Internet Engineering Task Force (IETF) M. Thomson
Request for Comments: 7105 Mozilla
Category: Standards Track J. Winterbottom
ISSN: 2070-1721 Unaffiliated
January 2014
Internet Engineering Task Force (IETF) M. Thomson
Request for Comments: 7105 Mozilla
Category: Standards Track J. Winterbottom
ISSN: 2070-1721 Unaffiliated
January 2014
Using Device-Provided Location-Related Measurements in Location Configuration Protocols
在位置配置协议中使用设备提供的位置相关测量
Abstract
摘要
This document describes a protocol for a Device to provide location-related measurement data to a Location Information Server (LIS) within a request for location information. Location-related measurement information provides observations concerning properties related to the position of a Device; this information could be data about network attachment or about the physical environment. A LIS is able to use the location-related measurement data to improve the accuracy of the location estimate it provides to the Device. A basic set of location-related measurements are defined, including common modes of network attachment as well as assisted Global Navigation Satellite System (GNSS) parameters.
本文档描述了设备在位置信息请求中向位置信息服务器（LIS）提供位置相关测量数据的协议。与位置相关的测量信息提供与设备位置相关的特性相关的观察结果；这些信息可能是有关网络连接或物理环境的数据。LIS能够使用与位置相关的测量数据来提高其提供给设备的位置估计的准确性。定义了一组与位置相关的基本测量值，包括网络连接的常见模式以及辅助全球导航卫星系统（GNSS）参数。
Status of This Memo
关于下段备忘
This is an Internet Standards Track document.
这是一份互联网标准跟踪文件。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。有关互联网标准的更多信息，请参见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7105.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc7105.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................4
2. Conventions Used in This Document ...............................5
3. Location-Related Measurements in LCPs ...........................6
4. Location-Related Measurement Data Types .........................7
4.1. Measurement Container ......................................7
4.1.1. Time of Measurement .................................8
4.1.2. Expiry Time on Location-Related Measurement Data ....8
4.2. RMS Error and Number of Samples ............................9
4.2.1. Time RMS Error ......................................9
4.3. Measurement Request .......................................10
4.4. Identifying Location Provenance ...........................11
5. Location-Related Measurement Data Types ........................13
5.1. LLDP Measurements .........................................13
5.2. DHCP Relay Agent Information Measurements .................14
5.3. 802.11 WLAN Measurements ..................................15
5.3.1. WiFi Measurement Requests ..........................18
5.4. Cellular Measurements .....................................18
5.4.1. Cellular Measurement Requests ......................22
5.5. GNSS Measurements .........................................22
5.5.1. GNSS: System Type and Signal .......................23
5.5.2. Time ...............................................24
5.5.3. Per-Satellite Measurement Data .....................24
5.5.4. GNSS Measurement Requests ..........................25
5.6. DSL Measurements ..........................................25
5.6.1. L2TP Measurements ..................................26
5.6.2. RADIUS Measurements ................................26
5.6.3. Ethernet VLAN Tag Measurements .....................27
5.6.4. ATM Virtual Circuit Measurements ...................28
1. Introduction ....................................................4
2. Conventions Used in This Document ...............................5
3. Location-Related Measurements in LCPs ...........................6
4. Location-Related Measurement Data Types .........................7
4.1. Measurement Container ......................................7
4.1.1. Time of Measurement .................................8
4.1.2. Expiry Time on Location-Related Measurement Data ....8
4.2. RMS Error and Number of Samples ............................9
4.2.1. Time RMS Error ......................................9
4.3. Measurement Request .......................................10
4.4. Identifying Location Provenance ...........................11
5. Location-Related Measurement Data Types ........................13
5.1. LLDP Measurements .........................................13
5.2. DHCP Relay Agent Information Measurements .................14
5.3. 802.11 WLAN Measurements ..................................15
5.3.1. WiFi Measurement Requests ..........................18
5.4. Cellular Measurements .....................................18
5.4.1. Cellular Measurement Requests ......................22
5.5. GNSS Measurements .........................................22
5.5.1. GNSS: System Type and Signal .......................23
5.5.2. Time ...............................................24
5.5.3. Per-Satellite Measurement Data .....................24
5.5.4. GNSS Measurement Requests ..........................25
5.6. DSL Measurements ..........................................25
5.6.1. L2TP Measurements ..................................26
5.6.2. RADIUS Measurements ................................26
5.6.3. Ethernet VLAN Tag Measurements .....................27
