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This document records a format whereby a network operator can publish a mapping of IP address prefixes to simplified geolocation information, colloquially termed a "geolocation feed". Interested parties can poll and parse these feeds to update or merge with other geolocation data sources and procedures. This format intentionally only allows specifying coarse-level location. Some technical organizations operating networks that move from one conference location to the next have already experimentally published small geolocation feeds. This document describes a currently deployed format. At least one consumer (Google) has incorporated these feeds into a geolocation data pipeline, and a significant number of ISPs are using it to inform them where their prefixes should be geolocated.

Introduction

Motivation Providers of services over the Internet have grown to depend on best-effort geolocation information to improve the user experience. Locality information can aid in directing traffic to the nearest serving location, inferring likely native language, and providing additional context for services involving search queries. When an ISP, for example, changes the location where an IP prefix is deployed, services that make use of geolocation information may begin to suffer degraded performance. This can lead to customer complaints, possibly to the ISP directly. Dissemination of correct geolocation data is complicated by the lack of any centralized means to coordinate and communicate geolocation information to all interested consumers of the data. This document records a format whereby a network operator (an ISP, an enterprise, or any organization that deems the geolocation of its IP prefixes to be of concern) can publish a mapping of IP address prefixes to simplified geolocation information, colloquially termed a "geolocation feed". Interested parties can poll and parse these feeds to update or merge with other geolocation data sources and procedures. This document describes a currently deployed format. At least one consumer (Google) has incorporated these feeds into a geolocation data pipeline, and a significant number of ISPs are using it to inform them where their prefixes should be geolocated.

Requirements Notation The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. As this is an informational document about a data format and set of operational practices presently in use, requirements notation captures the design goals of the authors and implementors.

Assumptions about Publication This document describes both a format and a mechanism for publishing data, with the assumption that the network operator to whom operational responsibility has been delegated for any published data wishes it to be public. Any privacy risk is bounded by the format, and feed publishers MAY omit prefixes or any location field associated with a given prefix to further protect privacy (see for details about which fields exactly may be omitted). Feed publishers assume the responsibility of determining which data should be made public. This document does not incorporate a mechanism to communicate acceptable use policies for self-published data. Publication itself is inferred as a desire by the publisher for the data to be usefully consumed, similar to the publication of information like host names, cryptographic keys, and Sender Policy Framework (SPF) records in the DNS.

Self-Published IP Geolocation Feeds The format described here was developed to address the need of network operators to rapidly and usefully share geolocation information changes. Originally, there arose a specific case where regional operators found it desirable to publish location changes rather than wait for geolocation algorithms to "learn" about them. Later, technical conferences that frequently use the same network prefixes advertised from different conference locations experimented by publishing geolocation feeds updated in advance of network location changes in order to better serve conference attendees. At its simplest, the mechanism consists of a network operator publishing a file (the "geolocation feed") that contains several text entries, one per line. Each entry is keyed by a unique (within the feed) IP prefix (or single IP address) followed by a sequence of network locality attributes to be ascribed to the given prefix.

Specification For operational simplicity, every feed should contain data about all IP addresses the provider wants to publish. Alternatives, like publishing only entries for IP addresses whose geolocation data has changed or differ from current observed geolocation behavior "at large", are likely to be too operationally complex. Feeds MUST use UTF-8 character encoding. Lines are delimited by a line break (CRLF) (as specified in ), and blank lines are ignored. Text from a '#' character to the end of the current line is treated as a comment only and is similarly ignored (note that this does not strictly follow , which has no support for comments). Feed lines that are not comments MUST be formatted as comma-separated values (CSV), as described in . Each feed entry is a text line of the form: The IP prefix field is REQUIRED, all others are OPTIONAL (can be empty), though the requisite minimum number of commas SHOULD be present.

Geolocation Feed Individual Entry Fields

IP Prefix REQUIRED: Each IP prefix field MUST be either a single IP address or an IP prefix in Classless Inter-Domain Routing (CIDR) notation in conformance with for IPv4 or for IPv6. Examples include "192.0.2.1" and "192.0.2.0/24" for IPv4 and "2001:db8::1" and "2001:db8::/32" for IPv6.

