Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information
draft-ietf-geopriv-dhcp-lci-option-03

Internet Engineering Task Force                                 J. Polk
Internet Draft                                            J. Schnizlein
Expiration: June 8th, 2004                                   M. Linsner
File: draft-ietf-geopriv-dhcp-lci-option-03.txt           Cisco Systems

            Dynamic Host Configuration Protocol Option for
          Coordinate-based Location Configuration Information 

                           December 8th, 2003 

Status of this Memo 

   This document is an Internet-Draft and is in full conformance with 
   all provisions of Section 10 of RFC2026. 

   Internet-Drafts are working documents of the Internet Engineering 
   Task Force (IETF), its areas, and its working groups.  Note that 
   other groups may also distribute working documents as Internet-
   Drafts. 

   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents
   at any time.  It is inappropriate to use Internet-Drafts as 
   reference material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at 
   http://www.ietf.org/ietf/1id-abstracts.txt 

   The list of Internet-Draft Shadow Directories can be accessed 
   at http://www.ietf.org/shadow.html. 

Abstract 

   This document specifies a Dynamic Host Configuration Protocol Option
   for the coordinate-based geographic location of the client.  The 
   Location Configuration Information (LCI) includes latitude, 
   longitude, and altitude, with resolution indicators for each.  The 
   reference datum for these values is also included.

Polk & Schnizlein & Linsner                                    [Page 1]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .  2
       1.1  Conventions  . . . . . . . . . . . . . . . . . . . . . .  3
       1.2  Motivation . . . . . . . . . . . . . . . . . . . . . . .  3
       1.3  Rationale  . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Location Configuration Information (LCI) Elements . . . . . .  4
       2.1 Elements of the Location Configuration Information  . . .  5
   3.  Security Considerations   . . . . . . . . . . . . . . . . . .  8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  8
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  9
   Appendix Calculations of Imprecision possible with the DHC LCI  .  9
       A.1 LCI of "White House" (Example 1)  . . . . . . . . . . . .  9
       A.2 LCI of "Sears Tower" (Example 2)  . . . . . . . . . . . . 12
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . 12
   7.  Informational References  . . . . . . . . . . . . . . . . . . 13
   8.  Author Information  . . . . . . . . . . . . . . . . . . . . . 13

1.  Introduction

   This document specifies a Dynamic Host Configuration Protocol [1] 
   Option for coordinate-based geographic location of the client, to be 
   provided by the server. 

   The DHCP server is assumed to have determined the location from the 
   Circuit-ID Relay Agent Information Option (RAIO) defined (as SubOpt 
   1) in [2].  In order to translate the circuit (switch port 
   identifier) into a location, the DHCP server is assumed to have 
   access to a service that maps from circuit-ID to the location at 
   which the circuit connected to that port terminates in the building;
   for example, the location of the wall jack.

   An important feature of this specification is that after the 
   relevant DHC exchanges have taken place, the location information 
   is stored on the end device rather than somewhere else, where 
   retrieving it might be difficult in practice.

   Another important feature of this LCI is its inclusion of a 
   resolution parameter for each of the dimensions of location. 
   Because this resolution parameter need not apply to all dimensions 
   equally, a resolution value is included for each of the 3 location 
   elements. 

   This resolution method provides a natural ability for the device to 
   hide from the center point of the bounding area as this resolution 
   method is determined via the inherent effects of binary 
   representation; or, this resolution mechanism could be used to 
   define a geographic area.  This would be useful when a group of 
   clients would want to be known as the same geo-location, possibly 
   all users in a room of a building would use the same LCI value.  

Polk & Schnizlein & Linsner                                    [Page 2]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   Then the using application could use that value as a key for lookup 
   in another data source.  This is similar to one of the mechanisms 
   utilized in the North American E911 systems today.

   Resolution does not define how Geographic Privacy policy should 
   relate to precision.
  
   The resulting location information using this resolution method is a
   small fixed length Configuration Information that can be easily 
   carried in protocols, such as DHCP, which have limited packet size 
   because this LCI is only 18 bytes long.

   Finally, the appendix this document provides some arithmetic 
   examples of the implication of different resolution values on the 
   La/Lo/Alt. 

1.1  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [3].

