Internet Engineering Task Force (IETF)                        Q. Wu, Ed.
Request for Comments: 6792                                        Huawei
Category: Informational                                          G. Hunt
ISSN: 2070-1721                                             Unaffiliated
                                                                P. Arden
                                                           November 2012
Internet Engineering Task Force (IETF)                        Q. Wu, Ed.
Request for Comments: 6792                                        Huawei
Category: Informational                                          G. Hunt
ISSN: 2070-1721                                             Unaffiliated
                                                                P. Arden
                                                           November 2012

Guidelines for Use of the RTP Monitoring Framework




This memo proposes an extensible Real-time Transport Protocol (RTP) monitoring framework for extending the RTP Control Protocol (RTCP) with a new RTCP Extended Reports (XR) block type to report new metrics regarding media transmission or reception quality. In this framework, a new XR block should contain a single metric or a small number of metrics relevant to a single parameter of interest or concern, rather than containing a number of metrics that attempt to provide full coverage of all those parameters of concern to a specific application. Applications may then "mix and match" to create a set of blocks that cover their set of concerns. Where possible, a specific block should be designed to be reusable across more than one application, for example, for all of voice, streaming audio, and video.


Status of This Memo


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


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


Copyright Notice


Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.

版权所有(c)2012 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 ( 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(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


   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. RTP Monitoring Framework ........................................5
      3.1. Overview of the RTP Monitoring Framework ...................5
      3.2. Location of Monitors .......................................7
   4. Issues with Reporting Metrics Blocks Using RTCP XR Extensions ...8
      4.1. Using a Compound Metrics Block .............................8
      4.2. Correlating RTCP XR with Non-RTP Data ......................8
      4.3. Measurement Information Duplication ........................9
      4.4. Consumption of XR Block Code Points ........................9
   5. Guidelines for Reporting Metrics Blocks Using RTCP XR ...........9
      5.1. Use a Single Metric in the Metrics Block ...................9
      5.2. Include the Payload Type in the Metrics Block .............10
      5.3. Use RTCP SDES to Correlate XRs with Non-RTP Data ..........10
      5.4. Reduce Measurement Information Repetition across
           Metrics Blocks ............................................11
   6. An Example of a Metrics Block ..................................11
   7. Application to RFC 5117 Topologies .............................12
      7.1. Applicability to Translators ..............................13
      7.2. Applicability to MCUs .....................................13
   8. Security Considerations ........................................14
   9. Acknowledgements ...............................................14
   10. Informative References ........................................15
   1. Introduction ....................................................3
   2. Terminology .....................................................3
   3. RTP Monitoring Framework ........................................5
      3.1. Overview of the RTP Monitoring Framework ...................5
      3.2. Location of Monitors .......................................7
   4. Issues with Reporting Metrics Blocks Using RTCP XR Extensions ...8
      4.1. Using a Compound Metrics Block .............................8
      4.2. Correlating RTCP XR with Non-RTP Data ......................8
      4.3. Measurement Information Duplication ........................9
      4.4. Consumption of XR Block Code Points ........................9
   5. Guidelines for Reporting Metrics Blocks Using RTCP XR ...........9
      5.1. Use a Single Metric in the Metrics Block ...................9
      5.2. Include the Payload Type in the Metrics Block .............10
      5.3. Use RTCP SDES to Correlate XRs with Non-RTP Data ..........10
      5.4. Reduce Measurement Information Repetition across
           Metrics Blocks ............................................11
   6. An Example of a Metrics Block ..................................11
   7. Application to RFC 5117 Topologies .............................12
      7.1. Applicability to Translators ..............................13
      7.2. Applicability to MCUs .....................................13
   8. Security Considerations ........................................14
   9. Acknowledgements ...............................................14
   10. Informative References ........................................15
1. Introduction
1. 介绍

Multimedia services using the Real-time Transport Protocol (RTP) are seeing increased use. Standard methods for gathering RTP performance metrics from these applications are needed to manage uncertainties in the behavior and availability of their services. Standards such as "RTP Control Protocol Extended Reports (RTCP XR)" [RFC3611] as well as other RTCP extensions to sender reports (SRs) and receiver reports (RRs) [RFC3550] are being developed for the purpose of collecting and reporting performance metrics from endpoint devices that can be used to correlate the metrics, provide end-to-end service visibility, and measure and monitor Quality of Experience (QoE) [RFC6390].

使用实时传输协议(RTP)的多媒体服务的使用越来越多。需要从这些应用程序收集RTP性能指标的标准方法来管理其服务的行为和可用性中的不确定性。正在开发诸如“RTP控制协议扩展报告(RTCP XR)”[RFC3611]以及发送报告(SRs)和接收报告(RRs)[RFC3550]的其他RTCP扩展的标准,以便从可用于关联度量的端点设备收集和报告性能度量,提供端到端服务可视性,并测量和监控体验质量(QoE)[RFC6390]。

However, the proliferation of RTP-/RTCP-specific metrics for transport and application quality monitoring has been identified as a potential problem for interoperability when using RTP/RTCP to communicate all the parameters of concern to a specific application. Given that different applications layered on RTP may have some monitoring requirements in common, these metrics should be satisfied by a common design.


The objective of this document is to describe an extensible RTP monitoring framework to provide a small number of reusable Quality of Service (QoS) / QoE metrics that facilitate reduced implementation costs and help maximize interoperability. "Guidelines for Extending the RTP Control Protocol (RTCP)" [RFC5968] has stated that where RTCP is to be extended with a new metric, the preferred mechanism is by the addition of a new RTCP XR [RFC3611] block. This memo assumes that all the guidelines from RFC 5968 must apply on top of the guidelines in this document. Guidelines for developing new performance metrics are specified in [RFC6390]. New RTCP XR report block definitions should not define new performance metrics but should rather refer to metrics defined elsewhere.

