Application Notes Contents Title Managing Cable Services Introduction...... 1 Series VoIP Performance Management Performance Management Date June 2004 & Cable Telephony...... 1 The New VoIP Performance Management Architecture...... 2 Overview Common VoIP Performance Metrics...... 4 This application note describes the typical performance issues that cable operators encounter Performance Management when deploying cable telephony networks and Reporting Protocols...... 5 introduces a management framework that enables Applying the VoIP Performance Management them to detect, address and resolve these Architecture To Cable Telephony...... 6 problems. Problem Resolution, Detection & Diagnosis...... 7 Summary...... 8

Introduction Performance Management & Cable Telephony Packet Telephony is an exciting new source of revenue for cable operators, so it is essential to build Cable operators are familiar with many of the fault and performance management systems that problems they will face when deploying cable support quick problem detection and resolution and telephony networks due to their past experiences avoid costly truck rolls. Cable operators are aware introducing service: that HFC networks can suffer from performance- related problems, but they are less familiar with the Ingress noise on the cable upstream that broader range of call quality issues associated with leads to high packet loss rates. Voice over IP networks and the interaction between traditional cable system and packet telephony Weather problems i.e., the affect of components. temperature extremes and thunderstorms on cable service. This application note describes the typical performance issues that cable operators encounter when In addition, Cable Telephony brings both an increased deploying cable telephony networks and introduces a sensitivity of the service to packet related problems and management framework that enables them to detect, addition problems that are particular to VoIP. address and resolve these problems.

VoIP Performance Management Managing Cable Telephony Services June 2004 1 Telchemy Application Notes

Wiring problems in subscribers’ homes It uses a distributed software probe architecture that require service calls. Existing cable to provide cost-effective, real-time call quality modem management statistics can help feedback with maximum network coverage. The new determine remote problems, but they framework’s monitoring functions provide real-time may not be sufficient for diagnosing IP visibility of network performance, detection of transient telephony-related problems. problems and comprehensive diagnostic data.

Network problems are transient in nature The framework incorporates QoS reporting and can occur at many places along the protocols that send key performance data back to packet path. By the time a user reports a network management and call control systems with problem, the network condition causing minimal network traffic overhead. High performance that problem may have disappeared. network probes are located within the core network and at head-ends to provide in-depth diagnosis they Some problems e.g., echo, result from the detect problems. interaction of the two endpoints (trunking gateway and IP phone) and the network. A key benefit of the new VoIP Performance Management Architecture is that small lightweight MSOs and operators need a performance management monitoring functions can be integrated directly into architecture that supports real-time monitoring of the MTAs, ATAs, IP phones, routers, gateways and similar service quality delivered to subscribers’ home locations and network elements. This “direct integration” provides probe fast, easy problem diagnosis. functionality in equipment where it would normally be cost prohibitive e.g., every customer home. The New VoIP Performance Management Architecture Embedded Monitoring Function

A new standards-based framework has emerged VQmon® technology is a major building block within the IP industry for VoIP Performance Management. of the new performance framework (Figure 1); it was the first and is the most widely deployed Call Server and monitoring function for VoIP CDR Database Network Management performance management System today. VQmon’s embedded monitoring technology Signaling-based QoS Reporting enables network managers to SNMP with VoIP RTCP XR MIB see call quality problems in Endpoint RTCP XR (RFC3611) real-time and identify the root Media Path Reporting VoIP Gateway cause of the problem for both Embedded monitoring active and completed calls. with VQmon® G.799.1 Trunking Gateway Network Probe or Analyzer

