Network Working Group H. Schulzrinne
Request for Comments: 4776 Columbia U.
Obsoletes: 4676 November 2006
Category: Standards Track
Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Option
for Civic Addresses Configuration Information
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The IETF Trust (2006).
RFC Editor Note
RFC 4776 is being published to correct an error in the assignment of
the numeric value of the DHCPv6 option-code in RFC 4676 (Section
3.2). This document obsoletes RFC 4676.
Abstract
This document specifies a Dynamic Host Configuration Protocol (DHCPv4
and DHCPv6) option containing the civic location of the client or the
DHCP server. The Location Configuration Information (LCI) includes
information about the country, administrative units such as states,
provinces, and cities, as well as street addresses, postal community
names, and building information. The option allows multiple
renditions of the same address in different scripts and languages.
Schulzrinne Standards Track [Page 1]RFC 4776 DHCP Civic November 2006
Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................5
3. Format of the DHCP Civic Location Option ........................5
3.1. Overall Format for DHCPv4 ..................................5
3.2. Overall Format for DHCPv6 ..................................6
3.3. Element Format .............................................7
3.4. Civic Address Components ...................................7
4. Postal Addresses ...............................................13
5. Example ........................................................14
6. Security Considerations ........................................15
7. IANA Considerations ............................................15
8. References .....................................................16
8.1. Normative References ......................................16
8.2. Informative References ....................................17
Acknowledgements ..................................................17
1. 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 civic
addresses. Geospatial coordinates indicate longitude, latitude, and
altitude, while civic addresses indicate a street address.
The civic address is commonly, but not necessarily, 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.
The term 'civil address' or 'jurisdictional address' is also
sometimes used instead of civic address. This document mainly
supports civic addresses, but allows the postal community name to be
indicated if it differs from the civic name.
A related document [15] describes a DHCPv4 [2] option for conveying
geospatial information to a device. This document describes how
DHCPv4 and DHCPv6 [6] can be used to convey the civic and postal
address to devices. Both geospatial and civic formats can be used
simultaneously, increasing the chance to deliver accurate and timely
Schulzrinne Standards Track [Page 2]RFC 4776 DHCP Civic November 2006
location information to emergency responders. The reader should also
be familiar with the concepts in [11], as many of the protocol
elements below are designed to dovetail with PIDF-LO elements.
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 [9], 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 [10] are in the Security Considerations (Section 6).
End systems that obtain location information via the mechanism
described here then use other protocol mechanisms to communicate this
information to an emergency call center or to convey it as part of
presence information.
Civic 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 civic and postal
information differs from country to country. The initial set of data
fields is derived from standards published by the United States
National Emergency Number Association (NENA) [18] and takes into
account addressing conventions for a number of countries in different
areas of the world. It is anticipated that other countries can reuse
many of the data elements, but the document also establishes an IANA
registry for defining additional civic location data fields.
The same civic and postal address information can often be rendered
in multiple languages and scripts. For example, Korean addresses are
often shown in Hangul, Latin, and Kanji, while some older cities have
multiple language variants (e.g., Munich, Muenchen, and Monaco).
Since DHCPv4 and DHCPv6 do not currently support a mechanism to query
for a specific script or language, the DHCP server SHOULD provide all
common renderings to the client and MUST provide at least the
rendering in the language and script appropriate to the location
indicated. For example, for use in presence information, the target
may be visiting from a foreign country and want to convey the
Schulzrinne Standards Track [Page 3]
RFC 4776 DHCP Civic November 2006
information in a format suitable for watchers in its home country.
For emergency services, the rendering in the local language is likely
to be most appropriate. To provide multiple renderings, the server
repeats sequences of address elements, prefixing each with a
'language' and/or 'script' element (see Section 3.3). The language
and script remain in effect for subsequent elements until overridden
by another language or script element. Since the DHCP client is
unlikely to be the final consumer of the location information, the
DHCP server has to provide all appropriate language and script
versions, which the client then passes on via some other GEOPRIV
using protocol, typically encoded in a presence-based GEOPRIV
location object format [16].
The DHCP server MAY provide location information for multiple
locations related to the target, for example, both the network
element and the network jack itself. This is likely to help in
debugging network problems, for example.