5.6.4. ATM Virtual Circuit Measurements ...................28
6. Privacy Considerations .........................................28
6.1. Measurement Data Privacy Model ............................28
6.2. LIS Privacy Requirements ..................................29
6.3. Measurement Data and Location URIs ........................29
6.4. Measurement Data Provided by a Third Party ................30
7. Security Considerations ........................................30
7.1. Threat Model ..............................................30
7.1.1. Acquiring Location Information without
Authorization ......................................31
7.1.2. Extracting Network Topology Data ...................32
7.1.3. Exposing Network Topology Data .....................32
7.1.4. Lying by Proxy .....................................33
7.1.5. Measurement Replay .................................33
7.1.6. Environment Spoofing ...............................34
7.2. Mitigation ................................................35
7.2.1. Measurement Validation .............................36
7.2.1.1. Effectiveness .............................36
7.2.1.2. Limitations (Unique Observer) .............37
7.2.2. Location Validation ................................38
7.2.2.1. Effectiveness .............................38
7.2.2.2. Limitations ...............................39
7.2.3. Supporting Observations ............................39
7.2.3.1. Effectiveness .............................40
7.2.3.2. Limitations ...............................40
7.2.4. Attribution ........................................40
7.2.5. Stateful Correlation of Location Requests ..........42
7.3. An Unauthorized or Compromised LIS ........................42
8. Measurement Schemas ............................................42
8.1. Measurement Container Schema ..............................43
8.2. Measurement Source Schema .................................45
8.3. Base Types Schema .........................................46
8.4. LLDP Measurement Schema ...................................49
8.5. DHCP Measurement Schema ...................................50
8.6. WiFi Measurement Schema ...................................51
8.7. Cellular Measurement Schema ...............................55
8.8. GNSS Measurement Schema ...................................57
8.9. DSL Measurement Schema ....................................59
9. IANA Considerations ............................................61
9.1. IANA Registry for GNSS Types ..............................61
9.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:pidf:geopriv10:lmsrc ...............62
9.3. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm .........................63
9.4. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:basetypes ...............63
9.5. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:lldp ....................64
6. Privacy Considerations .........................................28
6.1. Measurement Data Privacy Model ............................28
6.2. LIS Privacy Requirements ..................................29
6.3. Measurement Data and Location URIs ........................29
6.4. Measurement Data Provided by a Third Party ................30
7. Security Considerations ........................................30
7.1. Threat Model ..............................................30
7.1.1. Acquiring Location Information without
Authorization ......................................31
7.1.2. Extracting Network Topology Data ...................32
7.1.3. Exposing Network Topology Data .....................32
7.1.4. Lying by Proxy .....................................33
7.1.5. Measurement Replay .................................33
7.1.6. Environment Spoofing ...............................34
7.2. Mitigation ................................................35
7.2.1. Measurement Validation .............................36
7.2.1.1. Effectiveness .............................36
7.2.1.2. Limitations (Unique Observer) .............37
7.2.2. Location Validation ................................38
7.2.2.1. Effectiveness .............................38
7.2.2.2. Limitations ...............................39
7.2.3. Supporting Observations ............................39
7.2.3.1. Effectiveness .............................40
7.2.3.2. Limitations ...............................40
7.2.4. Attribution ........................................40
7.2.5. Stateful Correlation of Location Requests ..........42
7.3. An Unauthorized or Compromised LIS ........................42
8. Measurement Schemas ............................................42
8.1. Measurement Container Schema ..............................43
8.2. Measurement Source Schema .................................45
8.3. Base Types Schema .........................................46
8.4. LLDP Measurement Schema ...................................49
8.5. DHCP Measurement Schema ...................................50
8.6. WiFi Measurement Schema ...................................51
8.7. Cellular Measurement Schema ...............................55
8.8. GNSS Measurement Schema ...................................57
8.9. DSL Measurement Schema ....................................59