Figure 1: The new VoIP Performance Management Reference Model

2 VoIP Performance Management Managing Cable Telephony Services June 2004 Telchemy Application Notes

The technology measures key characteristics of MTA, ATA & Trunking Gateways: VQmon/EP the packet voice stream and calculates real-time performance data that network managers can use Leading equipment manufacturers are to detect, characterize and report service quality integrating VQmon/EP into their IP phones and affecting problems. gateways. VQmon/EP monitors the received packet VQmon provides detailed service quality metrics stream and extracts other vital information from and diagnostic information on transient problems; the VoIP CODEC. VQmon can use this information however, it uses a lower reporting frequency than to calculate accurate call quality estimates and older technologies thus requiring less . supporting diagnostic data, and sends QoS reports back to management systems via RTCP XR or VQmon is a high performance standards-based signaling based reports. non-intrusive call quality monitoring and diagnostic agent that can be integrated directly into VoIP CPE, CMTS, Analyzers and Probes: VQmon/SA SLA monitoring systems, probes, routers and generally any system that is on the path taken by voice packets. VQmon/SA is the core VoIP analysis software used VQmon agents are small and highly efficient and can in many probes, routers, SLA monitoring systems and be integrated into existing equipment without requiring analyzers. VQmon/SA monitors the packet stream, additional CPU or memory, scaling from systems that automatically recognizing individual call streams and monitor a single call to those that support “hundreds of the types of CODEC in use. VQmon determines which thousands” of calls. packets were lost or would be discarded due to jitter and uses this data to determine a call quality estimate using VQmon agents produce call quality metrics, the same algorithms as VQmon/EP. including listening and conversational quality scores. They also provide detailed information on the severity and distribution of packet loss and discards due to jitter and detect transient IP problems that affect service quality.

VQmon is an advanced VoIP perceptual quality estimation algorithm that incorporates support for key international standards including ITU-T P.564, ITU-T G.107, ITU-T G.1020, ETSI TS 101 329-5 Annex E and IETF RFC 3611. VQmon incorporates support for time varying IP impairments (typically caused by network congestion) and has been independently shown to provide significantly more accurate and stable metrics than other algorithms such as G.107 (E Model).

There are two versions of VQmon: VQmon/EP (End Point) and VQmon/SA (Stream Analysis). Both produce a rich set of diagnostic data, and support the common VoIP performance management metrics.

VoIP Performance Management Managing Cable Telephony Services June 2004 3 Telchemy Application Notes

Common VoIP Performance Metrics Mean Length and Density Of Bursts (where a burst is defined as the interval of The new VoIP Performance Management time during which the packet loss/discard Architecture incorporates a common set of VoIP rate is high enough to cause audio quality performance metrics supported by multiple QoS degradation) reporting protocols i.e., the same information is available regardless of the protocol used for reporting Mean Length and Density Of Gaps (Figure 2). These metrics are: Between Bursts

Percentage Of Packets Lost By the Network Both these metrics help to identify the extent to which the call is degraded by Percentage Of Packets Discarded By the loss/discard and provide some insight Jitter Buffer Due To Late Arrival into the user experience. Transient network congestion is a common Both these metrics help to identify problem resulting in a period of high the degree to which a call is being loss/discard lasting for several seconds affected by network packet loss or during which call quality is degraded; jitter. They also eliminate the need these transient call quality problems to “guess” how much effect jitter is are reported as “bursts.” having on packet discard rate.

IP Phone SLA Monitor VoIP Gateway Protocol Analyzer Router IP Network CODEC

VQmon VQmon RTCP XR

VQmon/SA VQmon/EP “Stream Analysis” “End Point”

Figure 2: VQmon's embedded monitoring technology

4 VoIP Performance Management Managing Cable Telephony Services June 2004 Telchemy Application Notes

Round Trip Delay Between VoIP Endpoints Performance Management Reporting Protocols End System Delay Within a VoIP Endpoint Reporting protocols have been developed for the Both these metrics help to identify media path, signaling system and network management. the sources of excessive delay It is important to realize that these are complementary which can lead to conversational i.e., they are designed to be used together. difficulty and greatly intensify the effects of echo. RTCP Reporting Extensions (RTCP XR)

