May 2002

Emerging Technology For Successful IP Telephony

BY BOB MASSAD

Cost savings derived from running one network for voice and data instead of �one each� for voice and data, as well as serving remote users more economically while providing access to the same services as their headquarter counterparts are just some of the reasons why enterprises are migrating to IP Telephony. According to a Synergy Research Group study released recently, LAN Telephony remains the largest business opportunity within the Enterprise IP Telephony market, totaling 72 percent of the total worldwide opportunity, which grew at 141 percent in 2001.

Technologies are emerging, geared towards realizing this potential. One of those is real-time, voice call quality monitoring that can be embedded in IP phones, PC �soft-phones,� IP PBXs, VoIP gateways and network management devices to provide instant and objective measurement of call quality. Call quality continues to be the most concerning issue for network managers, service providers and users. These new monitors not only assess the quality as provided by the network but also as it was perceived by the user. They also remedy the deficiencies of present generation quality measurement devices by focusing on parameters that really matter but have been too difficult to capture, such as burst packet loss and jitter buffer discards; by correlating parameters with each other and in time instead of providing isolated, discrete statistics; by working passively and in real time, instead of using up network resources for sampled information; and by including an objective assessment of the end user experience.

By implementing lightweight statistical models that can capture packet information including burst packet loss and jitter buffer discards, VQmon�, developed by Telchemy and incorporated into international standards, can provide VoIP users with an instant, unambiguous quality score, called either �R-factor� or MOS (mean opinion score). Beneath that, statistics are maintained that allow for drilling down into the score�s components enabling an understanding of causes and effects. When implemented in a gateway, the same level of information is available for every call and all calls terminating at particular ports.

This emerging technology is extended by another emerging technology, developed by Telchemy, that takes VQmon data as input, then models and analyzes variations in traffic characteristics to determine the cause and location of network impairments from a single location. Particular network problems have a �signature.� The expert understands these signatures, whereby after classifying the traffic characteristics, a first set of rules are applied to correlate these characteristics to the probable cause of the impairment. An example would be to discover the cause of �bad� call, where the drill down statistics indicate that short term jitter is high, the out-of-sequence-packet rate is high, but the rate of packet loss is low.

Extending this expert model further, multiple concurrent calls are observed, with metrics for correlated for each. A second set of rules is used to determine the probable location of the problem. An example would be to discover the location of a problem if the same impairment were occurring to all calls or to some calls.

Combined, these emerging technologies will enable high quality experiences for users of IP Telephony as well as quick diagnosis and problem correction for network managers and service providers.

Bob Massad is VP-marketing at Telchemy. Please visit their Web site at www.telchemy.com.

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