Internet Engineering Task Force (IETF)                    H. Schulzrinne
Request for Comments: 7406                           Columbia University
Category: Informational                                        S. McCann
ISSN: 2070-1721                                           BlackBerry Ltd
                                                                G. Bajko
                                                                MediaTek
                                                           H. Tschofenig
        
Internet Engineering Task Force (IETF)                    H. Schulzrinne
Request for Comments: 7406                           Columbia University
Category: Informational                                        S. McCann
ISSN: 2070-1721                                           BlackBerry Ltd
                                                                G. Bajko
                                                                MediaTek
                                                           H. Tschofenig
        

D. Kroeselberg Siemens Corporate Technology December 2014

D.Kroeselberg西门子公司技术部2014年12月

Extensions to the Emergency Services Architecture for Dealing With Unauthenticated and Unauthorized Devices

扩展应急服务体系结构,用于处理未经验证和未经授权的设备

Abstract

摘要

This document provides a problem statement, introduces terminology, and describes an extension for the base IETF emergency services architecture to address cases where an emergency caller is not authenticated, has no identifiable service provider, or has no remaining credit with which to pay for access to the network.

本文档提供了一个问题陈述,介绍了术语,并描述了基本IETF紧急服务体系结构的扩展,以解决紧急呼叫者未经身份验证、没有可识别的服务提供商或没有剩余信用支付网络访问费用的情况。

Status of This Memo

关于下段备忘

This document is not an Internet Standards Track specification; it is published for informational purposes.

本文件不是互联网标准跟踪规范;它是为了提供信息而发布的。

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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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。并非IESG批准的所有文件都适用于任何级别的互联网标准;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/rfc7406.

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/rfc7406.

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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Use-Case Categories . . . . . . . . . . . . . . . . . . . . .   5
   4.  ZBP Considerations  . . . . . . . . . . . . . . . . . . . . .  12
   5.  NASP Considerations . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  End-Host Profile  . . . . . . . . . . . . . . . . . . . .  15
       5.1.1.  LoST Server Discovery . . . . . . . . . . . . . . . .  15
       5.1.2.  ESRP Discovery  . . . . . . . . . . . . . . . . . . .  15
       5.1.3.  Location Determination and Location Configuration . .  15
       5.1.4.  Emergency Call Identification . . . . . . . . . . . .  15
       5.1.5.  SIP Emergency Call Signaling  . . . . . . . . . . . .  15
       5.1.6.  Media . . . . . . . . . . . . . . . . . . . . . . . .  16
       5.1.7.  Testing . . . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  IAP/ISP Profile . . . . . . . . . . . . . . . . . . . . .  16
       5.2.1.  ESRP Discovery  . . . . . . . . . . . . . . . . . . .  16
       5.2.2.  Location Determination and Location Configuration . .  16
     5.3.  ESRP Profile  . . . . . . . . . . . . . . . . . . . . . .  16
       5.3.1.  Emergency Call Routing  . . . . . . . . . . . . . . .  16
       5.3.2.  Emergency Call Identification . . . . . . . . . . . .  16
       5.3.3.  SIP Emergency Call Signaling  . . . . . . . . . . . .  17
   6.  Lower-Layer Considerations for NAA Case . . . . . . . . . . .  17
     6.1.  Link-Layer Emergency Indication . . . . . . . . . . . . .  18
     6.2.  Securing Network Attachment in NAA Cases  . . . . . . . .  19
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  21
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgments  . . . . . .  . . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25
        