9. IANA Considerations ............................................61
9.1. IANA Registry for GNSS Types ..............................61
9.2. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:pidf:geopriv10:lmsrc ...............62
9.3. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm .........................63
9.4. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:basetypes ...............63
9.5. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:lldp ....................64
9.6. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:dhcp ....................65
9.7. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:wifi ....................65
9.8. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:cell ....................66
9.9. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:gnss ....................67
9.10. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:dsl ....................67
9.11. XML Schema Registration for Measurement Source Schema ....68
9.12. XML Schema Registration for Measurement Container
Schema ...................................................68
9.13. XML Schema Registration for Base Types Schema ............69
9.14. XML Schema Registration for LLDP Schema ..................69
9.15. XML Schema Registration for DHCP Schema ..................69
9.16. XML Schema Registration for WiFi Schema ..................69
9.17. XML Schema Registration for Cellular Schema ..............70
9.18. XML Schema Registration for GNSS Schema ..................70
9.19. XML Schema Registration for DSL Schema ...................70
10. Acknowledgements ..............................................70
11. References ....................................................71
11.1. Normative References .....................................71
11.2. Informative References ...................................73
9.6. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:dhcp ....................65
9.7. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:wifi ....................65
9.8. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:cell ....................66
9.9. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:gnss ....................67
9.10. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:lm:dsl ....................67
9.11. XML Schema Registration for Measurement Source Schema ....68
9.12. XML Schema Registration for Measurement Container
Schema ...................................................68
9.13. XML Schema Registration for Base Types Schema ............69
9.14. XML Schema Registration for LLDP Schema ..................69
9.15. XML Schema Registration for DHCP Schema ..................69
9.16. XML Schema Registration for WiFi Schema ..................69
9.17. XML Schema Registration for Cellular Schema ..............70
9.18. XML Schema Registration for GNSS Schema ..................70
9.19. XML Schema Registration for DSL Schema ...................70
10. Acknowledgements ..............................................70
11. References ....................................................71
11.1. Normative References .....................................71
11.2. Informative References ...................................73
A Location Configuration Protocol (LCP) provides a means for a Device to request information about its physical location from an access network. A Location Information Server (LIS) is the server that provides location information that is available due to the knowledge it has about the network and physical environment.
位置配置协议（LCP）为设备从接入网络请求有关其物理位置的信息提供了一种方法。位置信息服务器（LIS）是一种提供位置信息的服务器，该信息由于其对网络和物理环境的了解而可用。
As a part of the access network, the LIS is able to acquire measurement results related to Device location from network elements. The LIS also has access to information about the network topology that can be used to turn measurement data into location information. This information can be further enhanced with information acquired from the Device itself.
作为接入网的一部分，LIS能够从网元获取与设备位置相关的测量结果。LIS还可以访问有关网络拓扑的信息，这些信息可用于将测量数据转换为位置信息。可以使用从设备本身获取的信息来进一步增强该信息。
A Device is able to make observations about its network attachment, or its physical environment. The location-related measurement data might be unavailable to the LIS; alternatively, the LIS might be able to acquire the data, but at a higher cost in terms of time or some other metric. Providing measurement data gives the LIS more options in determining location; this could in turn improve the quality of
设备能够对其网络连接或物理环境进行观察。与位置相关的测量数据可能对LIS不可用；或者，LIS可能能够获取数据，但在时间或某些其他指标方面的成本较高。提供测量数据使LIS在确定位置时有更多的选择；这反过来可以提高产品质量
the service provided by the LIS. Improvements in accuracy are one potential gain, but improved response times and lower error rates are also possible.
LIS提供的服务。准确度的提高是一个潜在的好处，但响应时间的提高和错误率的降低也是可能的。
This document describes a means for a Device to report location-related measurement data to the LIS. Examples based on the HTTP-Enabled Location Delivery (HELD) [RFC5985] location configuration protocol are provided.
本文件描述了设备向LIS报告位置相关测量数据的方法。提供了基于HTTP启用的位置传递（HOLD）[RFC5985]位置配置协议的示例。
The terms "LIS" and "Device" are used in this document in a manner consistent with the usage in [RFC5985].
