GEOPRIV WG M. Thomson
Internet-Draft J. Winterbottom
Obsoletes: 3825 (if approved) Andrew
Intended status: Standards Track December 13, 2006
Expires: June 16, 2007
Dynamic Host Configuration Protocol Option for Geodetic Location
Information
draft-thomson-geopriv-3825bis-00.txt
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Copyright (C) The IETF Trust (2006).
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Abstract
This document specifies a Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) Option for the coordinate-based geographic location of
the client. The Location Configuration Information (LCI) includes
latitude, longitude, and altitude, with an indication of uncertainty
for each. Separate parameters indicate the reference datum for each
of these values.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Uncertainty . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Major Changes from RFC 3825 . . . . . . . . . . . . . . . 4
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. DHCP Option Format . . . . . . . . . . . . . . . . . . . . . . 5
2.1. DHCPv4 Geodetic Location Option . . . . . . . . . . . . . 5
2.2. DHCPv6 Geodetic Location Option . . . . . . . . . . . . . 6
2.3. Latitude and Longitude Fields . . . . . . . . . . . . . . 6
2.4. Altitude . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.5. Datum . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. Encoding a Location into DHCP Geodetic Form . . . . . . . 10
3.2. Decoding a Location from DHCP Geodetic Form . . . . . . . 11
4. Security Considerations . . . . . . . . . . . . . . . . . . . 14
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Normative References . . . . . . . . . . . . . . . . . . . 16
6.2. Informative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
Intellectual Property and Copyright Statements . . . . . . . . . . 19
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1. Introduction
The physical location of a network device has a range of
applications. In particular, emergency telephony applications rely
on knowing the location of a caller in order to determine the correct
emergency center.
There are two primary means for representing the location of a
device; either through geospatial (or geodetic) coordinates, or
through civic addresses. A related document [RFC4676] describes a
DHCP encoding for civic addresses; this document defines an encoding
for geodetic location information. Different applications may be
more suited to one form of location information; therefore, both the
geodetic and civic forms may be used simultaneously.
This document specifies a Dynamic Host Configuration Protocol (DHCPv4
[RFC2131], DHCPv6 [RFC3315]) option for the coordinate-based
geographic location of the client, to be provided by the server.
The goal of this document is to enable a wired Ethernet host to
obtain its location. This location information is derived from a
wiremap by the DHCP server, using the Circuit-ID Relay Agent
Information Option (RAIO) defined (as Sub-Option 1) in RFC 3046
[RFC3046]. The DHCP server is assumed to have access to a service
that can correlate a Circuit-ID with the geographic location where
the identified circuit terminates. For instance, this might be an
Ethernet wall jack.
This geodetic location information option has limited application to
wireless technologies, or other instances where a client is able to
move without requiring new addressing information. DHCP provides
static configuration information, which is not dynamically or
automatically refreshed. If a client moves between when the
configuration was provided and when the information is used, the
information is incorrect.
This document only defines the delivery of location information from
the DHCP server to the client, due to security concerns related to
using DHCP to update the database. Within the GEOPRIV architecture
as defined by RFC 3693 [RFC3693], the defined mechanism in this
document for conveying initial location information is known as a
"sighting" function. Sighting functions are not required to have
security capabilities and are only intended to be configured in
trusted and controlled environments. (A classic example of the
sighting function is a Global Positioning System wired directly to a
network node.) Further discussion of the protections that must be
provided according to RFC 3694 [RFC3694] are in the Security
Considerations section of this document (Section 4).
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1.1. Uncertainty
In the context of location technology, uncertainty is a
quantification of errors. Any method for determining location is
subject to some sources of error; uncertainty describes the amount of
error that is present. Uncertainty might be the coverage area of a
wireless transmitter, the extent of a building or a single room.
Uncertainty is usually represented as an area within which the target
is located. In this document, each of the three axes can be assigned
an uncertainty value. In effect, this describes a rectangular prism.
When representing locations from sources that can quantify
uncertainty, the goal is to find the smallest possible rectangular
prism that this format can describe. This is acheived by taking the
minimum and maximum values on each axis and ensuring that the final
encoding covers these points. This increases the region of
uncertainty, but ensures that the region that is described
encompasses the target location.
1.2. Major Changes from RFC 3825
An option for DHCPv6 is included in this document.
The way in which uncertainty is described is changed from the
previous version. There was some confusion with the way that the
word "resolution" was used in the previous version.
The uncertainty components have changed in their meaning. The
previous version was unclear/misleading on how these values should be
interpreted. This is clarified. This is illustrated with a new set
of examples, including both encoding and decoding of these values.
