HTTP/1.1 200 OK Date: Mon, 08 Apr 2002 23:30:15 GMT Server: Apache/1.3.20 (Unix) Last-Modified: Tue, 22 Nov 1994 23:00:00 GMT ETag: "2e97c1-6c36-2ed277f0" Accept-Ranges: bytes Content-Length: 27702 Connection: close Content-Type: text/plain Network Working Group C. Davis Internet Draft Kapor Enterprises Updates: RFCs 1034, 1035 P. Vixie Vixie Enterprises T. Goodwin PIPEX I. Dickinson University of Warwick November 1994 A Means for Expressing Location Information in the Domain Name System Status of this Memo This document is an Internet-Draft. 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.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). 1. Abstract This Internet-Draft describes a mechanism to allow the DNS to carry location information about hosts, networks, and subnets. Such information for a small subset of hosts is currently contained in the flat-file UUCP maps. However, just as the DNS replaced the use of HOSTS.TXT to carry host and network address information, it is possible to replace the UUCP maps as carriers of location information. This Internet-Draft defines the format of a new Resource Record (RR) for the Domain Name System (DNS), and reserves a corresponding DNS type mnemonic (LOC) and numerical code (29). This Internet-Draft assumes that the reader is familiar with the DNS [RFC 1034, RFC 1035]. The data shown in our examples is for pedagogical use and does not necessarily reflect the real Internet. Davis, Vixie, Goodwin & Dickinson [Page 1] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 2. RDATA Format MSB LSB +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 0| VERSION | SIZE | HORIZ PRE | VERT PRE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 2| LATITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 4| LATITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 6| LONGITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 8| LONGITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 10| ALTITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 12| ALTITUDE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ (octet) where: VERSION Version number of the representation. This must be zero. Implementations are required to check this field and make no assumptions about the format of unrecognized versions. SIZE The size of the described entity, in log10(meters), expressed as a 4-bit integer, with 2^3 representing 0 and lower values representing negative numbers. For hosts, this will often be zero (i.e. 1m). Larger entities, such as multinational companies' domains, will use larger values. The largest possible value is 7 and the smallest possible value is -7. A value of all zero is prohibited. HORIZ PRE The horizontal precision of the data, in log10(meters), expressed as a 4-bit integer, with 2^3 representing 0 and lower values representing negative numbers. This is treated as an "accurate to within N meters" value. For example, if the latitude and longitude have been determined using differential GPS, this value would be 0 (i.e. 1m). If survey maps and building blueprints are used, the value might be 1 (i.e. 10m) or 2 (100m). If standard values for a large area are used, the value could be as high as 6 (100km). The largest possible value is 7 and the smallest possible value is -7. A value of all zero is prohibited. VERT PRE The vertical precision of the point described by the (LATITUDE, LONGITUDE, ALTITUDE) tuple, in log10(meters), Davis, Vixie, Goodwin & Dickinson [Page 2] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 expressed as a 4-bit integer, with 2^3 representing 0 and lower values representing negative numbers. This is treated as an "accurate to within N meters" value. The largest possible value is 7 and the smallest possible value is -7. A value of all zero is prohibited. LATITUDE The latitude of the center of the sphere described by the SIZE field, expressed as a 32-bit integer, most significant octet first (network standard byte order), in thousandsth of a second of arc. 2^31 represents the equator; numbers above that are north latitude. LONGITUDE The longitude of the center of the sphere described by the SIZE field, expressed as a 32-bit integer, most significant octet first (network standard byte order), in thousandths of a second of arc, rounded away from the prime meridian. 