本文件中术语“LIS”和“设备”的使用方式与[RFC5985]中的用法一致。
This document also uses the following definitions:
本文件还使用以下定义：
Location Measurement: An observation about the physical properties of a particular Device's position in time and space. The result of a location measurement -- "location-related measurement data", or simply "measurement data" given sufficient context -- can be used to determine the location of a Device. Location-related measurement data does not directly identify a Device, though it could do so indirectly. Measurement data can change with time if the location of the Device also changes.
位置测量：观察特定设备在时间和空间上的位置的物理特性。位置测量的结果——“与位置相关的测量数据”，或者简单地说是给定足够上下文的“测量数据”——可用于确定设备的位置。与位置相关的测量数据不能直接识别设备，尽管它可以间接识别设备。如果设备的位置也发生变化，测量数据可能会随时间而变化。
Location-related measurement data does not necessarily contain location information directly, but it can be used in combination with contextual knowledge and/or algorithms to derive location information. Examples of location-related measurement data are radio signal strength or timing measurements, Ethernet switch identifiers, and port identifiers.
与位置相关的测量数据不一定直接包含位置信息，但它可以与上下文知识和/或算法结合使用来推导位置信息。位置相关测量数据的示例包括无线电信号强度或定时测量、以太网交换机标识符和端口标识符。
Location-related measurement data can be considered sighting information, based on the definition in [RFC3693].
Location-related measurement data can be considered sighting information, based on the definition in [RFC3693].translate error, please retry
Location Estimate: An approximation of where the Device is located. Location estimates are derived from location measurements. Location estimates are subject to uncertainty, which arises from errors in measurement results.
位置估计：设备所在位置的近似值。位置估计值来自位置测量。位置估计受到测量结果误差引起的不确定性的影响。
GNSS: Global Navigation Satellite System. A satellite-based system that provides positioning and time information -- for example, the US Global Positioning System (GPS) or the European Galileo system.
全球导航卫星系统：全球导航卫星系统。提供定位和时间信息的基于卫星的系统——例如，美国全球定位系统（GPS）或欧洲伽利略系统。
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 [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
This document defines a standard container for the conveyance of location-related measurement parameters in location configuration protocols. This is an XML container that identifies parameters by type and allows the Device to provide the results of any measurement it is able to perform. A set of measurement schemas are also defined that can be carried in the generic container.
本文件定义了一个标准容器，用于在位置配置协议中传输与位置相关的测量参数。这是一个XML容器，它按类型标识参数，并允许设备提供其能够执行的任何测量的结果。还定义了一组可在通用容器中携带的度量模式。
A simple example of measurement data conveyance is illustrated by the example message in Figure 1. This shows a HELD location request message with an Ethernet switch and port measurement taken using the Link-Layer Discovery Protocol (LLDP) [IEEE.8021AB].
图1中的示例消息说明了测量数据传输的一个简单示例。这显示了使用链路层发现协议（LLDP）[IEEE.8021AB]进行以太网交换机和端口测量的保持位置请求消息。
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held">
<locationType exact="true">civic</locationType>
<measurements xmlns="urn:ietf:params:xml:ns:geopriv:lm"
time="2008-04-29T14:33:58">
<lldp xmlns="urn:ietf:params:xml:ns:geopriv:lm:lldp">
<chassis type="4">0a01003c</chassis>
<port type="6">c2</port>
</lldp>
</measurements>
</locationRequest>
<locationRequest xmlns="urn:ietf:params:xml:ns:geopriv:held">
<locationType exact="true">civic</locationType>
<measurements xmlns="urn:ietf:params:xml:ns:geopriv:lm"
time="2008-04-29T14:33:58">
<lldp xmlns="urn:ietf:params:xml:ns:geopriv:lm:lldp">
<chassis type="4">0a01003c</chassis>
<port type="6">c2</port>
</lldp>
</measurements>
</locationRequest>
Figure 1: HELD Location Request with Measurement Data
图1：带测量数据的保留位置请求
This LIS can ignore measurement data that it does not support or understand. The measurements defined in this document follow this rule: extensions that could result in backward incompatibility MUST be added as new measurement definitions rather than extensions to existing types.
