Internet Engineering Task Force (IETF)                           C. Shen
Request for Comments: 7200                                H. Schulzrinne
Category: Standards Track                                    Columbia U.
ISSN: 2070-1721                                                 A. Koike
                                                                     NTT
                                                              April 2014
        
Internet Engineering Task Force (IETF)                           C. Shen
Request for Comments: 7200                                H. Schulzrinne
Category: Standards Track                                    Columbia U.
ISSN: 2070-1721                                                 A. Koike
                                                                     NTT
                                                              April 2014
        

A Session Initiation Protocol (SIP) Load-Control Event Package

会话启动协议(SIP)负载控制事件包

Abstract

摘要

This specification defines a load-control event package for the Session Initiation Protocol (SIP). It allows SIP entities to distribute load-filtering policies to other SIP entities in the network. The load-filtering policies contain rules to throttle calls from a specific user or based on their source or destination domain, telephone number prefix. The mechanism helps to prevent signaling overload and complements feedback-based SIP overload control efforts.

本规范定义了会话启动协议(SIP)的负载控制事件包。它允许SIP实体将负载过滤策略分发给网络中的其他SIP实体。负载筛选策略包含限制来自特定用户或基于其源或目标域、电话号码前缀的呼叫的规则。该机制有助于防止信令过载,并补充了基于反馈的SIP过载控制工作。

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/rfc7200.

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/rfc7200.

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. Conventions .....................................................3
   3. SIP Load-Filtering Overview .....................................4
      3.1. Load-Filtering Policy Format ...............................4
      3.2. Load-Filtering Policy Computation ..........................4
      3.3. Load-Filtering Policy Distribution .........................4
      3.4. Applicable Network Domains .................................8
   4. Load-Control Event Package ......................................9
      4.1. Event Package Name .........................................9
      4.2. Event Package Parameters ...................................9
      4.3. SUBSCRIBE Bodies ...........................................9
      4.4. SUBSCRIBE Duration .........................................9
      4.5. NOTIFY Bodies .............................................10
      4.6. Notifier Processing of SUBSCRIBE Requests .................10
      4.7. Notifier Generation of NOTIFY Requests ....................10
      4.8. Subscriber Processing of NOTIFY Requests ..................10
      4.9. Handling of Forked Requests ...............................12
      4.10. Rate of Notifications ....................................12
      4.11. State Delta ..............................................12
   5. Load-Control Document ..........................................13
      5.1. Format ....................................................13
      5.2. Namespace .................................................13
      5.3. Conditions ................................................14
           5.3.1. Call Identity ......................................14
           5.3.2. Method .............................................16
           5.3.3. Target SIP Entity ..................................17
           5.3.4. Validity ...........................................18
      5.4. Actions ...................................................18
   6. XML Schema Definition for Load Control .........................20
   7. Security Considerations ........................................23
   8. IANA Considerations ............................................24
      8.1. Load-Control Event Package Registration ...................24
      8.2. application/load-control+xml Media Type Registration ......24
      8.3. URN Sub-Namespace Registration ............................25
      8.4. Load-Control Schema Registration ..........................26
   9. Acknowledgements ...............................................27
   10. References ....................................................27
      10.1. Normative References .....................................27
      10.2. Informative References ...................................28
   Appendix A. Definitions ...........................................30
   Appendix B. Design Requirements ...................................30
   Appendix C. Discussion of How This Specification Meets the
               Requirements of RFC 5390 ..............................31
   Appendix D. Complete Examples .....................................36
      D.1. Load-Control Document Examples ............................36
      D.2. Message Flow Examples .....................................40
        
   1. Introduction ....................................................3
   2. Conventions .....................................................3
   3. SIP Load-Filtering Overview .....................................4
      3.1. Load-Filtering Policy Format ...............................4
      3.2. Load-Filtering Policy Computation ..........................4
      3.3. Load-Filtering Policy Distribution .........................4
      3.4. Applicable Network Domains .................................8
   4. Load-Control Event Package ......................................9
      4.1. Event Package Name .........................................9
      4.2. Event Package Parameters ...................................9
      4.3. SUBSCRIBE Bodies ...........................................9
      4.4. SUBSCRIBE Duration .........................................9
      4.5. NOTIFY Bodies .............................................10
      4.6. Notifier Processing of SUBSCRIBE Requests .................10
      4.7. Notifier Generation of NOTIFY Requests ....................10
      4.8. Subscriber Processing of NOTIFY Requests ..................10
      4.9. Handling of Forked Requests ...............................12
      4.10. Rate of Notifications ....................................12
      4.11. State Delta ..............................................12
   5. Load-Control Document ..........................................13
      5.1. Format ....................................................13
      5.2. Namespace .................................................13
      5.3. Conditions ................................................14
           5.3.1. Call Identity ......................................14
           5.3.2. Method .............................................16
           5.3.3. Target SIP Entity ..................................17
           5.3.4. Validity ...........................................18
      5.4. Actions ...................................................18
   6. XML Schema Definition for Load Control .........................20
   7. Security Considerations ........................................23
   8. IANA Considerations ............................................24
      8.1. Load-Control Event Package Registration ...................24
      8.2. application/load-control+xml Media Type Registration ......24
      8.3. URN Sub-Namespace Registration ............................25
      8.4. Load-Control Schema Registration ..........................26
   9. Acknowledgements ...............................................27
   10. References ....................................................27
      10.1. Normative References .....................................27
      10.2. Informative References ...................................28
   Appendix A. Definitions ...........................................30
   Appendix B. Design Requirements ...................................30
   Appendix C. Discussion of How This Specification Meets the
               Requirements of RFC 5390 ..............................31
   Appendix D. Complete Examples .....................................36
      D.1. Load-Control Document Examples ............................36
      D.2. Message Flow Examples .....................................40
        
   Appendix E.  Related Work .........................................41
      E.1. Relationship to Load Filtering in PSTN ....................41
      E.2. Relationship with Other IETF SIP Overload Control Efforts .42
        
   Appendix E.  Related Work .........................................41
      E.1. Relationship to Load Filtering in PSTN ....................41
      E.2. Relationship with Other IETF SIP Overload Control Efforts .42
        
1. Introduction
1. 介绍

SIP load-control mechanisms are needed to prevent congestion collapse [RFC6357] in cases of SIP server overload [RFC5390]. There are two types of load-control approaches. In the first approach, feedback control, SIP servers provide load limits to upstream servers, to reduce the incoming rate of all SIP requests [SIP-OVERLOAD]. These upstream servers then drop or delay incoming SIP requests. Feedback control is reactive and affects signaling messages that have already been issued by user agent clients. This approach works well when SIP proxy servers in the core networks (core proxy servers) or destination-specific SIP proxy servers in the edge networks (edge proxy servers) are overloaded. By their nature, they need to distribute rate, drop, or window information to all upstream SIP proxy servers and normally affect all calls equally, regardless of destination.

在SIP服务器过载的情况下,需要SIP负载控制机制来防止拥塞崩溃[RFC6357][RFC5390]。有两种类型的负载控制方法。在第一种方法(反馈控制)中,SIP服务器向上游服务器提供负载限制,以降低所有SIP请求的传入速率[SIP-OVERLOAD]。然后,这些上游服务器丢弃或延迟传入的SIP请求。反馈控制是被动的,影响用户代理客户端已经发出的信令消息。当核心网络(核心代理服务器)中的SIP代理服务器或边缘网络(边缘代理服务器)中特定于目的地的SIP代理服务器过载时,此方法工作良好。就其性质而言,它们需要将速率、丢包或窗口信息分发到所有上游SIP代理服务器,并且通常会平等地影响所有呼叫,而不考虑目的地。

This specification proposes an additional, complementary load-control mechanism, called "load filtering". It is most applicable for situations where a traffic surge and its source/destination distribution can be predicted in advance. In those cases, network operators create load-filtering policies that indicate calls to specific destinations or from specific sources should be rate-limited or randomly dropped. These load-filtering policies are then distributed to SIP servers and possibly SIP user agents that are likely to generate calls to the affected destinations or from the affected sources. Load filtering works best if it prevents calls as close to the originating user agent clients as possible. The applicability of SIP load filtering can also be extended beyond overload control, e.g., to implement service level agreement commitments.