本文档的目的是描述一个可扩展的RTP监控框架,以提供少量可重用的服务质量(QoS)/QoE指标,从而降低实施成本并帮助最大限度地提高互操作性。“扩展RTP控制协议(RTCP)指南”[RFC5968]指出,如果要使用新指标扩展RTCP,首选机制是添加新的RTCP XR[RFC3611]块。本备忘录假设RFC 5968中的所有指南必须适用于本文件中的指南。[RFC6390]中规定了开发新性能指标的指南。新的RTCP XR报告块定义不应定义新的性能指标,而应参考其他地方定义的指标。

2. Terminology
2. 术语

This memo is informative and as such contains no normative requirements.


In addition, the following terms are defined:


Transport-level metrics


A set of metrics that characterize the three transport impairments of packet loss, packet delay, and jitter (also known as delay variation). These metrics should be usable by any application that uses RTP transport.


Application-level metrics


Metrics relating to application-specific parameters or QoE-related parameters. Application-specific parameters are measured at the application level and focus on quality of content rather than network performance. QoE-related parameters reflect the end-to-end performance at the services level and are usually measured at the user endpoint. One example of such metrics is the QoE metric as specified in the QoE Metrics Report Block; see [QOE_BLOCK].


End-system metrics


Metrics relating to the way a terminal deals with transport impairments affecting the incident RTP stream. These may include de-jitter buffering, packet loss concealment, and the use of redundant streams (if any) for correction of error or loss.


Direct metrics


Metrics that can be directly measured or calculated and are not dependent on other metrics.


Interval metrics


Metrics measured over the course of a single reporting interval between two successive report blocks. This may be the most recent RTCP reporting interval ([RFC3550], Section 6.2) or some other interval signaled using an RTCP Measurement Information XR Block [RFC6776]. An example interval metric is the count of the number of RTP packets lost over the course of the last RTCP reporting interval.


Cumulative metrics


Metrics measured over several reporting intervals for accumulating statistics. The time period over which measurements are accumulated can be the complete RTP session, or some other interval signaled using an RTCP Measurement Information XR Block [RFC6776]. An example cumulative metric is the total number of RTP packets lost since the start of the RTP session.


Sampled metrics


Metrics measured at a particular time instant and sampled from the values of a continuously measured or calculated metric within a reporting interval (generally, the value of some measurement as taken at the end of the reporting interval). An example is the inter-arrival jitter reported in RTCP SR and RR packets, which is

在特定时刻测量的指标,并从报告间隔内连续测量或计算的指标值中采样(通常,在报告间隔结束时采取的某些测量值)。例如,RTCP SR和RR数据包中报告的到达间抖动,即

continually updated as each RTP data packet arrives but is only reported based on a snapshot of the value that is sampled at the instant the reporting interval ends.


3. RTP Monitoring Framework
3. RTP监控框架

There are many ways in which the performance of an RTP session can be monitored. These include RTP-based mechanisms such as the RTP MIB module [RFC2959]; or the Session Initiation Protocol (SIP) event package for RTCP summary reports [RFC6035]; or non-RTP mechanisms such as generic MIBs, NetFlow [RFC3954], IP Flow Information Export (IPFIX) [RFC5101] [RFC5102], and so on. Together, these provide useful mechanisms for exporting data on the performance of an RTP session to non-RTP network management systems. It is desirable to also perform in-session monitoring of RTP performance. RTCP provides the means to do this. In the following, we review the RTP Monitoring Framework, and give guidance for using and extending RTCP for monitoring RTP sessions. One major benefit of such a framework is ease of integration with other RTP/RTCP mechanisms.

有许多方法可以监视RTP会话的性能。这些包括基于RTP的机制,如RTP MIB模块[RFC2959];或RTCP摘要报告的会话启动协议(SIP)事件包[RFC6035];或非RTP机制,如通用MIB、NetFlow[RFC3954]、IP流信息导出(IPFIX)[RFC5101][RFC5102]等。它们一起提供了将RTP会话性能数据导出到非RTP网络管理系统的有用机制。还希望执行RTP性能的会话内监视。RTCP提供了实现这一点的方法。在下文中,我们将回顾RTP监控框架,并为使用和扩展RTCP监控RTP会话提供指导。这种框架的一个主要优点是易于与其他RTP/RTCP机制集成。

3.1. Overview of the RTP Monitoring Framework
3.1. RTP监控框架概述

The RTP monitoring Framework comprises the following two key functional components described below:


o Monitor

o 班长

o RTP Metrics Block

o RTP度量块

"Monitor" is the functional component defined in the RTP specification [RFC3550]. It acts as a repository of information gathered for monitoring purposes.


According to the definition of "monitor" in [RFC3550], the end system that runs an application program that sends or receives RTP data packets, an intermediate system that forwards RTP packets to end devices, or a third party that observes the RTP and RTCP traffic but does not make itself visible to the RTP Session participants can play the role of the monitor within the RTP monitoring framework. As shown in Figure 1, the third-party monitor can be a passive monitor that sees the RTP/RTCP stream pass it, or a system that gets sent RTCP reports but not RTP and uses that to collect information. The third-party monitor should be placed on the RTP/RTCP path between the sender, the intermediate system, and the receiver.


The RTP Metrics Block (MB) conveys real-time application QoS/QoE metric information and is used by the monitor to exchange information with other monitors in the appropriate report block format. The


information contained in the RTP MBs is collected by monitors and can be formulated as various types of metrics, e.g., direct metrics/ composed performance metrics [RFC6390] or interval metrics/cumulative metrics/sampled metrics, etc. Both the RTCP and RTCP XR can be extended to transport these metrics, e.g., the basic RTCP reception report [RFC3550] that conveys reception statistics (i.e., transport-level statistics) for multiple RTP media streams, the RTCP XRs [RFC3611] that supplement the existing RTCP packets and provide more detailed feedback on reception quality, and an RTCP NACK [RFC4585] that provides feedback on the RTP sequence numbers for a subset of the lost packets or all the currently lost packets. Ultimately, the metric information collected by monitors within the RTP monitoring framework may go to the network management tools beyond the RTP monitoring framework; e.g., as shown in Figure 1, the monitors may export the metric information derived from the RTP monitoring framework to the management system using non-RTP means.