该LIS可以忽略其不支持或不理解的测量数据。本文档中定义的度量遵循以下规则：可能导致向后不兼容的扩展必须添加为新的度量定义，而不是现有类型的扩展。
Multiple sets of measurement data, either of the same type or from different sources, can be included in the "measurements" element. See Section 4.1.1 for details on repetition of this element.
“测量”元素中可以包含多组相同类型或不同来源的测量数据。有关该元素重复的详细信息，请参见第4.1.1节。
A LIS can choose to use or ignore location-related measurement data in determining location, as long as rules regarding use and retention (Section 6) are respected. The "method" parameter in the Presence Information Data Format - Location Object (PIDF-LO) [RFC4119] SHOULD be adjusted to reflect the method used. A correct "method" can assist location recipients in assessing the quality (both accuracy and integrity) of location information, though there could be reasons to withhold information about the source of data.
LIS可以选择在确定位置时使用或忽略与位置相关的测量数据，只要遵守有关使用和保留的规则（第6节）。应调整状态信息数据格式-位置对象（PIDF-LO）[RFC4119]中的“方法”参数，以反映所使用的方法。正确的“方法”可以帮助位置接收者评估位置信息的质量（准确性和完整性），尽管可能有理由保留有关数据源的信息。
Measurement data is typically only used to serve the request in which it is included. There may be exceptions, particularly with respect to location URIs. Section 6 provides more information on usage rules.
测量数据通常仅用于服务包含它的请求。可能存在例外情况，特别是关于位置URI。第6节提供了有关使用规则的更多信息。
Location-related measurement data need not be provided exclusively by Devices. A third-party location requester (for example, see [RFC6155]) can request location information using measurement data, if the requester is able to acquire measurement data and authorized to distribute it. There are specific privacy considerations relating to the use of measurements by third parties, which are discussed in Section 6.4.
与位置相关的测量数据不需要仅由设备提供。第三方位置请求者（例如，参见[RFC6155]）可以使用测量数据请求位置信息，前提是请求者能够获取测量数据并有权分发该数据。与第三方使用测量有关的具体隐私注意事项，在第6.4节中讨论。
Location-related measurement data and its use present a number of privacy and security challenges. These are described in more detail in Sections 6 and 7.
与位置相关的测量数据及其使用带来了许多隐私和安全挑战。第6节和第7节将对其进行更详细的描述。
A common container is defined for the expression of location measurement data, as well as a simple means of identifying specific types of measurement data for the purposes of requesting them.
定义了用于表示位置测量数据的通用容器，以及用于识别特定类型测量数据以请求它们的简单方法。
The following example shows a measurement container with measurement time and expiration time included. A WiFi measurement is enclosed.
以下示例显示了包含测量时间和过期时间的测量容器。随附WiFi测量。
<lm:measurements xmlns:lm="urn:ietf:params:xml:ns:geopriv:lm"
time="2008-04-29T14:33:58"
expires="2008-04-29T17:33:58">
<wifi xmlns="urn:ietf:params:xml:ns:geopriv:lm:wifi">
<ap serving="true">
<bssid>00-12-F0-A0-80-EF</bssid>
<ssid>wlan-home</ssid>
</ap>
</wifi>
</lm:measurements>
<lm:measurements xmlns:lm="urn:ietf:params:xml:ns:geopriv:lm"
time="2008-04-29T14:33:58"
expires="2008-04-29T17:33:58">
<wifi xmlns="urn:ietf:params:xml:ns:geopriv:lm:wifi">
<ap serving="true">
<bssid>00-12-F0-A0-80-EF</bssid>
<ssid>wlan-home</ssid>
</ap>
</wifi>
</lm:measurements>
Figure 2: Measurement Example
图2：测量示例
The "measurements" element is used to encapsulate measurement data that is collected at a certain point in time. It contains time-based attributes that are common to all forms of measurement data, and it permits the inclusion of arbitrary measurement data. The elements that are included within the "measurements" element are generically referred to as "measurement elements".
“测量”元素用于封装在特定时间点收集的测量数据。它包含所有形式的测量数据所共有的基于时间的属性，并允许包含任意测量数据。“测量”元素中包含的元素一般称为“测量元素”。
This container can be added to a request for location information in any protocol capable of carrying XML, such as a HELD location request [RFC5985].