Alpha2code (Previously: 'country') OPTIONAL: The alpha2code field, if non-empty, MUST be a 2-letter ISO country code conforming to ISO 3166-1 alpha 2 . Parsers SHOULD treat this field case-insensitively. Earlier versions of this document called this field "country", and it may still be referred to as such in existing tools/interfaces. Parsers MAY additionally support other 2-letter codes outside the ISO 3166-1 alpha 2 codes, such as the 2-letter codes from the "Exceptionally reserved codes" set. Examples include "US" for the United States, "JP" for Japan, and "PL" for Poland.

Region OPTIONAL: The region field, if non-empty, MUST be an ISO region code conforming to ISO 3166-2 . Parsers SHOULD treat this field case-insensitively. Examples include "ID-RI" for the Riau province of Indonesia and "NG-RI" for the Rivers province in Nigeria.

City OPTIONAL: The city field, if non-empty, SHOULD be free UTF-8 text, excluding the comma (',') character. Examples include "Dublin", "New York", and "Sao Paulo" (specifically "S" followed by 0xc3, 0xa3, and "o Paulo").

Postal Code OPTIONAL, DEPRECATED: The postal code field, if non-empty, SHOULD be free UTF-8 text, excluding the comma (',') character. The use of this field is deprecated; consumers of feeds should be able to parse feeds containing these fields, but new feeds SHOULD NOT include this field due to the granularity of this information. See for additional discussion. Examples include "106-6126" (in Minato ward, Tokyo, Japan).

Prefixes with No Geolocation Information Feed publishers may indicate that some IP prefixes should not have any associated geolocation information. It may be that some prefixes under their administrative control are reserved, not yet allocated or deployed, or in the process of being redeployed elsewhere and existing geolocation information can, from the perspective of the publisher, safely be discarded. This special case can be indicated by explicitly leaving blank all fields that specify any degree of geolocation information. For example: Historically, the user-assigned alpha2code identifier of "ZZ" has been used for this same purpose. This is not necessarily preferred, and no specific interpretation of any of the other user-assigned alpha2code codes is currently defined.

Additional Parsing Requirements Feed entries that do not have an IP address or prefix field or have an IP address or prefix field that fails to parse correctly MUST be discarded. While publishers SHOULD follow for IPv6 prefix fields, consumers MUST nevertheless accept all valid string representations. Duplicate IP address or prefix entries MUST be considered an error, and consumer implementations SHOULD log the repeated entries for further administrative review. Publishers SHOULD take measures to ensure there is one and only one entry per IP address and prefix. Multiple entries that constitute nested prefixes are permitted. Consumers SHOULD consider the entry with the longest matching prefix (i.e., the "most specific") to be the best matching entry for a given IP address. Feed entries with non-empty optional fields that fail to parse, either in part or in full, SHOULD be discarded. It is RECOMMENDED that they also be logged for further administrative review. For compatibility with future additional fields, a parser MUST ignore any fields beyond those it expects. The data from fields that are expected and that parse successfully MUST still be considered valid. Per , no extensions to this format are in use nor are any anticipated.

Examples Example entries using different IP address formats and describing locations at alpha2code ("country code"), region, and city granularity level, respectively: The IETF network publishes geolocation information for the meeting prefixes, and generally just comment out the last meeting information and append the new meeting information. The , at the time of this writing, contains: Experimentally, RIPE has published geolocation information for their conference network prefixes, which change location in accordance with each new event. , at the time of writing, contains: Similarly, ICANN has published geolocation information for their portable conference network prefixes. , at the time of writing, contains: A longer example is the Google Corp Geofeed, which lists the geolocation information for Google corporate offices. At the time of writing, Google processes approximately 400 feeds comprising more than 750,000 IPv4 and IPv6 prefixes.

Consuming Self-Published IP Geolocation Feeds Consumers MAY treat published feed data as a hint only and MAY choose to prefer other sources of geolocation information for any given IP prefix. Regardless of a consumer's stance with respect to a given published feed, there are some points of note for sensibly and effectively consuming published feeds.

Feed Integrity The integrity of published information SHOULD be protected by securing the means of publication, for example, by using HTTP over TLS . Whenever possible, consumers SHOULD prefer retrieving geolocation feeds in a manner that guarantees integrity of the feed.

Verification of Authority Consumers of self-published IP geolocation feeds SHOULD perform some form of verification that the publisher is in fact authoritative for the addresses in the feed. The actual means of verification is likely dependent upon the way in which the feed is discovered. Ad hoc shared URIs, for example, will likely require an ad hoc verification process. Future automated means of feed discovery SHOULD have an accompanying automated means of verification. A consumer should only trust geolocation information for IP addresses or prefixes for which the publisher has been verified as administratively authoritative. All other geolocation feed entries should be ignored and logged for further administrative review.

