Guidelines for Use of the RTP Monitoring Framework
Author(s): Philip Arden, Wenson Wu, Geoff Hunt
This memo proposes an extensible Real-Time Protocol (RTP) monitoring framework for extending 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,...
Audio/Video Transport Working Group Q. Wu, Ed. Internet-Draft Huawei Intended status: Informational G. Hunt Expires: March 29, 2013 Unaffiliated P. Arden BT September 25, 2012 Guidelines for Use of the RTP Monitoring Framework draft-ietf-avtcore-monarch-22.txt Abstract This memo proposes an extensible Real-Time Protocol (RTP) monitoring framework for extending 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 which 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 which covers their set of concerns. Where possible, a specific block should be designed to be re-usable across more than one application, for example, for all of voice, streaming audio and video. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on March 29, 2013. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. Wu, et al. Expires March 29, 2013 [Page 1] Internet-Draft RTP Monitoring Framework September 2012 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. RTP Monitoring Framework . . . . . . . . . . . . . . . . . . . 7 3.1. Overview of the RTP Monitoring Framework . . . . . . . . . 7 3.2. Location of Monitors . . . . . . . . . . . . . . . . . . . 9 4. Issues With Reporting Metric Block Using RTCP XR Extension . . 10 4.1. Using compound metrics block . . . . . . . . . . . . . . . 10 4.2. Correlating RTCP XR with the non-RTP data . . . . . . . . 10 4.3. Measurement Information duplication . . . . . . . . . . . 10 4.4. Consumption of XR block code points . . . . . . . . . . . 11 5. Guidelines For Reporting Metric Block Using RTCP XR . . . . . 12 5.1. Contain the single metrics in the Metric Block . . . . . . 12 5.2. Include the payload type in the Metric Block . . . . . . . 12 5.3. Use RTCP SDES to correlate XR reports with non-RTP data . 13 5.4. Reduce Measurement information repetition across metric blocks . . . . . . . . . . . . . . . . . . . . . . 13 6. An Example of a Metric Block . . . . . . . . . . . . . . . . . 15 7. Application To RFC 5117 Topologies . . . . . . . . . . . . . . 16 7.1. Applicability to Translators . . . . . . . . . . . . . . . 16 7.2. Applicability to MCU . . . . . . . . . . . . . . . . . . . 17 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 9. Security Considerations . . . . . . . . . . . . . . . . . . . 19 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 20 11. Informative References . . . . . . . . . . . . . . . . . . . . 21 Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 23 A.1. draft-ietf-avtcore-monarch-22 . . . . . . . . . . . . . . 23 A.2. draft-ietf-avtcore-monarch-20 . . . . . . . . . . . . . . 23 A.3. draft-ietf-avtcore-monarch-19 . . . . . . . . . . . . . . 23 A.4. draft-ietf-avtcore-monarch-18 . . . . . . . . . . . . . . 23 A.5. draft-ietf-avtcore-monarch-17 . . . . . . . . . . . . . . 23 A.6. draft-ietf-avtcore-monarch-16 . . . . . . . . . . . . . . 24 A.7. draft-ietf-avtcore-monarch-15 . . . . . . . . . . . . . . 24 A.8. draft-ietf-avtcore-monarch-14 . . . . . . . . . . . . . . 24 A.9. draft-ietf-avtcore-monarch-13 . . . . . . . . . . . . . . 24 A.10. draft-ietf-avtcore-monarch-12 . . . . . . . . . . . . . . 25 Wu, et al. Expires March 29, 2013 [Page 2] Internet-Draft RTP Monitoring Framework September 2012 A.11. draft-ietf-avtcore-monarch-11 . . . . . . . . . . . . . . 25 A.12. draft-ietf-avtcore-monarch-10 . . . . . . . . . . . . . . 25 A.13. draft-ietf-avtcore-monarch-09 . . . . . . . . . . . . . . 25 A.14. draft-ietf-avtcore-monarch-08 . . . . . . . . . . . . . . 26 A.15. draft-ietf-avtcore-monarch-07 . . . . . . . . . . . . . . 26 A.16. draft-ietf-avtcore-monarch-06 . . . . . . . . . . . . . . 26 A.17. draft-ietf-avtcore-monarch-05 . . . . . . . . . . . . . . 26 A.18. draft-ietf-avtcore-monarch-04 . . . . . . . . . . . . . . 26 A.19. draft-ietf-avtcore-monarch-03 . . . . . . . . . . . . . . 27 A.20. draft-ietf-avtcore-monarch-02 . . . . . . . . . . . . . . 27 A.21. draft-ietf-avtcore-monarch-01 . . . . . . . . . . . . . . 27 A.22. draft-ietf-avtcore-monarch-00 . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 Wu, et al. Expires March 29, 2013 [Page 3] Internet-Draft RTP Monitoring Framework September 2012 1. Introduction Multimedia services using the Real-Time 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] and other RTCP extension to Sender Reports (SR), Receiver Reports (RR) [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]. 