该容器可以添加到任何能够承载XML的协议中的位置信息请求中，例如保持位置请求[RFC5985]。
The "time" attribute records the time that the measurement or observation was made. This time can be different from the time that the measurement information was reported. Time information can be used to populate a timestamp on the location result or to determine if the measurement information is used.
“时间”属性记录进行测量或观察的时间。此时间可能与报告测量信息的时间不同。时间信息可用于填充位置结果上的时间戳，或确定是否使用测量信息。
The "time" attribute SHOULD be provided whenever possible. This allows a LIS to avoid selecting an arbitrary timestamp. Exceptions to this, where omitting time might make sense, include relatively static types of measurement (for instance, the DSL measurements in Section 5.6) or for legacy Devices that don't record time information (such as the Home Location Register/Home Subscriber Server for cellular).
应尽可能提供“时间”属性。这允许LIS避免选择任意时间戳。省略时间可能有意义的例外情况包括相对静态的测量类型（例如，第5.6节中的DSL测量）或不记录时间信息的传统设备（例如蜂窝电话的归属位置寄存器/归属订户服务器）。
The "time" attribute is attached to the root "measurement" element. Multiple measurements can often be given the same timestamp, even when the measurements were not actually taken at the same time (consider a set of measurements taken sequentially, where the difference in time between observations is not significant). Measurements cannot be grouped if they have different types or if there is a need for independent time values on each measurement. In these instances, multiple measurement sets are necessary.
“time”属性附加到根“measurement”元素。多个测量通常可以被赋予相同的时间戳，即使测量不是在同一时间进行的（考虑一组连续进行的测量，其中观测之间的时间差不显著）。如果测量值的类型不同，或者每个测量值都需要独立的时间值，则不能对测量值进行分组。在这些情况下，需要多个测量集。
A Device is able to indicate an expiry time in the location measurement using the "expires" attribute. Nominally, this attribute indicates how long information is expected to be valid, but it can also indicate a time limit on the retention and use of the measurement data. A Device can use this attribute to request that the LIS not retain measurement data beyond the indicated time.
设备能够使用“expires”（过期）属性在位置测量中指示过期时间。名义上，该属性表示预期信息有效的时间，但也可以表示保留和使用测量数据的时间限制。设备可以使用此属性请求LIS在指定时间之后不保留测量数据。
Note: Movement of the Device might result in the measurement data being invalidated before the expiry time.
注意：设备的移动可能会导致测量数据在到期之前失效。
A Device is advised to set the "expires" attribute to the earlier of the time that measurements are likely to be unusable and the time that it desires to have measurements discarded by the LIS. A Device that does not desire measurement data to be retained can omit the "expires" attribute. Section 6 describes more specific rules regarding measurement data retention.
建议设备将“expires”属性设置为可能无法使用测量值的时间和希望LIS丢弃测量值的时间中较早的时间。不希望保留测量数据的设备可以省略“expires”属性。第6节描述了有关测量数据保留的更具体规则。
Often a measurement is taken more than once. Reporting the average of a number of measurement results mitigates the effects of random errors that occur in the measurement process.
通常一次测量不止一次。报告多个测量结果的平均值可以减轻测量过程中出现的随机误差的影响。
Reporting each measurement individually can be the most effective method of reporting multiple measurements. This is achieved by providing multiple measurement elements for different times.
单独报告每个测量值可能是报告多个测量值的最有效方法。这是通过为不同的时间提供多个测量元素来实现的。
The alternative is to aggregate multiple measurements and report a mean value across the set of measurements. Additional information about the distribution of the results can be useful in determining location uncertainty.
另一种方法是聚合多个测量值，并报告整个测量集的平均值。关于结果分布的附加信息可用于确定位置不确定性。
Two attributes are provided for use on some measurement values:
提供两个属性用于某些测量值：
rmsError: The root-mean-squared (RMS) error of the set of measurement values used in calculating the result. RMS error is expressed in the same units as the measurement, unless otherwise stated. If an accurate value for the RMS error is not known, this value can be used to indicate an upper bound or estimate for the RMS error.
rmsError：用于计算结果的一组测量值的均方根（RMS）误差。除非另有说明，均方根误差以与测量值相同的单位表示。如果RMS误差的准确值未知，则该值可用于指示RMS误差的上限或估计值。
samples: The number of samples that were taken in determining the measurement value. If omitted, this value can be assumed to be large enough that the RMS error is an indication of the standard deviation of the sample set.