本规范提出了一种额外的补充性负载控制机制,称为“负载过滤”。它最适用于可以提前预测流量激增及其源/目的地分布的情况。在这些情况下,网络运营商创建负载过滤策略,指示对特定目的地或特定来源的呼叫应进行速率限制或随机丢弃。然后将这些负载过滤策略分发到SIP服务器,可能还有SIP用户代理,这些代理可能会生成到受影响目的地或来自受影响源的呼叫。如果负载过滤可以防止调用尽可能靠近原始用户代理客户端,则负载过滤效果最佳。SIP负载过滤的适用性也可以扩展到过载控制之外,例如,实现服务级别协议承诺。

2. Conventions
2. 习俗

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。

3. SIP Load-Filtering Overview
3. SIP负载过滤概述
3.1. Load-Filtering Policy Format
3.1. 加载筛选策略格式

Load-filtering policies are specified by sets of rules. Each rule contains both load-filtering conditions and actions. The load-filtering conditions define identities of the targets to be filtered (Section 5.3.1). For example, there are two typical resource limits in a possible overload situation, i.e., human destination limits (number of call takers) and node capacity limits. The load-filtering targets in these two cases can be the specific callee numbers or the destination domain corresponding to the overload. Load-filtering conditions also indicate the specific message type to be matched (Section 5.3.2), with which target SIP entity the filtering policy is associated (Section 5.3.3), and the period of time when the filtering policy should be activated and deactivated (Section 5.3.4). Load-filtering actions describe the desired control functions such as keeping the request rate below a specified level (Section 5.4).

负载筛选策略由一组规则指定。每个规则都包含加载筛选条件和操作。负载过滤条件定义了要过滤的目标的标识(第5.3.1节)。例如,在可能的过载情况下,有两种典型的资源限制,即人员目的地限制(呼叫接受者数量)和节点容量限制。这两种情况下的负载筛选目标可以是特定的被叫号码或与重载对应的目标域。负载过滤条件还指示要匹配的特定消息类型(第5.3.2节),过滤策略与之关联的目标SIP实体(第5.3.3节),以及应激活和停用过滤策略的时间段(第5.3.4节)。负载过滤动作描述了所需的控制功能,如将请求速率保持在指定水平以下(第5.4节)。

3.2. Load-Filtering Policy Computation
3.2. 负载过滤策略计算

When computing the load-filtering policies, one needs to take into consideration information such as overload time, scope and network topology, as well as service policies. It is also important to make sure that there is no resource allocation loop and that server capacity is allocated in a way that both prevents overload and maximizes effective throughput (commonly called goodput). In some cases, in order to better utilize system resources, it may be preferable to employ an algorithm that dynamically computes the load-filtering policies based on currently observed server load status, rather than using a purely static filtering policy assignment. The computation algorithm for load-filtering policies is beyond the scope of this specification.

在计算负载过滤策略时,需要考虑过载时间、范围和网络拓扑以及服务策略等信息。同样重要的是,确保没有资源分配循环,服务器容量的分配方式既能防止过载,又能最大限度地提高有效吞吐量(通常称为goodput)。在某些情况下,为了更好地利用系统资源,最好采用基于当前观察到的服务器负载状态动态计算负载过滤策略的算法,而不是使用纯静态过滤策略分配。负载筛选策略的计算算法超出了本规范的范围。

3.3. Load-Filtering Policy Distribution
3.3. 负载筛选策略分布

For distributing load-filtering policies, this specification defines the SIP event package for load control, which is an "instantiation" of the generic SIP event notification framework [RFC6665]. This specification also defines the XML schema of a load-control document (Section 5), which is used to encode load-filtering policies.

为了分发负载过滤策略,本规范定义了用于负载控制的SIP事件包,它是通用SIP事件通知框架[RFC6665]的“实例化”。本规范还定义了负载控制文档(第5节)的XML模式,用于对负载过滤策略进行编码。

In order for load-filtering policies to be properly distributed, each capable SIP entity in the network subscribes to the SIP load-control event package of each SIP entity to which it sends signaling requests. A SIP entity that accepts subscription requests is called a "notifier" (Section 4.6). Subscription is initiated and maintained during normal server operation. The subscription of neighboring SIP

为了适当地分发负载过滤策略,网络中的每个有能力的SIP实体订阅它向其发送信令请求的每个SIP实体的SIP负载控制事件包。接受订阅请求的SIP实体称为“通知者”(第4.6节)。订阅在正常服务器操作期间启动和维护。相邻SIP的订阅

entities needs to be persistent, as described in Sections 4.1 and 4.2 of [RFC6665]. The refresh procedure is described in Section 4.7 below. Subscribers may terminate the subscription if they have not received notifications for an extended time period, and can resubscribe if they determine that signaling with the notifier becomes active again.

实体需要持久化,如[RFC6665]第4.1节和第4.2节所述。下文第4.7节介绍了刷新程序。如果订阅者在一段较长的时间内未收到通知,则可以终止订阅;如果订阅者确定通知器的信令再次激活,则可以重新订阅。

An example architecture is shown in Figure 1 to illustrate SIP load-filtering policy distribution. This scenario consists of two networks belonging to Service Provider A and Service Provider B, respectively. Each provider's network is made up of two SIP core proxy servers and four SIP edge proxy servers. The core proxy servers and edge proxy servers of Service Provider A are denoted as CPa1 to CPa2 and EPa1 to EPa4; the core proxy servers and edge proxy servers of Service Provider B are denoted as CPb1 to CPb2 and EPb1 to EPb4.

图1显示了一个示例体系结构,以说明SIP负载过滤策略分布。此场景由分别属于服务提供商A和服务提供商B的两个网络组成。每个提供商的网络由两个SIP核心代理服务器和四个SIP边缘代理服务器组成。服务提供商A的核心代理服务器和边缘代理服务器分别表示为CPa1到CPa2和EPa1到EPa4;服务提供商B的核心代理服务器和边缘代理服务器表示为CPb1到CPb2和EPb1到EPb4。

      +-----------+   +-----------+   +-----------+   +-----------+
      |           |   |           |   |           |   |           |
      |   EPa1    |   |   EPa2    |   |   EPa3    |   |   EPa4    |
      |           |   |           |   |           |   |           |
      +-----------+   +-----------+   +-----------+   +-----------+
              \         /                    \          /
               \       /                      \        /
                \     /                        \      /
              +-----------+                  +-----------+
              |           |                  |           |
              |   CPa1    |------------------|   CPa2    |
              |           |                  |           |
              +-----------+                  +-----------+
                    |                              |
      Service       |                              |
      Provider A    |                              |
                    |                              |
     =================================================================
                    |                              |
      Service       |                              |
      Provider B    |                              |
                    |                              |
              +-----------+                  +-----------+
              |           |                  |           |
              |   CPb1    |------------------|   CPb2    |
              |           |                  |           |
              +-----------+                  +-----------+
                /      \                        /     \
               /        \                      /       \
              /          \                    /         \
      +-----------+   +-----------+   +-----------+   +-----------+
      |           |   |           |   |           |   |           |
      |   EPb1    |   |   EPb2    |   |   EPb3    |   |   EPb4    |
      |           |   |           |   |           |   |           |
      +-----------+   +-----------+   +-----------+   +-----------+
        
      +-----------+   +-----------+   +-----------+   +-----------+
      |           |   |           |   |           |   |           |
      |   EPa1    |   |   EPa2    |   |   EPa3    |   |   EPa4    |
      |           |   |           |   |           |   |           |
      +-----------+   +-----------+   +-----------+   +-----------+
              \         /                    \          /
               \       /                      \        /
                \     /                        \      /
              +-----------+                  +-----------+
              |           |                  |           |
              |   CPa1    |------------------|   CPa2    |
              |           |                  |           |
              +-----------+                  +-----------+
                    |                              |
      Service       |                              |
      Provider A    |                              |
                    |                              |
     =================================================================
                    |                              |
      Service       |                              |
      Provider B    |                              |
                    |                              |
              +-----------+                  +-----------+
              |           |                  |           |
              |   CPb1    |------------------|   CPb2    |
              |           |                  |           |
              +-----------+                  +-----------+
                /      \                        /     \
               /        \                      /       \
              /          \                    /         \
      +-----------+   +-----------+   +-----------+   +-----------+
      |           |   |           |   |           |   |           |
      |   EPb1    |   |   EPb2    |   |   EPb3    |   |   EPb4    |
      |           |   |           |   |           |   |           |
      +-----------+   +-----------+   +-----------+   +-----------+
        

Figure 1: Example Network Scenario Using SIP Load-Control Event Package Mechanism

图1:使用SIP负载控制事件包机制的示例网络场景

During the initialization stage, the proxy servers first identify all their outgoing signaling neighbors and subscribe to them. Service providers can provision neighbors, or the proxy servers can incrementally learn who their neighbors are by inspecting signaling messages that they send and receive. Assuming all signaling relationships in Figure 1 are bidirectional, after this initialization stage, each proxy server will be subscribed to all its neighbors.

