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VoIP Testing – Serious Business

By: Richard "Zippy" Grigonis

What’s been commonly referred to as VoIP testing has expanded in recent years to include all of IP Communications. Networks are simulated and as many tests as possible are done before actual deployments of VoIP, mobile or triple play networks and or equipment. Developers are spending more time in the interoperability testing labs as they face a combinatorial explosion of testing other equipment as well as load testing and simulating operations under typical hybrid network scenarios.

For as long as Yours Truly has been exposed to testing in telecom, computer telephony and IP communications, the name of Empirix (News - Alert) continues to stand head and shoulders above the rest. Empirix gained great notoriety in the 1990s with their Hammer testing platform that could subject computer telephony systems to full load tests, generating thousands of calls to simulate real world traffic. (I should know – I had two of their $40,000 boxes – along with an Ameritec Squirt analog call generator – in the lab I designed for the now-defunct Computer Telephony magazine.)

As IP began to infiltrate the world’s telecom infrastructure, Empirix has kept pace, expanding the number and capabilities of their testing portfolio. Perhaps their crowning achievement came last year when they debuted the mighty Hammer G5, a testing platform that embodies much the technical expertise they’ve accumulated over these many years.

VoIP, next-gen and IMS (IP Multimedia Subsystem (News - Alert)) devices and networks have unique sets of testing requirements. Many devices and technicians are often needed. Fortunately, the Empirix Hammer G5 has loads of super-scalable feature testing capabilities in a single box, accessed by one GUI. The G5’s comprehensive test environment can be used throughout a test lifecycle by application developers, network equipment manufacturers and service providers, from R&D prototype testing to service verification in trial lab situations.

The Hammer G5 can emulate an endpoint and simulate user interaction from virtually any point in a network on the call or session path. It can generate and/or analyze features, loads, voice quality, signaling, and media. It can scale up to thousands of calls, it supports and can run multiple protocols simultaneously using the same tests and scripts, calling upon such protocols as SIP, MGCP, NCS, H.323, QSIG, and Cisco (News - Alert)’s Skinny. It supports a plethora of narrowband and wideband codecs for wireline and wireless, as well as various real media types such as tones, DTMF, voice, fax, and video. Certainly the mysteries inherent in any new application server, call agent, firewall, gateway controller, IP PBX (News - Alert), IVR system, or session border controller will be revealed after getting a “hammering” (pardon the pun) by the Hammer G5. In short, it can handle just about any test scenario, from automatic failover/handoff to denial-of-service attacks, to mass calling events, to service oversubscriptions.

Empirix’ great rival, Tektronix (News - Alert), is no slouch either. As Keith Cobler, Marketing Manager, Network Management Solutions, says, “Let’s take a look at the technology lifecycle: you start with the Network Equipment Manufacturer [NEM] who may be developing some softswitch or other device for a VoIP network. From that point it moves into the carrier labs where they do the acceptance testing and interoperability testing on it. At that point the product goes out into a network pilot project, and if it’s successful there then it goes to a full network-wide deployment. All four of those stages are becoming ‘compressed’ because it all comes back to the importance of time-to-market and getting these services and applications turned up and generating revenue as quickly as possible.”

Cobler continues: “Our Spectra2 [now joined by the Spectra2XL] test platform for VoIP, IMS and converged networks is a protocol analyzer focused on use in the NEM and carrier labs to get a product stress and load tested and have the individual network elements fully optimized before it gets shipped over to the operator side. But once it arrives on the operator side, that’s where the network management aspects come into play. In any case, you’re starting to see more and more of the tools ‘bridge the gap’ between acceptance testing and interoperability testing in the labs, all the way over to the point where it’s first brought into a pilot, and eventually to full deployment.”

“So in terms of bringing and new products and services to market,” says Cobler, “there’s a telescoping or compression of that whole testing cycle. From my perspective, we focus more on the network management side. As for VoIP testing, we’ve definitely seen a couple of really key trends that are impacting what our customer needs are today as well as the monitoring and test products that we’re developing.”