   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Use-Case Categories . . . . . . . . . . . . . . . . . . . . .   5
   4.  ZBP Considerations  . . . . . . . . . . . . . . . . . . . . .  12
   5.  NASP Considerations . . . . . . . . . . . . . . . . . . . . .  12
     5.1.  End-Host Profile  . . . . . . . . . . . . . . . . . . . .  15
       5.1.1.  LoST Server Discovery . . . . . . . . . . . . . . . .  15
       5.1.2.  ESRP Discovery  . . . . . . . . . . . . . . . . . . .  15
       5.1.3.  Location Determination and Location Configuration . .  15
       5.1.4.  Emergency Call Identification . . . . . . . . . . . .  15
       5.1.5.  SIP Emergency Call Signaling  . . . . . . . . . . . .  15
       5.1.6.  Media . . . . . . . . . . . . . . . . . . . . . . . .  16
       5.1.7.  Testing . . . . . . . . . . . . . . . . . . . . . . .  16
     5.2.  IAP/ISP Profile . . . . . . . . . . . . . . . . . . . . .  16
       5.2.1.  ESRP Discovery  . . . . . . . . . . . . . . . . . . .  16
       5.2.2.  Location Determination and Location Configuration . .  16
     5.3.  ESRP Profile  . . . . . . . . . . . . . . . . . . . . . .  16
       5.3.1.  Emergency Call Routing  . . . . . . . . . . . . . . .  16
       5.3.2.  Emergency Call Identification . . . . . . . . . . . .  16
       5.3.3.  SIP Emergency Call Signaling  . . . . . . . . . . . .  17
   6.  Lower-Layer Considerations for NAA Case . . . . . . . . . . .  17
     6.1.  Link-Layer Emergency Indication . . . . . . . . . . . . .  18
     6.2.  Securing Network Attachment in NAA Cases  . . . . . . . .  19
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  20
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  21
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  21
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  22
   Acknowledgments  . . . . . .  . . . . . . . . . . . . . . . . . .  24
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  25
        
1. Introduction
1. 介绍

Summoning police, the fire department, or an ambulance in emergencies is one of the fundamental and most-valued functions of the telephone. As telephony functionality moves from circuit-switched telephony to Internet telephony, its users rightfully expect that this core functionality will continue to work at least as well as it has for the older technology. New devices and services are being made available that could be used to make a request for help; those devices are not traditional telephones, and users are increasingly expecting them to be able to place emergency calls.

在紧急情况下召集警察、消防部门或救护车是电话最基本和最有价值的功能之一。随着电话功能从电路交换电话转移到互联网电话,其用户理所当然地期望该核心功能将继续工作,至少与旧技术一样。正在提供可用于请求帮助的新设备和服务;这些设备不是传统电话,用户越来越希望它们能够拨打紧急电话。

Roughly speaking, the IETF emergency services architecture (see [RFC6881] and [RFC6443]) divides responsibility for handling emergency calls among the access network (Internet Access Provider (IAP) or ISP); the application service provider (ASP), which may be a VoIP service provider (VSP); and the provider of emergency signaling services, the emergency service network (ESN). The access network may provide location information to end systems but does not have to provide any ASP signaling functionality. The emergency caller can reach the ESN either directly or through the ASP's outbound proxy. Any of the three parties can provide the mapping from location to the Public Safety Answering Point (PSAP) URI by offering Location-to-Service Translation (LoST) [RFC5222] services.

粗略地说,IETF应急服务体系结构(见[RFC6881]和[RFC6443])将处理紧急呼叫的责任分配给接入网络(互联网接入提供商(IAP)或ISP);应用服务提供商(ASP),其可以是VoIP服务提供商(VSP);以及紧急信号服务提供商,紧急服务网络(ESN)。接入网络可以向终端系统提供位置信息,但不必提供任何ASP信令功能。紧急呼叫方可以直接或通过ASP的出站代理到达ESN。三方中的任何一方都可以通过提供位置到服务转换(LoST)[RFC5222]服务,提供从位置到公共安全应答点(PSAP)URI的映射。

In general, a set of automated configuration mechanisms allows a device to function in a variety of architectures, without the user being aware of the details on who provides location, mapping services, or call-routing services. However, if emergency calling is to be supported when the calling device lacks access network authorization or does not have an ASP, one or more of the providers may need to provide additional services and functions.