2^31 represents the prime meridian; numbers above that are east longitude. ALTITUDE The altitude of the center of the sphere described by the SIZE field, expressed as a 32-bit integer, most significant octet first (network standard byte order), in centimeters, from a base of 100,000m below the [WGS 84] reference spheroid used by GPS (semimajor axis a=6378137.0, reciprocal flattening rf=298.257223563). 3. Master File Format The LOC record is expressed in a master file in the following format: LOC ( d1 [m1 [s1]] {"N"|"S"} d2 [m2 [s2]] {"E"|"W"} alt["m"] [siz["m"] [hp["m"] [vp["m"]]]] ) (The parentheses are used for multi-line data as specified in [RFC 1035] section 5.1.) where: d1: [0 .. 90] (degrees latitude) d2: [0 .. 180] (degrees longitude) m1, m2: [0 .. 59] (minutes latitude/longitude) s1, s2: [0 .. 59.999] (seconds latitude/longitude) alt: [-100000.00 .. 42939672.96] BY .1 (altitude in meters) siz, hp, vp: "0.0000001" | "0.000001" | "0.00001" | "0.0001" | "0.001" | "0.01" | "0.1" | "1" | "10" | "100" | "1000" | "10000" | "100000" | "1000000" | Davis, Vixie, Goodwin & Dickinson [Page 3] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 "10000000" (size/precision in meters) If omitted, minutes and seconds default to zero, size defaults to 1m, horizontal precision defaults to 10000m, and vertical precision defaults to 10m. These defaults are chosen to represent typical ZIP/postal code area sizes, since it is often easy to find approximate geographical location by ZIP/postal code. 4. Application use of the LOC RR 4.1 Suggested Uses Some uses for the LOC RR have already been suggested, including the USENET backbone flow maps, a "visual traceroute" application showing the geographical path of an IP packet, and network management applications that could use LOC RRs to generate a map of hosts and routers being managed. 4.2 Search Algorithms This section specifies how to use the DNS to translate domain names and/or IP addresses into location information. If an application wishes to have a "fallback" behavior, displaying a less precise or larger area when a host does not have an associated LOC RR, it MAY support use of the algorithm in section 4.2.3, as noted in sections 4.2.1 and 4.2.2. If fallback is desired, this behaviour is the RECOMMENDED default, but in some cases it may need to be modified based on the specific requirements of the application involved. This search algorithm is designed to allow network administrators to specify the location of a network or subnet without requiring LOC RR data for each individual host. For example, a computer lab with 24 workstations, all of which are on the same subnet and in basically the same location, would only need a LOC RR for the subnet. (However, if the file server's location has been more precisely measured, a separate LOC RR for it can be placed in the DNS.) 4.2.1 Searching by Name If the application is beginning with a name, rather than an IP address (as the USENET backbone flow maps do), it MUST check for a LOC RR associated with that name. (CNAME records should be followed as for any other RR type.) If there is no LOC RR for that name, all A records (if any) associated with the name MAY be checked for network (or subnet) LOC Davis, Vixie, Goodwin & Dickinson [Page 4] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 RRs using the "Searching by Network or Subnet" algorithm (4.2.3). If multiple A records exist and have associated network or subnet LOC RRs, the application may choose to use any, some, or all of the LOC RRs found, possibly in combination. It is suggested that multi-homed hosts have LOC RRs for their name in the DNS to avoid any ambiguity in these cases. Note that domain names that do not have associated A records must have a LOC RR associated with their name in order for location information to be accessible. 