“If you look back ten years ago at PSTN networks, the types of test and monitoring solutions then available were very different,” says Cobler. “They were very much focused on testing individual elements or ‘nodes’ and things were assumed to be taking place at the network level. Now, moving to VoIP and IP networks in general, there has been an upshift towards the service level and monitoring applications and services at that service level. That in itself has really fundamentally changed the way testing and monitoring products have to address this need. Just the very nature of IP means that you must have a distributed monitoring system throughout your network to pick up all of the IP packets as they transverse the network.”

“If you think about today’s IP networks, including voice,” says Cobler, “they also carry video and data. You now have a wide variety of data traffic transversing your network, and you’ve got a constantly changing service and application mix. As new services and applications are brought to market, you see scenarios such as when the iPhone (News - Alert) was rolled out by AT&T Mobility. Suddenly the demands of the network change, and you have to be able to monitor those changes in real time within your network, so you can proactively provision your network resources and ensure that you can really offer a high quality of service to your end users.”

Zaid Ally, Marketing Manager of Active Test Solutions at Tektronix, adds, “What this all translates into is that you must ensure that you have a good end-to-end service across your network and a product travels from a NEMs lab all the way through to the carrier deployment phase, moving all of these technologies into a deployment means that you have a hybrid ‘mix’ of networks, whether they are 3G, WiMAX (News - Alert), PSTN or even just a plain simple IP environment. We perfected our original testing methodologies back in the days of the PSTN, some of the metrics that we examined in the PSTN are now creeping up into these newer technologies in the wireless 3G and IP/VoIP networks. So it’s all really about making sure that we can reach the ‘end dream’ of having some sort of session ‘persistency’ across all of these hybrid networks.”

Hybrid networks pose one set of challenges. Even more challenges are posed by networks having to deal with bundled services in a triple- or quad-play scenario. Ixia (News - Alert), a major provider of IP performance test systems, has distinguished itself by demonstrating triple-play testing for Gateway GPRS Support Nodes (GGSNs, pat of the packet-switched core network in both 2.5G and 3G mobile systems) using an enhanced version of their popular IxLoad 4.10 application. Ixia’s IxLoad emulates thousands of triple-play (voice, video and data) subscribers along with any associated protocols. Hardware vendors and mobile operators canuse it to run stress tests on devices and networks to gauge performance.

Ixia also offers ixChariot, a sophisticated test tool for simulating real-world applications to predict device and system performance under realistic load conditions, and ixVoice, a wide-ranging hardware and software test framework that provides unified VoIP and PSTN test solutions for the equipment makers, carriers and enterprises. It can handle any pretty much any VoIP protocol: SIP, SCCP (Skinny), H.323, MGCP, H.248 (MEGACO) as well as TDM and analog telephony services. Functional, load and interoperability tests are easily formulated via a drag and drop architecture, enabling quick creation of test scenarios with pre-defined visual blocks. IxVoice;’s semi-automated, multi-interface, multi-technology approach can facilitate the measurement and analysis of both voice and fax quality.

Ixia has also opened a new advanced testing facility in Silicon Valley, called iSimCity. iSimCity is a state-of-the-art proof-of-concept (PoC) lab and Executive Briefing Center adjacent to its sales and services offices in Santa Clara, California. Local companies such as Cisco and Force 10 Networks can use iSimCity to test their new products and services prior to deployment, including multi-play, VoIP, wireless, and other items.

Sounds Like My Network. . .

Corporate paranoia over how a new VoIP system is going to sound has spurred long-overdue pre-installation testing and simulation of networks. One interesting example of a tool in this area is Shunra (News - Alert) Virtual Enterprise (Shunra VE) by Shunra Software. It’s a flexible, feature-laden network simulation solution that can synthesize an exact replica of your pre-deployment production network and remote end-user locations right in your lab. It also integrates with and controls VoIP call generators, such as Ixia’s IxChariot, IxVoice, and Spirent’s Abacus. You can even attach SIP phones directly to Shunra VE and hear how voice calls will sound over existing or projected network conditions. It can scale up to point where it can accurately determine the network capacity resources needed to support triple play and it can be used to optimize QoS and MPLS architecture infrastructures. Shunra VE can also be used to assess the impact of planned changes to an existing network on VoIP performance.