1.2 Motivation

   As applications such as IP Telephony are replacing conventional 
   telephony, users are expecting the same (or greater) level of 
   services with the new technology.  One service offered by 
   conventional telephony that is missing, in any standardized fashion,
   within IP Telephony is for a user to be automatically located by 
   emergency responders, in a timely fashion, when the user summons 
   help (by dialing 911 in North America, for example).  Unless strict 
   administrative rules are followed, the mobility of a wired Ethernet 
   device within a campus negates any opportunity for an emergency 
   responder to locate the device with any degree of expediency.  Users
   do not want to give up the mobility IP Telephony offers.  Informing 
   the host device of its geo-location at host configuration time will 
   allow the device to utilize this geo-location information to inform 
   others of it's current geo-location, if the user and/or application 
   so desires.

   The goal of this option is to enable a wired Ethernet host to 
   obtain its location, which it could provide to an emergency 
   responder, as one example. 

   Wireless hosts can utilize this option to gain knowledge of the 
   location of the radio access point used during host configuration, 
   but would need some more exotic mechanisms, maybe GPS, or maybe a 
   future DHCP option, which includes a list of geo-locations like that
   defined here, containing the locations of the radio access points 

Polk & Schnizlein & Linsner                                    [Page 3]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   that are close to the client. 

1.3 Rationale

   Within the LCI described here, Latitude and Longitude are 
   represented in fixed-point 2s-complement binary degrees, for the 
   economy of a smaller option size compared to a string encoding of 
   digits in [7].  The integer parts of these fields are 9 bits long to
   accommodate +/- 180 degrees. The fractional part is 25 bits long, 
   better than the precision of 7 decimal digits.  Each parameter is 40
   bits total, in length.

   Altitude is determined by the Altitude Type (AT) indicated by the 
   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-
   complement fixed-point with 8 bits of fraction.  Additional 
   Altitude Types MAY be assigned by IANA.  The "floors" Altitude Type 
   is provided because altitude in meters may not be known within a 
   building, and a floor indication may be more useful. 

   GPS systems today can use WGS84 for horizontal and vertical datums, 
   [6] 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 
   sub-field accommodates the desire by some to easily adjust 
   the precision of a reported location.  Contents beyond the claimed 
   resolution MAY be randomized to obscure greater precision that might
   be available.

2.  DHC Location Configuration Information Elements 

   DHCP is a binary Protocol; using protocols of LCI are likely to be 
   text based. Since most coordinate systems translate fairly easily 
   between binary-based and text-based location output (even emergency 
   services within the US), translation/conversion is a non-issue with 
   DHCP's binary format. 

   This binary format provides a fortunate benefit in a mechanism for 
   making a true/correct location coordinate imprecise.  It further 
   provides the capability to have this binary representation be 
   deterministically imprecise.

Polk & Schnizlein & Linsner                                    [Page 4]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   The LCI format 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    |      16       |   LaRes   |     Latitude      +
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Latitude (cont'd)              |    LoRes  |   +
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                             Longitude                         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   AT  |   AltRes  |                Altitude                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Alt (cont'd) |     Datum     |                                
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                                

2.1 Elements of the Location Configuration Information

   Code TBD: The code for this DHCP option.

   16:       The length of this option is 16 bytes.

   LaRes:    Latitude resolution. 6 bits indicating the number 
             of valid bits in the fixed-point value of Latitude. 

   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 not be considered valid and might be purposely false, or 
   zeroed by the sending.

   The examples below in section 4.0, are to illustrate that a smaller 
   value in the resolution field increases the area within which the 
   device is located). 

   LaRes does not define how Geographic Privacy policy should relate to
   precision.

   Values of resolution above decimal 34 are Undefined and reserved 
   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
             and 25 bits of fraction. Latitude SHOULD be normalized to 
             within +/- 90 degrees.  Positive numbers are north of the 
             equator and negative numbers are south of the equator. 

   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 
   section 4.0).  A value of 34 in the LaRes field indicates a 
   precision of about 3.11 mm in Latitude at the equator.

Polk & Schnizlein & Linsner                                    [Page 5]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   LoRes:    Longitude resolution. 6 bits indicating the number of 
             valid bits in the fixed-point value of Longitude. 
             
   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 not be considered valid and might be purposely false, or 
   zeroed by the sending. 

   LoRes does not define how Geographic Privacy policy should relate to
   precision.

             Values above decimal 34 are undefined and reserved.

   Longitude:  a 34 bit fixed point value consisting of 9 bits of 
             integer and 25 bits of fraction. Longitude SHOULD be 
             normalized to within +/- 180 degrees.  Positive values are
             East of the prime meridian and negative (2s complement) 
             numbers are West of the prime meridian. 