RTP MBs中包含的信息由监控器收集,并可制定为各种类型的度量,例如,直接度量/合成性能度量[RFC6390]或间隔度量/累积度量/采样度量等。RTCP和RTCP XR均可扩展以传输这些度量,例如,基本RTCP接收报告[RFC3550]传输多个RTP媒体流的接收统计信息(即传输级别统计信息),RTCP XRs[RFC3611]补充现有RTCP数据包并提供更详细的接收质量反馈,以及RTCP NACK[RFC4585]它为丢失的数据包的子集或所有当前丢失的数据包提供关于RTP序列号的反馈。最终,RTP监控框架内的监控器收集的度量信息可能会转到RTP监控框架之外的网络管理工具;例如,如图1所示,监控器可能会导出metr使用非RTP方式从RTP监控框架导出的ic信息发送到管理系统。

                  +-----------+                  +----------+
                  |Third-Party|                  |Management|
                  |  Monitor  |          >>>>>>>>|  System  |<<<<<
                  +-----------+          ^       +----------+    ^
                      :   ^              ^                       ^
                      :   |              ^                       ^
   +---------------+  :   |       +-------------+        +-------------+
   | +-----------+ |  :   |       |+-----------+|        |+-----------+|
   | |  Monitor  | |..:...|.......||  Monitor  ||........||  Monitor  ||
   | +-----------+ |      |       |+-----------+|        |+-----------+|
   |               |------+------>|             |------->|             |
   | RTP Sender    |              |RTP Mixer or |        |RTP Receiver |
   |               |              |Translator   |        |             |
   +---------------+              +-------------+        +-------------+
                  +-----------+                  +----------+
                  |Third-Party|                  |Management|
                  |  Monitor  |          >>>>>>>>|  System  |<<<<<
                  +-----------+          ^       +----------+    ^
                      :   ^              ^                       ^
                      :   |              ^                       ^
   +---------------+  :   |       +-------------+        +-------------+
   | +-----------+ |  :   |       |+-----------+|        |+-----------+|
   | |  Monitor  | |..:...|.......||  Monitor  ||........||  Monitor  ||
   | +-----------+ |      |       |+-----------+|        |+-----------+|
   |               |------+------>|             |------->|             |
   | RTP Sender    |              |RTP Mixer or |        |RTP Receiver |
   |               |              |Translator   |        |             |
   +---------------+              +-------------+        +-------------+
   ----> RTP media traffic
   ..... RTCP control channel
   >>>>> Non-RTP/RTCP management flows
   ----> RTP media traffic
   ..... RTCP control channel
   >>>>> Non-RTP/RTCP management flows

Figure 1: Example Showing the Components of the RTP Monitoring Framework


RTP may be used with multicast groups: both Any-Source Multicast (ASM) and Source-Specific Multicast (SSM). These groups can be monitored using RTCP. In the ASM case, the monitor is a member of the multicast group and listens to RTCP reports from all members of the ASM group. In the SSM case, there is a unicast feedback target that receives RTCP feedback from receivers and distributes it to other members of the SSM group (see Figure 1 of [RFC5760]). The monitor will need to be co-located with the feedback target to


receive all feedback from the receivers (this may also be an intermediate system). In both ASM and SSM scenarios, receivers can send RTCP reports to enhance reception-quality reporting.


3.2. Location of Monitors
3.2. 监视器的位置

As shown in Figure 1, there are several possible locations from which RTP sessions can be monitored. These include end systems that terminate RTP sessions, intermediate systems that are an active part of an RTP session, and third-party devices that passively monitor an RTP session. Not every RTP session will include monitoring, and those sessions that are monitored will not all include each type of monitor. The performance metrics collected by monitors can be divided into end-system metrics, application-level metrics, and transport-level metrics. Some of these metrics may be specific to the measurement point of the monitor or may depend on where the monitors are located in the network, while others are more general and can be collected in any monitoring location.


End-system monitoring is monitoring that is deployed on devices that terminate RTP flows. Flows can be terminated in user equipment, such as phones, videoconferencing systems, or IPTV set-top boxes. Alternatively, they can be terminated in devices that gateway between RTP and other transport protocols. Transport-level metrics, end-system metrics, and application-level metrics that don't reflect the end-to-end user experience may be collected at all types of end systems, but some application-level metrics (i.e., quality of experience (QoE) metrics) may only be applicable for user-facing end systems.


RTP sessions can include intermediate systems that are an active part of the system. These intermediate systems include RTP mixers and translators, Multipoint Control Units (MCUs), retransmission servers, etc. If the intermediate system establishes separate RTP sessions to the other participants, then it must act as an end system in each of those separate RTP sessions for the purposes of monitoring. If a single RTP session traverses the intermediate system, then the intermediate system can be assigned a synchronization source (SSRC) in that session, which it can use for its reports. Transport-level metrics may be collected at such an intermediate system.


Third-party monitors may be deployed that passively monitor RTP sessions for network management purposes. Third-party monitors often do not send reports into the RTP session being monitored but instead collect transport-level metrics, end-system metrics, and application-level metrics. In some cases, however, third-party monitors can send reports to some or all participants in the session being monitored.


For example, in a media streaming scenario, third-party monitors may be deployed that passively monitor the session and send reception-quality reports to the media source but not to the receivers.


4. Issues with Reporting Metrics Blocks Using RTCP XR Extensions
4. 使用RTCP XR Extensions报告度量块的问题

The following sections discuss four issues that have come up in the past with reporting metrics blocks using RTCP XR extensions.

以下各节讨论了过去使用RTCP XR extensions报告度量块时出现的四个问题。

4.1. Using a Compound Metrics Block
4.1. 使用复合度量块

A compound metrics block is designed to contain a large number of parameters from different classes for a specific application in a single block. For example, "RTP Control Protocol Extended Reports (RTCP XR)" [RFC3611] defines seven report block formats for network management and quality monitoring. Some of these block types defined in the RTCP XRs [RFC3611] are only specifically designed for conveying multicast inference of network characteristics (MINC) or voice over IP (VoIP) monitoring. However, different applications layered on RTP may have different monitoring requirements. Designing a compound metrics block only for specific applications may increase implementation costs and minimize interoperability.

