RTP Control Protocol (RTCP) Extended Report (XR) Block for MPEG2 Transport Stream (TS) Program Specific Information (PSI) Independent Decodability Statistics Metrics reporting
draft-ietf-xrblock-rtcp-xr-decodability-12

Abstract

An MPEG2 Transport Stream (TS) is a standard container format used in the transmission and storage of multimedia data. Unicast/Multicast MPEG2 TS over RTP is widely deployed in IPTV systems. This document defines an RTP Control Protocol (RTCP) Extended Report (XR) Block that allows the reporting of MPEG2 TS decodability statistics metrics related to transmissions of MPEG2 TS over RTP. The metrics specified in the RTCP XR Block are not dependent on Program specific information carried in MPEG TS.

Status of This Memo

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This Internet-Draft will expire on December 02, 2013.

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Table of Contents

• 1. Introduction
• 1.1. MPEG2 Transport Stream Decodability Metrics
• 1.2. RTCP and RTCP XR Reports
• 1.3. Performance Metrics Framework
• 1.4. Applicability
• 2. Terminology
• 2.1. Standards Language
• 3. MPEG2 TS PSI Independent Decodability Statistics Metrics Block
• 4. SDP Signaling
• 4.1. SDP rtcp-xr-attrib Attribute Extension
• 4.2. Offer/Answer Usage
• 5. IANA Considerations
• 5.1. New RTCP XR Block Type value
• 5.2. New RTCP XR SDP Parameter
• 5.3. Contact information for registrations
• 6. Security Considerations
• 7. Acknowledgements
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

1.1. MPEG2 Transport Stream Decodability Metrics

The European Telecommunications Standards Institute (ETSI) has defined a set of syntax and information consistency tests and corresponding indicators [ETSI] that are recommended for the monitoring of MPEG2 Transport Streams [ISO-IEC.13818-1.2007]. The tests and corresponding indicators are grouped according to priority:

• First priority - Necessary for decodability (basic monitoring)
• Second priority - Recommended for continuous or periodic monitoring
• Third priority - Recommended for application-dependent monitoring

This memo is based on information consistency tests and resulting indicators defined by ETSI [ETSI] and defines a new block type to augment those defined in [RFC3611] for use with MPEG2 Transport Stream (TS) [ISO-IEC.13818-1.2007]. The new block type supports reporting of the number of occurrences of each Program Specific Information (PSI) Independent indicator in the first and second priorities; third priority indicators are not supported.

1.2. RTCP and RTCP XR Reports

The use of RTCP for reporting is defined in [RFC3550]. [RFC3611] defined an extensible structure for reporting using an RTCP Extended Report (XR). This document defines a new Extended Report block for use with [RFC3550] and [RFC3611].

1.3. Performance Metrics Framework

The Performance Metrics Framework [RFC6390] provides guidance on the definition and specification of performance metrics. The RTP Monitoring Architectures [RFC6792] provides guideline for reporting block format using RTCP XR. The new report block described in this memo is in compliance with the monitoring architecture specified in [RFC6792] and the Performance Metrics Framework [RFC6390].

1.4. Applicability

This block type allows a counts of MPEG Transport Stream quality metrics that are measured in accordance with ETSI TR 101290 [ETSI] to be reported by an endpoint. These metrics are useful for identifying bitstream packetization and transport stream encoding problems that may affect the user's perception of a video service delivered over RTP.

2. Terminology

2.1. Standards Language

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 [RFC2119].

3. MPEG2 TS PSI Independent Decodability Statistics 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=MTPID   |    Reserved   |         block length          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     SSRC of source                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          begin_seq            |             end_seq           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      TS_sync_loss_count                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Sync_byte_error_count                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                  Continuity_count_error_count                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Transport_error_count                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        PCR_error_count                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   PCR_repetition_error_count                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            PCR_discontinuity_indicator_error_count            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     PCR_accuracy_error_count                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       PTS_error_count                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

ETSI TR 101290 [ETSI] generally defines metrics related to error events while this document contains counts of those metrics defined in [ETSI]. The block defined in this document reports MPEG2 TS PSI Independent decodability statistics metrics beyond the information carried in the standard RTCP packet format, which are measured at the receiving end of the RTP stream. It contains counts of eight metrics defined in ETSI TR 101290 [ETSI]. Information is reported about basic monitoring parameters necessary to ensure that the TS can be decoded including:



[ETSI]. Note that when the report of this block spans across more than one measurement intervals [RFC6776], the count of the metrics (e.g., Sync byte errors, PCR errors )defined in [ETSI] may reflect a problem in the current or previous measurement interval.

The MPEG2 TS PSI Independent Decodability Metrics Block has the following format:

• Transport Stream Synchronization Losses
• Sync byte errors
• Continuity count errors
  
  

and continuous monitoring parameters necessary to ensure the continuous decoding including:

• Transport errors
• Program Clock Reference (PCR) errors
• PCR repetition errors
• PCR discontinuity indicator errors
• PCR accuracy errors
• Presentation Time Stamp (PTS) errors
  
  

The other parameters are ignored since they do not apply to all MPEG2 implementations. For further information on these parameters, see

block type (BT): 8 bits

The MPEG2 TS PSI Independent Decodability Metrics Block is identified by the constant <MTPID>.

Reserved: 8 bits

These bits are reserved. They MUST be set to zero by senders and ignored by receivers (See [RFC6709] section 4.2).

block length: 16 bits

The constant 11, in accordance with the definition of this field in Section 3 of RFC 3611. The block MUST be discarded if the block length is set to a different value.