This document calls for various operational decisions. For example,
an administrator has to decide when to provide the location of the
DHCP server or other network elements even if these may be a good
distance away from the client. The administrator must also consider
whether to include both civic and geospatial information if these may
differ. The document does not specify the criteria to be used in
making these choices, as these choices are likely to depend strongly
on local circumstances and need to be based on local, human
knowledge.
A system that works with location information configured by DHCP is
dependent that the administrators of the DHCP systems are careful
enough on a number of fronts, such as:
- if information about one location is provided in multiple forms
(e.g., in multiple languages), is it consistent?
- is the administrator certain that location information is
configured only to systems to which it applies (e.g., not to
systems topologically near, but geographically far)?
- if the location configured is not that of the target but that of a
'nearby' network node or the DHCP server, despite the
recommendation against this practice in Section 3.1, is the
administrator certain that this configuration is geographically
valid?
There are many other considerations in ensuring that location
information is handled safely and promptly for an emergency service
in particular. Those are in the province of the applications which
Schulzrinne Standards Track [Page 4]RFC 4776 DHCP Civic November 2006
make use of the configured location information, and they are beyond
the scope of this document. DHCP configuration SHOULD NOT be used
for emergency services without guidelines on these considerations.
Work on these is under way in the IETF ECRIT working group at the
time of publication of this document.
In addition, if a network provides civic location information via
both DHCPv4 and DHCPv6, the information conveyed by the two protocols
MUST be the same.
As discussed in the Security Considerations (Section 6), the
GEOCONF_CIVIC option SHOULD be returned by DHCPv4 servers only when
the DHCPv4 client has included this option in its 'parameter request
list' (RFC 2131 [2], Section 3.5). Similarly, the
OPTION_GEOCONF_CIVIC option SHOULD be returned by DHCPv6 servers only
when the DHCPv6 client has included this option in its OPTION_ORO.
The DHCPv4 long-options mechanism described in RFC 3396 [8] MUST be
used if the civic address option exceeds the maximum DHCPv4 option
size of 255 octets.
2. 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.
3. Format of the DHCP Civic Location Option
3.1. Overall Format for DHCPv4
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GEOCONF_CIVIC | N | what | country |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| code | civic address elements ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Code GEOCONF_CIVIC: The code for this DHCP option is 99.
N: The length of this option is variable. The minimum length is 3
octets.
Schulzrinne Standards Track [Page 5]RFC 4776 DHCP Civic November 2006
what: The 'what' element describes to which location the DHCP entry
refers. Currently, three options are defined: the location of the
DHCP server (a value of 0), the location of the network element
believed to be closest to the client (a value of 1), or the
location of the client (a value of 2). Option (2) SHOULD be used,
but may not be known. Options (0) and (1) SHOULD NOT be used
unless it is known that the DHCP client is in close physical
proximity to the server or network element.
country code: The two-letter ISO 3166 country code in capital ASCII
letters, e.g., DE or US. (Civic addresses always contain country
designations, suggesting the use of a fixed-format field to save
space.)
civic address elements: Zero or more elements comprising the civic
and/or postal address, with the format described below
(Section 3.3).
3.2. Overall Format for DHCPv6
The DHCPv6 [6] civic address option refers generally to the client as
a whole.
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_GEOCONF_CIVIC | option-len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| what | country code | .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ .
. civic address elements .
. ... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
option-code: OPTION_GEOCONF_CIVIC (36)
option-len: Length of the Countrycode, 'what' and civic address
elements in octets.
what: See above (Section 3.1).
country code: See above (Section 3.1).
civic address elements: See above (Section 3.1).
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3.3. Element Format
For both DHCPv4 and DHCPv6, each civic 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 ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CAtype: A one-octet descriptor of the data civic address value.
CAlength: The length, in octets, of the CAvalue, not including the
CAlength field itself.
CAvalue: The civic address value, as described in detail below.
3.4. Civic 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.
Component values MUST be encoded as UTF-8 [7]. They SHOULD be
written in mixed case, following the customary spelling. The script
indication (CAtype 128) MUST be written in mixed case, with the first
letter a capital letter.
Abbreviations MUST NOT be used unless indicated for each element.