Verification of Accuracy Errors and inaccuracies may occur at many levels, and publication and consumption of geolocation data are no exceptions. To the extent practical, consumers SHOULD take steps to verify the accuracy of published locality. Verification methodology, resolution of discrepancies, and preference for alternative sources of data are left to the discretion of the feed consumer. Consumers SHOULD decide on discrepancy thresholds and SHOULD flag, for administrative review, feed entries that exceed set thresholds.

Refreshing Feed Information As a publisher can change geolocation data at any time and without notification, consumers SHOULD implement mechanisms to periodically refresh local copies of feed data. In the absence of any other refresh timing information, it is recommended that consumers SHOULD refresh feeds no less often than weekly and no more often than is likely to cause issues to the publisher. For feeds available via HTTPS (or HTTP), the publisher MAY communicate refresh timing information by means of the standard HTTP expiration model (). Specifically, publishers can include either an Expires header () or a Cache-Control header () specifying the max-age. Where practical, consumers SHOULD refresh feed information before the expiry time is reached.

Privacy Considerations Publishers of geolocation feeds are advised to have fully considered any and all privacy implications of the disclosure of such information for the users of the described networks prior to publication. A thorough comprehension of the security considerations () of a chosen geolocation policy is highly recommended, including an understanding of some of the limitations of information obscurity () (see also ). As noted in , each location field in an entry is optional, in order to support expressing only the level of specificity that the publisher has deemed acceptable. There is no requirement that the level of specificity be consistent across all entries within a feed. In particular, the Postal Code field () can provide very specific geolocation, sometimes within a building. Such specific Postal Code values MUST NOT be published in geofeeds without the express consent of the parties being located. Operators who publish geolocation information are strongly encouraged to inform affected users/customers of this fact and of the potential privacy-related consequences and trade-offs.

Relation to Other Work While not originally done in conjunction with the GEOPRIV Working Group , Richard Barnes observed that this work is nevertheless consistent with that which the group has defined, both for address format and for privacy. The data elements in geolocation feeds are equivalent to the following XML structure ( ): country region city postal_code ]]> Providing geolocation information to this granularity is equivalent to the following privacy policy (the definition of the 'building' level of disclosure): building ]]>

Security Considerations As there is no true security in the obscurity of the location of any given IP address, self-publication of this data fundamentally opens no new attack vectors. For publishers, self-published data may increase the ease with which such location data might be exploited (it can, for example, make easy the discovery of prefixes populated with customers as distinct from prefixes not generally in use). For consumers, feed retrieval processes may receive input from potentially hostile sources (e.g., in the event of hijacked traffic). As such, proper input validation and defense measures MUST be taken (see the discussion in ). Similarly, consumers who do not perform sufficient verification of published data bear the same risks as from other forms of geolocation configuration errors (see the discussion in Sections and ). Validation of a feed's contents includes verifying that the publisher is authoritative for the IP prefixes included in the feed. Failure to verify IP prefix authority would, for example, allow ISP Bob to make geolocation statements about IP space held by ISP Alice. At this time, only out-of-band verification methods are implemented (i.e., an ISP's feed may be verified against publicly available IP allocation data).

Planned Future Work In order to more flexibly support future extensions, use of a more expressive feed format has been suggested. Use of JavaScript Object Notation (JSON) , specifically, has been discussed. However, at the time of writing, no such specification nor implementation exists. Nevertheless, work on extensions is deferred until a more suitable format has been selected. The authors are planning on writing a document describing such a new format. This document describes a currently deployed and used format. Given the extremely limited extensibility of the present format no extensions to it are anticipated. Extensibility requirements are instead expected to be integral to the development of a new format.

Finding Self-Published IP Geolocation Feeds The issue of finding, and later verifying, geolocation feeds is not formally specified in this document. At this time, only ad hoc feed discovery and verification has a modicum of established practice (see below); discussion of other mechanisms has been removed for clarity.

Ad Hoc 'Well-Known' URIs To date, geolocation feeds have been shared informally in the form of HTTPS URIs exchanged in email threads. Three example URIs (, , and ) describe networks that change locations periodically, the operators and operational practices of which are well known within their respective technical communities. The contents of the feeds are verified by a similarly ad hoc process, including:

• personal knowledge of the parties involved in the exchange and
• comparison of feed-advertised prefixes with the BGP-advertised prefixes of Autonomous System Numbers known to be operated by the publishers.