   A value of 2 in the LoRes field indicates precision of no greater 
   than 1/6th that of the globe (see first example in section 4.0).  A 
   value of 34 in the LoRes field indicates a precision of about 
   2.42 mm in longitude (at the equator).  Because lines of longitude 
   converge at the poles, the distance is smaller (better precision) 
   for locations away from the equator.

   Altitude: A 30 bit value defined by the AT field

   AltRes:   Altitude resolution. 6 bits indicating the number of valid
             bits in the altitude.  Values above 30 (decimal) are 
             undefined and reserved. 

   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 
                 8-bit fraction

   If AT = 1, an AltRes value 0.0 would indicate unknown altitude. 
   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 
                 8-bit fraction

   AT = 2 for Floors enables representing altitude in a form more 
   relevant in buildings which have different floor-to-floor 

Polk & Schnizlein & Linsner                                    [Page 6]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   dimensions.  An altitude coded as AT=2, AltRes = 30, and Altitude = 
   0.0 is meaningful even outside a building, and represents ground 
   level at the given latitude and longitude.  Inside a building, 0.0 
   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.

   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 LCI Altitude Types(s) to be defined for use via
   this DHC Option MUST be done through a Standards Track RFC.

   Datum: The Map Datum used for the coordinates given in this Option

   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 256 possibilities, of which 3 are to be 
   registered with IANA by this document (all derived from 
   specification in [5]):

      1: WGS 84  (Geographical 3D) - World Geodesic System 1984, CRS 
                 Code 4327, Prime Meridian Name: Greenwich

      2: NAD83 - North American Datum 1983, CRS Code 4269, Prime 
                 Meridian Name: Greenwich; The associated vertical 
                 datum is the North American Vertical Datum of 1988 
                 (NAVD88)

Polk & Schnizlein & Linsner                                    [Page 7]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

                 This datum pair to be used when referencing 
                 locations on land, not near tidal water (which would 
                 use Datum = 3 below)

      3: NAD83 - North American Datum 1983, CRS Code 4269, Prime 
                 Meridian Name: Greenwich; The associated vertical 
                 datum is Mean Lower Low Water (MLLW)

                 This datum pair to be used when referencing 
                 locations on water/sea/ocean

   Any additional LCI datum(s) to be defined for use via this DHC
   Option MUST be done through a Standards Track RFC.

3.  Security Considerations

   Where critical decisions might be based on the value of this 
   GeoLoc option, DHCP authentication in [4] 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 LCI.

   To minimize the unintended exposure of location information, the LCI
   option SHOULD be returned by DHCP servers only when the DHCP client 
   has included this option in its 'parameter request list' (section 
   3.5 [1]).

   When implementing a DHC server that will serve clients across an 
   uncontrolled network, one should consider the potential security 
   risks.
 

4.  IANA Considerations

   IANA has assigned a DHCP option code of TBD for the GeoLoc option 
   defined in this document. 

   The GeoLoc Option defines two fields for which IANA is to maintain 
   a registry: The Altitude (AT) field (see Section 2) and the Datum 
   field (see Section 2).  The datum indicator MUST include 
   specification of both horizontal and vertical datum.  New values 
   for the Altitude (AT) field are assigned through "Standards Action" 
   [RFC 2434]. The initial values of the Altitude registry are as 
   follows:

   AT = 1  meters of Altitude defined by the vertical datum 
           specified. 

Polk & Schnizlein & Linsner                                    [Page 8]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   AT = 2  building Floors of Altitude. 

   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 the vertical datum

   Datum = 2 denotes the vertical datum NAD83 as defined by the 
           EPSG as their CRS Code 4269; North American Vertical Datum 
           of 1988 (NAVD88) is the associated vertical datum for NAD83

   Datum = 3 denotes the vertical datum NAD83 as defined by the 
           EPSG as their CRS Code 4269; Mean Lower Low Water (MLLW) is 
           the associated vertical datum for NAD83

   Any additional LCI datum(s) to be defined for use via this DHC
   Option MUST be done through a Standards Track RFC.

5.  Acknowledgements

   The authors would like to thank Patrik Falstrom, Ralph Droms, Ted 
   Hardie, Jon Peterson and Nadine Abbott for their inputs and 
   constructive comments regarding this document.  Additionally, the 
   authors would like to thank Greg Troxel for the education on 
   vertical datums, and to Carl Reed.

Appendix: Calculations of Imprecision possible with the DHC LCI

   The following examples for two different locations demonstrate 
   how the Resolution values for Latitude, Longitude and Altitude 
   can be used.  In both examples the geo-location values were derived
   from maps using the WGS84 map datum, therefore in these examples, 
   the datum field would have a value = 1 (00000001, or 0x01).