在初始化阶段,代理服务器首先识别其所有传出信令邻居并订阅它们。服务提供商可以提供邻居,或者代理服务器可以通过检查其发送和接收的信令消息,以增量方式了解其邻居是谁。假设图1中的所有信令关系都是双向的,在这个初始化阶段之后,每个代理服务器都将订阅其所有邻居。

Case I: EPa1 serves a TV program hotline and decides to limit the total number of incoming calls to the hotline to prevent an overload. To do so, EPa1 sends a notification to CPa1 with the specific hotline number, time of activation, and total acceptable call rate. Depending on the load-filtering policy computation algorithm, CPa1 may allocate the received total acceptable call rate among its neighbors, namely, EPa2, CPa2, and CPb1, and notify them about the resulting allocation along with the hotline number and the activation time. CPa2 and CPb1 may perform further allocation among their own neighbors and notify the corresponding proxy servers. This process continues until all edge proxy servers in the network have been informed about the event and have proper load-filtering policies configured.

案例一:EPa1为电视节目热线提供服务,并决定限制热线的来电总数,以防止过载。为此,EPa1向CPa1发送通知,告知具体的热线号码、激活时间和可接受的总呼叫率。根据负载过滤策略计算算法,CPa1可以在其邻居(即EPa2、CPa2和CPb1)之间分配接收到的总可接受呼叫速率,并将结果分配以及热线号码和激活时间通知他们。CPa2和CPb1可以在它们自己的邻居之间执行进一步的分配,并通知相应的代理服务器。此过程将继续,直到网络中的所有边缘代理服务器都已被告知事件并配置了正确的负载筛选策略。

In the above case, the network entity where load-filtering policy is first introduced is the SIP server providing access to the resource that creates the overload situation. In other cases, the network entry point of introducing load-filtering policy could also be an entity that hosts this resource. For example, an operator may host an application server that performs toll-free-number ("800 number") translation services. The application server itself may be a SIP proxy server or a SIP Back-to-Back User Agent (B2BUA). If one of the toll-free numbers hosted at the application server creates the overload condition, the load-filtering policies can be introduced from the application server and then propagated to other SIP proxy servers in the network.

在上述情况下,首先引入负载过滤策略的网络实体是提供对造成过载情况的资源的访问的SIP服务器。在其他情况下,引入负载筛选策略的网络入口点也可以是承载此资源的实体。例如,运营商可以托管执行免费号码(“800号码”)翻译服务的应用服务器。应用服务器本身可以是SIP代理服务器或SIP背靠背用户代理(B2BUA)。如果托管在应用服务器上的某个免费电话号码造成过载情况,则可以从应用服务器引入负载过滤策略,然后传播到网络中的其他SIP代理服务器。

Case II: A hurricane affects the region covered by CPb2, EPb3, and EPb4. All three of these SIP proxy servers are overloaded. The rescue team determines that outbound calls are more valuable than inbound calls in this specific situation. Therefore, EPb3 and EPb4 are configured with load-filtering policies to accept more outbound calls than inbound calls. CPb2 may be configured the same way or receive dynamically computed load-filtering policies from EPb3 and EPb4. Depending on the load-filtering policy computation algorithm, CPb2 may also send out notifications to its outside neighbors, namely CPb1 and CPa2, specifying a limit on the acceptable rate of inbound calls to CPb2's responsible domain. CPb1 and CPa2 may subsequently notify their neighbors about limiting the calls to CPb2's area. The same process could continue until all edge proxy servers are notified and have load-filtering policies configured.

案例二:飓风影响CPb2、EPb3和EPb4覆盖的区域。这三个SIP代理服务器都过载。救援小组确定,在这种特定情况下,呼出电话比呼入电话更有价值。因此,EPb3和EPb4配置了负载过滤策略,以接受比入站呼叫更多的出站呼叫。CPb2可以以相同的方式配置,或者从EPb3和EPb4接收动态计算的负载过滤策略。根据负载过滤策略计算算法,CPb2还可以向其外部邻居(即CPb1和CPa2)发送通知,指定对CPb2负责域的入站呼叫的可接受速率的限制。CPb1和CPa2可能随后通知其邻居将呼叫限制在CPb2的区域。在通知所有边缘代理服务器并配置了负载筛选策略之前,可以继续执行相同的过程。

Note that this specification does not define the provisioning interface between the party who determines the load-filtering policy and the network entry point where the policy is introduced. One of the options for the provisioning interface is the Extensible Markup Language (XML) Configuration Access Protocol (XCAP) [RFC4825].

请注意,本规范未定义确定负载筛选策略的一方与引入该策略的网络入口点之间的配置接口。供应接口的选项之一是可扩展标记语言(XML)配置访问协议(XCAP)[RFC4825]。

3.4. Applicable Network Domains
3.4. 适用的网络域

This specification MUST be applied inside a "Trust Domain". The concept of a Trust Domain is similar to that defined in [RFC3324] and [RFC3325]. A Trust Domain, for the purpose of SIP load filtering, is a set of SIP entities such as SIP proxy servers that are trusted to exchange load-filtering policies defined in this specification. In the simplest case, a Trust Domain is a network of SIP entities belonging to a single service provider who deploys it and accurately knows the behavior of those SIP entities. Such simple Trust Domains may be joined to form larger Trust Domains by bilateral agreements between the service providers of the SIP entities.

此规范必须在“信任域”内应用。信任域的概念类似于[RFC3324]和[RFC3325]中定义的概念。出于SIP负载过滤的目的,信任域是一组SIP实体,例如SIP代理服务器,它们被信任以交换本规范中定义的负载过滤策略。在最简单的情况下,信任域是属于单个服务提供商的SIP实体网络,该服务提供商部署了信任域并准确地知道这些SIP实体的行为。通过SIP实体的服务提供商之间的双边协议,可以加入这样的简单信任域以形成更大的信任域。

The key requirement of a Trust Domain for the purpose of SIP load filtering is that the behavior of all SIP entities within a given Trust Domain is known to comply to the following set of specifications.