Signal Level The RTCP XR protocol (RFC3611) is a media path reporting protocol that exchanges call quality metrics Noise Level between VoIP endpoints. RTCP XR provides several useful functions: Echo Level Enables collection of call quality reports These three metrics enable detection of by the remote endpoint e.g., a trunking problems due to excessive variations in gateway or by intermediate probes signal, noise or echo level. They also allow mid-stream probes to detect signal, Provides ability to pass performance reports echo and noise level problems without transparently through firewall routers needing to decode voice packets. Supports the diagnosis of complex Call Quality Metrics In Both R and problems such as echo MOS Scaling Enables network probes to obtain analog These metrics provide an immediate signal information without the need to view of call quality. If it is apparent that decode voice packets there is a problem, other metrics can be used for diagnosis. Compatible with the emerging Secure RTP security framework. Jitter Buffer Configuration and Packet Loss Concealment Algorithm

This information is used to determine if poor call quality is due to an incorrectly configured end system and to allow mid-stream probes to automatically detect endpoint configuration.

VoIP Performance Management Managing Cable Telephony Services June 2004 5 Telchemy Application Notes

Signaling Protocol QoS Reporting of a VoIP connection; and SNMP would be used to retrieve call quality information from the gateway for Several new QoS Reporting protocols have been both in-bound and out-bound packet streams. developed within ITU and IETF that support call quality reporting to call management systems e.g., Applying the VoIP Performance softswitches. These protocols provide call quality Management Architecture information directly to the systems that maintain CDR To Cable Telephony databases and link service quality information directly to specific customers and their calls. QoS reporting The new VoIP performance management protocols for H.323 (H.460.9 Annex B) and Megaco architecture is essential to provide real-time visibility of (H.248.30) were approved in early 2004, and new user perceived quality in cable networks. (Figure 3) protocols for SIP and MGCP are expected in late 2004. VQmon is integrated into the MTA or SNMP and the RTCP XR MIB ATA in the customer’s home to monitor the quality of each live call. RTCP An RTCP XR Management Information Base XR reports are periodically inserted (MIB) is under development within the IETF for into the packet stream to provide real- use in gateways or probes to support the retrieval of time feedback to the service provider. metrics via SNMP. For example, RTCP XR could In addition, call quality reports may be used to relay call quality information from an IP be forwarded through MGCP/NCS phone to the gateway that forms the network end messages back to the softswitch.

Figure 3: The New VoIP Performance Management Architecture for Cable Telephony

6 VoIP Performance Management Managing Cable Telephony Services June 2004 Telchemy Application Notes

VQmon may be integrated into a probe Problem Resolution, Detection & Diagnosis located at the head-end or directly into the CMTS. This is an ideal location to The new VoIP Performance Management measure the quality of calls as they pass Architecture provides the basis for detecting and from the HFC network to the backbone diagnosing different types of call quality-related and to observe RTCP XR data sent by problems: MTAs. Upstream Ingress Noise VQmon is integrated into the media/ —If there is an upstream ingress noise problem, trunking gateway at the interconnection then VQmon located in either the head-end or to the telephone network (meeting trunking gateway can immediately detect the ITU G.799.1 requirements). During problem and assess its impact on call quality. an active call, service quality for the Ingress noise can appear as either a periodic customer-to-network direction of the or transient packet loss problem. VQmon will call is monitored at the network’s end- indicate a packet loss (versus packet discard) of-the-path. problem and provide statistics on the transient bursts of packet loss and their frequency. The Softswitch collects QoS reports sent via the signaling protocol. At the Echo In PSTN end of a call, a call quality report may —If there is a problem on a remote PSTN be sent from the IP endpoint through analog loop, the cable subscriber may the signaling protocol to the softswitch. experience audible echo. NOC staff can This data can be incorporated into the diagnose echo problems using VQmon- Call Detail Record database. generated call quality reports sent from the trunking gateway that show echo level and the VQmon is integrated into VoIP test level’s effect on conversational quality metrics equipment (probes and analyzers). as reported from the MTA. When problems are reported and detailed analysis is needed, Network Subscriber Reports “Noisy Call” Operations and Field Service personnel —VQmon located in the MTA at the customer use this test equipment to capture and home can monitor incoming calls and analyze call streams. VQmon can be provide reports back to the service provider used for both active i.e., on-demand or through RTCP XR, the signaling system or scheduled testing and passive i.e., live SNMP. The data provided by VQmon clearly call testing. identifies if the network problem was caused by jitter, packet loss or noise in the signal. VQmon may be integrated into probes and transponders located within the HFC network to support fast detection and identification of HFC network problems that affect call quality.

