From the SIP Trunking Experts

April 14, 2009

Tools for Diagnosing and Troubleshooting

By Steven Johnson President, Ingate Systems, Inc.

This column will appear in the May issue of Internet Telephony magazine.
SIP trunks can deliver excellent voice quality and reliability. However, employing tools for diagnosing and troubleshooting problems with the VoIP media stream helps avoid potential issues, including QoS. This is especially important for enterprise environments — where voice is a mission-critical application — and for carriers, who rely on delivering quality voice service.

For both carriers and enterprises the metrics that can be gathered at an enterprise network’s point of entry are valuable in identifying and diagnosing problems that could degrade voice quality. Enterprise Session Border Controllers (E-SBCs) are located at the right place in the network and are often equipped with diagnostic tools that can be used to isolate the source of problems.
For carriers, the demarcation point between their network and an enterprise network can also serve as the first line of defense. An E-SBC can sit in the network and serve as this demarcation point, gathering the statistics necessary to monitor service delivery to maintain QoS. This allows carriers to see the primary statistics for determining the quality of the call through the network and diagnose whether problems are caused on the public or private side.
Another tool (for enterprises and carriers) is media quality scoring. With the E-SBC as demarcation point, it can monitor the RTP stream and compute statistics for the number of packets sent, bytes sent, jitter, number of missing packets and maximum number of consecutive missing packets. This information can be gathered as separate data for each direction and reported individually. It can also be used to compute a Mean Opinion Score (MOS).
Last, the E-SBC can be placed in front of an existing firewall, allowing the E-SBC to employ QoS rules with the introduction of SIP. An E-SBC will enable the use of SIP, leave an existing SIP-unaware network firewall in place and still provide the bandwidth management necessary to ensure that voice receives priority, and therefore does not suffer from conflicts with data packets which can stand delay, where voice cannot.
Voice quality and reliability are competitive differentiators for carriers and enterprises alike. Taking the right steps to diagnose and troubleshoot issues before they become serious makes smart business sense.

Steven Johnson is President of Ingate Systems, Inc. To read more of Steven’s articles, please visit his columnist page.

Edited by Greg Galitzine
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