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 re-usable Quality of Service (QoS) / QoE metrics which facilitate reduced implementation costs and help maximize inter-operability. The "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 RFC5968 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. Wu, et al. Expires March 29, 2013 [Page 4] Internet-Draft RTP Monitoring Framework September 2012 2. Terminology 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 which characterise the three transport impairments of packet loss, packet delay, jitter (also known as delay variation). These metrics should be usable by any application which 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 specified in QoE metric reporting Block [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 signalled using an RTCP Measurement Information XR Block [MEASI]. An example interval metric is the count of the number of RTP packets lost over the course of the last RTCP reporting Wu, et al. Expires March 29, 2013 [Page 5] Internet-Draft RTP Monitoring Framework September 2012 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 signalled using an RTCP Measurement Information XR Block [MEASI]. 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 continually updated as each RTP data packet arrives, but only reported based on a snapshot of the value which is sampled at the instant the reporting interval ends. Wu, et al. Expires March 29, 2013 [Page 6] Internet-Draft RTP Monitoring Framework September 2012 3. RTP Monitoring Framework 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], 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 framework is ease of integration with other RTP/RTCP mechanisms. 3.1. Overview of the RTP Monitoring Framework The RTP monitoring Framework comprises the following two key functional components described below: o Monitor o RTP Metric Block Monitor is the functional component defined in the Real-time Transport Protocol [RFC3550]. It acts as a repository of information gathered for monitoring purposes. According to the definition of monitor in the RTP Protocol [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, intermediate and the receiver. The RTP Metric Block (MB) conveys real time Application QoS/QoE metric information and is used by the monitor to exchange 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 or RTCP XR can be extended to Wu, et al. Expires March 29, 2013 [Page 7] Internet-Draft RTP Monitoring Framework September 2012 transport these metrics, e.g., the basic RTCP Reception Report (RR) [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 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 Figure 1, the monitors may export the metric information derived from the RTP monitoring framework to the management system using non-RTP means. +-----------+ +----------+ |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 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 the reception quality reporting. Wu, et al. Expires March 29, 2013 [Page 8] Internet-Draft RTP Monitoring Framework September 2012 3.2. Location of Monitors As shown in Figure 1, there are several possible locations from where 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 sessions 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 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, video conferencing systems, or IPTV set-top boxes. Alternatively, they can be terminated in devices that gateway between RTP and other transport protocols. Transport and end system metrics, application level metrics that don't reflect end to end user experience may be collected at all types of end system, 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 an Synchronization source (SSRC) in that session which it can use for its reports. Transport level metrics may be collected at such 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. Wu, et al. Expires March 29, 2013 [Page 9] Internet-Draft RTP Monitoring Framework September 2012 4. Issues With Reporting Metric Block Using RTCP XR Extension The following sections discuss four issues that have come up in the past with reporting metric block using RTCP XR extensions. 4.1. Using compound metrics block 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, the RTCP Extended Reports (XRs) [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 compound metrics block only for specific applications may increase implementation cost and minimize interoperability. 4.2. Correlating RTCP XR with the non-RTP data Canonical End-Point Identifier SDES Item (CNAME), defined in the RTP Protocol [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. CNAME may be also fixed across multiple RTP sessions from the same source. However there may be situations where RTCP reports are sent to other participating endpoints using non-RTP protocol in a session. For example, as described in the SIP RTCP Summary Report Protocol [RFC6035], the data contained in RTCP XR VoIP metrics reports [RFC3611] are forwarded to a central collection server systems using SIP. In such case, there is a large portfolio of quality parameters that can be associated with real time application, e.g., VOIP application, but only a minimal number of parameters are included on the RTCP-XR reports. With these minimal number of RTCP statistics parameters mapped to non-RTCP measurements, it is hard to provide accurate measures of real time application quality, conduct detailed data analysis and creates alerts timely to the users. Therefore correlation between RTCP XR and non-RTP data should be provided. 