VoIP Performance Management Managing Cable Telephony Services June 2004 7 Telchemy Application Notes

Summary Notes

The new VoIP Performance Management ______Architecture provides an ideal solution for service ______quality monitoring and problem diagnosis. ______Important call quality and diagnostic data is ______obtained real-time from key points on the packet ______stream and routed to network management systems ______and CDR databases. ______Network managers can obtain a reasonable ______level of problem diagnosis simply by using data ______from VoIP call quality reports; however, in-depth ______problem analysis requires the use of probes and ______analyzers that support the new performance ______management framework as well as the use of ______VQmon for call quality analysis. ______Many of the industry’s leading equipment ______manufacturers are already implementing elements ______of the new management framework in IP phones, ______gateways, routers, probes and analyzers.

Acronyms

ATA Analog Telephone Adaptor MIB Management Information Base CDR Call Detail Record MSO Multiple System Operator CMTS Cable Modem Termination MTA Media Terminal Adaptor System NOC Network Operations Center HFC Hybrid Fiber Coax PBX Private Branch Exchange IETF Engineering Task QoS Force RTP Real Time Protocol IP Internet Protocol SLA Service Level Agreement ITU International SNMP Simple Network Management Union Protocol MGCP/NCS Media Gateway Control VoIP Voice Over Internet Protocol Protocol/Network-Based Call VPN Virtual Private Network Signaling VQmon/EP VQmon End Point VQmon/SA VQmon Stream Analysis

8 VoIP Performance Management Managing Cable Telephony Services June 2004 References Telchemy Application Notes

[1] IETF RFC3611 RTP Control Protocol Reporting Series Understanding VoIP Performance Extensions (RTCP XR), November 2003 Title Voice Quality Measurement [2] ITU-T G.799.1 “Functionality and Interface Title Impact of Delay on VoIP Services Specifications for GSTN Transport Network Title Impact of Echo on VoIP Services Equipment for Interconnecting GSTN and IP Title Data and Modem Performance on Networks” VoIP Services [3] ITU-T H.460.9 Annex B Support for online Title Voice Quality Estimation in & QoS-monitoring reporting within H.323 systems: TDM Environments Extended Performance Metrics [4] ITU-T H.248.30 RTCP Extended Performance Series VoIP Performance Management Metrics Packages Title Managing IP Centrex & Hosted PBX Services [5] IETF SIPPING draft-johnston-rtcp-summary.02.txt Title Managing Cable Telephony Services [6] ETSI, “Quality of Service (QoS) measurement Title Managing Enterprise IP Telephony methodologies,” ETSI TS 101 329-5 V1.1.1 Title Managing Wireless LANs & (2000-11), November 2000. Wi-Fi Services [7] ITU-T, “The E-Model, a computational model for use Title Six Steps to Getting Your Network Ready for in transmis­sion planning,” Recommendation G.107 Voice over IP

About Telchemy, Incorporated Download Application Notes @ www.telchemy.com

Telchemy, Incorporated is the global leader in VoIP Information and IP Video fault and performance management with Email Telchemy, Incorporated its VQmon® family of multimedia quality monitoring [email protected] 105 Nobel Ct and analysis software. Telchemy is the world's first [email protected] Suite 100 company to provide voice quality management Phone Alpharetta, GA 30005 technology that considers the effects of time-varying +1-678-387-3000 USA network impairments and the perceptual effects of time- varying call quality. Founded in 1999, the company has products deployed worldwide and markets its technology through leading networking, test and management product companies. Visit www.telchemy.com.

Telchemy and VQmon are registered trademarks and SQmon, SQprobe, SQmediator and the Telchemy logo are

trademarks of Telchemy, Incorporated. VQmon and SQmon contain technology described in four or more patents and

pending patents. © 2004 Telchemy, Incorporated, all rights reserved.

VoIP Performance Management Managing Cable Telephony Services June 2004 9