What Ever Happened to Quality of Service (QoS)?

Rick Gallaher is course director for CCI, President of Telecommunications Technical Services Inc., and author of  Rick Gallaher's MPLS Training Guide

July 9, 2002

Let’s take a trip down memory lane. Imagine walking into a restaurant in your hometown and being greeted by the owner who shakes your hand.  He knows your name and your favorite meal. You know that you will have quality service, for the owner consistently checks the speed of delivery, taste and presentation of the food, and staff performance to ensure that you have a quality meal.

In the telephone industry, Quality of Service has always been an issue. Technicians consistently monitor the lines to ensure that every word can be heard with a high degree of accuracy. The “pin-drop” company is so sure of its quality that it advertises that you can hear a pin drop.

In data communications, Quality of Service (QoS) has been an issue since the possibility of running Voice over IP (VoIP) was first aired.  In order to achieve voice “toll” quality, call-voice datagrams had to arrive in a timely manner with only a very few datagrams dropped on the path. Voice over IP is now a reality that has been implemented around the world with a good success rate.  Contrary to predictions, as VoIP increases in market share, there has been a sharp drop in QoS awareness.

What ever happened to QoS?  Two years ago, QoS was a real issue. There was a dedicated web site called the QoS Forum…now it is gone. The web keywords QoS and Quality of Service score very few hits on Google.  More networks are being designed with massive excesses in bandwidth as a means of controlling Quality of Service issues.

I submit that problems of Quality of Service (QoS) have not gone away.  Over provisioning and over engineering do not solve the QoS problems.  The current industry myth is that it is more cost effective to "buy" 200% more bandwidth than a network requires than it is to worry about QoS.   However, contrary to popular belief, bandwidth alone cannot solve QoS problems.   In this article, I will discuss the three elements of QoS, explain why bandwidth alone cannot solve these problems, examine how a combination of measures can effectively address QoS challenges, and explore genuine QoS solutions.

Vocabulary:

• 802.1Q/p - A layer-2 VLAN and Quality of Service  (QoS) protocol

• DiffServ - Differentiated Services; a layer-3 marking and classifying protocol

• Dropped Packets - Percentage of packets lost as they move from end to end

• FWQ - Fair-Weight Queuing

• IntServ - Integrated Services

• Jitter - Unpredictable variable in delay caused by congestion

• Latency - Time it takes a signal to move through a unit in test

• MOS - Mean Opinion Score

• MPLS - Multi-Protocol Label Switching

• Over Provisioning - Allocating more assets (bandwidth) than are needed

• QoS - Quality of Service

• RED - Random Early Detection

• RSVP - ReSource reserVation setup Protocol

• SUT - System Under Test

• WFWQ - Weighted Fair Weight Queuing

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