4.2.2 Searching by Address If the application is beginning with an IP address (as a "visual traceroute" application might be) it MUST first map the address to a name using the IN-ADDR.ARPA namespace (see [RFC 1034], section 5.2.1), then check for a LOC RR associated with that name. If there is no LOC RR for the name, the address MAY be checked for network (or subnet) LOC RRs using the "Searching by Network or Subnet" algorithm (4.2.3). 4.2.3 Searching by Network or Subnet Even if a host's name does not have any associated LOC RRs, the network(s) or subnet(s) it is on may. If the application wishes to search for such less specific data, the following algorithm SHOULD be followed to find a network or subnet LOC RR associated with the IP address. This algorithm is adapted slightly from that specified in [RFC 1101], sections 4.3 and 4.4. Since subnet LOC RRs are (if present) more specific than network LOC RRs, it is best to use them if available. In order to do so, we build a stack of network and subnet names found while performing the [RFC 1101] search, then work our way down the stack until a LOC RR is found. 1. create a host-zero address using the network portion of the IP address (one, two, or three bytes for class A, B, or C networks, respectively). For example, for the host 128.9.2.17, on the class B network 128.9, this would result in the address "128.9.0.0". 2. Reverse the octets, suffix IN-ADDR.ARPA, and query for PTR and A records. Retrieve: 0.0.9.128.IN-ADDR.ARPA. PTR isi-net.isi.edu. A 255.255.255.0 Davis, Vixie, Goodwin & Dickinson [Page 5] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 Push the name "isi-net.isi.edu" onto the stack of names to be searched for LOC RRs later. 3. Since an A RR was found, repeat using mask from RR (255.255.255.0), constructing a query for 0.2.9.128.IN-ADDR.ARPA. Retrieve: 0.2.9.128.IN-ADDR.ARPA. PTR div2-subnet.isi.edu. A 255.255.255.240 Push the name "div2-subnet.isi.edu" onto the stack of names to be searched for LOC RRs later. 4. Since another A RR was found, repeat using mask 255.255.255.240 (x'FFFFFFF0'), constructing a query for 16.2.9.128.IN-ADDR.ARPA. Retrieve: 16.2.9.128.IN-ADDR.ARPA. PTR inc-subsubnet.isi.edu. Push the name "inc-subsubnet.isi.edu" onto the stack of names to be searched for LOC RRs later. 5. Since no A RR is present at 16.2.9.128.IN-ADDR.ARPA., there are no more subnet levels to search. We now pop the top name from the stack and check for an associated LOC RR. Repeat until a LOC RR is found. In this case, assume that inc-subsubnet.isi.edu does not have an associated LOC RR, but that div2-subnet.isi.edu does. We will then use div2-subnet.isi.edu's LOC RR as an approximation of this host's location. (Note that even if isi-net.isi.edu has a LOC RR, it will not be used if a subnet also has a LOC RR.) 4.3 Applicability to non-IN Classes and non-IP Addresses The LOC record is defined for all RR classes, and may be used with non-IN classes such as HS and CH. The semantics of such use are not defined by this memo. The search algorithm in section 4.2.3 may be adapted to other addressing schemes by extending [RFC 1101]'s encoding of network names to cover those schemes. Such extensions are not defined by this memo. 5. References [RFC 1034] Mockapetris, P., "Domain Names - Concepts and Facilities", STD 13, RFC 1034, USC/Information Sciences Institute, Davis, Vixie, Goodwin & Dickinson [Page 6] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 November 1987. [RFC 1035] Mockapetris, P., "Domain Names - Implementation and Specification", STD 13, RFC 1035, USC/Information Sciences Institute, November 1987. [RFC 1101] Mockapetris, P., "DNS Encoding of Network Names and Other Types", RFC 1101, USC/Information Sciences Institute, April 1989. [WGS 84] United States Department of Defense; DoD WGS-1984 - Its Definition and Relationships with Local Geodetic Systems; Washington, D.C.; 1985; Report AD-A188 815 DMA; 6127; 7- R-138-R; CV, KV; 6. Security Considerations High-precision LOC RR information could be used to help plan a penetration of physical security, leading to potential denial-of- machine attacks. To avoid any appearance of suggesting this method to potential attackers, we declined the opportunity to name this RR "ICBM". 