4.3. Measurement Information duplication We may set a measurement interval for the session and monitor RTP packets within one or several consecutive report intervals. In such case, the extra measurement information (e.g., extended sequence number of 1st packet, measurement period) may be expected. However if we put such extra measurement information into each metric block, there may be situations where an RTCP XR packet containing multiple Wu, et al. Expires March 29, 2013 [Page 10] Internet-Draft RTP Monitoring Framework September 2012 metric blocks, reports on the same streams from the same source. In other words, duplicated data for the measurement is provided multiple times, once in every metric block. Though this design ensures immunity to packet loss, it may bring more packetization complexity and the processing overhead is not completely trivial in some cases. Therefore compromise between processing overhead and reliability should be taken into account. 4.4. Consumption of XR block code points 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. Anticipating the potential need to extend the block type space, it is noted that Block Type 255 is reserved for future extensions in [RFC3611]. Wu, et al. Expires March 29, 2013 [Page 11] Internet-Draft RTP Monitoring Framework September 2012 5. Guidelines For Reporting Metric Block Using RTCP XR 5.1. Contain the single metrics in the Metric Block 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 SDES packets) are sufficient. For other applications additional metrics may be required or at least sufficiently useful to justify the overhead, both of 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 optimise 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 larger blocks are defined containing multiple metrics to address the needs of each application, it becomes likely that many different such larger blocks are defined, which becomes 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 Metric Block 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 (MOS) were the triggering example, but there may be others). In such cases the correlation of 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 Wu, et al. Expires March 29, 2013 [Page 12] Internet-Draft RTP Monitoring Framework September 2012 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 an SDP offer/answer exchange). 5.3. Use RTCP SDES to correlate XR reports with non-RTP data 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 their different identities that are corresponding to different media transport. 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 Source Description (SDES) item, since such correlation information describes the source, rather than providing a quality report. An example use case is for a participant endpoint may convey a call identifier or a global call identifier associated with the SSRC of measured RTP stream. In such case, the participant endpoint uses the SSRC to bind the call identifier using SDES item in the SDES RTCP packet and send such correlation to the network management system. A flow measurement tool that is configured with the 5-tuple and not call-aware then forwards the RTCP XR reports 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. Network management system can then correlate this report using SSRC with other diagnostic information such as call detail records. 5.4. Reduce Measurement information repetition across metric blocks When multiple metric 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 metric blocks between metric blocks. "Measurement Identity and information Reporting using SDES item and XR Block" [MEASI] 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 measurements 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 metric blocks associated with this measurement information block. New RTCP XR metric blocks that rely Wu, et al. Expires March 29, 2013 [Page 13] Internet-Draft RTP Monitoring Framework September 2012 on the Measurement information block [MEASI] must specify the response in case the new RTCP XR metric 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 metric blocks, the measurement information shall be sent before the related metric blocks that are from the same reporting interval. Note that for packet loss robustness if the report blocks for the same interval span over more than one RTCP packet, then each must have the measurement identity information even though they will be the same. Wu, et al. Expires March 29, 2013 [Page 14] Internet-Draft RTP Monitoring Framework September 2012 6. An Example of a Metric Block 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 [PDV] 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 "interarrival jitter" field. There are