Abbreviations do not need a trailing period.
It is RECOMMENDED that all elements in a particular script (CAtype
128) and language (CAtype 0) be grouped together, as that reduces the
number of script and language identifiers needed.
For each script and language, elements SHOULD be included in numeric
order from lowest to highest of their CAtype. In general, an element
is labeled in its language and script by the most recent 'language
tag' (CAtype ) element preceding it. Since not all elements depend
on the script and language, a client accumulates the elements by
CAtype and then selects the most desirable language and script
rendition if there are multiple elements for the same CAtype.
Schulzrinne Standards Track [Page 7]RFC 4776 DHCP Civic November 2006
+--------+-------+--------------------------------------------------+
| CAtype | label | description |
+--------+-------+--------------------------------------------------+
| 1 | A1 | national subdivisions (state, canton, 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 | group of streets below the neighborhood level |
+--------+-------+--------------------------------------------------+
Table 1
For specific countries, the administrative sub-divisions are
described below.
CA (Canada): The mapping to NENA designations is shown in
parentheses. A1 designates the province (STA), A2 the county
(CNA), A3 the city, town, or MSAG community name (MCN).
DE (Germany): A1 represents the state (Bundesstaat), A2 the county
(Regierungsbezirk), A3 the city (Stadt, Gemeinde), A4 the district
(Bezirk). Street suffixes (STS) are used only for designations
that are a separate word (e.g., Marienthaler Strasse).
JP (Japan): A1 represents the metropolis (To, Fu) or prefecture
(Ken, Do), A2 the city (Shi) or rural area (Gun), A3 the ward (Ku)
or village (Mura), A4 the town (Chou or Machi), A5 the city
district (Choume), and A6 the block (Banchi or Ban).
KR (Korea): A1 represents the province (Do), A2 the county (gun), A3
the city or village (ri), A4 the urban district (gu), A5 the
neighborhood (dong).
US (United States): The mapping to NENA designations is shown in
parentheses. A1 designates the state (STA), using the two-letter
state and possession abbreviations recommended by the United
States Postal Service Publication 28 [17], Appendix B. A2
designates the county, parish (Louisiana), or borough (Alaska)
(CNA). A3 designates the civic community name, e.g., city or
town. It is also known as the municipal jurisdiction or MSAG
community name (MCN). The civic community name (A3) reflects the
Schulzrinne Standards Track [Page 8]RFC 4776 DHCP Civic November 2006
political boundaries. These boundaries may differ from postal
delivery assignments, the postal community name (PCN), for
historical or practical reasons. The optional element A4 contains
the community place name, such as "New Hope Community" or
"Urbanizacion" in Puerto Rico.
Mappings and considerations from additional countries may be
informally gathered from time to time in independent documents
published by the IETF. These should be titled "Civic Address
Considerations for [Country]" and should contain similar information
to the examples given here. As published by the IETF, they will be
non-normative and purely descriptive, like the examples here, and
will not purport to speak with authority for any country, but rather
be offered for information. If authors choose to label the document
with a country code, this does not preclude its use for labeling a
future coexisting document.