“Streamlining” Service Providers

Communicado, Inc., formerly known as SyncVoice (News - Alert) Communications, provides management software for managing converged voice/data communications that carry real-time person-to-person business communications. The VXTracker software product line and Communicado (News - Alert)’s Streamline Management as a Service Platform are used by more than 400 advanced technology adopters.

In particular, service providers or even integrators can offer their customers the benefits of a converged-communications solution with none of the risk or IT burden for them (and no capital expenditure by the provider) by franchising the Communicado Streamline Service Management Platform. It doesn’t matter with the provider specializes Microsoft (News - Alert)/Nortel, Avaya, Siemens, ShorTel or Cisco, Streamline can handle just about anything, enabling the remote management of a customer’s environment as the trusted provider of a complete converged-communications solution.

To make this functionality possible, some sophisticated testing capabilities had to be built into the product.

Kevin Strehlo, Vice President of Marketing for Communicado, says, “Communicado Streamline does network assessment testing based on modeling historic traffic in order to generate VoIP traffic as a way to test convergence readiness. Streamline then analyzes the impact deeply in terms of MOS scores and per-call QoS. Daycom used their testing techniques periodically on themselves and noted a gradual MOS score degradation, consequently looked at it and adjusted packet sizes, and fixed the problem before it caused user complaints.

Strehlo continues: “How do you test an intermittent, remote problem? Streamline can alarm on a problem and let you roll back in time and see what issues correlate with the problem. Then you can use Granted Access to start the protocol analyzer loaded on our premise device and look at the traffic captured at that point in time. There’s no requirement for — what would it take? — a truck roll to a remote site based on a premonition a problem is going to occur?”

“You can also store a packet capture file on the remote Streamline premise device for later analysis,” says Strehlo. “It works in combination with the Ethereal software loaded on the Streamline Remote Toolbox Appliance to allow rolling back in time for deep analysis and troubleshooting, which is especially effective when used with Streamline’s Correlated Zoom.”

Seeing What’s Wrong

Another great testing name, dating from 1996, is RADCOM, which provides probe-based network monitoring solutions for telecom service providers and equipment vendors. They specialize in next-gen cellular as well as voice, data and VoIP networks. Their products are used in support of facilitate fault management, service performance monitoring and analysis, troubleshooting and pre-mediation.

Even in the case of a complex, finicky service such as IPTV (News - Alert), RADCOM has a sterling testing tool – Omni-Q for IPTV, which gives service providers a detailed view of the various services available in their IPTV deployment. Omni-Q for IPTV monitors the transactions between the users set-top box (STB) and the middleware as well as those between the middleware and any external application servers. The system can reveal the performance of every component in the service delivery chain, with regard to each request generated by the STB and propagated to the middleware VOD (Voice on Demand) or other IPTV-related service delivery servers.

Wild Wireless

With all of our talk of packets traveling along fiber and copper, we forget that the future frontier of packetized communications (e.g. 4G) resides in the mobile world. In terms of testing, cellular wireless telephony has always had its own can of worms (make that a whole shelf of cans). Mobile services subscribers have a limited tolerance of problems such as incomplete or dropped calls, interrupted data downloads and device lock-ups, resulting in a lot of returned devices and cancelled service subscriptions. Rising to the occasion, however, is Spirent Communications (News - Alert), which has introduced a new UMTS Call Reliability Module for its 8100 Mobile Device Test System. Spirent claims to be the first company in the industry to provide mobile operators with comprehensive call reliability performance testing capability for UMTS devices under real-world conditions.

Spirent is also known for its Spirent Abacus voice, video and data over IP testing platform, often used to reveal scalability, performance interoperability, and QoS parameters prior to and during deployments. Spirent enables equipment manufacturers and service providers to test the migration from legacy to converged network equipment — including triple play testing for voice, video and data.

Any way you look at it, the testing of IP Communications products, services and networks can be done in a more thorough manner than ever before. Sometimes it seems that new stuff takes forever to make its appearance, but I’d rather wait for something that has passed every test with flying colors, rather than take a chance on unknown quantities. IT

Richard Grigonis (News - Alert) is Executive Editor of TMC’s IP Communications Group.


The following companies were mentioned in this article:

Communicado (

Empirix (

Ixia (


Shunra Software (

Sprient Communications (

Tektronix (


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