\documentclass[11pt]{article}
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\author{H. Schulzrinne}
\shorttitle{DHCP Option for Civil Addresses}
\filename{draft-ietf-geopriv-dhcp-civil-00}
\title{DHCP Option for Civil Location}
\wg{}
\expires{December 2003}
\address{Columbia U.}
\pubdate{\today}
\input{../defs}

\begin{document}
\maketitle
\tableofcontents

\begin{abstract}
This document specifies a Dynamic Host Configuration Protocol option for
the civil (country, street and community) location of the client. 
\end{abstract}

\section{Terminology}
\label{sec:terminology}

In this document, the key words ``{\MUST}'', ``{\MUSTNOT}'',  
``{\REQUIRED}'', ``{\SHALL}'', ``{\SHALLNOT}'', ``{\SHOULD}'',
``{\SHOULDNOT}'', ``{\RECOMMENDED}'', ``{\MAY}'', and ``{\OPTIONAL}''
are to be interpreted as described in RFC 2119 \citenorm{rfc2119} and
indicate requirement levels for compliant implementations.

\section{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. 

\motivation{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 \citeinform{draft-polk-dhcp-geo-loc-option} describes a
DHCP \citenorm{rfc2131} 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.  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) \citenorm{NENA0201:ALI}.  It is anticipated
that other countries can reuse many of the data elements.

\section{Format of the DHCP Civil Location Option}

\begin{verbatim}
      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                ... 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\end{verbatim}

Each civil address element has the following format:

\begin{verbatim}
      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                 ...
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
\end{verbatim}

\begin{description}
\item[Code TBD:] The code for this DHCP option is TBD by IANA.

\item[N:] The length of this option is variable.

\item[Countrycode:] The two-letter ISO 3166 country code in capital
ASCII letter, e.g., DE or US.

\item[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)
{\SHOULDNOT} be used unless it is known that the DHCP client is in close
physical proximity to the server or network element.

\motivation{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.}

\item[CAtype:] A one-octet descriptor of the data civil address value.

\item[CAlength:] The length, in octets, of the CAvalue, not including
the CAlength field itself. Data {\SHOULD} be encoded in uppercase.

\item[CAvalue:] The civil address value, encoded as UTF-8, and written
in uppercase letters where applicable.

\end{description}

\section{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.  

\begin{flushleft}
\begin{tabular}{rlll}
CAtype & label & description\\
\hline
 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\\
\end{tabular}
\end{flushleft}

For specific countries, the administrative sub-divisions are described
below.

\begin{description}
\item[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 \citenorm{USPS0011:Postal}, Appendix B; A2=county (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.

\item[CA:] The mapping to NENA designations is shown in parentheses.
A1=province (STA), A2=county (CNA), A3=city or town (MCN).

\item[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).

\item[DE:] A1=state (Bundesstaat); A2=county (Kreis); A3=city (Stadt,
Gemeinde); A6=street (Strasse).

\end{description}

Additional CA types appear in many countries and are simply omitted
where they are not used:

\begin{flushleft}
\begin{tabular}{rlll}
CAtype & NENA & description & examples\\
\hline
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\\
25 &     & type of place\\
26 &     & floor\\
27 &     & room number\\ 
\end{tabular}
\end{flushleft}

The CA types labeled in the second column correspond to items from the
NENA ``Recommended Formats \& Protocols For ALI Data Exchange, ALI
Response \& GIS Mapping'' \citenorm{NENA0201:ALI}, but are applicable to
most countries.  The ``NENA'' column refers to the data dictionary name
in Exhibit 18 of \citenorm{NENA0201:ALI}. 

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
Publication 28 \citenorm{USPS0011:Postal}, Appendix C, {\SHOULD} be
used.

The ``type of place'' item indicates whether the location is a 'home',
'office' or 'public', using text strings.  Additional text strings can
be registered with IANA and correspond to the ``placetype'' element in
\citenorm{draft-schulzrinne-simple-rpids}. 

The ``privacy'' object can have the string values 
\begin{description}
\item[public:]  Others may be able to see or hear the communications.

\item[private:] Inappropriate individuals are not likely to see or hear
the communications.

\item[quiet:]  The location is a place such as a library,
restaurant, place-of-worship, or theater that discourages
noise, conversation and other distractions.
\end{description}

Additional string values can be registered with IANA using the registry
established in \citenorm{draft-schulzrinne-simple-rpids}.

The DHCP long-options mechanism described in RFC 3396 \citenorm{rfc3396}
{\MUST} be used if the civil address option exceeds the maximum DHCP
option size of 255 octets.

\section{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 \citenorm{rfc3118} {\SHOULD} be used
to protect the integrity of the DHCP options.

\section{Acknowledgments}

Rohan Mahy and Stefan Berger provided helpful comments.

\section{References}
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\section{Authors' Addresses}

\begin{flushleft}
Henning Schulzrinne\\
Dept. of Computer Science\\
Columbia University\\
1214 Amsterdam Avenue\\
New York, NY 10027\\
USA\\
electronic mail: \textsf{schulzrinne@cs.columbia.edu}
\end{flushleft}

\copyrightnotice
\end{document}