Additional CA types appear in many countries and are simply omitted
where they are not needed or known:
+--------+------+------+---------------------------+----------------+
| CAtype | NENA | PIDF | Description | Examples |
+--------+------+------+---------------------------+----------------+
| 0 | | | language | i-default [3] |
| | | | | |
| 16 | PRD | PRD | leading street direction | N |
| | | | | |
| 17 | POD | POD | trailing street suffix | SW |
| | | | | |
| 18 | STS | STS | street suffix or type | Ave, Platz |
| | | | | |
| 19 | HNO | HNO | house number | 123 |
| | | | | |
| 20 | HNS | HNS | house number suffix | A, 1/2 |
| | | | | |
| 21 | LMK | LMK | landmark or vanity | Columbia |
| | | | address | University |
| | | | | |
| 22 | LOC | LOC | additional location | South Wing |
| | | | information | |
| | | | | |
| 23 | NAM | NAM | name (residence and | Joe's |
| | | | office occupant) | Barbershop |
| 24 | ZIP | PC | postal/zip code | 10027-1234 |
| | | | | |
| 25 | | | building (structure) | Low Library |
| | | | | |
+--------+------+------+---------------------------+----------------+
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+--------+------+------+---------------------------+----------------+
| CAtype | NENA | PIDF | Description | Examples |
+--------+------+------+---------------------------+----------------+
| 26 | | | unit (apartment, suite) | Apt 42 |
| | | | | |
| 27 | | FLR | floor | 4 |
| | | | | |
| 28 | | | room | 450F |
| | | | | |
| 29 | | | type of place | office |
| | | | | |
| 30 | PCN | | postal community name | Leonia |
| | | | | |
| 31 | | | post office box (P.O. | 12345 |
| | | | Box) | |
| | | | | |
| 32 | | | additional code | 13203000003 |
| | | | | |
| 33 | | SEAT | seat (desk, cubicle, | WS 181 |
| | | | workstation) | |
| | | | | |
| 34 | | | primary road name | Broadway |
| | | | | |
| 35 | | | road section | 14 |
| | | | | |
| 36 | | | branch road name | Lane 7 |
| | | | | |
| 37 | | | sub-branch road name | Alley 8 |
| | | | | |
| 38 | | | street name pre-modifier | Old |
| | | | | |
| 39 | | | street name post-modifier | Service |
| | | | | |
| 128 | | | script | Latn |
| | | | | |
| 255 | | | reserved | |
+--------+------+------+---------------------------+----------------+
The CA types labeled in the second column correspond to items from
the NENA "Recommended Formats and Protocols For ALI Data Exchange,
ALI Response and GIS Mapping" [18], but are applicable to most
countries. The "NENA" column refers to the data dictionary name in
Exhibit 18 of [18].
The column labeled PIDF indicates the element name from [16]. (Some
elements were added to this document after the PIDF location object
definition had been completed. These elements currently do not have
a PIDF-LO equivalent.)
Schulzrinne Standards Track [Page 10]
RFC 4776 DHCP Civic November 2006
Language: The "language" item (CAtype 0) optionally identifies the
language used for presenting the address information, drawing from
the tags for identifying languages in [4], as discussed in [13].
If omitted, the default value for this tag is "i-default" [3].
Script: The "script" item (CAtype 128) optionally identifies the
script used for presenting the address information, drawing from
the tags for identifying scripts described in [12] and elaborated
on in Section 2.2.3 of [13]. If omitted, the default value for
this tag is "Latn".
POD, PRD: The abbreviations N, E, S, W, and NE, NW, SE, SW SHOULD be
used for POD (trailing street suffix) and PRD (leading street
direction) in English-speaking countries.
STS: STS designates a street suffix or type. In the United States
(US), the abbreviations recommended by the United States Postal
Service Publication 28 [17], Appendix C, SHOULD be used.
HNS: HNS ("house number suffix") is a modifier to a street address;
it does not identify parts of a street address.
building: While a landmark (LMK, CAtype 21) can indicate a complex
of buildings, 'building' (CAtype 25) conveys the name of a single
building if the street address includes more than one building or
if the building name is helpful in identifying the location.
LOC: LOC ("location", CAtype 22) is an unstructured string
specifying additional information about the location, such as the
part of a building or other unstructured information.
PCN: The postal community name (CAtype 30) and the post office box
(CAtype 31) allow the recipient to construct a postal address.
The post office box field should contain the words "P.O. Box" or
other locally appropriate postal designation.
NAM: 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.
LMK: While a landmark (LMK, CAtype 21) can indicate a complex of
buildings, 'building' (CAtype 25) conveys the name of a single
building if the street address includes more than one building or
the building name is helpful in identifying the location. (For
example, on university campuses, the house number is often not
displayed on buildings, whereas the building name is prominently
shown.)
Schulzrinne Standards Track [Page 11]RFC 4776 DHCP Civic November 2006
Unit: The "unit" object (CAtype 26) contains the name or number of a
part of a structure where there are separate administrative units,
owners, or tenants, such as separate companies or families that
occupy that structure. Common examples include suite or apartment
designations.
Room: A "room" (CAtype 28) is the smallest identifiable subdivision
of a structure.