通常,一组自动配置机制允许设备在各种体系结构中运行,而用户不知道有关谁提供位置、映射服务或呼叫路由服务的详细信息。然而,如果在呼叫设备缺乏接入网络授权或不具有ASP时支持紧急呼叫,则一个或多个提供商可能需要提供附加服务和功能。

In all cases, the end device has to be able to perform a LoST lookup and otherwise conduct the emergency call in the same manner as when the three exceptional conditions discussed below do not apply.

在所有情况下,终端设备必须能够执行丢失查找,并以与下述三种例外情况不适用时相同的方式进行紧急呼叫。

We distinguish among three conditions:

我们区分三种情况:

No Access Authentication (NAA): In the NAA case, the emergency caller does not posses valid credentials for the access network. This includes the case where the access network allows pay-per-use, as is common for wireless hotspots, but there is insufficient time to enter credit card details and other registration information required for access. It also covers all cases where either no credentials are available at all or the available credentials do not work for the given IAP/ISP. As a result, the NAA case basically combines the No ASP (NASP) and zero-balance ASP (ZBP) cases below, but at the IAP/ISP level. Support for emergency call handling in the NAA case is subject to the local policy of the ISP. Such policy may vary substantially between ISPs and typically depends on external factors that are not under the ISP control.

无访问身份验证(NAA):在NAA情况下,紧急呼叫方不拥有访问网络的有效凭据。这包括接入网络允许按次付费的情况,这在无线热点中很常见,但没有足够的时间输入接入所需的信用卡详细信息和其他注册信息。它还涵盖所有情况,其中要么根本没有可用的凭据,要么可用的凭据不适用于给定的IAP/ISP。因此,NAA案例基本上结合了以下无ASP(NASP)和零平衡ASP(ZBP)案例,但处于IAP/ISP级别。在NAA情况下,对紧急呼叫处理的支持取决于ISP的当地政策。这种政策在不同的ISP之间可能有很大差异,通常取决于不受ISP控制的外部因素。

No ASP (NASP): The caller does not have an ASP at the time of the call. This can occur in case the caller either does not possess any valid subscription for a reachable ASP or does possess a valid subscription but none of the ASPs are reachable through the ISP.

无ASP(NASP):调用方在调用时没有ASP。如果调用方不拥有可访问ASP的任何有效订阅,或者拥有有效订阅,但ISP无法访问任何ASP,则可能发生这种情况。

Note: The interoperability need is increased with this scenario since the client software used by the emergency caller must be compatible with the protocols and extensions deployed by the ESN.

注意:由于紧急呼叫方使用的客户端软件必须与ESN部署的协议和扩展兼容,因此此场景增加了互操作性需求。

Zero-balance ASP (ZBP): In the case of a zero-balance ASP, the ASP can authenticate the caller, but the caller is not authorized to use ASP services, e.g., because the contract has expired or the prepaid account for the customer has been depleted.

零余额ASP(ZBP):在零余额ASP的情况下,ASP可以对调用方进行身份验证,但调用方无权使用ASP服务,例如,因为合同已过期或客户的预付费帐户已耗尽。

These three cases are not mutually exclusive. A caller in need of help may, for example, be both in an NAA and NASP situation, as explained in more detail in Figure 1. Depending on local policy and regulations, it may not be possible to place emergency calls in the NAA case. Unless local regulations require user identification, it should always be possible to place calls in the NASP case, with minimal impact on the ISP. Unless the ESN requires that all calls traverse a known set of Voice Service Providers (VSPs), it is technically possible to let a caller place an emergency call in the ZBP case. We discuss each case in more detail in Section 3.

这三种情况并不相互排斥。例如,需要帮助的呼叫者可能同时处于NAA和NASP状态,如图1所示。根据当地政策和法规,可能无法在NAA情况下拨打紧急电话。除非当地法规要求用户识别,否则应始终能够在NASP情况下拨打电话,对ISP的影响最小。除非ESN要求所有呼叫都经过一组已知的语音服务提供商(VSP),否则在ZBP情况下,技术上允许呼叫者拨打紧急呼叫。我们将在第3节中详细讨论每个案例。

Some of the functionality provided in this document is already available in the Public Switched Telephone Network (PSTN). Consequently, there is real-world experience available and not all of it is positive. For example, the functionality of calls without Subscriber Identity Modules (SIMs) in today's cellular system has lead to a fair amount of hoax or test calls in certain countries.

