The introduction of VoIP (Voice-over-IP and other media-over-IP) or IP Telephony can have major performance effects on existing networks and applications, and QoS implications for routed networks. To be useful VoIP must also deliver good voice quality, usually expressed as a MOS score (mean opinion score) or measured to PAMS, PESQ or PSQM+ standards.
To avoid implementation problems and surprises, pre-deployment testing and performance benchmarking is highly recommended if not essential. Post-implementation, VoIP is another application requiring protocol analysis and troubleshooting, not only for its own performance but also for the effects of VoIP data on overall network performance. Phoenix Datacom supplies a range of scaleable products appropriate to both pre-and post-deployment testing.
Pre-deployment Testing Pre-deployment testing reduces the risk by allowing you to run realistic and"worst-case" testing in a controlled way. Traffic generation, network traffic analysis and IP network simulation are vital tools that help reduce the risk.
Traffic Generation
Agilent N2X systems stress-test equipment, including switches, routers and server load balancers, networks and services by producing multi-port, multi-interface traffic streams with total control over all traffic parameters such as packet size and variation, errors and losses and data rates. Load modules cater for all major LAN, WAN, ATM and SAN interfaces from 10/100 ethernet up to 40Gigabit.
Arca Harmony systems provide bulk call generation for capacity, functional and inter-operability testing of telephony systems and components
IP Network Simulation
Perceived voice quality on VoIP systems is severely affected by packet loss, packet delay and jitter (variable packet arrival times) - all factors inherent to any packet-based system. The solution is to "tune" networks, giving higher priority to VoIP traffic, but this can adversely affect the performance of other applications! Changing the parameters of a live network can be a time-consuming and disruptive process. The alternative is to use a network simulator - a device that allows you to accurately model the target network and then see the effect of changing key parameters such as routing, link speeds, priorities etc
Packetstorm Network Emulator systems provide a "complete IP network in a box" which can be used stand-alone or in-circuit with a real network to allow consistent and worst-case testing of networked applications. The Packetstorm system simulates a complete packet-based network with multiple elements in the traffic path (LAN, Router, modem, WAN link etc), each of which can be set with specific parameters for impairments, modifiers and traffic conditioning. Advanced features include:- emulation of Routing & Bridging, Diff Serv with traffic conditioning, ToS emulation, IP monitoring, packet counters and timers, Tcl scripting language, network capture & replay, packet modifiers, multiple LAN, WAN and ATM network interfaces, network queues, and remote control.
Applications Performance Analysis
NIKSUN NetVoice delivers Voice-over-IP (VoIP) performance management and monitoring across the global enterprise network. NetVoice measures, records and reports on every VoIP flow in the network in real-time at production network traffic rates. It enables no-loss VoIP monitoring for enterprise and service provider networks. Its distributed and scaleable architecture enables complete end-to-end monitoring in large-scale environments.
NetVoice's multi-time scale (microseconds to minutes to hours) and multi-level (link to application level) monitoring capabilities make it an essential tool for any VoIP network performance monitoring or troubleshooting endeavor. NetVoice provides 100% visibility into a VoIP network and captures network incidents the first time , saving time and reducing costs for enterprises and service providers
Protocol Analysis
It is most important to measure traffic levels and benchmark the performance of the existing network before introducing a new VoIP application. This provides an objective basis for any performance tuning or problem troubleshooting that may be necessary after implementation. Agilent Network Analyzer provides expert analysis of a huge range of VoIP and non-VoIP protocols and is an excellent tool for pre-deployment benchmarking. Because Network Analyzer is available in software only, stand-alone hardware or distributed versions with a wide range of LAN, WAN and ATM interfaces, it is scaleable to the size of the project, from departmental segments to core backbones.
Post-deployment Testing
These questions arise after VoIP implementation:-
- Is the VoIP system delivering adequate perceived voice quality? (And if not, why not?)
- Is the VoIP application affecting the performance of other applications? (And if so, why?)
Answering these questions effectively will save time, money and arguments! Voice Quality Testing and Troubleshooting
Voice is, by definition, analogue in nature and voice quality is highly subjective and the same network may deliver different perceived quality for different voice types. When it comes to measuring voice quality, there are two basic approaches - analogue and digital.
An analogue voice quality tester works by generating a real voice call across a network and comparing the received call with the reference call. This gives the most objective independent test of voice quality, (whether IP based or conventional telephony), and the results are measured to established standards such as PAMS, PESQ or PSQM+
A digital voice quality tester works by analysing the packet data stream containing the VoIP data and measuring packet loss, packet delay and packet jitter (variation in inter-packet arrival time); this information is then used to calculate the likely voice quality, expressed as predictive Mean Opinion Score (MOS).
Depending on the scale and nature of the VoIP project, one or other or both methods may be appropriate. The Agilent VQT provides comprehensive testing across analogue, IP-based, and hybrid telephony systems. By including testing for voice clarity, delay, echo, silence suppression, DTMF, and signal loss, all on one box, the VQT provides a total solution for testing voice quality on next generation networks.
The Agilent VQT supports analog, T1, E1, and Ethernet interfaces to enable testing at different access points for network segmentation and fault isolation. Using different signaling types, including FXO, E&M, CAS, ISDN, SIP, and H.323, the VQT enables testing across any telephony network. VQT is also available in a software-only version for testing via a standard ethernet NIC card.
A good network analyser is essential for troubleshooting problems, which may show themselves in any part of the network. Agilent Network Analyzer provides expert analysis of a huge range of VoIP and non-VoIP protocols and is an excellent tool for pre-deployment benchmarking. Because Network Analyzer is available in software only, stand-alone hardware or distributed versions with a wide range of LAN, WAN and ATM interfaces, it is scaleable to the size of the project, from departmental segments to core backbones. The Telephony Network Analyzer provides expert analysis of VoIP related data and provides a predictive MOS score for voice quality on IP networks. Used as a software option with any of the Network Analyzer family, this effectively allows voice quality to be sampled at any point of a LAN/WAN/ATM network. This is vital in pinpointing the cause of problems.
Rapid assessment and troubleshooting of operational VoIP links is provided by the VoIP options on the ethernet testers supplied by Phoenix Datacom.
Applications Performance QOS Monitoring
VoIP as an application introduces new protocols on to the network and additional data traffic that may affect its own and other applications' performance. Traffic prioritisation to achieve good VoIP performance can also adversely affect the performance of other applications. Monitoring of the actual Quality of Service (QoS) and Quality of Experience (QoE) as perceived by users is essential - to provide a performance benchmark when troubleshooting problems -and to avoid a lot of finger-pointing between different suppliers of different parts of an overall IT solution!
NIKSUN NetVoice delivers Voice-over-IP (VoIP) performance management and monitoring across the global enterprise network. NetVoice measures, records and reports on every VoIP flow in the network in real-time at production network traffic rates. It enables no-loss VoIP monitoring for enterprise and service provider networks. Its distributed and scaleable architecture enables complete end-to-end monitoring in large-scale environments.
NetVoice's multi-time scale (microseconds to minutes to hours) and multi-level (link to application level) monitoring capabilities make it an essential tool for any VoIP network performance monitoring or troubleshooting endeavor. NetVoice provides 100% visibility into a VoIP network and captures network incidents the first time , saving time and reducing costs for enterprises and service providers
TAMS from Sunrise Telecom provides probe-based continuous monitoring of both signaling and data across networks and can report voice qualityfor both legacy PSTN and VOIP.
To find out more about VoIP related products and services, call Phoenix Datacom on 01296 397711 , send an email or use the Request More Info form.
For a full list of products and applications, click here. |