复合度量块被设计为在单个块中包含用于特定应用程序的来自不同类的大量参数。例如,“RTP控制协议扩展报告(RTCP XR)”[RFC3611]定义了用于网络管理和质量监控的七种报告块格式。RTCP XRs[RFC3611]中定义的某些块类型仅专门设计用于传输网络特性的多播推断(MINC)或IP语音(VoIP)监控。然而,在RTP上分层的不同应用程序可能有不同的监控需求。仅为特定应用程序设计复合度量块可能会增加实现成本并最小化互操作性。

4.2. Correlating RTCP XR with Non-RTP Data
4.2. 将RTCP XR与非RTP数据关联

The Canonical End-Point Identifier SDES Item (CNAME), as defined in RTP [RFC3550], is an example of an existing tool that allows binding an SSRC that may change to a name that is fixed within one RTP session. The CNAME may also be fixed across multiple RTP sessions from the same source. However, there may be situations where RTCP reports are sent to other participating endpoints using a non-RTP protocol in a session. For example, as described in [RFC6035] in relation to summary reports, the data contained in RTCP XR VoIP metrics reports [RFC3611] is forwarded to a central collection server system using SIP. In such a case, there is a large portfolio of quality parameters that can be associated with real-time applications, e.g., VOIP applications, but only a minimal number of parameters are included in the RTCP XRs. With this minimal number of RTCP statistical parameters mapped to non-RTCP measurements, it is hard to provide accurate measurements of real-time application quality, conduct detailed data analysis, and create timely alerts for users. Therefore, a correlation between RTCP XRs and non-RTP data should be provided.

RTP[RFC3550]中定义的规范端点标识符SDES项(CNAME)是现有工具的一个示例,该工具允许绑定可能更改为一个RTP会话内固定名称的SSRC。CNAME还可以跨来自同一源的多个RTP会话进行修复。但是,在某些情况下,RTCP报告可能会在会话中使用非RTP协议发送到其他参与的端点。例如,如[RFC6035]中有关摘要报告的描述,RTCP XR VoIP度量报告[RFC3611]中包含的数据使用SIP转发到中央采集服务器系统。在这种情况下,存在大量可与实时应用程序(例如VOIP应用程序)关联的质量参数组合,但RTCP XRs中仅包含少量参数。由于映射到非RTCP度量的RTCP统计参数数量很少,因此很难提供实时应用程序质量的准确度量、进行详细的数据分析以及为用户创建及时的警报。因此,应提供RTCP XRs和非RTP数据之间的相关性。

4.3. Measurement Information Duplication
4.3. 测量信息复制

We may set a measurement interval for the session and monitor RTP packets within one or several consecutive report intervals. In such a case, extra measurement information (e.g., extended sequence number of the first packet, measurement period) may be expected. However, if we put such extra measurement information into each metrics block, there may be situations where an RTCP XR packet that contains multiple metrics blocks will report on the same streams from the same source. In other words, duplicated data for the measurement is provided multiple times, once in every metrics block. Though this design ensures immunity to packet loss, it may result in more packetization complexity, and this processing overhead is not completely trivial in some cases. Therefore, a compromise between processing overhead and reliability should be taken into account.

我们可以为会话设置测量间隔,并在一个或多个连续报告间隔内监视RTP数据包。在这种情况下,可以期望额外的测量信息(例如,第一分组的扩展序列号、测量周期)。但是,如果我们将这些额外的度量信息放入每个度量块中,则可能存在这样的情况:包含多个度量块的RTCP XR数据包将报告来自同一源的相同流。换句话说,度量的重复数据被多次提供,在每个度量块中提供一次。尽管这种设计确保了对数据包丢失的免疫力,但它可能会导致更复杂的数据包化,并且在某些情况下,这种处理开销并非完全微不足道。因此,应考虑处理开销和可靠性之间的折衷。

4.4. Consumption of XR Block Code Points
4.4. XR块代码点的消耗

The RTCP XR block namespace is limited by the 8-bit block type field in the RTCP XR header. Space exhaustion may be a concern in the future. In anticipation of the potential need to extend the block type space, it is noted that Block Type 255 is reserved for future extensions in [RFC3611].

RTCP XR块命名空间受RTCP XR标头中8位块类型字段的限制。空间耗尽可能是未来的一个问题。考虑到可能需要扩展块类型空间,请注意,[RFC3611]中为将来的扩展保留了块类型255。

5. Guidelines for Reporting Metrics Blocks Using RTCP XR
5. 使用RTCP XR报告度量块的指南
5.1. Use a Single Metric in the Metrics Block
5.1. 在度量块中使用单个度量

Different applications using RTP for media transport certainly have differing requirements for metrics transported in RTCP to support their operation. For many applications, the basic metrics for transport impairments provided in RTCP SR and RR packets [RFC3550] (together with source identification provided in RTCP Source Description (SDES) packets) are sufficient. For other applications, additional metrics may be required or at least may be sufficiently useful to justify the overhead, in terms of both processing in endpoints and of increased session bandwidth. For example, an IPTV application using Forward Error Correction (FEC) might use either a metric of post-repair loss or a metric giving detailed information about pre-repair loss bursts to optimize payload bandwidth and the strength of FEC required for changing network conditions. However, there are many metrics available. It is likely that different applications or classes of applications will wish to use different metrics. Any one application is likely to require metrics for more than one parameter, but if this is the case, different applications will almost certainly require different combinations of metrics. If

使用RTP进行媒体传输的不同应用程序当然对RTCP中传输的指标有不同的要求,以支持其操作。对于许多应用,RTCP SR和RR数据包[RFC3550]中提供的传输损伤基本指标(以及RTCP源描述(SDES)数据包中提供的源标识)已足够。对于其他应用程序,可能需要额外的度量,或者至少可能足够有用,以证明在端点处理和增加会话带宽方面的开销。例如,使用前向纠错(FEC)的IPTV应用可以使用修复后丢失的度量或给出关于修复前丢失突发的详细信息的度量来优化净荷带宽和改变网络条件所需的FEC的强度。然而,有许多可用的指标。不同的应用程序或应用程序类别可能希望使用不同的度量。任何一个应用程序都可能需要多个参数的度量,但如果是这样,不同的应用程序几乎肯定需要不同的度量组合。如果

larger blocks are defined containing multiple metrics to address the needs of each application, it becomes likely that many such different larger blocks are defined, which poses a danger to interoperability.


