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QoS: Panacea or Snake Oil ?

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IT and Telecom professionals have long been infatuated with the concept commonly referred to as QoS (which stands for Quality of Service). Of course ensuring that Voice over IP meets high voice quality requirements is a key concern when it comes to designing networks. New QoS protocols: Differentiated Services (DiffServ), the Label Distribution Protocol (LDP) and the once almost forgotten Resource Reservation Protocol (RSVP) have been designed by some of the brightest minds in IP networking and data processing.

But here is the thing: even though every modern switch or router and every server can classify traffic by QoS standards, there is no way to make sure that QoS will work across different IP networks.

The problem with QoS lies in agreements between Internet Service Providers, and their different approaches to implementing routing protocols. Not only must service providers be in agreement on QoS standards but they also need to negotiate peering policies that would treat classes of traffic consistently the same way across the Internet and govern the billing for transporting one another’s traffic at different levels. This makes peering much more complicated. Already peering is not a standards-based process. The Internet is decentralized and each service provider/carrier plays by a different set of rules. An independent negotiation takes place every time a provider wishes to peer or even purchase service from another provider and a great connection with some is not indicative of the same with others.

Even with all the promise brought by QoS, some experts question whether QoS is merely a short-term fix than a long-term solution to the Internet traffic congestion problem. New Wide Area Network technologies such as wave division multiplexing are becoming available to ISP networks, solving the congestion problem merely with increased capacity.

When it comes to ensuring SLA over the last mile – choosing between Comcast cable modem, AT&T DSL and/or a T1 connection can be complicated for Internet users of today. That’s because each type of connection offers unique benefits to consider and a Comcast connection may not provide QoS. At the same time with the advent of DOCSIS 3.0 technology, Comcast cable modems can access Internet at speeds reaching 50 Mbps. With bursts like this it is easy to forget, that connection speeds of cable modems can be affected by many factors and that, like DSL, these connections are shared among multiple users.

In my 8 years of watching Voice and Video over IP and implementations I have seen our customer’s IT managers and engineers get completely wrapped up in QoS hype forgetting that it only provides benefit when the network is congested. Otherwise it becomes just another thing to manage.

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