Internet Engineering Task Force
Internet Draft H. Schulzrinne
Columbia U.
draft-schulzrinne-geopriv-dhcp-civil-01.txt
February 19, 2003
Expires: August 2003
DHCP Option for Civil Location
STATUS OF THIS MEMO
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
Abstract
This document specifies a Dynamic Host Configuration Protocol option
for the civil (country, street and community) location of the client.
1 Terminology
In this document, the key words "MUST", "MUST NOT", "REQUIRED",
"SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY",
and "OPTIONAL" are to be interpreted as described in RFC 2119 [1] and
indicate requirement levels for compliant implementations.
2 Introduction
Many end system services can benefit by knowing the approximate
location of the end device. In particular, IP telephony devices need
to know their location to contact the appropriate emergency response
agency and to be found by emergency responders.
There are two common ways to identify the location of an object,
either through geospatial coordinates or by so-called civil
coordinates. Geospatial coordinates indicate longitude, latitude and
altitude, while civil coordinates indicate a street address.
This is commonly, but not necessearily, closely related to
the postal address, used by the local postal service to
deliver mail. However, not all postal addresses correspond
to street addresses. For example, the author's address is a
postal address that does not appear on any street or
building sign. Naturally, post office boxes would be
unsuitable for the purposes described here.
A related draft [7] describes a DHCP [2] option for conveying
geospatial information to a device. This draft describes how DHCP can
be used to convey the civil location to devices. Both can be used
simultaneously, increasing the chance to deliver accurate and timely
location information to emergency responders.
End systems that obtain location information via the mechanism
described here then use other protocol mechanisms to communicate this
information to the emergency call center.
Civil information is useful since it often provides additional,
human-usable information particularly within buildings. Also,
compared to geospatial information, it is readily obtained for most
occupied structures and can often be interpreted even if incomplete.
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
For example, for many large university or corporate campuses,
geocoding information to building and room granularity may not be
readily available.
Unlike geospatial information, the format for civil information
differs from country to country. Thus, this draft establishes an IANA
registry for civil location data fields. The initial set of data
fields is derived from standards published by the United States
National Emergency Numbering Association (NENA) [3]. It is
anticipated that other countries can reuse many of the data elements.
3 Format of the DHCP Civil Location Option
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 | N | Countrycode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| What | civil address elements ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Each civil address element has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CAtype | CAlength | CAvalue ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code TBD: The code for this DHCP option is TBD by IANA.
N: The length of this option is variable.
Countrycode: The two-letter ISO country code in capital ASCII
letter, e.g., DE or US.
What: The 'what' element describes which location the DHCP
refers to. Currently, three options are defined: the
location of the DHCP server (0), the location of the
network element believed to be closest to the client (1) or
the location of the client (2). Option (2) SHOULD be used,
but may not be known. Options (1) and (2) SHOULD NOT be
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
used unless it is known that the DHCP client is in close
physical proximity to the server or network element.
In some cases, the local wiring plant makes it
difficult to ascertain the device location with
certainty. In that case, it is still preferable to
indicate the DHCP server, Ethernet switch or router,
but indicate the uncertainty. This avoids that the
emergency responders try to break into the LAN closet.
CAtype: A one-octet descriptor of the data civil address value.
CAlength: The length, in octets, of the CAvalue, not including
the CAlength field itself. Data SHOULD be encoded in
uppercase.
CAvalue: The civil address value, encoded as UTF-8, and written
in uppercase letters where applicable.
4 Civil Address Components
Since each country has different administrative hierarchies, with
often the same (English) names, this specification adopts a simple
hierarchical notation that is then instantiated for each country. We
assume that five levels are sufficient for sub-national divisions
above the street level.
All elements are OPTIONAL and can appear in any order. Abbreviations
do not need a trailing period.
CAtype label description
___________________________________________________________________________
1 A1 national subdivisions (state, region, province, prefecture)
2 A2 county, parish, gun (JP), district (IN)
3 A3 city, township, shi (JP)
4 A4 city division, borough, city district, ward, chou (JP)
5 A5 neighborhood, block
6 A6 street
For specific countries, the administrative sub-divisions are
described below.
US: The mapping to NENA designations is shown in parentheses.