To avoid this pitfall, this memo recommends the definition of metrics blocks containing a very small number of individual metrics characterizing only one parameter of interest to an application running over RTP. For example, at the RTP transport layer, the parameter of interest might be packet delay variation, and specifically the metric "IP Packet Delay Variation (IPDV)" defined by [Y1540]. See Section 6 for architectural considerations for a metrics block, using as an example a metrics block to report packet delay variation. Further, it is appropriate to not only define report blocks separately but also to do so in separate documents where possible. This makes it easier to evolve the reports (i.e., to update each type of report block separately) and also makes it easier to require compliance with a particular report block.


5.2. Include the Payload Type in the Metrics Block
5.2. 在度量块中包括有效负载类型

There are some classes of metrics that can only be interpreted with knowledge of the media codec that is being used (audio mean opinion scores (MOSs) were the triggering example, but there may be others). In such cases, the correlation of an RTCP XR with RTP data is needed. Report blocks that require such correlation need to include the payload type of the reported media. In addition, it is necessary to signal the details and parameters of the payload format to which that payload type is bound using some out-of-band means (e.g., as part of a Session Description Protocol (SDP) offer/answer exchange).

有一些指标类别只能在了解所使用的媒体编解码器的情况下进行解释(音频平均意见分数(MOSs)是触发示例,但也可能有其他指标)。在这种情况下,需要RTCP XR与RTP数据的相关性。需要这种相关性的报告块需要包括所报告介质的有效负载类型。此外,有必要使用一些带外手段(例如,作为会话描述协议(SDP)提供/应答交换的一部分)向该有效负载类型绑定到的有效负载格式的细节和参数发送信号。

5.3. Use RTCP SDES to Correlate XRs with Non-RTP Data
5.3. 使用RTCP SDE将XRs与非RTP数据关联起来

There may be situations where more than one media transport protocol is used by one application to interconnect to the same session in the gateway. For example, one RTCP XR packet is sent to the participating endpoints using non-RTP-based media transport (e.g., using SIP) in a VoIP session. One crucial factor lies in how to handle the different identities that correspond to these different media transport protocols.

在某些情况下,一个应用程序使用多个媒体传输协议互连到网关中的同一会话。例如,在VoIP会话中,使用基于非RTP的媒体传输(例如,使用SIP)将一个RTCP XR分组发送到参与的端点。一个关键因素在于如何处理对应于这些不同媒体传输协议的不同身份。

This memo recommends an approach to facilitate the correlation of the RTCP session with other session-related non-RTP data. That is to say, if there is a need to correlate RTP sessions with non-RTP sessions, then the correlation information needed should be conveyed in a new RTCP SDES item, since such correlation information describes the source rather than providing a quality report. An example use case is where a participant endpoint may convey a call identifier or a global call identifier associated with the SSRC of a measured RTP

本备忘录建议采用一种方法来促进RTCP会话与其他会话相关的非RTP数据的关联。也就是说,如果需要将RTP会话与非RTP会话关联起来,那么所需的关联信息应该在新的RTCP SDES项目中传递,因为此类关联信息描述源,而不是提供质量报告。一个示例用例是参与者端点可以传递与所测量的RTP的SSRC相关联的呼叫标识符或全局呼叫标识符

stream. In such a case, the participant endpoint uses the SSRC to bind the call identifier using the SDES item in the SDES RTCP packet and sends this correlation to the network management system. A flow measurement tool that is configured with the 5-tuple and is not call-aware then forwards the RTCP XRs along with the SSRC of the measured RTP stream, which is included in the XR Block header and 5-tuple to the network management system. The network management system can then correlate this report using SSRC with other diagnostic information, such as call detail records.

流动在这种情况下,参与者端点使用SSRC使用SDES RTCP数据包中的SDES项绑定呼叫标识符,并将此关联发送到网络管理系统。配置了5元组且不支持呼叫的流量测量工具随后将RTCP XR与测量的RTP流的SSRC一起转发到网络管理系统,该SSRC包含在XR块头和5元组中。然后,网络管理系统可以使用SSRC将此报告与其他诊断信息(如呼叫详细记录)关联起来。

5.4. Reduce Measurement Information Repetition across Metrics Blocks
5.4. 减少跨度量块的度量信息重复

When multiple metrics blocks are carried in one RTCP XR packet, reporting on the same stream from the same source for the same time period, RTCP should use the SSRC to identify and correlate the multiple metrics blocks placed between Measurement Information Blocks; see "Measurement Identity and Information Reporting Using a Source Description (SDES) Item and an RTCP Extended Report (XR) Block" [RFC6776]. [RFC6776] enables an RTCP sender to convey the common time period and the number of packets sent during this period. If the measurement interval for a metric is different from the RTCP reporting interval, then this measurement duration in the Measurement Information Block should be used to specify the interval. When there may be multiple Measurement Information Blocks with the same SSRC in one RTCP XR compound packet, the Measurement Information Block should be put in order and followed by all the metrics blocks associated with this Measurement Information Block. New RTCP XR metrics blocks that rely on the Measurement Information Block must specify the response in case the new RTCP XR metrics block is received without an associated Measurement Information Block. In most cases, it is expected that the correct response is to discard the received metric. In order to reduce measurement information repetition in one RTCP XR compound packet containing multiple metrics blocks, the measurement information shall be sent before the related metrics blocks that are from the same reporting interval. Note that for packet loss robustness, if the report blocks for the same interval span more than one RTCP packet, then each block must have the measurement identity information sent together with itself in the same RTCP compound packet, even though the information will be the same.

