]> Telchemy Incorporated

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Network Zen

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Real-time Applications and Infrastructure Area Audio/Video Transport Working Group RFC Request for Comments I-D Internet-Draft Real Time Control Protocol This document defines two RTCP XR Report Blocks that allows the reporting of concealment metrics for audio applications of RTP.

At any instant, the audio output at a receiver may be classified as either 'normal' or 'concealed'. 'Normal' refers to playout of audio payload received from the remote end, and also includes locally generated signals such as announcements, tones and comfort noise. Concealment refers to playout of locally-generated signals used to mask the impact of network impairments or to reduce the audibility of jitter buffer adaptations. This draft defines two new concealment related block types to augment those defined in [RFC3611] for use in a range of RTP applications. These two block types extend packet loss concealment mechanism defined in section 4.7.6 of RFC3611. The first block type provides metrics for actions taken by the receiver to mitigate the effect of packet loss and packet discard. Specifically, the first metric (On-Time Playout Duration) reports the duration of normal playout of data which the receiver obtained from the sender's stream. A second metric (Loss Concealment Duration) reports the total time during which the receiver played out media data which was manufactured locally, because the sender's data for these periods was not available due to packet loss or discard. A similar metric (Buffer Adjustment Concealment Duration) reports the duration of playout of locally-manufactured data replacing data which is unavailable due to adaptation of an adaptive de-jitter buffer. Further metrics (Playout Interrupt Count and Mean Playout Interrupt Size) report the number of times normal playout was interrupted, and the mean duration of these interruptions. Loss Concealment Duration and Buffer Adjustment Concealment Duration are reported separately because buffer adjustment is typically arranged to occur in silence periods so may have very little impact on user experience, whilst loss concealment may occur at any time. The second block type provides metrics for concealment seconds, which are measured at the receiving end of the RTP stream. Specifically, the first metric (Unimpaired Seconds) reports the number of whole seconds occupied only with normal playout of data which the receiver obtained from the sender's stream. The second metric (Concealed Seconds) reports the number of whole seconds during which the receiver played out any locally-generated media data. A third metric, Severely Concealed Seconds (SCS), reports the number of whole seconds during which the receiver played out locally-generated data for more than SCS Threshold. These metrics belongs to the class of transport-related terminal metrics defined in .

The use of RTCP for reporting is defined in . defined an extensible structure for reporting using an RTCP Extended Report (XR). This draft defines a new Extended Report block that MUST be used as defined in and .

The Performance Metrics Framework provides guidance on the definition and specification of performance metrics. The RTP Monitoring Architectures provides guideline for reporting block format using RTCP XR. The Metrics Block described in this document are in accordance with those guidelines.

These metrics are applicable to audio applications of RTP and the audio component of Audio/Video applications in which the packet loss concealment machinery is contained at the receiving end to mitigate the impact of network impairments to user's perception of media quality.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119.

This report block makes use of binary fractions. The terminology used is Numeric formats S X:Y where S indicates a two's complement signed representation, X the number of bits prior to the decimal place and Y the number of bits after the decimal place. Hence 8:8 represents an unsigned number in the range 0.0 to 255.996 with a granularity of 0.0039. S7:8 would represent the range -127.996 to +127.996. 0:16 represents a proper binary fraction with range 0.0 to 1 - 1/65536 = 0.9999847 though note that use of flag values at the top of the numeric range slightly reduces this upper limit. For example, if the 16- bit values 0xfffe and 0xffff are used as flags for "over-range" and "unavailable" conditions, a 0:16 quantity has range 0.0 to 1 - 3/65536 = 0.9999542

The metrics block described here are intended to be used as described in this section, in conjunction with information from the Measurement Information block . Instances of this Metrics Block refer by Synchronization source (SSRC) to the separate auxiliary Measurement Information block which describes measurement periods in use (see section 4.2). This Metrics Block relies on the measurement period in the Measurement Information block indicating the span of the report and SHOULD be sent in the same compound RTCP packet as the measurement information block. If the measurement period is not received in the same compound RTCP packet as this Metrics Block, this metrics block MUST be discarded.