Geographic Markup Language (GML) [OGC.GML-3.1.1] is used for these
examples.
An altitude type of 0 (no altitude) was previously described in text,
but not registered in the IANA registry. This document formally
registers this type.
1.3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. DHCP Option Format
This section defines the format for the DHCPv4 and DHCPv6 options.
These options use the same basic format, differing only in the option
code.
2.1. DHCPv4 Geodetic Location Option
The format of the geodetic option for DHCPv4 [RFC2131] 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 (123) | OptLen (16) | LatUnc | Latitude .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) | LongUnc | .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Longitude (cont'd) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AType | AltUnc | Altitude .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Alt (cont'd) | Datum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code: GEOCONF_GEODETIC (8 bits). The code for this DHCPv4 option is
123.
OptLen: Option Length (8 bits). This option is fixed size, the
value of this octet will always be 16.
LatUnc: Latitude Uncertainty (6 bits). See Section 2.3.1.
Latitude: Latitude (34 bits). See Section 2.3.
LongUnc: Latitude Uncertainty (6 bits). See Section 2.3.1.
Longitude: Longitude (34 bits). See Section 2.3.
AType: Altitude Type (4 bits). See Section 2.4.
AltUnc: Altitude Uncertainty (6 bits). See Section 2.4.4.
Altitude: Altitude (30 bits). See Section 2.4.
Datum: Datum (8 bits). See Section 2.5.
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2.2. DHCPv6 Geodetic Location Option
The format of the geodetic option for DHCPv6 [RFC3315] 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Code (TBD) | OptLen (16) | LatUnc | .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Latitude (cont'd) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LongUnc | Longitude .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Long (cont'd) | AType | AltUnc | Altitude .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Altitude (cont'd) | Datum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Option Code: OPTION_GEOCONF_GEODETIC (16 bits). The code for this
DHCPv6 option is TBD.
OptLen: Option Length (8 bits). This option is fixed size, the
value of this octet will always be 16.
The remaining fields are identical to the DHCPv4 fields.
2.3. Latitude and Longitude Fields
The Latitude and Longitude values in this format are encoded as 34
bit, twos complement, fixed point values with 9 integer bits and 25
fractional bits. The exact meaning of these values is determined by
the datum; the description in this section applies to the datums
defined in this document. New datums MAY change the way that the 34
bit values and the respective 6 bit uncertainties are interpreted.
Latitude values MUST be constrained to the range from -90 to +90
degrees. Positive latitudes are north of the equator; negative
latitude are south of the equator.
Longitude values SHOULD be normalized to the range from -180 to +180
degrees. Values outside this range are normalized by adding or
subtracting 360 until they fall within this range. Positive
longitudes are east of the Prime Meridian (Greenwich); negative
longitudes are west of the Prime Meridian.
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2.3.1. Latitude and Longitude Uncertainty
The latitude and longitude uncertainty fields are encoded as 6 bit,
unsigned integer values. These values quantify the amount of
uncertainty in each of the latitude and longitude values
respectively. A value of 0 is reserved to indicate that the
uncertainty is unknown; values greater than 34 are reserved.
The amount of uncertainty can be determined by taking 2 to the power
of 8, less the encoded value. As is shown in the following formula,
where x is the encoded integer value:
uncertainty = 2 ^ ( 8 - x )
The result of this formula is expressed in degrees of latitude or
longitude. The uncertainty is added to the base latitude or
longitude value to determine the maximum value in the uncertainty
range; similarly, the uncertainty is subtracted from the base value
to determine the minimum value. Note that because lines of longitude
converge at the poles, the actual distance represented by this
uncertainty changes with the distance from the equator.
If the maximum or minimum latitude values derived from applying
uncertainty are outside the range of -90 to +90, these value SHOULD
be trimmed to within this range. If the maximum or minimum longitude
values derived from applying uncertainty are outside the range of
-180 to +180, then these values can be normalized to this range by
adding or subtracting 360 as necessary.
The encoded value is determined by subtracting the next highest
integer value for the base 2 logarithm of uncertainty from 8. As is
shown by the following formula, where uncertainty is the midpoint of
the known range less the lower bound of that range:
x = 8 - ceil( log2( uncertainty ) )
Note that the result of encoding this value increases the range of
uncertainty to the next available power of two; subsequent repeated
encodings and decodings do not change the value.
2.4. Altitude
The altitude is expressed as a 30 bit, fixed point, twos complement
integer with 22 integer bits and 8 fractional bits. How the altitude
value is interpreted depends on the type of altitude and the selected
datum. New altitude types MAY change the way that the 30 bit value
and the associated 6 bit uncertainty are interpreted.