Type of place: The "type of place" item (CAtype 29) describes the
type of place described by the civic coordinates. For example, it
describes whether it is a home, office, street, or other public
space. The values are drawn from the items in the location types
registry [11]. This information makes it easy, for example, for
the DHCP client to then populate the presence information. Since
this is an IANA-registered token, the language and script
designations do not apply for this element.
Additional code: The "additional code" item (CAtype 32) provides an
additional, country-specific code identifying the location. For
example, for Japan, it contains the Japan Industry Standard (JIS)
address code. The JIS address code provides a unique address
inside of Japan, down to the level of indicating the floor of the
building.
SEAT: The "seat" item (CAtype 33) designates a place where a person
might sit, such as a seat in a stadium or theater, or a cubicle in
an open-plan office or a booth in a trade show.
Primary road name: The "primary road" item (CAtype 34) is given to
the road or street name associated with the address. If CAtypes
35 through 37 are not specified, the building or designated
location is found on that street. If some of CAtypes 35 through
37 are specified, this designates the main road, off of which the
smaller streets branch off and where the structure or building is
actually located.
Road section: The "road section" item (CAtype 35) designates a
specific section or stretch of a primary road. This is a new
thoroughfare element and is useful where a primary road is divided
into sections that re-use the same street number ranges.
Branch road name: The "branch road name" item (CAtype 36) represents
the name or identifier of a road or street that intersects or is
associated with a primary road. The branch road name is used only
in countries where side streets do not have unique names within a
municipality or other administrative unit, but rather must be
Schulzrinne Standards Track [Page 12]RFC 4776 DHCP Civic November 2006
qualified by the name of the primary road name that they branch
off of.
Sub-Branch road name: The "sub-branch road name" (CAtype 37) item
represents the name of a street that branches off a branch road
(CAtype 36). The sub-branch road name is used only in countries
where such streets are named relative to the primary road name and
branch road that they connect with.
Street name pre-modifier: The "street name pre-modifier" (CAtype 38)
is an optional element of the complete street name. It is a word
or phrase that precedes all other elements of the street name and
modifies it, but is separated from the street name by a street
name pre-directional. An example is "Old" in "Old North First
Street".
Street name post-modifier: The "street name post-modifier" (CAtype
39) is an optional element of the complete street name. It is a
word or phrase that follows all other elements of the street name
and modifies it, but is separated from the street name by a street
name post-directional and/or street suffix. An example is
"Extended" in "East End Avenue Extended".
4. Postal Addresses
In general, a recipient can construct a postal address by using all
language-appropriate elements, including the postal code (ZIP, CAtype
24). However, certain elements override the civic address components
to create a postal address. If the elements include a post office
box (CAtype 31), the street address components (CAtype 34, PRD, POD,
STS, HNO, HNS) are replaced with the post office box element. If a
postal community name is specified, the civic community name
(typically, A3) is replaced by the postal community name (PCN, CAtype
30). Country-specific knowledge is required to create a valid postal
address. The formating of such addresses is beyond the scope of this
document.
Schulzrinne Standards Track [Page 13]RFC 4776 DHCP Civic November 2006
5. Example
Rather than showing the precise byte layout of a DHCP option, we show
a symbolic example below, representing the civic address of the
Munich city hall in Bavaria, Germany. The city and state name are
also conveyed in English and Italian in addition to German; the other
items are assumed to be common across all languages. All languages
use the latin script.
+--------+---------------------+
| CAtype | CAvalue |
+--------+---------------------+
| 0 | de |
| | |
| 128 | Latn |
| | |
| 1 | Bayern |
| | |
| 2 | Oberbayern |
| | |
| 3 | M=U+00FCnchen |
| | |
| 6 | Marienplatz |
| | |
| 19 | 8 |
| | |
| 21 | Rathaus |
| | |
| 24 | 80331 |
| | |
| 29 | government-building |
| | |
| 31 | Postfach 1000 |
| | |
| 0 | en |
| | |
| 1 | Bavaria |
| | |
| 3 | Munich |
| | |
| 0 | it |
| | |
| 1 | Baviera |
| | |
| 3 | Monaco |
+--------+---------------------+
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6. Security Considerations
The security considerations discussed in the GEOPRIV architecture
defined by RFC 3693 [9] apply.