A1=state (STA), using the the two-letter state and
possession abbreviations recommended by the United States
Postal Service Publication 28 [4], Appendix B; A2=county
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
(CNA); A3=civil community name (city or town) (MCN);
A6=street (STN). A4 and A5 are not used. The civil
community name (MCN) reflects the political boundaries.
These may differ from postal delivery assignments for
historical or practical reasons.
CA: The mapping to NENA designations is shown in parentheses.
A1=province (STA), A2=county (CNA), A3=city or town (MCN).
JP: A1=metropolis (To, Fu) or prefecture (Ken, Do); A2=city
(Shi) or rural area (Gun); A3=ward (Ku) or village (Mura);
A4=town (Chou or Machi); A5=city district (Choume);
A6=block (Banchi or Ban).
DE: A1=state (Bundesstaat); A2=county (Kreis); A3=city (Stadt,
Gemeinde); A6=street (Strasse).
Additional CA types appear in many countries and are simply omitted
where they are not used:
CAtype NENA description examples
___________________________________________________________________________
16 PRD leading street direction N
17 POD trailing street suffix SW
18 STS street suffix AVE, PLATZ
19 HNO house number 123
20 HNS house number suffix A, 1/2
21 LMK landmark or vanity address SHADELAND CRESCENT APTS
22 LOC additional location information APT 17
23 NAM name (residence and office occupant) JOE'S BARBERSHOP
24 ZIP postal/zip code 10027-1234
These CA types correspond to items from the NENA "Recommended Formats
& Protocols For ALI Data Exchange, ALI Response & GIS Mapping" [3],
but are applicable to most countries. The "NENA" column refers to the
data dictionary name in Exhibit 18 of [3].
The NAM object is used to aid user location ("Joe Miller" "Alice's
Dry Cleaning"). It does not identify the person using a
communications device, but rather the person or organization
associated with the address.
For POD and PRD, in English-speaking countries, the abbreviations N,
E, S, W, and NE, NW, SE, SW should be used.
STS designates a street suffix. In the United States (US), the
abbreviations recommended by the United States Postal Service
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
Publication 28 [4], Appendix C, SHOULD be used.
The DHCP long-options mechanism described in RFC 3396 [5] MUST be
used if the civil address option exceeds the maximum DHCP option size
of 255 octets.
5 Security Considerations
The information in this option may be used for a variety of tasks. In
some cases, integrity of the information may be of great importance.
In such cases, DHCP authentication in [6] SHOULD be used to protect
the integrity of the DHCP options.
6 Acknowledgments
Rohan Mahy provided helpful comments.
7 Authors' Addresses
Henning Schulzrinne
Dept. of Computer Science
Columbia University
1214 Amsterdam Avenue
New York, NY 10027
USA
electronic mail: schulzrinne@cs.columbia.edu
8 Normative References
[1] S. Bradner, "Key words for use in RFCs to indicate requirement
levels," RFC 2119, Internet Engineering Task Force, Mar. 1997.
[2] R. Droms, "Dynamic host configuration protocol," RFC 2131,
Internet Engineering Task Force, Mar. 1997.
[3] National Emergency Number Association, "Nena recommended formats
& protocols for ali data exchange, ali response & gis mapping,"
Standard NENA-02-010, NENA, Washington, DC, 2002 Jan.
[4] United States Postal Service, "Postal addressing standards,"
Publication 28, USPS, Washington, DC, Nov. 2000.
[5] T. Lemon and S. Cheshire, "Encoding long options in the dynamic
host configuration protocol (DHCPv4)," RFC 3396, Internet Engineering
Task Force, Nov. 2002.
[6] R. Droms and W. Arbaugh, eds., "Authentication for DHCP
messages," RFC 3118, Internet Engineering Task Force, June 2001.
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Internet Draft DHCP Option for Civil Addresses February 19, 2003
9 Informative References
[7] J. Polk et al., "DHCP option for geographic location," Internet
Draft, Internet Engineering Task Force, Oct. 2002. Work in progress.
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H. Schulzrinne [Page 7]
Table of Contents
1 Terminology ......................................... 2
2 Introduction ........................................ 2
3 Format of the DHCP Civil Location Option ............ 3
4 Civil Address Components ............................ 4
5 Security Considerations ............................. 6
6 Acknowledgments ..................................... 6
7 Authors' Addresses .................................. 6
8 Normative References ................................ 6
9 Informative References .............................. 7
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