Loss Concealment Metrics Block

0 1 2 3 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BT=NLC | I |plc| rsv. | block length=6 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of Source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | On-time Playout Duration | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Loss Concealment Duration | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Buffer Adjustment Concealment Duration | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Playout Interrupt Count | Reserved. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mean Playout Interrupt Size | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A Loss Concealment Metrics Report Block is identified by the constant NLC. [Note to RFC Editor: please replace NLC with the IANA provided RTCP XR block type for this block.] This field is used to indicate whether the Loss Concealment metrics are Sampled, Interval or Cumulative metrics: I=10: Interval Duration - the reported value applies to the most recent measurement interval duration between successive metrics reports. I=11: Cumulative Duration - the reported value applies to the accumulation period characteristic of cumulative measurements. I=01: Sampled Value - the reported value is a sampled instantaneous value ( Not allowed in this block). I=00: Reserved value- this value is reserved for future use. In this document, Loss Concealment Metrics can only be measured over definite intervals, and cannot be sampled. Senders MUST NOT use the values I=00 or I=01. If a block is received with I=00 or I=01, the receiver MUST discard the block. This field is used to identify the packet loss concealment method in use at the receiver, according to the following code: bits 014-015 0 = silence insertion 1 = simple replay, no attenuation 2 = simple replay, with attenuation 3 = enhancement Other values reserved Note that the enhancement method (plc =3 ) for packet loss concealment offers an improved audio quality and a better robustness against packet losses [G.711] and is equivalent to enhanced in section 4.7.6 of [RFC3611]. These bits are reserved. They MUST be set to zero by senders and ignored by receivers (See section 4.2). The length of this report block in 32-bit words, minus one. For the Loss Concealment Block, the block length is equal to 6. As defined in Section 4.1 of . 'On-time' playout is the uninterrupted, in-sequence playout of valid decoded audio information originating from the remote endpoint. This includes comfort noise during periods of remote talker silence, if VAD is used, and locally generated or regenerated tones and announcements. An equivalent definition is that on-time playout is playout of any signal other than those used for concealment. On-time playout duration is expressed in units of RTP timestamp and MUST include both speech and silence intervals, whether VAD is used or not. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable. The duration, expressed in units of RTP timestamp, of audio playout corresponding to Loss-type concealment. Loss-type concealment is reactive insertion or deletion of samples in the audio playout stream due to effective frame loss at the audio decoder. "Effective frame loss" is the event in which a frame of coded audio is simply not present at the audio decoder when required. In this case, substitute audio samples are generally formed, at the decoder or elsewhere, to reduce audible impairment. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable. The duration, expressed in units of RTP timestamp, of audio playout corresponding to Buffer Adjustment-type concealment, if known. Buffer Adjustment-type concealment is proactive or controlled insertion or deletion of samples in the audio playout stream due to jitter buffer adaptation, re-sizing or re-centering decisions within the endpoint. Because this insertion is controlled, rather than occurring randomly in response to losses, it is typically less audible than loss-type concealment. For example, jitter buffer adaptation events may be constrained to occur during periods of talker silence, in which case only silence duration is affected, or sophisticated time-stretching methods for insertion/deletion during favorable periods in active speech may be employed. Concealment events which cannot be classified as Buffer Adjustment-type MUST be classified as Loss-type. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable. The number of interruptions to normal playout which occurred during the reporting period. Two values are reserved: A value of 0xFFFE indicates out of range (that is, a measured value exceeding 0xFFFD) and a value of 0xFFFF indicates that the measurement is unavailable. These bits are reserved. They MUST be set to zero by senders and ignored by receivers (See section 4.2). The mean duration, expressed in units of RTP timestamp, of interruptions to normal playout which occurred during the reporting period. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable.

This sub-block described here is intended to be used as described in this section, in conjunction with information from the Measurement Information block and provides a description of potentially audible impairments due to lost and discarded packets at the endpoint, expressed on a time basis analogous to a traditional PSTN T1/E1 errored seconds metric. Instances of this Metrics Block refer by Synchronization source (SSRC) to the separate auxiliary Measurement Information block which describes measurement periods in use (see section 4.2). This Metrics Block relies on the measurement period in the Measurement Information block indicating the span of the report and SHOULD be sent in the same compound RTCP packet as the measurement information block. If the measurement period is not received in the same compound RTCP packet as this Metrics Block, this metrics block MUST be discarded. The following metrics are based on successive one second intervals as declared by a RTP clock. This RTP clock does not need to be synchronized to any external time reference. The starting time of this clock is unspecified. Note that this implies that the same loss pattern could result in slightly different count values, depending on where the losses occur relative to the particular one-second demarcation points. For example, two loss events occurring 50ms apart could result in either one concealed second or two, depending on the particular one second boundaries used. The seconds in this sub-block are not necessarily calendar seconds. At the tail end of a session, periods of time of less than one second shall be incorporated into these counts if they exceed 500ms and shall be disregarded if they are less than 500ms.