SSRC of source: 32 bits

As defined in Section 4.1 of RFC 3611.

begin_seq: 16 bits

The RTP sequence number corresponding to the start of the measurement period, as defined in Section 4.1 of RFC 3611.

end_seq: 16 bits

The RTP sequence number corresponding to the end of the measurement period, as defined in Section 4.1 of RFC 3611.

TS_sync_loss_count: 32 bits

A count of the number of TS_sync_loss errors that occurred in the above sequence number interval. A TS_sync_loss error occurs when there are two or more consecutive incorrect sync bytes within the MPEG TS stream, as defined in section 5.2.1 of [ETSI].

Sync_byte_error_count: 32 bits

A count of the number of Sync_byte_errors that occurred in the above sequence number interval. A sync byte error occurs when the sync byte is not equal to 0x47 in any TS packet contained in the MPEG TS stream, as defined in section 5.2.1 of [ETSI].

Continuity_count_error_count: 32 bits

A count of the number of Continuity_count_errors that occurred in the above sequence number interval. A Continuity_count_error occurs when any of the following faults happen within the MPEG TS stream - incorrect packet order, a packet occurs more than twice or a packet is lost,as defined in the section 5.2.1 of [ETSI].

Transport_error_count: 32 bits

A count of the number of Transport_errors that occurred in the above sequence number interval. A Transport_error occurs when erroneous TS packet can not be corrected within the MPEG TS stream. as defined in the section 5.2.2 of [ETSI].

PCR_error_count: 32 bits

A count of the number of PCR_errors that occurred in the above sequence number interval. A PCR_error occurs if the primary clock reference (PCR) is not seen for more than 100ms within the MPEG TS stream, as defined in the section 5.2.2 of [ETSI]. The time interval between two consecutive PCR values should be no more than 40ms.

PCR_repetition_error_count: 32 bits

A count of the number of PCR_repetition_errors that occurred in the above sequence number interval. A PCR_repeition_error occurs when the time interval between two consecutive PCR values is more than 40ms within the MPEG TS stream,as defined in the section 5.2.2 of [ETSI].

PCR_discontinuity_indicator_error_count: 32 bits

A count of the number of PCR_discontinuity_indicator_errors that occurred in the above sequence number interval. A PCR_discontinuity_indicator_error occurs if the time interval between two consecutive PCR values is more than 100ms within the MPEG TS stream, as defined in the section 5.2.2 of [ETSI].

PCR_accuracy_error_count: 32 bits

A count of the Number of PCR_accuracy_errors that occurred in the above sequence number interval. A PCR_accuracy_error occurs when the PCR accuracy of the selected program is outside the range of ±500ns within the MPEG TS stream,as defined in the section 5.2.2 of [ETSI].

PTS_error_count: 32 bits

A count of the number of PTS_errors that occurred in the above sequence number interval. A PTS_error occurs when the PTS repetition is more than 700ms within the MPEG TS stream, as defined in the section 5.2.2 of[ETSI]. Note that the PTS is contained in the MPEG-2 TS stream and is used to aid the decoder in presenting the program on time, at the correct speed and synchronized.

4. SDP Signaling

RFC 3611 defines the use of SDP (Session Description Protocol) [RFC4566] for signaling the use of RTCP XR blocks. However XR blocks MAY be used without prior signaling (See section 5 of RFC3611).

4.1. SDP rtcp-xr-attrib Attribute Extension

xr-format =/  xr-tpid-block

xr-tpid-block = "ts-psi-indep-decodability"

This session augments the SDP attribute "rtcp-xr" defined in Section 5.1 of RFC 3611 by providing an additional value of "xr-format" to signal the use of the report block defined in this document.

4.2. Offer/Answer Usage

When SDP is used in offer-answer context, the SDP Offer/Answer usage defined in [RFC3611] for unilateral "rtcp-xr" attribute parameters applies. For detailed usage of Offer/Answer for unilateral parameter, refer to section 5.2 of [RFC3611].

5. IANA Considerations

New report block types for RTCP XR are subject to IANA registration. For general guidelines on IANA allocations for RTCP XR, refer to Section 6.2 of RFC 3611.

5.1. New RTCP XR Block Type value

This document assigns the block type value MTPID in the IANA " RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry " to the "MPEG2 Transport Stream PSI Independent Decodability Statistics Metrics Block".

[Note to RFC Editor: please replace MPITD with the IANA provided RTCP XR block type for this block.]

5.2. New RTCP XR SDP Parameter

This document also registers a new parameter "ts-psi-indep-decodability" in the "RTP Control Protocol Extended Reports (RTCP XR) Session Description Protocol (SDP) Parameters Registry".

5.3. Contact information for registrations

The contact information for the registrations is:

Qin Wu
sunseawq@huawei.com
101 Software Avenue, Yuhua District 
Nanjing, JiangSu 210012 China

6. Security Considerations

There might be some relationship between reported error counters and contractual Service Level Agreements (SLA)s and hence an attack (e.g., RTP endpoints report fake information, or an attacker in the path modifies the data being reported ) may deliberately corrupt these error counters fields and will result in financial implications for the network operator (either as a result of un-needed Performance metrics, or penalty charges for SLA failure).

A solution to prevent such attack is to apply an authentication and integrity protection framework for the RTCP XR report block. This can be accomplished using the RTP profile that combines Secure RTP [RFC3711] and AVPF into SAVPF [RFC5124].

Besides this, the proposed RTCP XR report block in this document introduces no other new security considerations beyond those described in [RFC3611].

7. Acknowledgements

Thanks to Ray van Brandenburg, Claire Bi, Colin Perkin, Roni Even, Dan Romascanu, Ali Begen and Alan Clark for useful review and suggestions.

8. References

8.1. Normative References

8.2. Informative References

Authors' Addresses