当在一个RTCP XR数据包中携带多个度量块,在同一时间段内报告来自同一来源的同一数据流时,RTCP应使用SSRC识别并关联放置在度量信息块之间的多个度量块;请参阅“使用源描述(SDES)项和RTCP扩展报告(XR)块的测量标识和信息报告”[RFC6776]。[RFC6776]使RTCP发送方能够传送公共时间段和在此期间发送的数据包数。如果度量的测量间隔与RTCP报告间隔不同,则应使用测量信息块中的此测量持续时间来指定间隔。当一个RTCP XR复合数据包中可能存在多个具有相同SSRC的测量信息块时,应将该测量信息块按顺序排列,然后是与该测量信息块关联的所有度量块。依赖测量信息块的新RTCP XR度量块必须指定在接收到新RTCP XR度量块时没有关联测量信息块的响应。在大多数情况下,正确的响应应该是放弃接收到的度量。为了减少包含多个度量块的一个RTCP XR复合数据包中的测量信息重复,测量信息应在来自相同报告间隔的相关度量块之前发送。注意,对于数据包丢失稳健性,如果相同间隔的报告块跨越多个RTCP数据包,则每个数据块必须在同一RTCP复合数据包中与其自身一起发送测量标识信息,即使信息相同。

6. An Example of a Metrics Block
6. 度量块的示例

This section uses the example of an existing proposed metrics block to illustrate the application of the principles set out in Section 5.


The example [RFC6798] is a block to convey information about packet delay variation (PDV) only, consistent with the principle that a metrics block should address only one parameter of interest. One


simple metric of PDV is available in the RTCP RR packet as the "inter-arrival jitter" field. There are other PDV metrics with a certain similarity in metric structure that may be more useful to certain applications. Two such metrics are the IPDV metric ([Y1540] [RFC3393]) and the mean absolute packet delay variation 2 (MAPDV2) metric [G1020]. The use of these metrics is consistent with the principle in Section 5 of the RTCP guidelines document [RFC5968] that metrics should usually be defined elsewhere, so that RTCP standards define only the transport of the metric rather than its nature. The purpose of this section is to illustrate the architectural considerations, using the example of [RFC6798], rather than to document the design of the PDV metrics block or to provide a tutorial on PDV in general.

在RTCP RR数据包中,PDV的简单度量可用作“到达间抖动”字段。还有其他在度量结构中具有某种相似性的PDV度量,可能对某些应用程序更有用。两个这样的度量是IPDV度量([Y1540][RFC3393])和平均绝对分组延迟变化2(MAPDV2)度量[G1020]。这些指标的使用符合RTCP指南文件[RFC5968]第5节的原则,即指标通常应在其他地方定义,因此RTCP标准仅定义指标的传输,而不是其性质。本节的目的是以[RFC6798]为例说明体系结构注意事项,而不是记录PDV度量块的设计或提供一般PDV教程。

Given the availability of at least three metrics for PDV, there are design options for the allocation of metrics to RTCP XR blocks:

鉴于PDV至少有三个指标可用,有一些设计选项可用于将指标分配给RTCP XR块:

o Provide an RTCP XR block per metric.

o 提供每个度量的RTCP XR块。

o Provide a single RTCP XR block that contains all three metrics.

o 提供包含所有三个指标的单个RTCP XR块。

o Provide a single RTCP block to convey any one of the three metrics, together with an identifier to inform the receiving RTP system of the specific metric being conveyed.

o 提供一个RTCP块来传输三个指标中的任何一个,并提供一个标识符来通知接收RTP系统正在传输的特定指标。

In choosing between these options, extensibility is important, because additional metrics of PDV may well be standardized and require inclusion in this framework. The first option is extensible but only by the use of additional RTCP XR blocks, which may consume the limited namespace for RTCP XR blocks at an unacceptable rate. The second option is not extensible and so could be rejected on that basis, but in any case a single application is quite unlikely to require the transport of more than one metric for PDV. Hence, the third option was chosen. This implies the creation of a subsidiary namespace to enumerate the PDV metrics that may be transported by this block, as discussed further in [RFC6798].

在选择这些选项时,可扩展性很重要,因为PDV的其他指标很可能会标准化,并且需要包含在这个框架中。第一个选项是可扩展的,但只能通过使用额外的RTCP XR块来扩展,这可能以不可接受的速率消耗RTCP XR块的有限命名空间。第二个选项是不可扩展的,因此可以在此基础上拒绝,但在任何情况下,单个应用程序都不太可能要求传输一个以上的PDV度量。因此,选择了第三种选择。这意味着创建一个辅助名称空间来枚举此块可能传输的PDV度量,如[RFC6798]中进一步讨论的。

7. Application to RFC 5117 Topologies
7. RFC5117拓扑的应用

The topologies specified in [RFC5117] fall into two categories. The first category relates to the RTP system model utilizing multicast and/or unicast. The topologies in this category are specifically Topo-Point-to-Point, Topo-Multicast, Topo-Translator (both variants Topo-Trn-Translator and Topo-Media-Translator as well as combinations of the two), and Topo-Mixer. These topologies use RTP end systems, RTP mixers, and RTP translators as defined in [RFC3550]. For the purposes of reporting connection quality to other RTP systems, RTP mixers and RTP end systems are very similar. Mixers resynchronize


packets and do not relay RTCP reports received from one cloud towards other cloud(s). Translators do not resynchronize packets and should forward certain RTCP reports between clouds. In this category, the RTP system (end system, mixer, or translator) that originates, terminates, or forwards RTCP XR blocks is expected to handle RTCP, including RTCP XR, according to RTP [RFC3550]. Provided this expectation is met, an RTP system using RTCP XR is architecturally no different from an RTP system of the same class (end system, mixer, or translator) that does not use RTCP XR. The second category relates to deployed system models used in many H.323 [H323] videoconferences. The topologies in this category are Topo-Video-switch-MCU and Topo-RTCP-terminating-MCU. Such topologies based on systems (e.g., MCUs) do not behave according to RTP [RFC3550].