Concealed Seconds Metrics Block

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BT=NCS | I |plc|Rserved| block length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC of Source | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unimpaired Seconds | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Concealed Seconds | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Severely Concealed Seconds | RESERVED | SCS Threshold | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

A Concealed Seconds Metrics Report Block is identified by the constant NCS. [Note to RFC Editor: please replace NCS with the IANA provided RTCP XR block type for this block.] This field is used to indicate whether the Concealment Seconds Metrics are Sampled, Interval or Cumulative metrics: I=10: Interval Duration - the reported value applies to the most recent measurement interval duration between successive metrics reports. I=11: Cumulative Duration - the reported value applies to the accumulation period characteristic of cumulative measurements. I=01: Sampled Value - the reported value is a sampled instantaneous value (Not allowed in this block). I=00: Reserved value- this value is reserved for future use. In this document, Concealment Seconds Metrics can only be measured over definite intervals, and cannot be sampled. Senders MUST NOT use the values I=00 or I=01. If a block is received with I=00 or I=01, the receiver MUST discard the block. This field is used to identify the packet loss concealment method in use at the receiver, according to the following code: bits 014-015 0 = silence insertion 1 = simple replay, no attenuation 2 = simple replay, with attenuation 3 = enhancement Other values reserved Note that the enhancement method (plc =3 ) for packet loss concealment offers an improved audio quality and a better robustness against packet losses [G.711] and is equivalent to enhanced in section 4.7.6 of [RFC3611]. These bits are reserved. They MUST be set to zero by senders and ignored by receivers (See section 4.2). The length of this report block in 32-bit words, minus one. For the Concealment Seconds Block, the block length is equal to 4. As defined in Section 4.1 of . A count of the number of unimpaired Seconds that have occurred.An unimpaired Second is defined as a continuous period of one second during which no frame loss or discard due to late arrival has occurred. Every second in a session must be classified as either OK or Concealed. Normal playout of comfort noise or other silence concealment signal during periods of talker silence, if VAD is used, shall be counted as unimpaired seconds. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable. A count of the number of Concealed Seconds that have occurred.A Concealed Second is defined as a continuous period of one second during which any frame loss or discard due to late arrival has occurred. Equivalently, a concealed second is one in which some Loss-type concealment has occurred. Buffer adjustment-type concealment SHOULD NOT cause Concealed Seconds to be incremented, with the following exception. An implementation MAY cause Concealed Seconds to be incremented for 'emergency' buffer adjustments made during talkspurts. Loss-type concealment is reactive insertion or deletion of samples in the audio playout stream due to effective frame loss at the audio decoder. "Effective frame loss" is the event in which a frame of coded audio is simply not present at the audio decoder when required. In this case, substitute audio samples are generally formed, at the decoder or elsewhere, to reduce audible impairment. Buffer Adjustment-type concealment is proactive or controlled insertion or deletion of samples in the audio playout stream due to jitter buffer adaptation, re-sizing or re-centering decisions within the endpoint. Because this insertion is controlled, rather than occurring randomly in response to losses, it is typically less audible than loss-type concealment. For example, jitter buffer adaptation events may be constrained to occur during periods of talker silence, in which case only silence duration is affected, or sophisticated time-stretching methods for insertion/deletion during favorable periods in active speech may be employed. For these reasons, buffer adjustment-type concealment MAY be exempted from inclusion in calculations of Concealed Seconds and Severely Concealed Seconds. However, an implementation SHOULD include buffer-type concealment in counts of Concealed Seconds and Severely Concealed Seconds if the event occurs at an 'inopportune' moment, with an emergency or large, immediate adaptation during active speech, or for unsophisticated adaptation during speech without regard for the underlying signal, in which cases the assumption of low-audibility cannot hold. In other words, jitter buffer adaptation events which may be presumed to be audible SHOULD be included in Concealed Seconds and Severely Concealed Seconds counts. Concealment events which cannot be classified as Buffer Adjustment- type MUST be classified as Loss-type. For clarification, the count of Concealed Seconds MUST include the count of Severely Concealed Seconds. Two values are reserved: A value of 0xFFFFFFFE indicates out of range (that is, a measured value exceeding 0xFFFFFFFD) and a value of 0xFFFFFFFF indicates that the measurement is unavailable. A count of the number of Severely Concealed Seconds.A Severely Concealed Second is defined as a non-overlapping period of one second during which the cumulative amount of time that has been subject to frame loss or discard due to late arrival, exceeds the SCS Threshold. Two values are reserved: A value of 0xFFFE indicates out of range (that is, a measured value exceeding 0xFFFD) and a value of 0xFFFF indicates that the measurement is unavailable. These bits are reserved. They MUST be set to zero by senders and ignored by receivers (See [RFC6709] section 4.2). The SCS Threshold is defined as the percentage of packets corresponding to lost or discarded frames that must occur within a one second period in order for the second to be classified as a Severely Concealed Second. This is expressed in numeric format 0:8 and hence can represent a range of 0 to 99.6 percent loss or discard. A default threshold of 5% effective frame loss (50ms effective frame loss ) per second is suggested. This corresponds to an SCS Threshold in hexadecimal of 0x0D.