本文档中提供的一些功能已在公共交换电话网(PSTN)中提供。因此,有现实世界的经验可供利用,并不是所有的都是积极的。例如,在当今的蜂窝系统中,没有用户识别模块(SIM)的呼叫功能导致在某些国家出现相当数量的欺骗或测试呼叫。

This causes overload situations at PSAPs, which is considered harmful to the overall availability and reliability of emergency services.

这导致PSAP出现过载情况,这被认为对应急服务的整体可用性和可靠性有害。

As an example, the Federal Office of Communications (OFCOM, Switzerland) provided statistics about emergency (112) calls in Switzerland from Jan. 1997 to Nov. 2001. Switzerland did not offer SIM-less emergency calls except for almost a month in July 2000 where a significant increase in hoax and test calls was reported. As a consequence, the functionality was disabled again. More details can be found in the panel presentations of the 3rd Standards Development Organization (SDO) Emergency Services Workshop [esw07].

例如,联邦通信办公室(OFCOM,瑞士)提供了1997年1月至2001年11月期间瑞士紧急电话(112)的统计数据。瑞士没有提供无SIM卡的紧急呼叫,但2000年7月有近一个月的时间,据报道,骗局和测试呼叫显著增加。因此,该功能再次被禁用。更多详细信息,请参见第三届标准发展组织(SDO)应急服务研讨会[esw07]的专题介绍。

2. Terminology
2. 术语

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 in [RFC2119].

本文件中的关键词“必须”、“不得”、“要求”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中的说明进行解释。

This document reuses terminology from [RFC5687] and [RFC5012], namely Internet Access Provider (IAP), Internet Service Provider (ISP), Application Service Provider (ASP), Voice Service Provider (VSP), Emergency Service Routing Proxy (ESRP), Public Safety Answering Point (PSAP), Location Configuration Server (LCS), (emergency) service dial string, and (emergency) service identifier.

本文件重复使用[RFC5687]和[RFC5012]中的术语,即互联网接入提供商(IAP)、互联网服务提供商(ISP)、应用服务提供商(ASP)、语音服务提供商(VSP)、紧急服务路由代理(ESRP)、公共安全应答点(PSAP)、位置配置服务器(LCS)、(紧急)服务拨号字符串、,和(紧急)服务标识符。

3. Use-Case Categories
3. 用例类别

An end host needs to perform the following steps if it is not attached to the network and the user is starting to place an emergency call:

如果终端主机未连接到网络且用户开始拨打紧急电话,则需要执行以下步骤:

Link-Layer Attachment: Some networks have added support for unauthenticated emergency access while others have advertised these capabilities using layer beacons (multicast or broadcast announcements). The end host learns about these unauthenticated emergency services capabilities from either the link layer type or advertisement.

链路层连接:一些网络增加了对未经验证的紧急访问的支持,而另一些网络则使用层信标(多播或广播公告)宣传这些功能。终端主机通过链路层类型或公告了解这些未经验证的紧急服务功能。

The end host uses the link-layer-specific network attachment procedures defined for unauthenticated network access in order to get access to the network.

终端主机使用为未经验证的网络访问定义的链路层特定网络连接过程来访问网络。

Pre-emergency Service Configuration: When the link-layer network attachment procedure is completed, the end host learns basic configuration information using DHCP from the ISP. The end host uses a Location Configuration Protocol (LCP) to retrieve location information. Subsequently, the LoST protocol [RFC5222] is used to learn the relevant emergency numbers and to obtain the PSAP URI applicable for that location.

应急前服务配置:当链路层网络连接程序完成时,终端主机使用DHCP从ISP学习基本配置信息。终端主机使用位置配置协议(LCP)检索位置信息。随后,使用丢失协议[RFC5222]学习相关的紧急号码,并获取适用于该位置的PSAP URI。

Emergency Call: In case of the need for help, a user dials an emergency number and the SIP User Agent (UA) initiates the emergency call procedures by communicating with the PSAP.