other PDV metrics with a certain similarity in metric structure which 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]. Use of these metrics is consistent with the principle in Section 5 of RTCP guideline [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 consideration using the example of [PDV] rather than to document the design of the PDV metrics block or to provide a tutorial on PDV in general. Given the availability of at least three metrics for PDV, there are design options for the allocation of metrics to RTCP XR blocks: o provide an RTCP XR block per metric o provide a single RTCP XR block which contains all three metrics o provide a single RTCP block to convey any one of the three metrics, together with a identifier to inform the receiving RTP system of the specific metric being conveyed 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 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, so could be rejected on that basis, but in any case a single application is quite unlikely to require 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 which may be transported by this block, as discussed further in [PDV]. Wu, et al. Expires March 29, 2013 [Page 15] Internet-Draft RTP Monitoring Framework September 2012 7. Application To RFC 5117 Topologies The topologies specified in [RFC 5117] 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, and combinations of the two), and Topo-Mixer. These topologies use RTP end systems, RTP mixers and RTP translators defined in the RTP protocol [RFC3550]. For 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) which originates, terminates or forwards RTCP XR blocks is expected to handle RTCP, including RTCP XR, according to the RTP protocol [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) which does not use RTCP XR. The second category relates to deployed system models used in many H.323 [H323] video conferences. 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 the RTP protocol [RFC3550]. Considering 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 report works in different RFC 5117 topologies. 7.1. Applicability to Translators Section 7.2 of the RTP protocol [RFC3550] describes processing of RTCP by translators. RTCP XR is within the scope of the recommendations of the RTP protocol [RFC3550]. Some RTCP XR metrics blocks may usefully be measured at, and reported by, translators. As described in the RTP protocol [RFC3550] this creates a requirement for the translator to allocate an SSRC for the monitor collocated with itself so that the monitor may populate the SSRC in the RTCP XR packet header as packet sender SSRC and send it out(although the translator is not a Synchronisation Source in the sense of originating RTP media packets). It must also supply this SSRC and the corresponding CNAME in RTCP SDES packets. In RTP sessions where one or more translators generate any RTCP traffic towards their next-neighbour RTP system, other translators in the session have a choice as to whether they forward a translator's Wu, et al. Expires March 29, 2013 [Page 16] Internet-Draft RTP Monitoring Framework September 2012 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 behaviour based on local policy, which might differ between different interfaces of the same translator. 7.2. Applicability to MCU Topo-Video-Switch-MCU and Topo-RTCP-terminating-MCU, suffer from the difficulties described in [RFC 5117]. 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 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 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. Wu, et al. Expires March 29, 2013 [Page 17] Internet-Draft RTP Monitoring Framework September 2012 8. IANA Considerations There is no IANA action in this document. Wu, et al. Expires March 29, 2013 [Page 18] Internet-Draft RTP Monitoring Framework September 2012 9. Security Considerations 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 RTP layer. The security issues with monitoring needs to be considered. In RTP sessions, a RTP system may use its own SSRC to send its monitoring reports towards its next-neighbour RTP system. Other RTP system in the session may have a choice as to whether they forward this RTP system's RTCP packets. This present 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 as 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 deploy 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 is allowed to access to the metric) and forward it to the third party monitor, otherwise, the third party monitor SHOULD discard the received encrypted monitoring report. Wu, et al. Expires March 29, 2013 [Page 19] Internet-Draft RTP Monitoring Framework September 2012 10. Acknowledgement The authors would also 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,Stephen Farrell for their valuable comments and suggestions on the early version of this document. Wu, et al. Expires March 29, 2013 [Page 20] Internet-Draft RTP Monitoring Framework September 2012 