A.1 Location Configuration Information of "White House" (Example 1)

   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 easily identifiable location on our planet.

   Postal Address:
     White House
     1600 Pennsylvania Ave. NW
     Washington, DC 20006

   Standing on the sidewalk, north side of White House, between 
   driveways.

Polk & Schnizlein & Linsner                                    [Page 9]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   Latitude 38.89868 degrees North (or +38.89868 degrees)
      Using 2s complement, 34 bit fixed point, 25 bit fraction 
      Latitude = 0x04dcc1fc8, 
      Latitude = 0001001101110011000001111111001000

   Longitude 77.03723 degrees West (or -77.03723 degrees)
      Using 2s complement, 34 bit fixed point, 25 bit fraction 
      Longitude = 0xf65ecf031, 
      Longitude = 1101100101111011001111000000110001

   Altitude 15

   In this example we are not inside a structure, therefore we will 
   assume an altitude value of 15 meters, interpolated from the US 
   Geological survey map, Washington West quadrangle.

     AltRes = 30, 0x1e, 011110
     AT = 1, 0x01, 000001
     Altitude = 15, 0x0F00, 00000000000000000000000001111100000000

   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 
       geo-location region that is north of the equator and extends 
       from -1 degree (west of the meridian) to -128 degrees.  This 
       would include the area from approximately 600km south of 
       Saltpond, Ghana, due north to the North Pole and approximately 
       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,
       approximately 20 million square nautical miles (nm).

   If: LaRes is expressed as value 3 (0x03 or 000011) and LoRes is 
       expressed as value 3, (0x03 or 000011) then it would describe a 
       geo-location area that is north from the equator to 63 degrees 
       north, and -65 degrees to -128 degrees longitude.  This area 
       includes south of a line from Anchorage, AL to eastern Nunavut, 
       CN. and from the Amazons of northern Brazil to approximately 
       4400km south-southwest of Los Angeles, CA.  This area would 
       include North America, Central America, and parts of Venezuela 
       and Columbia, except portions of Alaska and northern and eastern
       Canada, approximately 10 million square nm.

   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 
       geo-location area that is latitude 32 north of the equator to 
       latitude 48 and extends from -64 degrees to -80 degrees 
       longitude.  This is approximately an east-west boundary of a 
       time zone, an area of approximately 700,000 square nm.

   If: LaRes is expressed as value 9 (0x09 or 001001) and LoRes is 
       expressed as value 9 (0x09 or 001001), which includes all the 

Polk & Schnizlein & Linsner                                   [Page 10]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

       integer bits, then it would describe a geo-location area that is
       latitude 38 north of the equator to latitude 39 and extends from
       -77 degrees to -78 degrees longitude.  This is an area of 
       approximately 9600 square km (111.3km x 86.5km).

   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
       geo-location area that is latitude 38.8984375 north to latitude 
       38.9003906 and extends from -77.0390625 degrees to -77.0371094 
       degrees longitude.  This is an area of approximately 36,600 
       square meters (169m x 217m).

   If: LaRes is expressed as value 22 (0x16 or 010110) and LoRes is 
       expressed as value 22 (0x16 or 010110), then it would describe a
       geo-location area that is latitude 38.896816 north to latitude 
       38.8985596 and extends from -77.0372314 degrees to -77.0371094 
       degrees longitude.  This is an area of approximately 143 square 
       meters (10.5m x 13.6m).

   If: LaRes is expressed as value 28 (0x1c or 011100) and LoRes is 
       expressed as value 28 (0x1c or 011100), then it would describe a
       geo-location area that is latitude 38.8986797 north to latitude 
       38.8986816 and extends from -77.0372314 degrees to -77.0372296 
       degrees longitude.  This is an area of approximately 339 square 
       centimeters (20.9cm x 16.23cm).

   If: LaRes is expressed as value 30 (0x1e or 011110) and LoRes is 
       expressed as value 30 (0x1e or 011110), then it would describe a
       geo-location area that is latitude 38.8986797 north to latitude 
       38.8986802 and extends from -77.0372300 degrees to -77.0372296 
       degrees longitude.  This is an area of approximately 19.5 square
       centimeters (50mm x 39mm).