为了进行SIP负载过滤,信任域的关键要求是已知给定信任域中所有SIP实体的行为符合以下一组规范。

o SIP entities in the Trust Domain agree on the mechanisms used to secure the communication among SIP entities within the Trust Domain.

o 信任域中的SIP实体同意用于保护信任域中SIP实体之间通信的机制。

o SIP entities in the Trust Domain agree on the manner used to determine which SIP entities are part of the Trust Domain.

o 信任域中的SIP实体同意用于确定哪些SIP实体是信任域的一部分的方式。

o SIP entities in the Trust Domain are compliant to SIP [RFC3261].

o 信任域中的SIP实体符合SIP[RFC3261]。

o SIP entities in the Trust Domain are compliant to SIP-Specific Event Notification[RFC6665].

o 信任域中的SIP实体符合SIP特定事件通知[RFC6665]。

o SIP entities in the Trust Domain are compliant to this specification.

o 信任域中的SIP实体符合此规范。

o SIP entities in the Trust Domain agree on what types of calls can be affected by this SIP load-filtering mechanism. For example, <call-identity> condition elements (Section 5.3.1) <one> and <many> might be limited to describe within certain prefixes.

o 信任域中的SIP实体同意该SIP负载过滤机制会影响哪些类型的呼叫。例如,<call identity>条件元素(第5.3.1节)<one>和<many>可能仅限于在某些前缀内描述。

o SIP entities in the Trust Domain agree on the destinations to which calls may be redirected when the "redirect" action (Section 5.4) is used. For example, the URI might have to match a given set of domains.

o 信任域中的SIP实体同意在使用“重定向”操作(第5.4节)时呼叫可以重定向到的目的地。例如,URI可能必须匹配给定的一组域。

SIP load filtering is only effective if all neighbors that are possible signaling sources participate and enforce the designated load-filtering policies. Otherwise, a single non-conforming neighbor could make all filtering efforts useless by pumping in excessive traffic to overload the server. Therefore, the SIP server that

SIP负载过滤只有在所有可能的信令源邻居都参与并实施指定的负载过滤策略时才有效。否则,一个不一致的邻居可能会通过注入过多的流量使服务器过载,从而使所有过滤工作无效。因此,SIP服务器

distributes load-filtering policies needs to take countermeasures towards any non-conforming neighbors. A simple method is to reject excessive requests with 503 "Service Unavailable" response messages as if they were obeying the rate. Considering the rejection costs, a more complicated but fairer method would be to allocate at the overloaded server the same amount of processing to the combination of both normal processing and rejection as the overloaded server would devote to processing requests for a conforming upstream SIP server. These approaches work as long as the total rejection cost does not overwhelm the entire server resources. In addition, SIP servers need to handle message prioritization properly while performing load filtering, which is described in Section 4.8.

分布式负载过滤策略需要对任何不一致的邻居采取对策。一个简单的方法是拒绝包含503条“Service Unavailable”(服务不可用)响应消息的过多请求,就像它们遵守速率一样。考虑到拒绝成本,一种更复杂但更公平的方法是在过载的服务器上分配与过载的服务器用于处理一致的上游SIP服务器的请求相同的处理量,以同时进行正常处理和拒绝。只要总拒绝成本不超过整个服务器资源,这些方法就可以工作。此外,SIP服务器在执行负载过滤时需要正确处理消息优先级,如第4.8节所述。

4. Load-Control Event Package
4. 负载控制事件包

The SIP load-filtering mechanism defines a load-control event package for SIP based on [RFC6665].

SIP负载过滤机制基于[RFC6665]为SIP定义负载控制事件包。

4.1. Event Package Name
4.1. 事件包名称

The name of this event package is "load-control". This name is carried in the Event and Allow-Events header, as specified in [RFC6665].

此事件包的名称为“负载控制”。按照[RFC6665]中的规定,此名称包含在事件和允许事件标题中。

4.2. Event Package Parameters
4.2. 事件包参数

No package-specific event header field parameters are defined for this event package.

没有为此事件包定义包特定的事件标头字段参数。

4.3. SUBSCRIBE Bodies
4.3. 订阅机构

This specification does not define the content of SUBSCRIBE bodies. Future specifications could define bodies for SUBSCRIBE messages, for example, to request specific types of load-control event notifications.

本规范未定义订阅主体的内容。未来的规范可以定义订阅消息的主体,例如,请求特定类型的负载控制事件通知。

A SUBSCRIBE request sent without a body implies the default subscription behavior as specified in Section 4.7.

不带正文发送的订阅请求意味着第4.7节中指定的默认订阅行为。

4.4. SUBSCRIBE Duration
4.4. 订阅期限

The default expiration time for a subscription to load-filtering policy is one hour. Since the desired expiration time may vary significantly for subscriptions among SIP entities with different signaling relationships, the subscribers and notifiers are RECOMMENDED to explicitly negotiate appropriate subscription duration when knowledge about the mutual signaling relationship is available.

订阅加载筛选策略的默认过期时间为一小时。由于具有不同信令关系的SIP实体之间的订阅的期望到期时间可能显著不同,因此建议订阅者和通知者在关于相互信令关系的知识可用时显式地协商适当的订阅持续时间。

4.5. NOTIFY Bodies
4.5. 通知机构

The body of a NOTIFY request in this event package contains load-filtering policies. The format of the NOTIFY request body MUST be in one of the formats defined in the Accept header field of the SUBSCRIBE request or be the default format, as specified in [RFC6665]. The default data format for the NOTIFY request body of this event package is "application/load-control+xml" (defined in Section 5). This means that when a NOTIFY request body exists but no Accept header field is specified in a SUBSCRIBE request, the NOTIFY request body MUST contain content conforming to the "application/ load-control+xml" format.

此事件包中的NOTIFY请求主体包含负载筛选策略。NOTIFY请求正文的格式必须是订阅请求的Accept header字段中定义的格式之一,或者是[RFC6665]中指定的默认格式。此事件包的NOTIFY请求主体的默认数据格式为“应用程序/负载控制+xml”(在第5节中定义)。这意味着,当存在NOTIFY请求正文,但订阅请求中未指定Accept header字段时,NOTIFY请求正文必须包含符合“应用程序/负载控制+xml”格式的内容。

4.6. Notifier Processing of SUBSCRIBE Requests
4.6. 订阅请求的通知程序处理

The notifier accepts a new subscription or updates an existing subscription upon receiving a valid SUBSCRIBE request.

通知程序在收到有效的订阅请求后接受新订阅或更新现有订阅。

If the identity of the subscriber sending the SUBSCRIBE request is not allowed to receive load-filtering policies, the notifier MUST return a 403 "Forbidden" response.

如果发送订阅请求的订户的身份不允许接收负载筛选策略,则通知程序必须返回403“禁止”响应。

If none of the media types specified in the Accept header of the SUBSCRIBE request are supported, the notifier SHOULD return a 406 "Not Acceptable" response.

如果订阅请求的Accept标头中指定的媒体类型均不受支持,则通知程序应返回406“不可接受”响应。

4.7. Notifier Generation of NOTIFY Requests
4.7. 通知程序生成通知请求

A notifier MUST send a NOTIFY request with its current load-filtering policy to the subscriber upon successfully accepting or refreshing a subscription. If no load-filtering policy needs to be distributed when the subscription is received, the notifier SHOULD sent a NOTIFY request without a body to the subscriber. The content-type header field of this NOTIFY request MUST indicate the correct body format as if the body were present (e.g., "application/load-control+xml"). Notifiers are likely to send NOTIFY requests without a body when a subscription is initiated for the first time, e.g., when a SIP entity is just introduced, because there may be no planned events that require load filtering at that time. A notifier SHOULD generate NOTIFY requests each time the load-filtering policy changes, with the maximum notification rate not exceeding values defined in Section 4.10.

在成功接受或刷新订阅后,通知程序必须向订阅服务器发送带有当前负载筛选策略的通知请求。如果在收到订阅时需要分发无负载筛选策略,则通知程序应向订阅服务器发送一个无正文的通知请求。此NOTIFY请求的content type标头字段必须指示正确的正文格式,就像正文存在一样(例如,“应用程序/负载控制+xml”)。当首次启动订阅时(例如,当刚刚引入SIP实体时),通知程序可能会在没有正文的情况下发送NOTIFY请求,因为此时可能没有需要负载筛选的计划事件。通知程序应在每次负载筛选策略更改时生成通知请求,最大通知率不超过第4.10节中定义的值。

4.8. Subscriber Processing of NOTIFY Requests
4.8. 订户处理通知请求

The subscriber is the load-filtering server that enforces load-filtering policies received from the notifier. The way subscribers process NOTIFY requests depends on the load-filtering policies

订阅服务器是执行从通知程序接收的负载筛选策略的负载筛选服务器。订阅者处理通知请求的方式取决于负载筛选策略

conveyed in the notifications. Typically, load-filtering policies consist of rules specifying actions to be applied to requests matching certain conditions. A subscriber receiving a notification first installs these rules and then enforces corresponding actions on requests matching those conditions, for example, limiting the sending rate of call requests destined for a specific callee.