Ad hoc mechanisms, while useful for early experimentation by producers and consumers, are unlikely to be adequate for long-term, widespread use by multiple parties. Future versions of any such self-published geolocation feed mechanism SHOULD address scalability concerns by defining a means for automated discovery and verification of operational authority of advertised prefixes.

Other Mechanisms Previous versions of this document referenced use of the WHOIS service operated by Regional Internet Registries (RIRs), as well as possible DNS-based schemes to discover and validate geofeeds. To the authors' knowledge, support for such mechanisms has never been implemented, and this speculative text has been removed to avoid ambiguity.

IANA Considerations This document has no IANA actions.

References Normative References ISO ISO Informative References Réseaux IP Européens Network Coordination Centre ICANN Google, LLC IETF Google Inc. Google Inc. ISO

Sample Python Validation Code Included here is a simple format validator in Python for self-published ipgeo feeds. This tool reads CSV data in the self-published ipgeo feed format from the standard input and performs basic validation. It is intended for use by feed publishers before launching a feed. Note that this validator does not verify the uniqueness of every IP prefix entry within the feed as a whole but only verifies the syntax of each single line from within the feed. A complete validator MUST also ensure IP prefix uniqueness. The main source file "ipgeo_feed_validator.py" follows. It requires use of the open source ipaddr Python library for IP address and CIDR parsing and validation . 0) is_correct = self._IsIPAddressOrPrefixCorrect(fields[0]) if len(fields) > 1: if not self._IsAlpha2CodeCorrect(fields[1]): is_correct = False if len(fields) > 2 and not self._IsRegionCodeCorrect(fields[2]): is_correct = False if len(fields) != 5: self._ReportWarning('5 fields were expected (got %d).' % len(fields)) ############################################################ def _IsIPAddressOrPrefixCorrect(self, field): if '/' in field: return self._IsCIDRCorrect(field) return self._IsIPAddressCorrect(field) def _IsCIDRCorrect(self, cidr): try: ipprefix = ipaddr.IPNetwork(cidr) if ipprefix.network._ip != ipprefix._ip: self._ReportError('Incorrect IP Network.') return False if ipprefix.is_private: self._ReportError('IP Address must not be private.') return False except: self._ReportError('Incorrect IP Network.') return False return True def _IsIPAddressCorrect(self, ipaddress): try: ip = ipaddr.IPAddress(ipaddress) except: self._ReportError('Incorrect IP Address.') return False if ip.is_private: self._ReportError('IP Address must not be private.') return False return True ############################################################ def _IsAlpha2CodeCorrect(self, alpha2code): if len(alpha2code) == 0: return True if len(alpha2code) != 2 or not alpha2code.isalpha(): self._ReportError( 'Alpha 2 code must be in the ISO 3166-1 alpha 2 format.') return False return True def _IsRegionCodeCorrect(self, region_code): if len(region_code) == 0: return True if '-' not in region_code: self._ReportError('Region code must be in ISO 3166-2 format.') return False parts = region_code.split('-') if not self._IsAlpha2CodeCorrect(parts[0]): return False return True ############################################################ def _ReportError(self, message): self._ReportWithSeverity('ERROR', message) def _ReportWarning(self, message): self._ReportWithSeverity('WARNING', message) def _ReportWithSeverity(self, severity, message): self.is_correct_line = False output_line = '%s: %s\n' % (severity, message) if severity not in self.output_log: self.output_log[severity] = [] self.output_log[severity].append(output_line) if self.output_stream is not None: self.output_stream.write(output_line) def _FlushOutputStream(self): if self.is_correct_line: return if self.output_stream is None: return self.output_stream.write('line %d: %s\n\n' % (self.line_number, self.line)) ############################################################ def main(): feed_validator = IPGeoFeedValidator() feed_validator.Validate(sys.stdin) if feed_validator.CountErrors('ERROR'): sys.exit(1) if __name__ == '__main__': main() ]]> A unit test file, "ipgeo_feed_validator_test.py" is provided as well. It provides basic test coverage of the code above, though does not test correct handling of non-ASCII UTF-8 strings.

Acknowledgements The authors would like to express their gratitude to reviewers and early implementors, including but not limited to , , , , , , , , , , , , , , and . In particular, and contributed substantial review, text, and advice.