紧急呼叫:如果需要帮助,用户拨打紧急号码,SIP用户代理(UA)通过与PSAP通信启动紧急呼叫程序。

Figure 1 compiles the basic logic taking place during network entry for requesting an emergency service and shows the interrelation between the three conditions described earlier.

图1汇总了网络进入期间请求紧急服务的基本逻辑,并显示了前面描述的三种情况之间的相互关系。

                         +-----Y
                         |Start|
                         `...../
                            |
                            | Are credentials
                            | for network attachment
                            | available?
                            |
               NO           v         YES
             +----------------------------+
             |                            |
             |                            |
             V                            v
        ..............               ................
        | Idle: Wait |               |Execute       |
        | for ES Call|               |LLA Procedures|
        | Initiation |               "--------------'
        "------------'                    |
    Is        |               +---------->O
    emergency |               |           | Is ASP
    service   | NO +-----Y    |           | configured?
    network   +--->| End |    |           +---------------+
    attachment|    `...../    |       YES |               | NO
    possible? |               |           |               |
              v               |           v               v
        
                         +-----Y
                         |Start|
                         `...../
                            |
                            | Are credentials
                            | for network attachment
                            | available?
                            |
               NO           v         YES
             +----------------------------+
             |                            |
             |                            |
             V                            v
        ..............               ................
        | Idle: Wait |               |Execute       |
        | for ES Call|               |LLA Procedures|
        | Initiation |               "--------------'
        "------------'                    |
    Is        |               +---------->O
    emergency |               |           | Is ASP
    service   | NO +-----Y    |           | configured?
    network   +--->| End |    |           +---------------+
    attachment|    `...../    |       YES |               | NO
    possible? |               |           |               |
              v               |           v               v
        
        +------------+        |     +------------+    +------------+
        | Execute    |        |     | Execute    |    | Execute    |
        | NAA        |--------+     | Phone BCP  |    | NASP       |
        | Procedures |              | Procedures |    | Procedures |
        +------------+              +------------+    +------------+
                         Authorization for|                |
                            making an     |                |
                         emergency call   |                |
                         with the ASP/VSP?|                |
                           +--------------+                v
                           | NO           | YES         +-----Y
                           |              |             | Done|
                           v              v             `...../
                    +------------+  +------------+
                    | Execute    |  | Execute    |
                    | ZBP        |  | Phone BCP  |
                    | Procedures |  | Procedures |
                    +------------+  +------------+
                           |              |
                           |              |
                           v              v
                        +-----Y        +-----Y
                        | Done|        | Done|
                        `...../        `...../
        
        +------------+        |     +------------+    +------------+
        | Execute    |        |     | Execute    |    | Execute    |
        | NAA        |--------+     | Phone BCP  |    | NASP       |
        | Procedures |              | Procedures |    | Procedures |
        +------------+              +------------+    +------------+
                         Authorization for|                |
                            making an     |                |
                         emergency call   |                |
                         with the ASP/VSP?|                |
                           +--------------+                v
                           | NO           | YES         +-----Y
                           |              |             | Done|
                           v              v             `...../
                    +------------+  +------------+
                    | Execute    |  | Execute    |
                    | ZBP        |  | Phone BCP  |
                    | Procedures |  | Procedures |
                    +------------+  +------------+
                           |              |
                           |              |
                           v              v
                        +-----Y        +-----Y
                        | Done|        | Done|
                        `...../        `...../
        

Abbreviations: LLA: Link-Layer Attachment ES: Emergency Services

缩写:LLA:链路层附件ES:应急服务

Figure 1: Flow Diagram: NAA, ZBP, and NSAP Scenarios

图1:流程图:NAA、ZBP和NSAP场景

The diagrams below highlight the most important steps for the three cases.

