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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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