Three altitude types are defined in this document: unknown (0),
meters (1) and floors (2). Additional altitude types MUST be defined
in a Standards Track RFC.
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2.4.1. No Known Altitude (AT = 0)
In some cases, the altitude of the location might not be known. An
altitude type of 0 indicates that the altitude is not known. In this
case, the altitude and altitude uncertainty fields can contain any
value and SHOULD be ignored.
2.4.2. Altitude in Meters (AT = 1)
If the altitude type has a value of 1, the altitude is measured in
meters. The altitude is measured in relation to the zero set by the
vertical datum.
2.4.3. Altitude in Floors (AT = 2)
A value of 2 for altitude type indicates that the altitude value is
measured in floors. This value is relevant only in relation to a
building; the value is relative to the ground level of the building.
Non-integer values can be used to represent intermediate or sub-
floors, such as mezzanine levels. For instance, a mezzanine between
floors 4 and 5 could be represented as 4.1.
Use of altitude in floors is deprecated in favor of the floors field
(CAtype 27) in the civic address option [RFC4676].
2.4.4. Altitude Uncertainty
Altitude uncertainty is expressed in a similar fashion to latitude or
longitude uncertainty. Like latitude and longitude, a value of 0 is
reserved to indicate that uncertainty is not known; values above 30
are also reserved.
The amount of altitude uncertainty can be determined by the following
formula, where x is the encoded integer value:
uncertainty = 2 ^ ( 21 - x )
This value uses the same units as the associated altitude.
Similarly, a value for the encoded integer value can be derived by
the following formula:
x = 21 - ceil( log2( x ) )
2.5. Datum
The datum field determines how coordinates are organized and related
to the real world. Three datums are defined in this document:, based
on the definitions in [OGP.Geodesy]:
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1: WGS84 (Latitude, Longitude, Altitude):
The World Geodesic System 1984 [WGS84] coordinate reference
system.
This datum is identified by the European Petroleum Survey Group
(EPSG)/International Association of Oil & Gas Producers (OGP) with
the code 4979, or by the URN "urn:ogc:def:crs:EPSG::4979".
Without altitude, this datum is identified by the EPSG/OGP code
4326 and the URN "urn:ogc:def:crs:EPSG::4326".
2: NAD83 (Latitude, Longitude) + NAVD88:
This datum uses a combination of the North American Datum 1983
(NAD83) for horizontal (latitude and longitude) values, plus the
North American Vertical Datum of 1988 (NAVD88) vertical datum.
This datum is used for referencing location on land (not near
tidal water) within North America.
NAD83 is identified by the EPSG/OGP code of 4269, or the URN
"urn:ogc:def:crs:EPSG::4269". NAVD88 is identified by the EPSG/
OGP code of 5703, or the URN "urn:ogc:def:crs:EPSG::5703".
3: NAD83 (Latitude, Longitude) + MLLW:
This datum uses a combination of the North American Datum 1983
(NAD83) for horizontal (latitude and longitude) values, plus the
Mean Lower Low Water (MLLW) vertical datum.
This datum is used for referencing location on or near tidal water
within North America.
NAD83 is identified by the EPSG/OGP code of 4269, or the URN
"urn:ogc:def:crs:EPSG::4269". MLLW does not have a specific code
or URN.
New datum codes can be registered in the IANA registry (Section 5) by
a Standards Track RFC. New geodetic coordinate datums MUST be three
dimensional that define both horizontal and vertical components.
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3. Examples
This section describes a few examples of encoding and decoding the
geodetic DHCP option. The textual results are expressed in GML
[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
altitude type of meters (AT = 1).
3.1. Encoding a Location into DHCP Geodetic Form
This example draws a rough polygon around the Sydney Opera House.
This polygon consists of the following six points:
33.856625 S, 151.215906 E
33.856299 S, 151.215343 E
33.856326 S, 151.214731 E
33.857533 S, 151.214495 E
33.857720 S, 151.214613 E
33.857369 S, 151.215375 E
The top of the building 67.4 meters above sea level, and a starting
altitude of 0 meters above the WGS84 geoid is assumed.
The first step is to determine the range of latitude and longitude
values. Latitude ranges from -33.857720 to -33.856299; longitude
ranges from 151.214495 to 151.215906.
The encoded values for latitude and longitude assume the middle of
this range, that is (-33.8570095, 151.2152005). These are encoded as
(1110111100010010010011011000001110,
0100101110011011100010111011000011) in binary, or (3BC49360E,
12E6E2EC3) in hexadecimal notation (with an extra 2 bits of padding
on each). Altitude is set at 33.7 meters, which is
000000000000000010000110110011 (binary) or 000021B3 (hexadecimal).