在通知中传达。通常,负载筛选策略由指定要应用于符合特定条件的请求的操作的规则组成。接收通知的订户首先安装这些规则,然后对符合这些条件的请求强制执行相应的操作,例如,限制发送给特定被叫方的呼叫请求的发送速率。

In the case when load-filtering policies specify a future validity, it is possible that when the validity time arrives, the subscription to the specific notifier that conveyed the rules has expired. In this case, it is RECOMMENDED that the subscriber re-activate its subscription with the corresponding notifier. Regardless of whether or not this re-activation of subscription is successful, when the validity time is reached, the subscriber SHOULD enforce the corresponding rules.

在负载筛选策略指定未来有效性的情况下,当有效性时间到达时,传递规则的特定通知程序的订阅可能已过期。在这种情况下,建议订阅服务器使用相应的通知程序重新激活其订阅。无论订阅的重新激活是否成功,当达到有效期时,订阅方应强制执行相应的规则。

Upon receipt of a NOTIFY request with a Subscription-State header field containing the value "terminated", the subscription status with the particular notifier will be terminated. Meanwhile, subscribers MUST also terminate previously received load-filtering policies from that notifier.

收到包含“已终止”值的订阅状态标头字段的NOTIFY请求后,特定通知程序的订阅状态将终止。同时,订阅者还必须终止以前从该通知程序收到的负载筛选策略。

The subscriber MUST discard unknown bodies. If the NOTIFY request contains several bodies, none of them being supported, it SHOULD unsubscribe unless it has knowledge that it will possibly receive NOTIFY requests with supported bodies from that notifier. A NOTIFY request without a body indicates that no load-filtering policies need to be updated.

订阅服务器必须丢弃未知实体。如果NOTIFY请求包含多个实体,但其中没有一个被支持,则它应该取消订阅,除非它知道它可能会从该通知程序接收具有受支持实体的NOTIFY请求。没有正文的NOTIFY请求表示无负载筛选策略需要更新。

When the subscriber enforces load-filtering policies, it needs to prioritize requests and select those requests that need to be rejected or redirected. This selection is largely a matter of local policy. It is expected that the subscriber will follow local policy as long as the result in reduction of traffic is consistent with the overload algorithm in effect at that node. Accordingly, the normative behavior described in the next three paragraphs should be interpreted with the understanding that the subscriber will aim to preserve local policy to the fullest extent possible.

当订户强制执行负载筛选策略时,它需要对请求进行优先级排序,并选择需要拒绝或重定向的请求。这种选择在很大程度上取决于当地政策。只要通信量减少的结果与该节点上有效的过载算法一致,则预期订户将遵循本地策略。因此,在解释下三段中描述的规范性行为时,应理解认购人的目标是尽可能充分地维护当地政策。

o The subscriber SHOULD honor the local policy for prioritizing SIP requests such as policies based on message type, e.g., INVITEs versus requests associated with existing sessions.

o 订阅者应遵守对SIP请求进行优先级排序的本地策略,例如基于消息类型的策略,例如邀请与现有会话相关的请求。

o The subscriber SHOULD honor the local policy for prioritizing SIP requests based on the content of the Resource-Priority header (RPH, [RFC4412]). Specific (namespace.value) RPH contents may indicate high-priority requests that should be preserved as much

o 订阅者应遵守根据资源优先级头(RPH,[RFC4412])的内容对SIP请求进行优先级排序的本地策略。特定(namespace.value)RPH内容可能表示应尽可能保留的高优先级请求

as possible during overload. The RPH contents can also indicate a low-priority request that is eligible to be dropped during times of overload.

在过载期间,尽可能多地使用。RPH内容还可以指示低优先级请求,该请求在过载期间有资格被丢弃。

o The subscriber SHOULD honor the local policy for prioritizing SIP requests relating to emergency calls as identified by the sos URN [RFC5031] indicating an emergency request.

o 订阅者应遵守本地政策,按照指示紧急请求的sos URN[RFC5031]确定的与紧急呼叫相关的SIP请求的优先级。

A local policy can be expected to combine both the SIP request type and the prioritization markings and SHOULD be honored when overload conditions prevail.

可以预期本地策略将结合SIP请求类型和优先级标记,并且在过载条件盛行时应遵守该策略。

4.9. Handling of Forked Requests
4.9. 分叉请求的处理

Forking is not applicable when this load-control event package mechanism is used within a single-hop distance between neighboring SIP entities. If communication scope of the load-control event package mechanism is among multiple hops, forking is also not expected to happen because the subscription request is addressed to a clearly defined SIP entity. However, in the unlikely case when forking does happen, the load-control event package only allows the first potential dialog-establishing message to create a dialog, as specified in Section 5.4.9 of [RFC6665].

当在相邻SIP实体之间的单跳距离内使用此负载控制事件包机制时,分叉不适用。如果负载控制事件包机制的通信范围在多个跃点之间,则也不会发生分叉,因为订阅请求是针对明确定义的SIP实体的。但是,在不太可能发生分叉的情况下,负载控制事件包仅允许第一个潜在的对话框建立消息来创建对话框,如[RFC6665]第5.4.9节所述。

4.10. Rate of Notifications
4.10. 通知率

The rate of notifications is unlikely to be of concern for this local control event package mechanism when it is used in a non-real-time mode for relatively static load-filtering policies. Nevertheless, if a situation does arise in which a rather frequently used load filtering policy update is needed, it is RECOMMENDED that the notifier not generate notifications at a rate higher than once per second in all cases, in order to avoid the NOTIFY request itself overloading the system.

当此本地控制事件包机制在非实时模式下用于相对静态的负载筛选策略时,通知速率不太可能与此本地控制事件包机制有关。但是,如果确实出现需要更新频繁使用的负载筛选策略的情况,建议通知程序在所有情况下都不要以高于每秒一次的速率生成通知,以避免通知请求本身使系统过载。

4.11. State Delta
4.11. 州三角洲

It is likely that updates to specific load-filtering policies are made by changing only part of the policy parameters (e.g., acceptable request rate or percentage, but not matching identities). This will typically be because the utilization of a resource subject to overload depends upon dynamic unknowns such as holding time and the relative distribution of offered loads over subscribing SIP entities. The updates could originate manually or be determined automatically by an algorithm that dynamically computes the load-filtering policies (Section 3.2). Another factor that is usually not known precisely or

对特定负载筛选策略的更新可能仅通过更改部分策略参数(例如,可接受的请求速率或百分比,但不匹配标识)来实现。这通常是因为过载资源的利用率取决于动态未知因素,如等待时间和订阅SIP实体上提供的负载的相对分布。更新可以手动发起,也可以由动态计算负载过滤策略的算法自动确定(第3.2节)。另一个通常无法准确或准确了解的因素

needs to be computed automatically is the duration of the event requiring load filtering. Therefore, it would also be common for the validity to change frequently.

需要自动计算的是需要负载筛选的事件的持续时间。因此,有效性经常变化也是很常见的。

This event package allows the use of state delta as in [RFC6665] to accommodate frequent updates of partial policy parameters. For each NOTIFY transaction in a subscription, a version number that increases by exactly one MUST be included in the NOTIFY request body when the body is present. When the subscriber receives a state delta, it associates the partial updates to the particular policy by matching the appropriate rule id (Appendix D). If the subscriber receives a NOTIFY request with a version number that is increased by more than one, it knows that it has missed a state delta and needs to ask for a full state snapshot. Therefore, the subscriber ignores that NOTIFY request containing the state delta, and resends a SUBSCRIBE request to force a NOTIFY request containing a complete state snapshot.