数据包,不将从一个云接收到的RTCP报告转发给其他云。转换器不会重新同步数据包,应该在云之间转发某些RTCP报告。在此类别中,根据RTP[RFC3550],发起、终止或转发RTCP XR块的RTP系统(终端系统、混音器或转换器)预计将处理RTCP,包括RTCP XR。如果满足这一期望,使用RTCP XR的RTP系统在架构上与不使用RTCP XR的同类RTP系统(终端系统、混音器或转换器)没有什么不同。第二类涉及许多H.323[H323]视频会议中使用的已部署系统模型。此类别中的拓扑为拓扑视频开关MCU和拓扑RTCP终端MCU。基于系统(如MCU)的此类拓扑不符合RTP[RFC3550]的规定。

Considering that the translator and MCU are two typical intermediate systems in these two categories mentioned above, this document will take them as two typical examples to explain how RTCP XR works in different [RFC5117] topologies.

考虑到翻译器和MCU是上述两类中的两个典型中间系统,本文件将以它们为两个典型示例来解释RTCP XR如何在不同的[RFC5117]拓扑中工作。

7.1. Applicability to Translators
7.1. 对译者的适用性

Section 7.2 of the RTP specification [RFC3550] describes the processing of RTCP by translators. RTCP XR is within the scope of the recommendations of [RFC3550]. Some RTCP XR metrics blocks may usefully be measured at, and reported by, translators. As described in [RFC3550], this creates a requirement for the translator to allocate an SSRC for the monitor co-located with itself so that the monitor may populate the SSRC in the RTCP XR packet header as the packet sender SSRC and send it out (although the translator is not a synchronization source in the sense of originating RTP media packets). It must also supply this SSRC and the corresponding CNAME in RTCP SDES packets.

RTP规范[RFC3550]第7.2节描述了翻译人员对RTCP的处理。RTCP XR在[RFC3550]的建议范围内。一些RTCP XR度量块可以在转换器处测量并由转换器报告。如[RFC3550]中所述,这要求转换器为与其共存的监视器分配SSRC,以便监视器可以在RTCP XR数据包头中填充SSRC作为数据包发送方SSRC并将其发送出去(尽管转换器不是原始RTP媒体数据包意义上的同步源). 它还必须在RTCP SDES数据包中提供此SSRC和相应的CNAME。

In RTP sessions where one or more translators generate any RTCP traffic towards their next-neighbor RTP system, other translators in the session have a choice as to whether they forward a translator's RTCP packets. Forwarding may provide additional information to other RTP systems in the connection but increases RTCP bandwidth and may in some cases present a security risk. RTP translators may have forwarding behavior based on local policy, which might differ between different interfaces of the same translator.


7.2. Applicability to MCUs
7.2. MCU的适用性

Topo-Video-switch-MCU and Topo-RTCP-terminating-MCU suffer from the difficulties described in [RFC5117]. These difficulties apply to systems sending, and expecting to receive, RTCP XR blocks as much as to systems using other RTCP packet types. For example, a participant

Topo视频开关MCU和Topo RTCP终端MCU遇到[RFC5117]中描述的困难。这些困难适用于发送和预期接收RTCP XR块的系统,同样适用于使用其他RTCP数据包类型的系统。例如,参与者

RTP end system may send media to a video switch MCU. If the media stream is not selected for forwarding by the switch, neither RTCP RR packets nor RTCP XR blocks referring to the end system's generated stream will be received at the RTP end system. Strictly speaking, the RTP end system can only conclude that its RTP has been lost in the network, though an RTP end system complying with the robustness principle of [RFC1122] should survive with essential functions (i.e., media distribution) unimpaired.

RTP终端系统可以向视频开关MCU发送媒体。如果交换机未选择媒体流进行转发,RTP终端系统将不会接收到引用终端系统生成流的RTCP RR数据包或RTCP XR块。严格地说,RTP终端系统只能得出其RTP已在网络中丢失的结论,尽管符合[RFC1122]健壮性原则的RTP终端系统应在基本功能(即媒体分发)不受影响的情况下生存。

8. Security Considerations
8. 安全考虑

This document focuses on the RTCP reporting extension using RTCP XR and should not give rise to any new security vulnerabilities beyond those described in RTCP XRs [RFC3611]. However, it also describes the architectural framework to be used for monitoring at the RTP layer. The security issues with monitoring need to be considered.

本文档重点介绍使用RTCP XR的RTCP报告扩展,不应产生RTCP XRs[RFC3611]中所述之外的任何新安全漏洞。然而,它也描述了用于RTP层监控的体系结构框架。需要考虑监控的安全问题。

In RTP sessions, an RTP system may use its own SSRC to send its monitoring reports towards its next-neighbor RTP system. Other RTP systems in the session may have a choice as to whether they forward this RTP system's RTCP packets. This presents a security issue, since the information in the report may be exposed by the other RTP system to any malicious node. Therefore, if the information is considered sensitive, the monitoring reports should be secured to the same extent as the RTP flows that they measure. If encryption is used and the encrypted monitoring report is received by the RTP system that deploys the third-party monitor, the RTP system may decrypt the monitor report for the third-party monitor based on local policy (e.g., third-party monitors are allowed access to the metric) and forward it to the third-party monitor; otherwise, the third-party monitor should discard the received encrypted monitoring report.


9. Acknowledgements
9. 致谢

The authors would like to thank Colin Perkins, Charles Eckel, Robert Sparks, Salvatore Loreto, Graeme Gibbs, Debbie Greenstreet, Keith Drage, Dan Romascanu, Ali C. Begen, Roni Even, Magnus Westerlund, Meral Shirazipour, Tina Tsou, Barry Leiba, Benoit Claise, Russ Housley, and Stephen Farrell for their valuable comments and suggestions on early versions of this document.