下图强调了这三种情况下最重要的步骤。

               +-----Y
               |Start|
               `...../
                  |
                  | No
                  | credentials
                  | for network access
                  | available
                  v
            ..............
            | Idle: Wait |
            | for ES Call|
            | Initiation |
            "------------'
                  |
                  |
                  |
                  v
                  --
                //  --
               /      --
             //  Is     --
            /  emergency  --
            |  service     |  NO   +--------+
            |  network     |------>| Call   |
            |  attachment  |         Failed |
            \  possible?   /       `......../
             \           //
              \\       //
                \    //
                 \--/
                  |
                  | YES
                  |
                  |
                  v
            +------------+
            | Execute    |
            | NAA        |
            | Procedures |
            +------------+
        
               +-----Y
               |Start|
               `...../
                  |
                  | No
                  | credentials
                  | for network access
                  | available
                  v
            ..............
            | Idle: Wait |
            | for ES Call|
            | Initiation |
            "------------'
                  |
                  |
                  |
                  v
                  --
                //  --
               /      --
             //  Is     --
            /  emergency  --
            |  service     |  NO   +--------+
            |  network     |------>| Call   |
            |  attachment  |         Failed |
            \  possible?   /       `......../
             \           //
              \\       //
                \    //
                 \--/
                  |
                  | YES
                  |
                  |
                  v
            +------------+
            | Execute    |
            | NAA        |
            | Procedures |
            +------------+
        
                  |
                  | Network
                  | attachment
                  | in progress
                  v
                /--\  Continue
               |    | with
               |    | application-layer
                \--/  interaction
        
                  |
                  | Network
                  | attachment
                  | in progress
                  v
                /--\  Continue
               |    | with
               |    | application-layer
                \--/  interaction
        

Figure 2: Flow Diagram: NAA Scenario

图2:流程图:NAA场景

                        +-----+
           +------------|Start|-----------------+
           |            `...../                 |
           v                                    v
     +------------+                     +----------------+
     | NAA        |                     | Regular        |
     | Procedures |                     | Network Access |
     +------------+                     | Procedures     |
           |                            +----------------+
           |                                    |
           |                                    |
           ----------------o--------------------+
                           |
                           |
                           |
                           |
                       Network
                       Attachment
                       Completed
                           |
                           |
                           |
                           |
                           v
        
                        +-----+
           +------------|Start|-----------------+
           |            `...../                 |
           v                                    v
     +------------+                     +----------------+
     | NAA        |                     | Regular        |
     | Procedures |                     | Network Access |
     +------------+                     | Procedures     |
           |                            +----------------+
           |                                    |
           |                                    |
           ----------------o--------------------+
                           |
                           |
                           |
                           |
                       Network
                       Attachment
                       Completed
                           |
                           |
                           |
                           |
                           v
        
                     +------------+      +---------+
                     | ASP        |  NO  | See     |
                     | Configured?|----->| main    |
                     +------------+      | diagram |
                           |             `........./
                           |
                           | YES
                           |
                           v
                        //----
                       /      --
                     //         --
                    /              -       +---------+
                    | Authorization|  YES  | See     |
                    | for making   |------>| main    |
                    |   ES call    |       | diagram |
                    \    with      /       `........./
                     \  VSP/ASP? //
                      \\       //
                        \    //
                         \--/
                           |
                           | NO
                           |
                           |
                           v
                     +------------+
                     | Execute    |
                     | ZBP        |
                     | Procedures |
                     +------------+
                           |
                           | Call
                           | in progress
                           |
                           v
                       +--------+
                       | Call   |
                         Success|
                       `......../
        
                     +------------+      +---------+
                     | ASP        |  NO  | See     |
                     | Configured?|----->| main    |
                     +------------+      | diagram |
                           |             `........./
                           |
                           | YES
                           |
                           v
                        //----
                       /      --
                     //         --
                    /              -       +---------+
                    | Authorization|  YES  | See     |
                    | for making   |------>| main    |
                    |   ES call    |       | diagram |
                    \    with      /       `........./
                     \  VSP/ASP? //
                      \\       //
                        \    //
                         \--/
                           |
                           | NO
                           |
                           |
                           v
                     +------------+
                     | Execute    |
                     | ZBP        |
                     | Procedures |
                     +------------+
                           |
                           | Call
                           | in progress
                           |
                           v
                       +--------+
                       | Call   |
                         Success|
                       `......../
        