此事件包允许使用[RFC6665]中的状态增量来适应部分策略参数的频繁更新。对于订阅中的每个NOTIFY事务,当正文存在时,必须在NOTIFY请求正文中包含一个增加1的版本号。当订户收到状态增量时,它通过匹配适当的规则id将部分更新与特定策略相关联(附录D)。如果订阅服务器收到一个版本号增加了一个以上的NOTIFY请求,则它知道它错过了状态增量,需要请求完整状态快照。因此,订户忽略包含状态增量的NOTIFY请求,并重新发送订阅请求以强制包含完整状态快照的NOTIFY请求。

5. Load-Control Document
5. 负荷控制文件
5.1. Format
5.1. 总体安排

A load-control document is an XML document that describes the load-filtering policies. It inherits and enhances the common policy document defined in [RFC4745]. A common policy document contains a set of rules. Each rule consists of three parts: conditions, actions, and transformations. The conditions part is a set of expressions containing attributes such as identity, domain, and validity time information. Each expression evaluates to TRUE or FALSE. Conditions are matched on "equality" or "greater than" style comparison. There is no regular expression matching. Conditions are evaluated on receipt of an initial SIP request for a dialog or standalone transaction. If a request matches all conditions in a rule set, the action part and the transformation part are consulted to determine the "permission" on how to handle the request. Each action or transformation specifies a positive grant to the policy server to perform the resulting actions. Well-defined mechanism are available for combining actions and transformations obtained from more than one sources.

负载控制文档是描述负载筛选策略的XML文档。它继承并增强了[RFC4745]中定义的通用策略文档。公共策略文档包含一组规则。每个规则由三部分组成:条件、操作和转换。条件部分是一组表达式,包含标识、域和有效期时间信息等属性。每个表达式的计算结果为TRUE或FALSE。在“相等”或“大于”样式比较中匹配条件。没有正则表达式匹配。在收到对话或独立事务的初始SIP请求时,将评估条件。如果请求与规则集中的所有条件都匹配,则会咨询操作部分和转换部分,以确定如何处理请求的“权限”。每个操作或转换都为策略服务器指定一个正授权,以执行生成的操作。定义良好的机制可用于组合从多个源获得的操作和转换。

5.2. Namespace
5.2. 名称空间

The namespace URI for elements defined by this specification is a Uniform Resource Namespace (URN) ([RFC2141]), using the namespace identifier "ietf" defined by [RFC2648] and extended by [RFC3688]. The URN is as follows:

本规范定义的元素的名称空间URI是统一资源名称空间(URN)([RFC2141]),使用[RFC2648]定义并由[RFC3688]扩展的名称空间标识符“ietf”。骨灰盒如下:

   urn:ietf:params:xml:ns:load-control
        
   urn:ietf:params:xml:ns:load-control
        
5.3. Conditions
5.3. 条件

[RFC4745] defines three condition elements: <identity>, <sphere>, and <validity>. This specification defines new condition elements and reuses the <validity> element. The <sphere> element is not used.

[RFC4745]定义了三个条件元素:<identity>、<sphere>和<validity>。本规范定义了新的条件元素并重用<validity>元素。未使用<sphere>元素。

5.3.1. Call Identity
5.3.1. 呼叫标识

Since the problem space of this specification is different from that of [RFC4745], the [RFC4745] <identity> element is not sufficient for use with load filtering. First, load filtering may be applied to different identities contained in a request, including identities of both the receiving entity and the sending entity. Second, the importance of authentication varies when different identities of a request are concerned. This specification defines new identity conditions that can accommodate the granularity of specific SIP identity header fields. The requirement for authentication depends on which field is to be matched.

由于本规范的问题空间不同于[RFC4745],因此[RFC4745]<identity>元素不足以用于负载过滤。首先,负载过滤可以应用于请求中包含的不同标识,包括接收实体和发送实体的标识。第二,当涉及请求的不同身份时,身份验证的重要性会有所不同。本规范定义了新的标识条件,可适应特定SIP标识头字段的粒度。身份验证的要求取决于要匹配的字段。

The identity condition for load filtering is specified by the <call-identity> element and its sub-element <sip>. The <sip> element itself contains sub-elements representing SIP sending and receiving identity header fields: <from>, <to>, <request-uri>, and <p-asserted-identity>. All those sub-elements are of an extended form of the [RFC4745] <identity> element. In addition to the sub-elements including <one>, <except>, and <many> in the <identity> element from [RFC4745], the extended form adds two new sub-elements, namely, <many-tel> and <except-tel>, which will be explained later in this section.

负载筛选的标识条件由<call identity>元素及其子元素<sip>指定。<sip>元素本身包含表示sip发送和接收标识头字段的子元素:<from>、<to>、<request uri>和<p-asserted-identity>。所有这些子元素都是[RFC4745]<identity>元素的扩展形式。除了[RFC4745]中<identity>元素中的<one>、<Exception>和<many>等子元素外,扩展形式还添加了两个子元素,即<many tel>和<Exception tel>,这将在本节后面进行解释。

The [RFC4745] <one> and <except> elements may contain an "id" attribute, which is the URI of a single entity to be included or excluded in the condition. When used in the <from>, <to>, <request-uri>, and <p-asserted-identity> elements, this "id" value is the URI contained in the corresponding SIP header field, i.e., From, To, Request-URI, and P-Asserted-Identity.

[RFC4745]<one>和<except>元素可能包含一个“id”属性,该属性是要在条件中包括或排除的单个实体的URI。当在<from>、<to>、<request uri>和<p-asserted-identity>元素中使用时,该“id”值是相应SIP头字段中包含的uri,即from、to、request uri和p-asserted-identity。

   When the <call-identity> element contains multiple <sip> sub-
   elements, the result is combined using logical OR.  When the <from>,
   <to>, <request-uri>, and <p-asserted-identity> elements contain
   multiple <one>, <many>, or <many-tel> sub-elements, the result is
   also combined using logical OR.  When the <many> sub-element further
   contains one or more <except> sub-elements, or when the <many-tel>
   sub-element further contains one or more <except-tel> sub-elements,
   the result of each <except> or <except-tel> sub-element is combined
   using a logical OR, similar to that of the [RFC4745] <identity>
   element.  However, when the <sip> element contains multiple <from>,
   <to>, <request-uri>, and <p-asserted-identity> sub-elements, the
        
   When the <call-identity> element contains multiple <sip> sub-
   elements, the result is combined using logical OR.  When the <from>,
   <to>, <request-uri>, and <p-asserted-identity> elements contain
   multiple <one>, <many>, or <many-tel> sub-elements, the result is
   also combined using logical OR.  When the <many> sub-element further
   contains one or more <except> sub-elements, or when the <many-tel>
   sub-element further contains one or more <except-tel> sub-elements,
   the result of each <except> or <except-tel> sub-element is combined
   using a logical OR, similar to that of the [RFC4745] <identity>
   element.  However, when the <sip> element contains multiple <from>,
   <to>, <request-uri>, and <p-asserted-identity> sub-elements, the
        

result is combined using logical AND. This allows the call identity to be specified by multiple fields of a SIP request simultaneously, e.g., both the From and the To header fields.

使用逻辑AND组合结果。这允许SIP请求的多个字段同时指定呼叫标识,例如,From和to报头字段。

The following shows an example of the <call-identity> element, which matches call requests whose To header field contains the SIP URI "sip:alice@hotline.example.com" or the 'tel' URI "tel:+1-212-555-1234".

下面显示了<call identity>元素的示例,该元素匹配的调用请求的To头字段包含SIP URI“SIP:alice@hotline.example.com或“电话”URI“电话:+1-212-555-1234”。

               <call-identity>
                   <sip>
                       <to>
                           <one id="sip:alice@hotline.example.com"/>
                           <one id="tel:+1-212-555-1234"/>
                       </to>
                   </sip>
               </call-identity>
        
               <call-identity>
                   <sip>
                       <to>
                           <one id="sip:alice@hotline.example.com"/>
                           <one id="tel:+1-212-555-1234"/>
                       </to>
                   </sip>
               </call-identity>
        

Before evaluating <call-identity> conditions, the subscriber shall convert URIs received in SIP header fields in canonical form as per [RFC3261], except that the "phone-context" parameter shall not be removed, if present.

在评估<call identity>条件之前,用户应按照[RFC3261]将SIP报头字段中接收到的URI转换为规范格式,但“电话上下文”参数(如果存在)除外。

The [RFC4745] <many> and <except> elements may take a "domain" attribute. The "domain" attribute specifies a domain name to be matched by the domain part of the candidate identity. Thus, it allows matching a large and possibly unknown number of entities within a domain. The "domain" attribute works well for SIP URIs.