The latitude uncertainty is given by inserting the difference between
the center value and the outer value into the formula from
Section 2.3.1. This gives:
x = 8 - ceil( log2( -33.8570095 - -33.857720 ) )
The result of this equation is 18, therefore the uncertainty is
encoded as 010010 in binary.
Similarly, longitude uncertainty is given by the formula:
x = 8 - ceil( log2( 151.2152005 - 151.214495 ) )
The result of this equation is also 18, or 010010 in binary.
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Altitude uncertainty uses the formula from Section 2.4.4:
x = 21 - ceil( log2( 33.7 - 0 ) )
The result of this equation is 15, which is encoded as 001111 in
binary.
Adding an Altitude Type of 1 (meters) and a Datum of 1 (WGS84), this
gives the following DHCPv4 form:
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 (123) | 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.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. 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 1 0|0 1 0 0 1 0|0 1.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. 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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Alt (cont'd) | Datum |
.1 0 1 1 0 0 1 1|0 0 0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In hexadecimal, this is 7B104BBC 49360E49 2E6E2EC3 13C00021 B301.
The DHCPv6 form only differs in the code.
3.2. Decoding a Location from DHCP Geodetic Form
If receiving the binary form created in the previous section, this
section describes how that would be interpreted. The result is then
represented as a GML object, as defined in
[I-D.thomson-geopriv-geo-shape].
A latitude value of 1110111100010010010011011000001110 decodes to a
value of -33.8570094705 (to 10 decimal places). The longitude value
of 0100101110011011100010111011000011 decodes to 151.2152005136.
Decoding Tip: If the raw values of latitude and longitude are placed
in integer variables, the actual value can be derived by the
following process:
1. If the highest order bit is set (i.e. the number is a twos
complement negative), then subtract 2 to the power of 34 (the
total number of bits).
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2. Divide the result by 2 to the power of 25 (the number of
fractional bits) to determine the final value.
The same principle can be applied when decoding altitude values,
except with different powers of 2 (30 and 8 respectively).
The latitude and longitude uncertainty are both 18, which gives an
uncertainty value using the formula from Section 2.3.1 of
0.0009765625. Therefore, the decoded latitudes is -33.8570094705 +/-
0.0009765625 (or the range from -33.857986033 to -33.856032908) and
the decoded longitude is 151.2152005136 +/- 0.0009765625 (or the
range from 151.2142239511 to 151.2161770761).
The encoded altitude of 000000000000000010000110110011 decodes to
33.69921875. The encoded uncertainty of 15 gives a value of 64,
therefore the final uncertainty is 33.69921875 +/- 64 (or the range
from -30.30078125 to 97.69921875).
3.2.1. GML Representation of Decoded Locations
The GML representation of a decoded DHCP option depends on what
fields are specified. Uncertainty can be omitted from all of the
respective fields, and altitude can also be absent.
In the absence of uncertainty information, the value decoded from the
DHCP form can be expressed as a single point. If the point includes
altitude, it uses a three dimensional CRS, otherwise it uses a two
dimensional CRS.
The following GML shows the value decoded in the previous example as
a point in a three dimensional CRS:
-33.8570094705 151.2152005136 33.69921875
If all fields are included along with uncertainty, the shape
described is a rectangular prism.
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The following example uses all of the decoded information from the
previous example:
-33.857986033 151.2142239511 -30.30078125
-33.857986033 151.2161770761 -30.30078125
-33.856032908 151.2161770761 -30.30078125
-33.856032908 151.2142239511 -30.30078125
-33.857986033 151.2142239511 -30.30078125
128
Note that this representation is only appropriate if the uncertainty
is sufficiently small. [I-D.thomson-geopriv-geo-shape] recommends
that distances between polygon vertices be kept short. A GML
representation like this one is only appropriate where uncertainty is
less than 1 degree (an encoded value of 9).
If altitude or altitude uncertainty is not specified, the shape is
described as a rectangle using the "gml:Polygon" shape. If altitude
is available, a three dimensional CRS is used, otherwise a two
dimensional CRS is used.
For Datum values of 2 or 3 (NAD83), there is no available CRS URN
that covers three dimensional coordinates. By necessity, locations
described in these datums can be represented by two dimensional
shapes only; that is, either a two dimensional point or a polygon.
If the altitude type is 2 (floors), then this value can be
represented using a civic address object
[I-D.ietf-geopriv-revised-civic-lo] that is linked to the geodetic
object.
