Editor Profile - Tim O’Neill is an independent technology consultant. He has over 30 years experience working in the WAN, Analog, ISDN, ATM and LAN test market. Tim has worked with companies like Navtel, Network General, Ganymede and ClearSight Networks and is now helping companies get lab recognition and technology verification. Tim is also the Chief Contributing Editor for LoveMyTool.com, a website designed to help network managers gain access to valuable information and real solution stories from other customers. Tim is a patent holding, published and degreed engineer, who has seen this technology grow from Teletype (current loop) data analysis to today’s 10 Gigabit LAN’s focused on business applications with heavy compliance demands. Tim can be reached at oldcommguy (at) bellsouth (dot) net.
VoIP and Video Measurements - Where are the standards?
As pointed out by a previous article by Scott Haugdahl, as VoIP, IPTV and Video technologies continue to grow, the need for uniform standards-based and consistent measurement methodologies is imperative.
There are three main methods currently in the market for measuring VoIP and Video quality.
Method #1 - This is the least recommended method but has been applied by many if not all of the vendors of software only general data analyzers. It is the method I call “FM” and it stands for Fricking Magic, but there is no magic here, just shortcuts! This method is where vendors build their own algorithm by which they measure the quality of the voice or video flow. These vendors typically will not give you the algorithms that they use, and in almost all cases, they are far inferior to any standards-based or real measurement technology. The measurements are usually non-repeatable and are not consistent with any other real measurement technology like Method #3. The reason for the vendors to create their own algorithms is that their software based products simply are not robust enough to handle the standard based algorithms and therefore they take many mathematical and programming short cuts resulting in irregular, faulty and non-comparative measurement values.
Method #2 – Another method is one where companies base their measurements on the RTSP and RTSP-XR frames that are interleaved into the RTP streams (RFC-2326). The vendor products receive the packets, analyze the timing information from the RTSP frames and display their measurements based on these frames and the information embedded in them. The big problem with this method is that not every RTP stream has unique RTSP frames to give data on the quality of the flow. Further, most SIP calls do not support or have any RTSP frames thus, there is no data to base any real measurement information on and the Network Manager is left with no data on the quality of his VoIP or Video. This can be an OK method if used in circumstances where there are managed streams. Some VoIP only analyzers use this method but it will only cover a small portion of the common flows available today. Be sure when you purchase it that it will give you what you need to validate your activity.
Method #3 – This method is all about standards and we are very lucky to have the resident industry experts explain these methods in detail.
Robert Merrill of Telchemy has been kind enough to write a 4-part series explaining the ways that Telchemy, the most used technology for quality measurement, handles these measurements. The first article is titled Accurately Measuring VoIP Performance.
The next three articles to follow are:
- The ITU-T's P.564 Recommendation defining minimum criteria for objective speech quality assessment models, why compliance with P.564 is important, and how Telchemy's VQmon algorithm exceeds the requirements of P.564 by including analog metrics and conversational factors in its computation of call quality scores (please click here, article has been published on May 21, 2008 and is entitled "P.564 - Putting VoIP Quality Assessment to the Test").
- Strategies for active testing of VoIP services, its benefits for pre-deployment testing, SLA monitoring, and troubleshooting, and the advantages of using Telchemy's DVQattest distributed active test application with real use cases.
- Strategies for Video and IPTV Monitoring, Analysis and Troubleshooting.
We are very happy to work with Robert, Dr. Clark and the Telchemy team to get real technology information to our readers.
We are proud to offer you Robert’s first article in the series. I know you will enjoy it as I have.
My Best….Oldcommguy
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