Figure 3: Flow Diagram: ZBP Scenario

图3:流程图:ZBP场景

                              +-----+
                 +------------|Start|-----------------+
                 |            `...../                 |
                 v                                    v
           +------------+                     +----------------+
           | NAA        |                     | Regular        |
           | Procedures |                     | Network Access |
           +------------+                     | Procedures     |
                 |                            +----------------+
                 |                                    |
                 |                                    |
                 ----------------o--------------------+
                                 |
                                 |
                                 |
                                 |
                             Network
                             Attachment
                             Completed
                                 |
                                 |
                                 |
                                 |
                                 v
                           +------------+      +---------+
                           | ASP        |  YES | See     |
                           | Configured?|----->| main    |
                           +------------+      | diagram |
                                 |             `........./
                                 |
                                 | NO
                                 |
                                 v
                           +------------+
                           | Execute    |
                           | NASP       |
                           | Procedures |
                           +------------+
                                 |
                                 | Call
                                 | in progress
                                 |
                                 v
                             +--------+
                             | Call   |
                             | Success|
                             `......../
                   Figure 4: Flow Diagram: NASP Scenario
        
                              +-----+
                 +------------|Start|-----------------+
                 |            `...../                 |
                 v                                    v
           +------------+                     +----------------+
           | NAA        |                     | Regular        |
           | Procedures |                     | Network Access |
           +------------+                     | Procedures     |
                 |                            +----------------+
                 |                                    |
                 |                                    |
                 ----------------o--------------------+
                                 |
                                 |
                                 |
                                 |
                             Network
                             Attachment
                             Completed
                                 |
                                 |
                                 |
                                 |
                                 v
                           +------------+      +---------+
                           | ASP        |  YES | See     |
                           | Configured?|----->| main    |
                           +------------+      | diagram |
                                 |             `........./
                                 |
                                 | NO
                                 |
                                 v
                           +------------+
                           | Execute    |
                           | NASP       |
                           | Procedures |
                           +------------+
                                 |
                                 | Call
                                 | in progress
                                 |
                                 v
                             +--------+
                             | Call   |
                             | Success|
                             `......../
                   Figure 4: Flow Diagram: NASP Scenario
        

The NAA procedures are described in Section 6. The ZBP procedures are described in Section 4. The NASP procedures are described in Section 5. The Phone BCP procedures are described in [RFC6881]. The LLA procedures are not described in this document since they are specific to the link-layer technology in use.

NAA程序见第6节。第4节介绍了ZBP程序。NASP程序见第5节。[RFC6881]中描述了电话BCP程序。由于LLA程序特定于所使用的链路层技术,因此本文档中未对其进行描述。

4. ZBP Considerations
4. ZBP考虑因素

ZBP includes all cases where a subscriber is known to an ASP but lacks the necessary authorization to access regular ASP services. Example ZBP cases include empty prepaid accounts, barred accounts, roaming and mobility restrictions, or any other conditions set by ASP policy.

ZBP包括ASP已知订户但缺乏访问常规ASP服务所需授权的所有情况。示例ZBP案例包括空预付费帐户、禁止帐户、漫游和移动限制,或ASP策略设置的任何其他条件。

Local regulation might demand that emergency calls cannot proceed without successful service authorization. In some regulatory regimes, however, it may be possible to allow emergency calls to continue despite authorization failures. To distinguish an emergency call from a regular call, an ASP can identify emergency sessions by inspecting the service URN [RFC5031] used in call setup. The ZBP case, therefore, only affects the ASP.