11. Informative References [G1020] ITU-T, "ITU-T Rec. G.1020, Performance parameter definitions for quality of speech and other voiceband applications utilizing IP networks", July 2006. [H323] ITU-T, "ITU-T Rec. H.323, Packet-based multimedia communications systems", June 2006. [MEASI] Wu, Q., "Measurement Identity and information Reporting using SDES item and XR Block", ID draft-ietf-xrblock-rtcp-xr-meas-identity-10, August 2012. [PDV] Hunt, G., Clark, A., and Q. Wu, "RTCP XR Report Block for Packet Delay Variation Metric Reporting", ID draft-ietf-xrblock-rtcp-xr-pdv-05, August 2012. [QOE_BLOCK] Hunt, G., Clark, A., Wu, Q., Schott, R., and G. Zorn, "RTCP XR Blocks for QoE Metric Reporting", ID draft-ietf-xrblock-rtcp-xr-qoe-02, July 2012. [RFC1122] Braden, R., "Requirements for Internet Hosts -- Communication Layers", RFC1122, October 1989. [RFC2959] Baugher, M., Strahm, B., and I. Suconick, "Real-Time Transport Protocol Management Information Base", RFC2959, October 2000. [RFC3393] Demichelis, C., "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC3393, November 2002. [RFC3550] Schulzrinne, H., "RTP: A Transport Protocol for Real-Time Applications", RFC3550, July 2003. [RFC3611] Friedman, T., "RTP Control Protocol Extended Reports (RTCP XR)", RFC3611, November 2003. [RFC3954] Claise, B., "Cisco Systems NetFlow Services Export Version 9", RFC3954, October 2004. [RFC4585] Ott, J. and S. Wenger, "Extended RTP Profile for Real-time Transport Control Protocol (RTCP)-Based Feedback (RTP/ AVPF)", RFC4585, July 2006. [RFC5101] Claise, B., "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of IP Traffic Wu, et al. Expires March 29, 2013 [Page 21] Internet-Draft RTP Monitoring Framework September 2012 Flow Information", RFC5101, January 2008. [RFC5102] Quittek, J., , S., Claise, B., Aitken, P., and J. Meyer, "Information Model for IP Flow Information Export", RFC5102, January 2008. [RFC 5117] Westerlund, M., "RTP Topologies", RFC 5117, January 2008. [RFC5760] Ott, J., Chesterfield, J., and E. Schooler, "RTP Control Protocol (RTCP) Extensions for Single-Source Multicast Sessions with Unicast Feedback", RFC5760, February 2010. [RFC5968] Ott, J. and C. Perkins, "Guidelines for Extending the RTP Control Protocol (RTCP)", RFC5968, September 2010. [RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich, "Session Initiation Protocol Event Package for Voice Quality Reporting", RFC6035, November 2010. [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New Performance Metric Development", RFC6390, October 2011. [Y1540] ITU-T, "ITU-T Rec. Y.1540, IP packet transfer and availability performance parameters", November 2007. Wu, et al. Expires March 29, 2013 [Page 22] Internet-Draft RTP Monitoring Framework September 2012 Appendix A. Change Log Note to the RFC-Editor: please remove this section prior to publication as an RFC. A.1. draft-ietf-avtcore-monarch-22 The following are the major changes compared to 20,21: o Editorial changes based on Benoit and WG Review. A.2. draft-ietf-avtcore-monarch-20 The following are the major changes compared to 19: o Editorial changes based on IESG Review. o Some new text in the security section to clarify encryption issue for third party monitoring. o Some new text in introduction section to clarify the relationship with RFC5968 and RFC6390. A.3. draft-ietf-avtcore-monarch-19 The following are the major changes compared to 18: o Editorial changes based on Meral Shirazipour's second Gen-Art review. o Transport level metrics definition simplifying based on Robert's comment. A.4. draft-ietf-avtcore-monarch-18 The following are the major changes compared to 17: o Some Editorial changes based on Gen-Art review and Secdir Review. A.5. draft-ietf-avtcore-monarch-17 The following are the major changes compared to 16: o Some Editorial changes. Wu, et al. Expires March 29, 2013 [Page 23] Internet-Draft RTP Monitoring Framework September 2012 A.6. draft-ietf-avtcore-monarch-16 The following are the major changes compared to 15: o A few modification to the figure 1. o Change RTCP XR reports into RTCP reports in the section 3.1. o References Update. A.7. draft-ietf-avtcore-monarch-15 The following are the major changes compared to 14: o Add figure 1 in section 3 to describe RTP monitoring framework. o Change the title as Guidelines for Use of the RTP Monitoring Framework. o Other editorial change to get in line with the title change in the section 3. A.8. draft-ietf-avtcore-monarch-14 The following are the major changes compared to 13: o Incorporate the key points in the section 3.2 into overview section. o Remove the figure 1 and use the description instead. o Add description in the section 3.3 to discuss the possible location of the monitors and the types of metric at that location. o Add the description to make the definition of Interval metrics/ cumulative metrics/sampled metrics clear. o Editorial Changes. A.9. draft-ietf-avtcore-monarch-13 The following are the major changes compared to 12: o Editorial Changes. Wu, et al. Expires March 29, 2013 [Page 24] Internet-Draft RTP Monitoring Framework September 2012 A.10. draft-ietf-avtcore-monarch-12 The following are the major changes compared to 11: o Editorial Changes based on Charles' Comments. o Reference update. o Add one new section 5.2 to discuss Correlating RTCP XR with RTP data. o Add text in section 5.1 to highlight it is more appropriate to define each block in a separate draft. A.11. draft-ietf-avtcore-monarch-11 The following are the major changes compared to 10: o Editorial Changes. A.12. draft-ietf-avtcore-monarch-10 The following are the major changes compared to 09: o Discuss what exist already for monitoring in section 3.1. o Provide benefit using RTCP XR based monitoring in section 3.1. o add one new paragraph in section 3.1 to describe how monitoring architecture is applied to ASM/SSM. o Other Editorial Changes. A.13. draft-ietf-avtcore-monarch-09 The following are the major changes compared to 07: o Rephrase application level metric definition. o Add one new section to clarify where to measure QoE related parameters. o Add text in section 5.3 to clarify the failure case when measurement interval is not sent. o Add text in section 5.3 to clarify how to deal with multiple measurements information blocks carried in the same packet. Wu, et al. Expires March 29, 2013 [Page 25] Internet-Draft RTP Monitoring Framework September 2012 A.14. draft-ietf-avtcore-monarch-08 The following are the major changes compared to 07: o Editorial change to the reference. A.15. draft-ietf-avtcore-monarch-07 The following are the major changes compared to 06: o Clarify the XR block code points consumption issue in the section 4 and new section 5.4. o Other editorial changes. A.16. draft-ietf-avtcore-monarch-06 The following are the major changes compared to 05: o Some editorial changes. A.17. draft-ietf-avtcore-monarch-05 The following are the major changes compared to 04: o Replace "chunk" with "new SDES item". o Add texts in security section to discussion potential security issues. o Add new sub-section 5.3 to discuss Reducing Measurement information repetition. o Other editorial changes. A.18. draft-ietf-avtcore-monarch-04 The following are the major changes compared to 03: o Update section 5.2 to clarify using SDES packet to carry correlation information. o Remove section 5.3 since additional identity information goes to SDES packet and using SSRC to identify each block is standard RTP feature. o Swap the last two paragraphs in the section 4 since identity information duplication can not been 100% avoided. Wu, et al. Expires March 29, 2013 [Page 26] Internet-Draft RTP Monitoring Framework September 2012 o Other editorial changes. A.19. draft-ietf-avtcore-monarch-03 The following are the major changes compared to 02: o Update bullet 2 in section 4 to explain the ill-effect of Identity Information duplication. o Update bullet 3 in section 4 to explain why Correlating RTCP XR with the non-RTP data is needed. o Update section 5.2 to focus on how to reduce the identity information repetition o Update section 5.3 to explain how to correlate identity information with the non-RTP data A.20. draft-ietf-avtcore-monarch-02 The following are the major changes compared to 01: o Deleting first paragraph of Section 1. o Deleting Section 3.1, since the interaction with the management application is out of scope of this draft. o Separate identity information correlation from section 5.2 as new section 5.3. o Remove figure 2 and related text from section 5.2. o Editorial changes in the section 4 and the first paragraph of section 7. A.21. draft-ietf-avtcore-monarch-01 The following are the major changes compared to 00: o Restructure the document by merging section 4 into section 3. o Remove section 4.1,section 5 that is out of scope of this document. o Remove the last bullet in section 6 and section 7.3 based on conclusion of last meeting. Wu, et al. Expires March 29, 2013 [Page 27] Internet-Draft RTP Monitoring Framework September 2012 o Update figure 1 and related text in section 3 according to the monitor definition in RFC3550. o Revise section 9 to address monitor declaration issue. o Merge the first two bullet in section 6. o Add one new bullet to discuss metric block association in section 6. A.22. draft-ietf-avtcore-monarch-00 The following are the major changes compared to draft-hunt-avtcore-monarch-02: o Move Geoff Hunt and Philip Arden to acknowledgement section. Wu, et al. Expires March 29, 2013 [Page 28] Internet-Draft RTP Monitoring Framework September 2012 Authors' Addresses Qin Wu (editor) Huawei 101 Software Avenue, Yuhua District Nanjing, Jiangsu 210012 China Email: firstname.lastname@example.org Geoff Hunt Unaffiliated Email: email@example.com Philip Arden BT Orion 3/7 PP4 Adastral Park Martlesham Heath Ipswich, Suffolk IP5 3RE United Kingdom Phone: +44 1473 644192 Email: firstname.lastname@example.org Wu, et al. Expires March 29, 2013 [Page 29]