样本数：确定测量值时采集的样本数。如果省略，可以假设该值足够大，使得RMS误差表示样本集的标准偏差。
For some measurement techniques, measurement error is largely dependent on the measurement technique employed. In these cases, measurement error is largely a product of the measurement technique and not the specific circumstances, so the RMS error does not need to be actively measured. A fixed value MAY be provided for the RMS error where appropriate.
对于某些测量技术，测量误差在很大程度上取决于所采用的测量技术。在这些情况下，测量误差很大程度上是测量技术的产物，而不是特定情况的产物，因此不需要主动测量RMS误差。适当时，可为RMS误差提供固定值。
The "rmsError" and "samples" elements are added as attributes of specific measurement data types.
“rmsError”和“samples”元素被添加为特定测量数据类型的属性。
Measurement of time can be significant in certain circumstances. The GNSS measurements included in this document are one such case where a small error in time can result in a large error in location. Factors such as clock drift and errors in time synchronization can result in small, but significant, time errors. Including an indication of the quality of time measurements can be helpful.
在某些情况下，时间测量可能很重要。本文件中包括的全球导航卫星系统测量就是这样一种情况，在这种情况下，时间上的小误差可能导致位置上的大误差。时钟漂移和时间同步中的错误等因素可能会导致较小但显著的时间错误。包括时间测量质量的指示可能会有所帮助。
A "timeError" attribute MAY be added to the "measurement" element to indicate the RMS error in time. "timeError" indicates an upper bound on the time RMS error in seconds.
可在“测量”元素中添加“timeError”属性，以指示时间上的RMS误差。“timeError”表示时间RMS错误的上限（以秒为单位）。
The "timeError" attribute does not apply where multiple samples of a measurement are taken over time. If multiple samples are taken, each SHOULD be included in a different "measurement" element.
“timeError”属性不适用于随时间采集多个测量样本的情况。如果采集了多个样本，每个样本应包含在不同的“测量”元素中。
A measurement request is used by a protocol peer to describe a set of measurement data that it desires. A "measurementRequest" element is defined that can be included in a protocol exchange.
协议对等方使用测量请求来描述所需的一组测量数据。定义了“measurementRequest”元素，该元素可以包含在协议交换中。
For instance, a LIS can use a measurement request in HELD responses. If the LIS is unable to provide location information, but it believes that a particular measurement type would enable it to provide a location, it can include a measurement request in an error response.
例如，LIS可以在保留的响应中使用度量请求。如果LIS无法提供位置信息，但认为特定的测量类型将使其能够提供位置，则可以在错误响应中包含测量请求。
The "measurement" element of the measurement request identifies the type of measurement that is requested. The "type" attribute of this element indicates the type of measurement, as identified by an XML qualified name. A "samples" attribute MAY be used to indicate how many samples of the identified measurement are requested.
测量请求的“测量”元素标识所请求的测量类型。此元素的“type”属性表示由XML限定名标识的度量类型。“样本”属性可用于指示所识别测量的样本数量。
The "measurement" element can be repeated to request multiple (or alternative) measurement types.
可以重复“测量”元素以请求多种（或替代）测量类型。
Additional XML content might be defined for a particular measurement type that is used to further refine a request. These elements either constrain what is requested or specify non-mandatory components of the measurement data that are needed. These are defined along with the specific measurement type.
可以为用于进一步细化请求的特定度量类型定义其他XML内容。这些元素要么约束所请求的内容，要么指定所需测量数据的非强制性组件。这些是与特定测量类型一起定义的。
In the HELD protocol, the inclusion of a measurement request in an error response with a code of "locationUnknown" indicates that providing measurements would increase the likelihood of a subsequent request being successful.
在HOLD协议中，将测量请求包含在错误响应中，代码为“locationUnknown”，表示提供测量