当地法规可能要求,未经成功的服务授权,紧急呼叫不得继续。然而,在一些监管制度中,即使授权失败,也可能允许紧急呼叫继续进行。为了区分紧急呼叫和常规呼叫,ASP可以通过检查呼叫设置中使用的服务URN[RFC5031]来识别紧急会话。因此,ZBP案例只影响ASP。

Permitting a call despite authorization failures could present an opportunity for abuse. The ASP may choose to verify the destination of the emergency calls and to only permit calls to certain, preconfigured entities (e.g., to local PSAPs). Section 7 discusses this topic in more detail.

在授权失败的情况下允许呼叫可能会导致滥用。ASP可以选择验证紧急呼叫的目的地,并且只允许呼叫某些预先配置的实体(例如,本地PSAP)。第7节更详细地讨论了这个主题。

An ASP without a regulatory requirement to authorize emergency calls can deny emergency call setup. Where an ASP does not authorize an emergency call, the caller may be able to fall back to NASP procedures.

没有授权紧急呼叫的法规要求的ASP可以拒绝紧急呼叫设置。当ASP未授权紧急呼叫时,呼叫者可以退回到NASP程序。

5. NASP Considerations
5. NASP考虑因素

To start the description, we consider the sequence of steps that are executed in an emergency call based on Figure 5.

为了开始描述,我们考虑基于图5的急诊科呼叫执行的步骤序列。

o As an initial step, the devices attach to the network as shown in step (1). This step is outside the scope of this section.

o 作为初始步骤,设备连接到网络,如步骤(1)所示。此步骤不在本节的范围内。

o When the link-layer network attachment procedure is completed, the end host learns basic IP configuration information using DHCP from the ISP, as shown in step (2).

o 链路层网络连接过程完成后,终端主机使用DHCP从ISP学习基本IP配置信息,如步骤(2)所示。

o When the end host has configured the IP address, it starts an interaction with the discovered LCS at the ISP, as shown in step (3). In certain deployments, the ISP may need to interact with the IAP. This protocol exchange is shown in step (4).

o 当终端主机配置了IP地址后,它将开始与ISP上发现的LCS进行交互,如步骤(3)所示。在某些部署中,ISP可能需要与IAP交互。该协议交换如步骤(4)所示。

o Once location information is obtained, the end host triggers the LoST protocol to obtain the address of the ESRP/PSAP. This is shown in step (5).

o 一旦获得位置信息,终端主机将触发丢失协议以获取ESRP/PSAP的地址。这在步骤(5)中显示。

o In step (6), the SIP UA initiates a SIP INVITE request towards the indicated ESRP. The INVITE message contains all the necessary parameters required by Section 5.1.5.

o 在步骤(6)中,SIP UA向指示的ESRP发起SIP INVITE请求。INVITE消息包含第5.1.5节要求的所有必要参数。

o The ESRP receives the INVITE and processes it according to the description in Section 5.3.3.

o ESRP接收邀请并根据第5.3.3节中的说明进行处理。

o The ESRP routes the call to the PSAP, as shown in step (8), potentially interacting with a LoST server first to determine the route.

o ESRP将调用路由到PSAP,如步骤(8)所示,可能首先与丢失的服务器交互以确定路由。

o The PSAP evaluates the initial INVITE and aims to complete the call setup.

o PSAP评估初始邀请并旨在完成呼叫设置。

o Finally, when the call setup is completed, media traffic can be exchanged between the PSAP and the SIP UA.

o 最后,当呼叫设置完成时,可以在PSAP和SIP UA之间交换媒体流量。

For brevity, the end-to-end SIP and media exchange between the PSAP and SIP UA are not shown in Figure 5.

为简洁起见,图5中未显示PSAP和SIP UA之间的端到端SIP和媒体交换。

                                  +-------+
                                  | PSAP  |
                                  |       |
                                  +-------+
                                      ^
                                      | (8)
                                      |
               +----------+(7) +----------+
               | LoST     |<-->| ESRP     |
               | Server   |    |          |
               +----------+    +----------+
                     ^                ^
    +----------------+----------------|--------------+
    | ISP            |                |              |
    |+----------+    |                |  +----------+|
    || LCS-ISP  | (3)|                |  | DHCP     ||
    ||          |<-+