[RFC4745]<many>和<except>元素可能具有“domain”属性。“域”属性指定要与候选身份的域部分匹配的域名。因此,它允许在一个域中匹配大量可能未知数量的实体。“domain”属性对于SIPURI很有效。

A URI identifying a SIP user, however, can also be a 'tel' URI. Therefore, a similar way to match a group of 'tel' URIs is needed. There are two forms of 'tel' URIs: for global numbers and local numbers. According to [RFC3966], "All phone numbers MUST use the global form unless they cannot be represented as such...Local numbers MUST be tagged with a 'phone-context'". The global number 'tel' URIs start with a "+". The "phone-context" parameter of local numbers may be labeled as a global number or any number of its leading digits or a domain name. Both forms of the 'tel' URI make the resulting URI globally unique.

但是,标识SIP用户的URI也可以是“tel”URI。因此,需要一种类似的方法来匹配一组“tel”uri。“电话”URI有两种形式:全球号码和本地号码。根据[RFC3966],“所有电话号码必须使用全局形式,除非它们不能表示为全局形式……本地号码必须用‘电话上下文’标记。”。全局编号“tel”URI以“+”开头。本地号码的“phone context”参数可以标记为全局号码或其前导数字的任何数字或域名。“tel”URI的两种形式都使生成的URI全局唯一。

'tel' URIs of global numbers can be grouped by prefixes consisting of any number of common leading digits. For example, a prefix formed by a country code or both the country and area code identifies telephone numbers within a country or an area. Since the length of the country and area code for different regions are different, the length of the number prefix also varies. This allows further flexibility such as

全局编号的“tel”URI可以通过由任意数量的公共前导数字组成的前缀进行分组。例如,由国家代码或国家和地区代码组成的前缀标识国家或地区内的电话号码。由于不同地区的国家代码和区号长度不同,因此号码前缀的长度也不同。这允许进一步的灵活性,例如

grouping the numbers into sub-areas within the same area code. 'tel' URIs of local numbers can be grouped by the value of the "phone-context" parameter.

将号码分组到同一区号内的子区域中。”本地号码的电话URI可以根据“phone context”参数的值进行分组。

The <many> and <except> sub-elements in the <identity> element of [RFC4745] do not allow additional attributes to be added directly. Redefining behavior of their existing "domain" attribute creates backward-compatibility issues. Therefore, this specification defines the <many-tel> and <except-tel> sub-elements that extend the [RFC4745] <identity> element. Both of them have a "prefix" attribute for grouping 'tel' URIs, similar to the "domain" attribute for grouping SIP URIs in existing <many> and <except> sub-elements. For global numbers, the "prefix" attribute value holds any number of common leading digits, for example, "+1-212" for US phone numbers within area code "212" or "+1-212-854" for the organization with US area code "212" and local prefix "854". For local numbers, the "prefix" attribute value contains the "phone-context" parameter value. It should be noted that visual separators (such as the "-" sign) in 'tel' URIs are not used for URI comparison as per [RFC3966].

[RFC4745]的<identity>元素中的<many>和<except>子元素不允许直接添加其他属性。重新定义其现有“域”属性的行为会产生向后兼容性问题。因此,本规范定义了扩展[RFC4745]<identity>元素的<many tel>和<except tel>子元素。它们都有一个“prefix”属性用于对“tel”uri进行分组,类似于在现有的<many>和<except>子元素中对SIP uri进行分组的“domain”属性。对于全局号码,“prefix”属性值保存任意数量的公共前导数字,例如,对于区号为“212”的美国电话号码,“+1-212”或对于区号为“212”且本地前缀为“854”的组织,“+1-212-854”。对于本地号码,“前缀”属性值包含“电话上下文”参数值。应该注意的是,根据[RFC3966],在“tel”URI中的可视分隔符(如“-”号)不用于URI比较。

The following example shows the use of the "prefix" attribute along with the "domain" attribute. It matches those requests calling to the number "+1-202-999-1234" but are not calling from a "+1-212" prefix or a SIP From URI domain of "manhattan.example.com".

下面的示例显示了“prefix”属性和“domain”属性的用法。它匹配那些调用号码“+1-202-999-1234”但不是从“+1-212”前缀或“manhattan.example.com”URI域调用的请求。

               <call-identity>
                   <sip>
                       <from>
                           <many>
                               <except domain="manhattan.example.com"/>
                           </many>
                           <many-tel>
                               <except-tel prefix="+1-212"/>
                           </many-tel>
                       </from>
                       <to>
                           <one id="tel:+1-202-999-1234"/>
                       </to>
                   </sip>
               </call-identity>
        
               <call-identity>
                   <sip>
                       <from>
                           <many>
                               <except domain="manhattan.example.com"/>
                           </many>
                           <many-tel>
                               <except-tel prefix="+1-212"/>
                           </many-tel>
                       </from>
                       <to>
                           <one id="tel:+1-202-999-1234"/>
                       </to>
                   </sip>
               </call-identity>
        
5.3.2. Method
5.3.2. 方法

The load created on a SIP server depends on the type of initial SIP requests for dialogs or standalone transactions. The <method> element specifies the SIP method to which the load-filtering action applies. When this element is not included, the load-filtering actions are applicable to all applicable initial requests. These

在SIP服务器上创建的负载取决于对话框或独立事务的初始SIP请求的类型。元素指定应用负载筛选操作的SIP方法。如果不包括此元素,则负载筛选操作适用于所有适用的初始请求。这些

requests include INVITE, MESSAGE, REGISTER, SUBSCRIBE, OPTIONS, and PUBLISH. Non-initial requests, such as ACK, BYE, and CANCEL MUST NOT be subjected to load filtering. In addition, SUBSCRIBE requests are not filtered if the event-type header field indicates the event package defined in this specification.

请求包括邀请、消息、注册、订阅、选项和发布。非初始请求(如ACK、BYE和CANCEL)不得进行负载筛选。此外,如果事件类型标头字段指示本规范中定义的事件包,则不会过滤订阅请求。

The following example shows the use of the <method> element in the case the filtering actions should be applied to INVITE requests.

下面的示例显示了在过滤操作应应用于INVITE请求的情况下<method>元素的使用。

           <method>INVITE</method>
        
           <method>INVITE</method>
        
5.3.3. Target SIP Entity
5.3.3. 目标SIP实体

A SIP server that performs load-filtering may have multiple paths to route call requests matching the same set of call identity elements. In those situations, the SIP load-filtering server may desire to take advantage of alternative paths and only apply load-filtering actions to matching requests for the next-hop SIP entity that originated the corresponding load-filtering policy. To achieve that, the SIP load-filtering server needs to associate every load-filtering policy with its originating SIP entity. The <target-sip-entity> element is defined for that purpose, and it contains the URI of the entity that initiated the load-filtering policy, which is generally the corresponding notifier. A notifier MAY include this element as part of the condition of its filtering policy being sent to the subscriber, as below.

执行负载过滤的SIP服务器可能有多条路径来路由与同一组呼叫标识元素匹配的呼叫请求。在这些情况下,SIP负载过滤服务器可能希望利用替代路径,并且仅将负载过滤动作应用于针对发起相应负载过滤策略的下一跳SIP实体的匹配请求。为了实现这一点,SIP负载过滤服务器需要将每个负载过滤策略与其原始SIP实体相关联。<target sip entity>元素是为此目的定义的,它包含启动负载筛选策略的实体的URI,该实体通常是相应的通知程序。通知程序可以将此元素作为其过滤策略发送给订阅服务器的条件的一部分,如下所示。

   <target-sip-entity>sip:biloxi.example.com</target-sip-entity>
        
   <target-sip-entity>sip:biloxi.example.com</target-sip-entity>
        

When a SIP load-filtering server receives a policy with a <target-sip-entity> element, it SHOULD record it and take it into consideration when making load-filtering decisions. If the load-filtering server receives a load-filtering policy that does not contain a <target-sip-entity> element, it MAY still record the URI of the load-filtering policy's originator as the <target-sip-entity> information and consider it when making load-filtering decisions.

当SIP负载筛选服务器接收到包含<target SIP entity>元素的策略时,它应该记录该策略,并在做出负载筛选决策时将其考虑在内。如果负载过滤服务器接收到一个不包含“目标SIP实体>元素”的负载过滤策略,则它仍然可以将负载过滤策略的始发者的URI记录为“目标SIP实体>信息”,并在进行负载过滤决策时考虑它。

The following are two examples of using the <target-sip-entity> element.