defines the use of SDP (Session Description Protocol) for signaling the use of XR blocks. XR blocks MAY be used without prior signaling.

This section augments the SDP attribute "rtcp-xr" by providing two additional values of "xr-format" to signal the use of two report blocks defined in this document.

xr-format =/ xr-conceal-block / xr-conc-sec-block xr-conceal-block = "loss-conceal" xr-conc-sec-block = "conc-sec" ["=" thresh] thresh = 1*DIGIT ; threshold for SCS (ms) DIGIT = <as defined in Section 3 of [RFC5234]>

When SDP is used in offer-answer context, the SDP Offer/Answer usage defined in applies. Note that “thresh” is declared by the offer.

New block types for RTCP XR are subject to IANA registration. For general guidelines on IANA considerations for RTCP XR, refer to .

This document assigns two block type values in the IANA "RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry ":

Name: LCB Long Name: Loss Concealment Block Value <NLC> Reference: Section 3.1 Name: CSB Long Name: Concealment Seconds Block Value <NCS> Reference: Section 4.1

[Note to RFC Editor: please replace <NLC> and <NCS> with the RTCP XR block type assigned by IANA for this block.]

This document also registers two new parameters in the "RTP Control Protocol Extended Reports (RTCP XR) Session Description Protocol (SDP) Parameters Registry": "loss-conceal" "conc-sec"

The contact information for the registrations is: RAI Area Directors rai-ads@tools.ietf.org

It is believed that this proposed RTCP XR report block introduces no new security considerations beyond those described in . This block does not provide per-packet statistics so the risk to confidentiality documented in Section 7, paragraph 3 of does not apply.

Geoff Hunt wrote the initial draft of this document.

The authors gratefully acknowledge reviews and feedback provided by Bruce Adams, Philip Arden, Amit Arora, Bob Biskner, Kevin Connor, Claus Dahm, Randy Ethier, Roni Even, Jim Frauenthal, Albert Higashi, Tom Hock, Shane Holthaus, Paul Jones, Rajesh Kumar, Keith Lantz, Mohamed Mostafa, Amy Pendleton, Colin Perkins, Mike Ramalho, Ravi Raviraj, Albrecht Schwarz, Tom Taylor, Hideaki Yamada ,Alissa Cooper,Meral Shirazipour and ,MORTON, ALFRED C (AL),Adrian Farrel and Pete Resnick.

Harvard University

1350 Mass. Ave. Cambridge MA 02138 - +1 617 495 3864 sob@harvard.edu

General keyword In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. Authors who follow these guidelines should incorporate this phrase near the beginning of their document: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. Note that the force of these words is modified by the requirement level of the document in which they are used. This document defines the Extended Report (XR) packet type for the RTP Control Protocol (RTCP), and defines how the use of XR packets can be signaled by an application if it employs the Session Description Protocol (SDP). XR packets are composed of report blocks, and seven block types are defined here. The purpose of the extended reporting format is to convey information that supplements the six statistics that are contained in the report blocks used by RTCP's Sender Report (SR) and Receiver Report (RR) packets. Some applications, such as multicast inference of network characteristics (MINC) or voice over IP (VoIP) monitoring, require other and more detailed statistics. In addition to the block types defined here, additional block types may be defined in the future by adhering to the framework that this document provides. This memo defines the Session Description Protocol (SDP). SDP is intended for describing multimedia sessions for the purposes of session announcement, session invitation, and other forms of multimedia session initiation. [STANDARDS-TRACK] Columbia University

