Internet Engineering Task Force James M. Polk Internet Draft John Schnizlein Expiration: April 1st, 2003 Marc Linsner File: draft-polk-dhcp-loc-insertion-00.txt Cisco Systems DHCP Option for Location Insertion October 1st, 2002 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document specifies a Dynamic Host Configuration Protocol option for the geographic location of the client. The location includes longitude, latitude and altitude, with accuracy indicators for each. Polk/Schnizlein/Linsner Page 1 Internet Draft DHCP Option for Location Insertion Oct 1st, 2002 Table of Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.0 Format of DHCP Location Option . . . . . . . . . . . . . . . . . . 3 2.1 Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.0 Security Considerations . . . . . . . . . . . . . . . . . . . . . 4 4.0 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . . 4 5.0 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.0 Author Information . . . . . . . . . . . . . . . . . . . . . . . . 5 1.0 Introduction This document specifies a Dynamic Host Configuration Protocol [1] Option for the geographic location of the client. The DHCP server is assumed to have determined the location from the Circuit-ID RAIO defined (as SubOpt 1) in [2]. In order to translate the circuit (switch port identifier) into a location, the DHCP server is assumed to have access to a service that maps from circuit-ID to the location at which the circuit connected to that port terminates in the building; for example, the location of the wall jack. 1.1 Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [3]. 1.2 Motivation As applications such as IP Telephony are replacing conventional telephony, users are expecting the same (or greater) level of services with the new technology. One service offered by conventional telephony that is missing, in any standardized fashion, within IP Telephony is for a user to be automatically located by emergency responders, in a timely fashion, when the user summons help (by dialing 911 in North America, for example). Unless strict administrative rules are followed, the mobility of a wired Ethernet device within a campus negates any opportunity for an emergency responder to locate the device with any degree of expediency. Users do not want to give up this mobility. Informing the host device of its geo- location at host configuration time will allow the device to utilize this geo-location information to inform others of itĘs current geo-location, if the user and/or application so desires. The goal of this option is to enable a wired Ethernet host to provide its location to an emergency responder, as one example. Polk/Schnizlein/Linsner Page 2 Internet Draft DHCP Option for Location Insertion Oct 1st, 2002 Wireless hosts can utilize this option to gain knowledge of the location of the radio access point used during host configuration, but will need some more exotic mechanisms, maybe GPS, or maybe a future DHCP option, which includes a list of geo-loc objects like what we define here, that has the locations of the radio access points that are close to the access- point. 1.3 Rationale Longitude and Latitude are represented in fixed-point 2s-complement binary degrees, for the economy of a smaller option size compared to the string encoding of digits in [4]. The integer parts of these fields are 9 bits long to accommodate +/- 180 degrees. The fractional part is 25 bits long, better than the precision of 7 decimal digits of precision. Each parameter is 40 bits total, in length. Altitude is represented in measurement units (MU) indicated by the MU field, which is 4 bits long. Two measurement units are defined here, meters (code=1) and floors (code=2), both of which are 2s-complement integers. Additional measurement units MAY be assigned by IANA. The floor of a building is often the relevant location information, and not necessarily computable from meters of altitude. The length of this field of 30 bits accommodates values greater than 8 decimal digits. Each of these variables is preceded by an accuracy sub-field of 6 bits, indicating how many bits of the variable is considered accurate. This accuracy sub-field accommodates the [GEOPRIV] requirement to easily adjust the accuracy of a reported location. Contents beyond the claimed accuracy MAY be randomized to obscure greater precision that might be available. 2.0 Format of DHCP 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opt Code | LoAcc | LoInt | LoFrac | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LoFrac (cont) | LaAcc | LaInt | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LaFrac | AltAcc | M | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | U | Altitude | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2.1 Elements Opt Code: The DHCP option code is TBD by IANA. LoAcc: Longitude accuracy. 6 bits indicating the number of reliable bits in the fixed-point value composed of LoInt | LoFrac. LoInt: Longitude integer part of 2s-complement value. 9 bits Polk/Schnizlein/Linsner Page 3 Internet Draft DHCP Option for Location Insertion Oct 1st, 2002 LoFrac: Longitude fraction part of 2s-complement value. 25 bits LaAcc: Latitude accuracy. 6 bits indicating the number of reliable bits in the fixed-point value composed of LaInt | LaFrac. LaInt: Latitude integer part of 2s-complement value. 9 bits LaFrac: Latitude fraction part of 2s-complement value. 25 bits AltAcc: Altitude accuracy. 6 bits indicating the number of reliable bits in the fixed-point value MU: Measurement unit for altitude. Codes defined here are: 1: meters in 2s-complement integer 2: floors in 2s-complement integer Other codes TBD by IANA. Altitude: 30-bit value with format defined by the Measurement Unit. 3.0 Security Considerations Where critical decisions might be based on the value of this GeoLoc option, DHCP authentication in [5] SHOULD be used to protect the integrity of the DHCP options. 4.0 IANA Considerations The DHCP option code for the GeoLoc option is TBD. Altitude Measurement Units beyond the two defined in this document are TBD. 5.0 References [1] Droms R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997 [2] Patrick M., "DHCP Relay Agent Information Option", RFC 3046, January 2001 [3] Bradner S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997 [4] Farrell C., Schulze M., Pleitner S. and Baldoni D., "DNS Encoding of Geographical Location", RFC 1712, November 1994. [5] Droms R., "Authentication for DHCP Messages", RFC 3118, June 2001 Polk/Schnizlein/Linsner Page 4 Internet Draft DHCP Option for Location Insertion Oct 1st, 2002 6.0 Author Information James M. Polk Cisco Systems 2200 East President George Bush Turnpike Richardson, Texas 75082 USA jmpolk@cisco.com John Schnizlein Cisco Systems 9123 Loughran Road Fort Washington, MD 20744 USA john.schnizlein@cisco.com Marc Linsner Cisco Systems 210 Waterway Ct. #101 Marco Island, FL 34145 USA marc.linsner@cisco.com "Copyright (C) The Internet Society (February 23rd, 2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. 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The Expiration date for this Internet Draft is: April 1st, 2003 Polk/Schnizlein/Linsner Page 5