作者要感谢科林·珀金斯、查尔斯·埃克尔、罗伯特·斯帕克斯、萨尔瓦托·洛雷托、格雷姆·吉布斯、黛比·格林斯特雷特、基思·德拉格、丹·罗马斯坎努、阿里·C·贝根、甚至罗尼、马格纳斯·韦斯特隆德、梅拉尔·西拉齐普尔、蒂娜·祖、巴里·莱巴、贝诺伊特·克莱斯、罗斯·霍斯利、,以及Stephen Farrell,感谢他们对本文件早期版本的宝贵意见和建议。

10. Informative References
10. 资料性引用

[G1020] ITU-T, "Performance parameter definitions for quality of speech and other voiceband applications utilizing IP networks", ITU-T Rec. G.1020, July 2006.

[G1020]ITU-T,“利用IP网络的语音质量和其他声带应用的性能参数定义”,ITU-T Rec.G.1020,2006年7月。

[H323] ITU-T, "Packet-based multimedia communications systems", ITU-T Rec. H.323, December 2009.

[H323]ITU-T,“基于分组的多媒体通信系统”,ITU-T Rec.H.323,2009年12月。

[QOE_BLOCK] Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTP Control Protocol (RTCP) Extended Report (XR) Blocks for QoE Metric Reporting", Work in Progress, October 2012.


[RFC1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 3, RFC 1122, October 1989.

[RFC1122]Braden,R.,“互联网主机的要求-通信层”,标准3,RFC 1122,1989年10月。

[RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time Transport Protocol Management Information Base", RFC 2959, October 2000.

[RFC2959]Baugher,M.,Strahm,B.,和I.Suconick,“实时传输协议管理信息库”,RFC 2959,2000年10月。

[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, November 2002.

[RFC3393]Demichelis,C.和P.Chimento,“IP性能度量的IP数据包延迟变化度量(IPPM)”,RFC 3393,2002年11月。

[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003.

[RFC3550]Schulzrinne,H.,Casner,S.,Frederick,R.,和V.Jacobson,“RTP:实时应用的传输协议”,STD 64,RFC 35502003年7月。

[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003.

[RFC3611]Friedman,T.,Caceres,R.,和A.Clark,“RTP控制协议扩展报告(RTCP XR)”,RFC 36112003年11月。

[RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version 9", RFC 3954, October 2004.

[RFC3954]Claise,B.,“Cisco Systems NetFlow服务导出版本9”,RFC 3954,2004年10月。

[RFC4585] Ott, J., Wenger, S., Sato, N., Burmeister, C., and J. Rey, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/AVPF)", RFC 4585, July 2006.

[RFC4585]Ott,J.,Wenger,S.,Sato,N.,Burmeister,C.,和J.Rey,“基于实时传输控制协议(RTCP)的反馈(RTP/AVPF)的扩展RTP配置文件”,RFC 45852006年7月。

[RFC5101] Claise, B., "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of IP Traffic Flow Information", RFC 5101, January 2008.

[RFC5101]Claise,B.,“用于交换IP流量信息的IP流量信息导出(IPFIX)协议规范”,RFC 5101,2008年1月。

[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J. Meyer, "Information Model for IP Flow Information Export", RFC 5102, January 2008.

[RFC5102]Quitek,J.,Bryant,S.,Claise,B.,Aitken,P.,和J.Meyer,“IP流信息导出的信息模型”,RFC 5102,2008年1月。

[RFC5117] Westerlund, M. and S. Wenger, "RTP Topologies", RFC 5117, January 2008.

[RFC5117]Westerlund,M.和S.Wenger,“RTP拓扑”,RFC 51172008年1月。

[RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control Protocol (RTCP) Extensions for Single-Source Multicast Sessions with Unicast Feedback", RFC 5760, February 2010.

[RFC5760]Ott,J.,Chesterfield,J.,和E.Schooler,“具有单播反馈的单源多播会话的RTP控制协议(RTCP)扩展”,RFC 57602010年2月。

[RFC5968] Ott, J. and C. Perkins, "Guidelines for Extending the RTP Control Protocol (RTCP)", RFC 5968, September 2010.

[RFC5968]Ott,J.和C.Perkins,“RTP控制协议(RTCP)扩展指南”,RFC 5968,2010年9月。

[RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich, "Session Initiation Protocol Event Package for Voice Quality Reporting", RFC 6035, November 2010.

[RFC6035]Pendleton,A.,Clark,A.,Johnston,A.,和H.Sinnreich,“语音质量报告的会话启动协议事件包”,RFC 60352010年11月。

[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New Performance Metric Development", BCP 170, RFC 6390, October 2011.

[RFC6390]Clark,A.和B.Claise,“考虑新性能指标开发的指南”,BCP 170,RFC 63902011年10月。

[RFC6776] Clark, A. and Q. Wu, "Measurement Identity and Information Reporting Using a Source Description (SDES) Item and an RTCP Extended Report (XR) Block", RFC 6776, October 2012.

[RFC6776]Clark,A.和Q.Wu,“使用源描述(SDES)项和RTCP扩展报告(XR)块的测量标识和信息报告”,RFC 6776,2012年10月。

[RFC6798] Clark, A. and Q. Wu, "RTP Control Protocol (RTCP) Extended Report (XR) Block for Packet Delay Variation Metric Reporting", RFC 6798, November 2012.

[RFC6798]Clark,A.和Q.Wu,“用于数据包延迟变化度量报告的RTP控制协议(RTCP)扩展报告(XR)块”,RFC 6798,2012年11月。

[Y1540] ITU-T, "IP packet transfer and availability performance parameters", ITU-T Rec. Y.1540, March 2011.

[Y1540]ITU-T,“IP数据包传输和可用性性能参数”,ITU-T Rec.Y.1540,2011年3月。

Authors' Addresses


Qin Wu (editor) Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China



Geoff Hunt Unaffiliated



Philip Arden BT Orion 3/7 PP4 Adastral Park Martlesham Heath Ipswich, Suffolk IP5 3RE United Kingdom

Philip Arden BT Orion 3/7 PP4英国萨福克郡马特勒沙姆希思伊普斯维奇阿达斯特拉尔公园IP5 3RE

   Phone: +44 1473 644192
   Phone: +44 1473 644192