5 square degrees longitude. This is an area of approximately 19.5 square
centimeters (50mm x 39mm). centimeters (50mm x 39mm).
If: LaRes is expressed as value 34 (0x22 or 100010) and LoRes is If: LaRes is expressed as value 34 (0x22 or 100010) and LoRes is
expressed as value 34 (0x22 or 100010), then it would describe a expressed as value 34 (0x22 or 100010), then it would describe a
geo-location area that is latitude 38.8986800 north to latitude geo-location area that is latitude 38.8986800 north to latitude
38.8986802 and extends from -77.0372300 degrees to -77.0372296 38.8986802 and extends from -77.0372300 degrees to -77.0372296
degrees longitude. This is an area of approximately 7.5 square degrees longitude. This is an area of approximately 7.5 square
millimeters (3.11mm x 2.42mm).
In the (White House) example, the requirement of emergency In the (White House) example, the requirement of emergency
responders in North America via their NENA Model Legislation [6], responders in North America via their NENA Model Legislation [6],
could be met by a LaRes value of 21 and a LoRes value of 20. could be met by a LaRes value of 21 and a LoRes value of 20.
This would yield a geo-location that is latitude 38.8984375 north This would yield a geo-location that is latitude 38.8984375 north
to latitude 38.8988616 north and longitude -77.0371094 to to latitude 38.8988616 north and longitude -77.0371094 to
longitude -77.0375977. This is an area of approximately 89 feet longitude -77.0375977. This is an area of approximately 89 feet
by 75 feet or 6669 square feet, which is very close to the 7000 by 75 feet or 6669 square feet, which is very close to the 7000
square feet asked for by NENA. In this example a service square feet asked for by NENA. In this example a service
provider could enforce that a device send a Location provider could enforce that a device send a Location
skipping to change at page 12, line 50 skipping to change at page 13, line 33
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 In this example we are inside a structure, therefore we will
assume an altitude value of 103 to indicate the floor we are on. assume an altitude value of 103 to indicate the floor we are on.
The measurement unit value is 2 indicating floors. The AltRes The Altitude Type value is 2 indicating floors. The AltRes
field would indicate that all bits in the Altitude field are field would indicate that all bits in the Altitude field are
true, as we want to accurately represent the floor of the true, as we want to accurately represent the floor of the
structure where we are located. structure where we are located.
AltRes = 30, 0x1e, 011110 AltRes = 30, 0x1e, 011110
MU = 2, 0x02, 000010 AT = 2, 0x02, 000010
Altitude = 103, 0x00006700, 000000000000000110011100000000 Altitude = 103, 0x00006700, 000000000000000110011100000000
For the accuracy of the latitude and longitude, the best For the accuracy of the latitude and longitude, the best
information available to us was supplied by a generic mapping information available to us was supplied by a generic mapping
service that shows a single geo-loc for all of the Sears Tower. service that shows a single geo-loc for all of the Sears Tower.
Therefore we are going to show LaRes as value 18 (0x12 or 010010) Therefore we are going to show LaRes as value 18 (0x12 or 010010)
and LoRes as value 18 (0x12 or 010010). This would be describing and LoRes as value 18 (0x12 or 010010). This would be describing
a geo-location area that is latitude 41.8769531 to latitude a geo-location area that is latitude 41.8769531 to latitude
41.8789062 and extends from -87.6367188 degrees to -87.6347657 41.8789062 and extends from -87.6367188 degrees to -87.6347657
degrees longitude. This is an area of approximately 373412 degrees longitude. This is an area of approximately 373412
square feet (713.3 ft. x 523.5 ft.). square feet (713.3 ft. x 523.5 ft.).
7. References
[1] Droms R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997
[2] Patrick M., "DHCP Relay Agent Information Option", RFC 3046,
January 2001
[3] Cuellar J., Morris J., Mulligan D., "GEOPRIV Requirements",
[4] Bradner S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997
[5] Farrell C., Schulze M., Pleitner S. and Baldoni D., "DNS
Encoding of Geographical Location", RFC 1712, November 1994.
[6] National Emergency Number Association (NENA) www.nena.org
NENA Technical Information Document on Model Legislation
Enhanced 911 for Multi-Line Telephone Systems
(http://www.nena.org/9%2D1%2D1techstandards/TechInfoDocs/
MLTS_ModLeg_Nov200.PDF)
[7] Droms R., "Authentication for DHCP Messages", RFC 3118, June
2001
[8] European Petroleum Survey Group, http://www.epsg.org/ and
http://www.ihsenergy.com/epsg/geodetic2.html
[9] World Geodetic System 1984 (WGS 84), MIL-STD-2401,
http://164.214.2.59/publications/specs/printed/WGS84/wgs84.html
and http://www.wgs84.com/
8. Author Information
James M. Polk
Cisco Systems
2200 East President George Bush Turnpike
Richardson, Texas 75082 USA
jmpolk@cisco.com
John Schnizlein
Cisco Systems
9123 Loughran Road
Fort Washington, MD 20744 USA
john.schnizlein@cisco.com
Marc Linsner
Cisco Systems
Marco Island, FL 34145 USA
marc.linsner@cisco.com
9. Full Copyright Statement 9. Full Copyright Statement
"Copyright (C) The Internet Society (February 23rd, 2001). "Copyright (C) The Internet Society (February 23rd, 2001).
All Rights Reserved. All Rights Reserved.
This document and translations of it may be copied and furnished This document and translations of it may be copied and furnished
to others, and derivative works that comment on or otherwise to others, and derivative works that comment on or otherwise
explain it or assist in its implementation may be prepared, explain it or assist in its implementation may be prepared,
copied, published and distributed, in whole or in part, without copied, published and distributed, in whole or in part, without
restriction of any kind, provided that the above copyright notice restriction of any kind, provided that the above copyright notice
skipping to change at page 13, line 51 skipping to change at page 15, line 42
This document and the information contained herein is provided on This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE
OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE." PURPOSE."
The Expiration date for this Internet Draft is: The Expiration date for this Internet Draft is:
Dec 16th, 2003 Feb. 8, 2004
 End of changes. 

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