RTP Stream Quality Information Export using IPFIX
draft-scholz-ipfix-rtp-audio-quality-00

Abstract

This draft defines a set of Information Elements and matching Templates to convey RTP media stream quality information in IPFIX packets. The Information Elements describe the RTP quality using the R-factor and Mean Opinion score (MOS) for the entire duration of a monitored stream or for a smaller time slice thereof.

Status of this Memo

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This Internet-Draft will expire on January 08, 2013.

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Table of Contents

• 1. Introduction
• 1.1. Use Cases
• 1.1.1. Quality of Service (QoS) Monitoring
• 1.1.2. Service Level Agreement (SLA)
• 1.1.3. Troubleshooting
• 2. Conventions
• 3. MOS measurement
• 3.1. rtpMOSCAlg
• 3.2. rtpMOSClass1
• 3.3. rtpMOSClass2
• 3.4. rtpMOSClass3
• 3.5. rtpMOSClass4
• 3.6. rtpMOSClass5
• 3.7. rtpMinMOS
• 3.8. rtpAvgMOS
• 3.9. rtpMaxMOS
• 3.10. rtpMinRFactor
• 3.11. rtpAvgRFactor
• 3.12. rtpMaxRFactor
• 4. Recommended Templates
• 4.1. Entire stream
• 4.2. Time slice
• 5. Examples
• 6. Acknowledgements
• 7. IANA Considerations
• 8. Security Considerations
• 9. References
• 9.1. Normative References
• 9.2. Informative References
• Author's Address

1. Introduction

IPFIX [RFC5101] and [RFC5102] define a framework allowing to export arbitrary data from so called IPFIX exporters. One type of IPFIX exporter may be co-located with Session Initiation Protocol (SIP) [RFC3261] based VoIP entities or passively observe SIP based VoIP calls. The signaling messages can be exported using [I-D.trammell-ipfix-sip-msg] and Real Time Protocol (RTP) [RFC3550] media streams are covered in [I-D.akhter-ipfix-perfmon]. Media quality is out of the scope of both these documents. This document defines a set of additional IPFIX Information Elements (IEs) to describe RTP audio stream quality.

1.1. Use Cases

RTP stream flow information contained in IPFIX flow records can be used for various tasks such as Quality of Service (QoS) monitoring, Service Level Agreement (SLA) validation and general troubleshooting of VoIP networks.

1.1.1. Quality of Service (QoS) Monitoring

Aggregated to higher-level metrics the in-depth information provided by the RTP (and optionally SIP) flow records allow service providers to gauge the overall quality of their network in terms of the quality of experience (QoE). On this level an individual call is less important but the overall quality (e.g. amount of minutes meeting certain quality standards) can be used to get a quick overview on the network and service performance.

1.1.2. Service Level Agreement (SLA)

SLAs are typically used as part of contracts between two network operators. The requirements on the reliability of the data may be higher compared to QoS Monitoring as the failure to meet contractually agreed quality standards often has a direct commercial impact.

1.1.3. Troubleshooting

An active network component (SIP proxy, B2BUA, media server) may not have the capabilities to store session related information for a long time to facilitate troubleshooting capabilities (e.g. due to missing hard-disk). Such a system or a group of systems may run the metering process and export the data to a collector for processing or troubleshooting purposes.

2. Conventions

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. MOS measurement

A multitude of Mean Opinion Score (MOS) assessment algorithms have been defined of which only one or few may be available to an IPFIX Metering Process. The quality (i.e. accuracy) of these algorithms varies and has to be noted when transporting MOS values.

An IPFIX Metering Process may use these Information Elements to convey information on the duration of the stream in which the quality fell into the respective category as well as the measurement algorithm used to obtain the information.

3.1. rtpMOSCAlg

The values carried in this IE are taken from the "RTCP XR QoE metric block - Calculation Algorithm" sub-registry of the "RTP Control Protocol Extended Reports (RTCP XR) Block Type Registry" as defined in [I-D.wu-xrblock-rtcp-xr-quality-monitoring].

Even when an algorithm other than G.107 is used the rtpMOSClassN Information Elements use the R-Factor based classes as defined in the G.107 documentation.

Description:

The calculation algorithm (CAlg) used by the Metering Process to calculate the MOS value.

0:

undefined: The algorithm is not known/specified.

1:

ITU-T P.564

2:

G.107

3:

G.107 / ETSI TS 101 329-5 Annex E

4:

ITU-T P.NAMS

5:

ITU-T P.NBAMS

6:

RTCP - Real Time Control Protocol (not fefined in registry!)

Data Type:

unsigned8

Data Type Semantics:

identifier

PEN (provisional):

tbd

ElementId (provisional):

tbd

The MOS values calculated are separated into MOS classes based on the ITU-T G.107 classes.

3.2. rtpMOSClass1

Description:

Number of seconds the monitored stream had a MOS quality lower than 3.10

Data Type:

float32

Data Type Semantics:

deltaCounter

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.3. rtpMOSClass2

Description:

Number of seconds the monitored stream had a MOS quality larger than or equal 3.10 and lower than 3.60

Data Type:

float32

Data Type Semantics:

deltaCounter

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.4. rtpMOSClass3

Description:

Number of seconds the monitored stream had a MOS quality larger than or equal 3.60 and lower than 4.03

Data Type:

float32

Data Type Semantics:

deltaCounter

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.5. rtpMOSClass4

Description:

Number of seconds the monitored stream had a MOS quality larger than or equal 4.03 and lower than 4.34

Data Type:

float32

Data Type Semantics:

deltaCounter

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.6. rtpMOSClass5

Description:

Number of seconds the monitored stream had a MOS quality larger than or equal 4.34

Data Type:

float32

Data Type Semantics:

deltaCounter

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.7. rtpMinMOS

Description:

Minimum MOS value measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.8. rtpAvgMOS

Description:

Average MOS value measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.9. rtpMaxMOS

Description:

Maximum MOS value measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.10. rtpMinRFactor

Description:

Minimum R-Factor measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.11. rtpAvgRFactor

Description:

Average R-Factor measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

3.12. rtpMaxRFactor

Description:

Maximum R-Factor measured in the monitoring interval.

Data Type:

float32

Data Type Semantics:

quantity

PEN (provisional):

tbd

ElementId (provisional):

tbd

4. Recommended Templates

The defined RTP stream IPFIX templates must support both IPv4 and IPv6 transport. They need to carry either flow information regarding the entire duration of an RTP stream or specific to a shorter observation interval.

The template incorporates IEs from [I-D.akhter-ipfix-perfmon] to describe the RTP stream.

In order to correlate the RTP quality information with signaling information (e.g. subscriber IDs) a correlation ID may be added to the template. Note that this ID has yet to be defined and is outside the scope of this document.

4.1. Entire stream

tbd

4.2. Time slice

tbd, based on previous template. Split a single RTP stream in three flow records as example including (empty) 'RTP stream ended' flow record.

5. Examples

tbd

6. Acknowledgements

tbd

7. IANA Considerations

tbd

8. Security Considerations

tbd

9. References

9.1. Normative References

9.2. Informative References

Author's Address