下面是使用<target sip entity>元素的两个示例。

Use case I: The network has user A connected to SIP Proxy 1 (SP1), user B connected to SIP Proxy 3 (SP3), SP1 and SP3 connected via SIP Proxy 2 (SP2), and SP2 connected to an Application Server (AS). Under normal load conditions, a call from A to B is routed along the following path: A-SP1-SP2-AS-SP3-B. The AS provides a nonessential service and can be bypassed in case of overload. Now let's assume that AS is overloaded and sends to SP2 a load-filtering policy requesting that 50% of all INVITE requests be

用例一:网络中用户A连接到SIP代理1(SP1),用户B连接到SIP代理3(SP3),SP1和SP3通过SIP代理2(SP2)连接,SP2连接到应用服务器(AS)。在正常负载条件下,从a到B的调用沿以下路径路由:a-SP1-SP2-AS-SP3-B。AS提供非必要服务,在过载情况下可以绕过。现在让我们假设AS过载,并向SP2发送一个负载过滤策略,请求删除所有INVITE请求的50%

dropped. SP2 can maintain AS as the <target-sip-entity> for that policy so that it knows the 50% drop action is only applicable to call requests that must go through AS, without affecting those calls directly routed through SP3 to B.

下降。SP2可以为该策略维护AS<target sip entity>,以便它知道50%丢弃操作仅适用于必须通过AS的呼叫请求,而不会影响通过SP3直接路由到B的呼叫。

Use case II: A translation service for toll-free numbers is installed on two Application Servers, AS1 and AS2. User A is connected to SP1 and calls 800-1234-4529, which is translated by AS1 and AS2 into a regular E.164 number depending on, e.g., the caller's location. SP1 forwards INVITE requests with Request-URI = "800 number" to AS1 or AS2 based on a load-balancing strategy. As calls to 800-1234-4529 create a pre-overload condition in AS1, AS1 sends to SP1 a load-filtering policy requesting that 50% of calls towards 800-1234-4529 be rejected. In this case, SP1 can maintain AS1 as the <target-sip-entity> for the rule, and only apply the load-filtering policy on incoming requests that are intended to be sent to AS1. Those requests that are sent to AS2, although matching the <call-identity> of the filter, will not be affected.

用例二:免费电话号码的翻译服务安装在两个应用服务器AS1和AS2上。用户A连接到SP1并呼叫800-1234-4529,AS1和AS2根据呼叫方的位置将其转换为常规的E.164号码。SP1根据负载平衡策略将请求URI为“800 number”的INVITE请求转发给AS1或AS2。当对800-1234-4529的呼叫在AS1中创建预过载条件时,AS1向SP1发送负载筛选策略,请求拒绝对800-1234-4529的50%呼叫。在这种情况下,SP1可以将AS1维护为规则的<target sip entity>,并且只对打算发送到AS1的传入请求应用负载筛选策略。发送到AS2的那些请求虽然与筛选器的<call identity>匹配,但不会受到影响。

5.3.4. Validity
5.3.4. 有效性

A filtering policy is usually associated with a validity period condition. This specification reuses the <validity> element of [RFC4745], which specifies a period of validity time by pairs of <from> and <until> sub-elements. When multiple time periods are defined, the validity condition is evaluated to TRUE if the current time falls into any of the specified time periods. That is, it represents a logical OR operation across all validity time periods.

筛选策略通常与有效期条件相关联。本规范重用[RFC4745]的<validity>元素,该元素通过成对的<from>和<till>子元素指定有效期。定义多个时间段时,如果当前时间属于任何指定的时间段,则有效性条件将评估为TRUE。也就是说,它表示跨越所有有效期的逻辑OR操作。

The following example shows a <validity> element specifying a valid period from 12:00 to 15:00 US Eastern Standard Time on 2008-05-31.

以下示例显示了一个<validity>元素,该元素指定2008-05-31美国东部标准时间12:00至15:00的有效期。

               <validity>
                   <from>2008-05-31T12:00:00-05:00</from>
                   <until>2008-05-31T15:00:00-05:00</until>
               </validity>
        
               <validity>
                   <from>2008-05-31T12:00:00-05:00</from>
                   <until>2008-05-31T15:00:00-05:00</until>
               </validity>
        
5.4. Actions
5.4. 行动
   The actions a load-filtering server takes on loads matching the load-
   filtering conditions are defined by the <accept> element in the load-
   filtering policy, which includes any one of the three sub-elements
   <rate>, <percent>, and <win>.  The <rate> element denotes an absolute
   value of the maximum acceptable request rate in requests per second;
   the <percent> element specifies the relative percentage of incoming
   requests that should be accepted; the <win> element describes the
   acceptable window size supplied by the receiver, which is applicable
        
   The actions a load-filtering server takes on loads matching the load-
   filtering conditions are defined by the <accept> element in the load-
   filtering policy, which includes any one of the three sub-elements
   <rate>, <percent>, and <win>.  The <rate> element denotes an absolute
   value of the maximum acceptable request rate in requests per second;
   the <percent> element specifies the relative percentage of incoming
   requests that should be accepted; the <win> element describes the
   acceptable window size supplied by the receiver, which is applicable
        

in window-based load-filtering. In static load-filtering policy configuration scenarios, using the <rate> sub-element is RECOMMENDED because it is hard to enforce the percentage rate or window-based load filtering when incoming load from upstream or reactions from downstream are uncertain. (See [SIP-OVERLOAD] and [RFC6357] for more details on rate-based, loss-based, and window-based load control.)

基于窗口的负载过滤。在静态负载过滤策略配置场景中,建议使用<rate>子元素,因为当来自上游的输入负载或来自下游的反应不确定时,很难实施百分比率或基于窗口的负载过滤。(有关基于速率、基于损耗和基于窗口的负载控制的更多详细信息,请参阅[SIP-重载]和[RFC6357])

In addition, the <accept> element takes an optional "alt-action" attribute that can be used to explicitly specify the desired action in case a request cannot be processed. The "alt-action" can take one of the following three values: "reject", "redirect", or "drop".

此外,<accept>元素采用可选的“alt action”属性,该属性可用于在无法处理请求的情况下显式指定所需的操作。“alt action”可以采用以下三个值之一:“reject”、“redirect”或“drop”。

o The "reject" action is the default value for "alt-action". It means that the load-filtering server will reject the request with a 503 "Service Unavailable" response message.

o “拒绝”操作是“alt操作”的默认值。这意味着负载筛选服务器将使用503“服务不可用”响应消息拒绝请求。

o The "redirect" action means redirecting the request to another target. When it is used, an "alt-target" attribute MUST be defined. The "alt-target" specifies one URI or a list of URIs where the request should be redirected. The server sends out the redirect URIs in a 300-class response message.

o “重定向”操作意味着将请求重定向到另一个目标。使用时,必须定义“alt target”属性。“alt target”指定一个URI或URI列表,请求应重定向到该URI或URI列表。服务器在300类响应消息中发送重定向URI。

o The "drop" action means simply ignoring the request without doing anything, which can, in certain cases, help save processing capability during overload. For example, when SIP is running over a reliable transport such as TCP, the "drop" action does not send out the rejection response, neither does it close the transport connection. However, when running SIP over an unreliable transport such as UDP, using the "drop" action will create message retransmissions that further worsen the possible overload situation. Therefore, any "drop" action applied to an unreliable transport MUST be treated as if it were "reject".

o “drop”操作意味着忽略请求而不做任何事情,在某些情况下,这有助于在过载期间节省处理能力。例如,当SIP在可靠传输(如TCP)上运行时,“drop”操作不会发送拒绝响应,也不会关闭传输连接。但是,当在不可靠的传输(如UDP)上运行SIP时,使用“drop”操作将创建消息重传,从而进一步恶化可能的过载情况。因此,应用于不可靠传输的任何“丢弃”操作必须视为“拒绝”。

The above "alt-action" processing can also be illustrated through the following pseudocode