   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
       geo-location area that is latitude 38.8986800 north to latitude 
       38.8986802 and extends from -77.0372300 degrees to -77.0372296 
       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 
   responders in North America via their NENA Model Legislation [8], 
   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 
   to latitude 38.8988616 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 is very close to the 7000 
   square feet asked for by NENA.  In this example a service 
   provider could enforce that a device send a Location 
   Configuration Information with this minimum amount of resolution 
   for this particular location when calling emergency services.

Polk & Schnizlein & Linsner                                   [Page 11]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

A.2 Location Configuration Information of "Sears Tower" (Example 2)

   Postal Address:
   Sears Tower
   103rd Floor
   233 S. Wacker Dr.
   Chicago, IL  60606

   Viewing the Chicago area from the Observation Deck of the Sears 
   Tower.

   Latitude 41.87884 degrees North (or +41.87884 degrees)
   Using 2s complement, 34 bit fixed point, 25 bit fraction 
   Latitude = 0x053c1f751, 
   Latitude = 0001010011110000011111011101010001

   Longitude 87.63602 degrees West (or -87.63602 degrees)
   Using 2s complement, 34 bit fixed point, 25 bit fraction 
   Longitude = 0xf50ba5b97, 
   Longitude = 1101010000101110100101101110010111

   Altitude 103

   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 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 accurately represent the floor of the 
   structure where we are located.

   AltRes = 30, 0x1e, 011110
   AT = 2, 0x02, 000010
   Altitude = 103, 0x00006700, 000000000000000110011100000000

   For the accuracy of the latitude and longitude, the best 
   information 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 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 is latitude 41.8769531 to latitude 
   41.8789062 and extends from -87.6367188 degrees to -87.6347657 
   degrees longitude.  This is an area of approximately 373412 
   square feet (713.3 ft. x 523.5 ft.).

6.  Normative References

 [1] Droms R., "Dynamic Host Configuration Protocol", RFC 2131, 
     March 1997

Polk & Schnizlein & Linsner                                   [Page 12]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

 [2] Patrick M., "DHCP Relay Agent Information Option", RFC 3046, 
     January 2001

 [3] Bradner S., "Key words for use in RFCs to Indicate Requirement 
     Levels", RFC 2119, March 1997

 [4] Droms R., "Authentication for DHCP Messages", RFC 3118, June 
     2001

 [5] European Petroleum Survey Group, http://www.epsg.org/ and 
     http://www.ihsenergy.com/epsg/geodetic2.html

 [6] 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/

7.  Informational References

 [7] Farrell C., Schulze M., Pleitner S. and Baldoni D., "DNS 
     Encoding of Geographical Location", RFC 1712, November 1994.

 [8] 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)

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

  Intellectual Property Statement

   The IETF takes no position regarding the validity or scope of any 
   intellectual property or other rights that might be claimed to 
   pertain to the implementation or use of the technology described in 

Polk & Schnizlein & Linsner                                   [Page 13]

Internet Draft       DHCP Option for Coordinate LCI       Dec 8th, 2003

   this document or the extent to which any license under such rights 
   might or might not be available; neither does it represent that it 
   has made any effort to identify any such rights. Information on the 
   IETF's procedures with respect to rights in standards-track and 
   standards-related documentation can be found in BCP-11. Copies of 
   claims of rights made available for publication and any assurances 
   of licenses to be made available, or the result of an attempt made 
   to obtain a general license or permission for the use of such 
   proprietary rights by implementers or users of this specification 
   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any 
   copyrights, patents or patent applications, or other proprietary 
   rights which may cover technology that may be required to practice 
   this standard. Please address the information to the IETF Executive 
   Director.

  Full Copyright Statement

   "Copyright (C) The Internet Society (February 23rd, 2001). 
   All Rights Reserved.

   This document and translations of it may be copied and furnished 
   to others, and derivative works that comment on or otherwise 
   explain it or assist in its implementation may be prepared, 
   copied, published and distributed, in whole or in part, without 
   restriction of any kind, provided that the above copyright notice 
   and this paragraph are included on all such copies and derivative 
   works.  However, this document itself may not be modified in any 
   way, such as by removing the copyright notice or references to 
   the Internet Society or other Internet organizations, except as 
   needed for the purpose of developing Internet standards in which 
   case the procedures for copyrights defined in the Internet 
   Standards process must be followed, or as required to translate 
   it into languages other than English.

   The limited permissions granted above are perpetual and will not 
   be revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on 
   an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET 
   ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR 
   IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE 
   OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY 
   IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR 
   PURPOSE."

   The Expiration date for this Internet Draft is:

   June 8th, 2004

Polk & Schnizlein & Linsner                                   [Page 14]