Where critical decisions might be based on the value of this
GEOCONF_CIVIC option, DHCPv4 authentication in RFC 3118 [5] 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 the information contained in this
option. Thus, usage of this option on networks without access
restrictions or network-layer or link-layer privacy mechanisms is NOT
RECOMMENDED.
To minimize the unintended exposure of location information, the
GEOCONF_CIVIC option SHOULD be returned by DHCPv4 servers only when
the DHCPv4 client has included this option in its 'parameter request
list' (RFC 2131 [2], Section 3.5). Similarly, the
OPTION_GEOCONF_CIVIC 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 [10]. 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.
7. IANA Considerations
The IANA has registered new DHCPv4 and DHCPv6 option codes for the
Civic Address (GEOCONF_CIVIC and OPTION_GEOCONF_CIVIC, respectively).
This document establishes a new IANA registry for CAtypes designating
civic address components. Referring to RFC 2434 [14], this registry
operates under both "Expert Review" and "Specification Required"
rules. The IESG will appoint an Expert Reviewer who will advise IANA
promptly on each request for a new or updated CAtype.
CAtype: Numeric identifier, assigned by IANA.
Brief description: Short description identifying the meaning of the
element.
Schulzrinne Standards Track [Page 15]RFC 4776 DHCP Civic November 2006
Reference to published specification: A stable reference to an RFC
or other permanent and readily available reference, in sufficient
detail so that interoperability between independent
implementations is possible.
Country-specific considerations: If applicable, notes whether the
element is only applicable or defined for certain countries.
The initial list of registrations is contained in Section 3.4.
Updates to country-specific considerations for previously-defined
CAtypes are not defined by IANA registrations since they are purely
descriptive, not a registration of identifiers. As noted earlier,
country-specific conventions may optionally be written up in
documents titled "Civic Addresses for [Country]".
8. References
8.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[3] Alvestrand, H., "IETF Policy on Character Sets and Languages",
BCP 18, RFC 2277, January 1998.
[4] Alvestrand, H., "Tags for the Identification of Languages", BCP
47, RFC 3066, January 2001.
[5] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages",
RFC 3118, June 2001.
[6] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", RFC 3315, July 2003.
[7] Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
63, RFC 3629, November 2003.
[8] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
November 2002.
[9] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and J.
Polk, "Geopriv Requirements", RFC 3693, February 2004.
Schulzrinne Standards Track [Page 16]RFC 4776 DHCP Civic November 2006
[10] Danley, M., Mulligan, D., Morris, J., and J. Peterson, "Threat
Analysis of the Geopriv Protocol", RFC 3694, February 2004.
[11] Schulzrinne, H. and H. Tschofenig, "Location Types Registry",
RFC 4589, July 2006.
[12] International Organization for Standardization, ISO., "ISO
15924:2004. Information and documentation - Codes for the
representation of names of scripts", January 2004.
8.2. Informative References
[13] Phillips, A. and M. Davis, "Tags for Identifying Languages",
Work in Progress, October 2005.
[14] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October
1998.
[15] Polk, J., Schnizlein, J., and M. Linsner, "Dynamic Host
Configuration Protocol Option for Coordinate-based Location
Configuration Information", RFC 3825, July 2004.
[16] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005.
[17] United States Postal Service, "Postal Addressing Standards",
November 2000.
[18] National Emergency Number Assocation, "NENA Recommended Formats
and Protocols For ALI Data Exchange, ALI Response and GIS
Mapping", NENA NENA-02-010, January 2002.
Acknowledgements
Harald Alvestrand, Stefan Berger, Peter Blatherwick, Joel M. Halpern,
David Kessens, Cheng-Hong Li, Rohan Mahy, James Polk, Martin Thomson
and Hannes Tschofenig provided helpful comments. Examples and
inspiration were drawn from the Street Address Data Standard of the
Federal Geographic Data Committee.
Schulzrinne Standards Track [Page 17]RFC 4776 DHCP Civic November 2006
Author's Address
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
EMail: hgs+geopriv@cs.columbia.edu
URI: http://www.cs.columbia.edu
Schulzrinne Standards Track [Page 18]
RFC 4776 DHCP Civic November 2006
Full Copyright Statement
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Schulzrinne Standards Track [Page 19]
