RTP Stream Quality Information Export using IPFIX

IPFIX and 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) based VoIP entities or passively observe SIP based VoIP calls. The signaling messages can be exported using and Real Time Protocol (RTP) media streams are covered in . 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.

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.

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.

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.

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.

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 .

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.

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 . 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. The calculation algorithm (CAlg) used by the Metering Process to calculate the MOS value. undefined: The algorithm is not known/specified. ITU-T P.564 G.107 G.107 / ETSI TS 101 329-5 Annex E ITU-T P.NAMS ITU-T P.NBAMS RTCP - Real Time Control Protocol (not fefined in registry!) unsigned8 identifier tbd tbd The MOS values calculated are separated into MOS classes based on the ITU-T G.107 classes.

Number of seconds the monitored stream had a MOS quality lower than 3.10 float32 deltaCounter tbd tbd

Number of seconds the monitored stream had a MOS quality larger than or equal 3.10 and lower than 3.60 float32 deltaCounter tbd tbd

Number of seconds the monitored stream had a MOS quality larger than or equal 3.60 and lower than 4.03 float32 deltaCounter tbd tbd

Number of seconds the monitored stream had a MOS quality larger than or equal 4.03 and lower than 4.34 float32 deltaCounter tbd tbd

Number of seconds the monitored stream had a MOS quality larger than or equal 4.34 float32 deltaCounter tbd tbd

Minimum MOS value measured in the monitoring interval. float32 quantity tbd tbd

Average MOS value measured in the monitoring interval. float32 quantity tbd tbd

Maximum MOS value measured in the monitoring interval. float32 quantity tbd tbd

Minimum R-Factor measured in the monitoring interval. float32 quantity tbd tbd

Average R-Factor measured in the monitoring interval. float32 quantity tbd tbd

Maximum R-Factor measured in the monitoring interval. float32 quantity tbd tbd

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 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.

tbd

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

tbd