RFC EDITOR NOTE: please change XXXX in [RFCXXXX] by the new RFC number, when assigned. On-time Playout Duration Metric Metric Name: On-time Playout Duration Metric Description: 'On-time' playout is the uninterrupted, in-sequence playout of valid decoded audio information originating from the remote endpoint. On-time playout Duration is playout duration of any signal other than those used for concealment Method of Measurement or Calculation: See section 3. 2, On-time Playout Duration definition [RFCXXXX]. Units of Measurement: See section 3.2, On-time Playout Duration definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 3rd paragraph [RFCXXXX]. Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for measurement timing and section 3.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Loss Concealment Duration Metric Metric Name: Loss Concealment Duration Metric Description: The duration of audio playout corresponding to Loss-type concealment. Method of Measurement or Calculation: See section 3.2, Loss Concealment Duration definition [RFCXXXX]. Units of Measurement: See section 3.2, Loss Concealment Duration definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 3rd paragraph [RFCXXXX]. Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for measurement timing and section 3. 2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Buffer Adjustment Concealment Duration Metric Metric Name: Buffer Adjustment Concealment Duration Metric Description: The duration of audio playout corresponding to Buffer Adjustment-type concealment. Method of Measurement or Calculation: See section 3. 2, Buffer Adjustment Concealment Duration definition [RFCXXXX]. Units of Measurement: See section 3.2, Buffer Adjustment Concealment Duration definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 3rd paragraph [RFCXXXX]. Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for measurement timing and section 3.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Playout Interrupt Count Metric Metric Name: Playout Interrupt Count Metric Description: The number of interruptions to normal playout which occurred during the reporting period. Method of Measurement or Calculation: See section 3. 2, Playout Interrupt Count definition [RFCXXXX]. Units of Measurement: See section 3.2, Playout Interrupt Count definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 3rd paragraph [RFCXXXX]. Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for measurement timing and section 3.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Mean Playout Interrupt Size Metric Metric Name: Mean Playout Interrupt Size Metric Description: The mean duration of interruptions to normal playout which occurred during the reporting period. Method of Measurement or Calculation: See section 3. 2, Playout Interrupt Count definition [RFCXXXX]. Units of Measurement: See section 3.2, Playout Interrupt Count definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 3rd paragraph [RFCXXXX]. Measurement Timing: See section 3, 1st paragraph [RFCXXXX] for measurement timing and section 3.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Unimpaired Seconds Metric Metric Name: Unimpaired Seconds Metric Description: A count of the number of unimpaired Seconds that have occurred. Method of Measurement or Calculation: See section 4. 2, Unimpaired Seconds definition [RFCXXXX]. Units of Measurement: See section 4.2, Unimpaired Seconds definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 5th paragraph [RFCXXXX]. Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for measurement timing and section 4.2 paragraph [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Concealed Seconds Metric Metric Name: Concealed Seconds Metric Description: A count of the number of Concealed Seconds that have occurred. Method of Measurement or Calculation: See section 4. 2, Concealed Seconds definition [RFCXXXX]. Units of Measurement: See section 4.2, Concealed Seconds definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 5th paragraph [RFCXXXX]. Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for measurement timing and section 4.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. Severely Concealed Seconds Metric Metric Name: Severely Concealed Seconds Metric Description: A count of the number of Severely Concealed Seconds that have occurred. Method of Measurement or Calculation: See section 4. 2, Severely Concealed Seconds definition [RFCXXXX]. Units of Measurement: See section 4.2, Severely Concealed Seconds definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 5th paragraph [RFCXXXX]. Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for measurement timing and section 4.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611. SCS Threshold Metric Metric Name: SCS Threshold Metric Description: The amount of time corresponding to lost or discarded frames that must occur within a one second period in order for the second to be classified as a Severely Concealed Second. Method of Measurement or Calculation: See section 4. 2, SCS Threshold definition [RFCXXXX]. Units of Measurement: See section 4.2, SCS Threshold definition [RFCXXXX]. Measurement Point(s) with Potential Measurement Domain: See section 1.1, 5th paragraph [RFCXXXX]. Measurement Timing: See section 4, 1st paragraph [RFCXXXX] for measurement timing and section 4.2 [RFCXXXX] for Interval Metric flag. Use and applications: See section 1.4 [RFCXXXX]. Reporting model: See RFC3611.

Note to the RFC-Editor: please remove this section prior to publication as an RFC.

The following are the major changes to previous version : Address comments recieved in Gen-Art Review and OPS-DIR Review.

The following are the major changes to previous version : Only Version Number changes.

The following are the major changes to previous version : Change units for threshold and units used for reporting in loss concealment block and concealment seconds block. Change 16bit "Mean Playout Interrupt Size" into 32bits.

The following are the major changes to previous version : Comments in the WGLC are addressed in this version.

The following are the major changes to previous version : Add text to clarify the definition of enhanced method. Add appendix to apply RFC6390 template to the metrics.

The following are the major changes to previous version : Merge Concealment Seconds draft into this draft (i.e.,Loss Concealment draft). Updated references.