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Network Working Group                                     H. SchulzrinneRequest for Comments: 4676                                   Columbia U.Category: Standards Track                                   October 2006Dynamic Host Configuration Protocol (DHCPv4 and DHCPv6) Optionfor Civic Addresses Configuration InformationStatus 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 Internet Society (2006).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.Table of Contents1. Introduction ....................................................22. Terminology .....................................................53. Format of the DHCP Civic Location Option ........................53.1. Overall Format for DHCPv4 ..................................53.2. Overall Format for DHCPv6 ..................................63.3. Element Format .............................................63.4. Civic Address Components ...................................74. Postal Addresses ...............................................135. Example ........................................................146. Security Considerations ........................................157. IANA Considerations ............................................158. References .....................................................168.1. Normative References ......................................168.2. Informative References ....................................17   Acknowledgements ..................................................17Schulzrinne                 Standards Track                     [Page 1]

RFC 4676                       DHCP Civic                   October 20061.  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   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 byRFC 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   toRFC 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.Schulzrinne                 Standards Track                     [Page 2]

RFC 4676                       DHCP Civic                   October 2006   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   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 (seeSection 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 goodSchulzrinne                 Standards Track                     [Page 3]

RFC 4676                       DHCP Civic                   October 2006   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 inSection 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   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 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 inRFC 3396 [8] MUST be   used if the civic address option exceeds the maximum DHCPv4 option   size of 255 octets.Schulzrinne                 Standards Track                     [Page 4]

RFC 4676                       DHCP Civic                   October 20062.  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 inRFC 2119 [1] and   indicate requirement levels for compliant implementations.3.  Format of the DHCP Civic Location Option3.1.  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.   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).Schulzrinne                 Standards Track                     [Page 5]

RFC 4676                       DHCP Civic                   October 20063.2.  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 (37)   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).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.Schulzrinne                 Standards Track                     [Page 6]

RFC 4676                       DHCP Civic                   October 20063.4.  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.   +--------+-------+--------------------------------------------------+   | 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 1Schulzrinne                 Standards Track                     [Page 7]

RFC 4676                       DHCP Civic                   October 2006   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      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:Schulzrinne                 Standards Track                     [Page 8]

RFC 4676                       DHCP Civic                   October 2006   +--------+------+------+---------------------------+----------------+   | 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    |   |        |      |      |                           |                |   | 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       |   +--------+------+------+---------------------------+----------------+Schulzrinne                 Standards Track                     [Page 9]

RFC 4676                       DHCP Civic                   October 2006   +--------+------+------+---------------------------+----------------+   | CAtype | NENA | PIDF | Description               | Examples       |   +--------+------+------+---------------------------+----------------+   | 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.)   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.Schulzrinne                 Standards Track                    [Page 10]

RFC 4676                       DHCP Civic                   October 2006   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.)   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.Schulzrinne                 Standards Track                    [Page 11]

RFC 4676                       DHCP Civic                   October 2006   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      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".Schulzrinne                 Standards Track                    [Page 12]

RFC 4676                       DHCP Civic                   October 2006   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 4676                       DHCP Civic                   October 20065.  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              |                     +--------+---------------------+Schulzrinne                 Standards Track                    [Page 14]

RFC 4676                       DHCP Civic                   October 20066.  Security Considerations   The security considerations discussed in the GEOPRIV architecture   defined byRFC 3693 [9] apply.   Where critical decisions might be based on the value of this   GEOCONF_CIVIC option, DHCPv4 authentication inRFC 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 inRFC 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 toRFC 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 4676                       DHCP Civic                   October 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 inSection 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.  References8.1.  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",BCP47,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 4676                       DHCP Civic                   October 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 4676                       DHCP Civic                   October 2006Author'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.eduSchulzrinne                 Standards Track                    [Page 18]

RFC 4676                       DHCP Civic                   October 2006Full Copyright Statement   Copyright (C) The Internet Society (2006).   This document is subject to the rights, licenses and restrictions   contained inBCP 78, and except as set forth therein, the authors   retain all their rights.   This document and the information contained herein are provided on an   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET   ENGINEERING TASK FORCE DISCLAIM 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.Intellectual Property   The IETF takes no position regarding the validity or scope of any   Intellectual Property Rights or other rights that might be claimed to   pertain to the implementation or use of the technology described in   this document or the extent to which any license under such rights   might or might not be available; nor does it represent that it has   made any independent effort to identify any such rights.  Information   on the procedures with respect to rights in RFC documents can be   found inBCP 78 andBCP 79.   Copies of IPR disclosures made to the IETF Secretariat 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 on-line IPR repository athttp://www.ietf.org/ipr.   The IETF invites any interested party to bring to its attention any   copyrights, patents or patent applications, or other proprietary   rights that may cover technology that may be required to implement   this standard.  Please address the information to the IETF at   ietf-ipr@ietf.org.Acknowledgement   Funding for the RFC Editor function is provided by the IETF   Administrative Support Activity (IASA).Schulzrinne                 Standards Track                    [Page 19]

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