• United States
by Steve Taylor and Larry Hettick

Vendors offer info on QoS

Apr 02, 20032 mins
Cisco SystemsNetworkingVoIP

* Three vendor white papers help put perspective on QoS

We’ve been discussing how we can be assured that data applications won’t be adversely affected when we implement voice over IP. In one approach, engineers can prioritize data first and voice second, with the public switched telephone network providing a backup when voice quality degrades. In another approach, engineers can statistically prereserve bandwidth for voice and data equally.

We believe both approaches are sound; however, in either case we must stress (in all caps): THE MOST IMPORTANT STEP IN IMPLEMENTING VoIP IS A THROUGH ANALYSIS OF BOTH YOUR VOICE AND DATA REQUIREMENTS.

Enterprise telecom and datacom managers, and vendors who support them, would – without exception – concur. Make sure you and your vendors work together to understand what is required on several dimensions, including (but not limited to) availability, delay/latency, throughput, packet loss and variation.

To assist you, we’d like to recommend three reference points you may want to use in you planning. The first is offered by Avaya, and can be found at:

It details basic network requirements that are foundational for good voice quality when using Avaya IP telephony products over a data network. The document summary provides a short list of requirements, allowances and recommendations. The rest of the document explains basic networking and telephony concepts for those who haven’t been exposed to a converged implementation. It also explains why voice-over-IP applications can yield poor results while data traffic on the same network doesn’t seem to have problems.

Alcatel offers a white paper that looks at the issues relating to VoIP deployment and is not focused on a single product. We believe that it’s a good read for end users who have not yet decided what product to deploy and that it provides another very good basic overview of QoS considerations. It’s available at:.

Cisco has a paper that is a bit more specific to Cisco’s AVVID implementation. It provides significant detail in the design and engineering of both voice and data applications as we covered in our last newsletter. It can be found at:

As our readers provide additional information on advances in QoS engineering we’ll be sure to share the most relevant details with you.