7. Authors' Addresses Christopher Davis Kapor Enterprises, Inc. 238 Main Street, Suite 400 Cambridge, MA 02142 Phone: +1 617 576 4532 Email: ckd@kei.com Paul Vixie Vixie Enterprises Star Route Box 159A Woodside, CA 94062 Phone: +1 415 747 0204 Email: paul@vix.com Tim Goodwin Public IP Exchange Ltd (PIPEX) 216 The Science Park Davis, Vixie, Goodwin & Dickinson [Page 7] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 Cambridge CB4 4WA UK Phone: +44 1223 250250 Email: tim@pipex.net Ian Dickinson Computing Services University of Warwick Coventry CV4 7AL UK Phone: +44 1203 524217 Email: cudep@csv.warwick.ac.uk Appendix A: Sample Conversion Routines These routines are the ones used in BIND 4.9.3 for conversion between zone file and RDATA formats. /* * loc_rr.c. includes routines to convert between on-the-wire RR format * and zone file format. Does not contain conversion to/from decimal * degrees; divide or multiply by 60*60*1000 for that. */ #include /* abort() */ #include #include /* ntohl/htonl */ #include /* for PUTLONG, bit types if needed */ #include "../conf/portability.h" /* "signed" version of ntohl. host 0 = net (1<<31) */ static int32_t ntohls(x) u_int32_t x; { return (ntohl(x) - (1<<31)); } /* "signed" version of htonl. host 0 = net (1<<31) */ static u_int32_t htonls(x) int32_t x; Davis, Vixie, Goodwin & Dickinson [Page 8] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 { return (htonl(x) + (1<<31)); } /* takes a log10 precision value, returns a string representation. */ static const char * precision2string(precval) int8_t precval; { switch (precval) { case -7: return ("0.0000001"); case -6: return ("0.000001"); case -5: return ("0.00001"); case -4: return ("0.0001"); case -3: return ("0.001"); case -2: return ("0.01"); case -1: return ("0.1"); case 0: return ("1"); case 1: return ("10"); case 2: return ("100"); case 3: return ("1000"); case 4: return ("10000"); case 5: return ("100000"); case 6: return ("1000000"); case 7: return ("10000000"); default: return ("1"); /* XXX error checking? */ } /* NOTREACHED */ abort(); } /* converts lat/lon to unsigned encoded 32-bit number. moves pointer. */ Davis, Vixie, Goodwin & Dickinson [Page 9] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 static u_int32_t latlon2ul(latlonstrptr) char **latlonstrptr; { register char *cp; u_int32_t retval; int deg = 0, min = 0, secs = 0, secsfrac = 0; cp = *latlonstrptr; while (isdigit(*cp)) deg = deg * 10 + (*cp++ - '0'); while (isspace(*cp)) cp++; if (!(isdigit(*cp))) goto fndhemi; while (isdigit(*cp)) min = min * 10 + (*cp++ - '0'); while (isspace(*cp)) cp++; if (!(isdigit(*cp))) goto fndhemi; while (isdigit(*cp)) secs = secs * 10 + (*cp++ - '0'); if (*cp == '.') { /* decimal seconds */ cp++; if (isdigit(*cp)) { secsfrac = (*cp++ - '0') * 100; if (isdigit(*cp)) { secsfrac += (*cp++ - '0') * 10; if (isdigit(*cp)) { secsfrac += (*cp++ - '0'); } } } } while (isspace(*cp)) cp++; fndhemi: Davis, Vixie, Goodwin & Dickinson [Page 10] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 switch (*cp) { case 'N': case 'n': case 'E': case 'e': retval = (1<<31) + (((((deg * 60) + min) * 60) + secs) * 1000) + secsfrac; break; case 'S': case 's': case 'W': case 'w': retval = (1<<31) - (((((deg * 60) + min) * 60) + secs) * 1000) - secsfrac); break; default: /* XXX error checking? */ break; } cp++; /* skip the hemisphere */ while (isspace(*cp)) /* move to next field */ cp++; *latlonstrptr = cp; return (retval); } /* converts a zone file representation in a string to an RDATA on-the-wire * representation. */ u_int loc_aton(ascii, binary) const char *ascii; u_char *binary; { char *cp,*maxcp; u_char *bcp; u_int32_t latit = 0, longit = 0, alt = 0; int altmeters = 0, altfrac = 0, altsign = 1; int hp = 4; /* default = 10000m or 10km */ int vp = 1; /* default = 10m */ int siz = 0; /* default = 1m */ cp = ascii; maxcp = cp + strlen(ascii); latit = latlon2ul(&cp); Davis, Vixie, Goodwin & Dickinson [Page 11] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 longit = latlon2ul(&cp); /* altitude */ if (*cp == '-') { altsign = -1; cp++; } if (*cp == '+') cp++; while (isdigit(*cp)) altmeters = altmeters * 10 + (*cp++ - '0'); if (*cp == '.') { /* decimal meters */ cp++; if (isdigit(*cp)) { altfrac = (*cp++ - '0') * 10; if (isdigit(*cp)) { altfrac += (*cp++ - '0'); } } } alt = (10000000 + (altsign * (altmeters * 100 + altfrac))); while (isspace(*cp) || (*cp == 'm') || (*cp == 'M')) cp++; if (cp >= maxcp) goto defaults; siz = 0; /* get log10s for hp, vp, siz */ /* size */ if (*cp == '1') { /* positive or 0 log */ for (cp++; *cp == '0'; cp++) siz++; } else if (*cp == '0') { /* negative log */ for (cp++; *cp != '1'; cp++) siz--; } cp++; while (isspace(*cp) || *cp == 'm' || *cp == 'M') Davis, Vixie, Goodwin & Dickinson [Page 12] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 cp++; if (cp >= maxcp) goto defaults; hp = 0; /* horiz precision */ if (*cp == '1') { /* positive or 0 log */ for (cp++; *cp == '0'; cp++) hp++; } else if (*cp == '0') { /* negative log */ for (cp++; *cp != '1'; cp++) hp--; } cp++; while (isspace(*cp) || *cp == 'm' || *cp == 'M') cp++; if (cp >= maxcp) goto defaults; vp = 0; /* vertical precision */ if (*cp == '1') { /* positive or 0 log */ for (cp++; *cp == '0'; cp++) vp++; } else if (*cp == '0') { /* negative log */ for (cp++; *cp != '1'; cp++) vp--; } defaults: if ((hp > 7) || (hp < -7)) return (0); if ((vp > 7) || (vp < -7)) return (0); if ((siz > 7) || (siz < -7)) return (0); /* convert hp/vp/siz sign bits as with lat/long */ hp += 8; Davis, Vixie, Goodwin & Dickinson [Page 13] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 vp += 8; siz += 8; bcp = binary; *bcp++ = (u_int8_t) siz; *bcp++ = (u_int8_t) ((hp << 4) + vp); PUTLONG(latit,bcp); PUTLONG(longit,bcp); PUTLONG(alt,bcp); return (14); } /* takes an on-the-wire LOC RR and prints it in zone file (human readable) format. */ char * loc_ntoa(binary,ascii) const u_char *binary; char *ascii; { char tmpbuf[255*3]; register char *cp; register u_char *rcp; int latdeg, latmin, latsec, latsecfrac; int longdeg, longmin, longsec, longsecfrac; char northsouth, eastwest; int altmeters, altfrac; int32_t latval, longval, altval; u_int32_t templ; char sizeval, hpval, vpval, versionval, tempc; char *sizestr, *hpstr, *vpstr; rcp = binary; if (ascii) cp = ascii; else { ascii = tmpbuf; cp = tmpbuf; } tempc = *rcp++; versionval = tempc & 0xF0; sizeval = (tempc & 0x0F) - 8; Davis, Vixie, Goodwin & Dickinson [Page 14] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 if (versionval) { sprintf(cp,"; error: unknown LOC RR version"); return (cp); } tempc = *rcp++; hpval = ((tempc & 0xF0) >> 4) - 8; vpval = (tempc & 0x0F) - 8; GETLONG(templ,rcp); latval = ntohls(templ); GETLONG(templ,rcp); longval = ntohls(templ); GETLONG(templ,rcp); altval = ntohl(templ) - 10000000; /* XXX might need long long */ if (latval < 0) { northsouth = 'S'; latval = -latval; } else northsouth = 'N'; latsecfrac = latval % 1000; latval = latval / 1000; latsec = latval % 60; latval = latval / 60; latmin = latval % 60; latval = latval / 60; latdeg = latval; if (longval < 0) { eastwest = 'W'; longval = -longval; } else eastwest = 'E'; longsecfrac = longval % 1000; longval = longval / 1000; longsec = longval % 60; longval = longval / 60; longmin = longval % 60; longval = longval / 60; longdeg = longval; Davis, Vixie, Goodwin & Dickinson [Page 15] Expires 1994-05-25 draft-davis-dns-loc-00.txt November 1994 altfrac = altval % 100; altmeters = altval / 100; /* XXX might truncate wrong way if neg? */ sizestr = strdup(precision2string(sizeval)); hpstr = strdup(precision2string(hpval)); vpstr = strdup(precision2string(vpval)); sprintf(cp, "%d %.2d %.2d.%.3d %c %d %.2d %.2d.%.3d %c %d.%dm %sm %sm %sm", latdeg, latmin, latsec, latsecfrac, northsouth, longdeg, longmin, longsec, longsecfrac, eastwest, altmeters, altfrac, sizestr, hpstr, vpstr); free(sizestr); free(hpstr); free(vpstr); return (cp); } Davis, Vixie, Goodwin & Dickinson [Page 16]