* AT&T explains how it bases VoIP quality on ITU's R-Factor
We’ve received many insightful comments and questions from readers about our series on the service-level agreements offered by top-tier carriers. Today, I’ll share a few thoughts from readers who are interested in IP network performance as it relates to emerging applications such as VoIP and interactive video.
One reader had a follow-up question for AT&T about its SLAs, which were enhanced this fall. AT&T made several improvements to the SLAs for its IP network including guaranteeing 99.999% availability as well as reduced latency and quicker repairs.
However, AT&T did not add jitter to its SLAs because a year ago it added a metric called R-Factor, which AT&T claims will measure the performance of VoIP applications better than jitter alone.
One reader of the ISP News Report asked us for a full explanation of R-Factor. Here’s what AT&T has to say:
“In September 2003, AT&T introduced the industry’s first global VoIP service-level guarantee for voice quality based on the International Telephone Union’s (ITU) R-Factor standard. R-Factor determines voice quality based on a calculation of three combined network factors: latency (one-way transit across the network), packet loss (includes latency and lost packets) and jitter (the inter-arrival rate between voice packets).”
Here are links to two network management vendors that have products to support ITU/ETSI’s Standard R-Factor Passive QoS Test: Network Media https://www.networkmedia.com.hk/portal.asp?ContentID=38&CategoryID=10https://www.elexo.fr/Fournisseurs/Finisar/Finisar.htm
and Finisar:
Meanwhile, one reader shared the following thoughts about how SLAs will change with emerging applications such as VoIP: “I believe availability and bandwidth performance will continue to be the major factors [in SLAs]. However, as more and more subscribers are using their connections to support real-time applications (VoIP, interactive video, etc.), packet delay and jitter will become the important performance metrics that the ISPs will find difficult to assure. They are so used to blindly throwing bandwidth at problems. I am not sure how they will classify, police, shape and prioritize different traffic types when they do not own the network end-to-end.”
If you have an opinion you’d like to share about SLAs, here’s your chance to speak out. Send us me an e-mail (mailto:cmarsan@nww.com) and we’ll print it in a future article. Or send us a question, and we’ll chase down an answer.
To read our series on the SLAs offered by top-tier ISPs, visit the following area of Network World’s Web site: https://www.nwfusion.com/newsletters/isp/index.html