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4. Security Considerations
Security considerations related to the privacy of location
information as discussed in the GEOPRIV documents RFC 3693 [RFC3693]
and RFC 3694 [RFC3694] apply.
Where critical decisions might be based on the value of this option,
DHCPv4 authentication in RFC 3118 [RFC3118] SHOULD be used to 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 option. Thus, usage of the
option on networks without access restrictions or network-layer or
link-layer privacy protection is NOT RECOMMENDED.
To minimize the unintended exposure of location information, the
GEOCONF_GEODETIC option SHOULD be returned by DHCPv4 servers only
when the DHCPv4 client has included this option in its 'parameter
request list' (RFC 2131 [RFC2131], Section 3.5). Similarly, the
OPTION_GEOCONF_GEODETIC option SHOULD be returned by DHCPv6 servers
only when the DHCPv6 client has included this option in its
OPTION_ORO.
After initial location information has been introduced, it MUST be
afforded the protections defined in RFC 3694 [RFC3694]. Therefore,
location information SHOULD NOT be sent from a DHCP client to a DHCP
server. If a client decides to send location information to the
server, it is implicitly granting that server unlimited retention and
distribution permissions.
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5. IANA Considerations
The IANA has registered DHCPv4 and DHCPv6 option codes for the
Geodetic Location option (GEOCONF_GEODETIC and
OPTION_GEOCONF_GEODETIC, respectively).
The IANA has established two registries for GeoConf items: the
altitude type field (Section 2.4) and the datum field (Section 2.5).
New values for both these registries require "Standards Action"
[RFC2434].
Values registered in the Altitude Type registry are:
AT = 0 denotes that no altitude information is present
AT = 1 denotes an altitude in meters as defined by the associated
datum
AT = 2 denotes an altitude in floors within the context of a
building
Values registered in the Datum registry are:
Datum = 1 denotes the WGS datum as defined by the EPSG/OGP with the
code 4326 (with no altitude) or 4979 (with altitude)
Datum = 2 denotes the NAD83 datum for latitude and longitude as
defined by the EPSG/OGP with the code of 4269 (no altitude); the
corresponding vertical datum is the North American Vertical Datum
of 1988 (NAVD88) as defined by the EPSG/OGP with the code of 5703
Datum = 3 denotes the NAD83 datum for latitude and longitude as
defined by the EPSG/OGP with the code of 4269 (no altitude); the
corresponding vertical datum is the Mean Lower Low Water (MLLW)
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6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP
Messages", RFC 3118, June 2001.
[RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C.,
and M. Carney, "Dynamic Host Configuration Protocol for
IPv6 (DHCPv6)", RFC 3315, July 2003.
6.2. Informative References
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC3694] Danley, M., Mulligan, D., Morris, J., and J. Peterson,
"Threat Analysis of the Geopriv Protocol", RFC 3694,
February 2004.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[RFC4676] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCPv4 and DHCPv6) Option for Civic Addresses
Configuration Information", RFC 4676, October 2006.
[I-D.thomson-geopriv-geo-shape]
Thomson, M., "Geodetic Shapes for the Representation of
Uncertainty in PIDF-LO",
draft-thomson-geopriv-geo-shape-02 (work in progress),
May 2006.
[I-D.ietf-geopriv-revised-civic-lo]
Thomson, M. and J. Winterbottom, "Revised Civic Location
Thomson & Winterbottom Expires June 16, 2007 [Page 16]
Internet-Draft DHCP Geodetic December 2006
Format for PIDF-LO",
draft-ietf-geopriv-revised-civic-lo-04 (work in progress),
September 2006.
[OGP.Geodesy]
OGP, "International Association of Oil & Gas Producers
(OGP) Geodesy Resources",
.
[WGS84] US National Imagery and Mapping Agency, "Department of
Defense (DoD) World Geodetic System 1984 (WGS 84), Third
Edition", NIMA TR8350.2, January 2000.
[OGC.GML-3.1.1]
Cox, S., Daisey, P., Lake, R., Portele, C., and A.
Whiteside, "Geographic information - Geography Markup
Language (GML)", OpenGIS 03-105r1, April 2004,
.
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Internet-Draft DHCP Geodetic December 2006
Authors' Addresses
Martin Thomson
Andrew
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2915
Email: martin.thomson@andrew.com
URI: http://www.andrew.com/
James Winterbottom
Andrew
PO Box U40
Wollongong University Campus, NSW 2500
AU
Phone: +61 2 4221 2938
Email: james.winterbottom@andrew.com
URI: http://www.andrew.com/
Thomson & Winterbottom Expires June 16, 2007 [Page 18]
Internet-Draft DHCP Geodetic December 2006
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