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QoS Facts and Myths

Quality of Service or QoS is the latest in widely used and misunderstood acronyms. To simplify QoS it is the ability to prioritise and queue different IP packets depending on their application. Its recent popularity is due to the rising interest in using broadband to carry voice as well as email and web traffic. When networks slow down due to congestion, voice packets need to be prioritized so that the parties can understand what each other is saying.

1. BT’s IPStream network does not support QoS

FACT however the BT network is generally not congested and therefore the ‘pinch points’ in the network, where congestion can occur, tend to be the subscribers own network or the ISPs’ interconnect into the BT network. Choose an ISP that guarantees not to be congested.

2. You need QoS for VoIP

MYTH you only need QoS if the VOIP is competing with other applications for bandwidth. If you are using your broadband circuit only for voice, your ISP and LAN are not congested and you are not trying to squeeze too many simultaneous conversations down it, you will be fine. The whole point of convergence however is that you can mix applications on the same broadband circuit and to do this safely you will need QoS.

3. Only Datastream and LLU can offer uncontended DSL

FACT with LLU and Datastream the ISP controls the path back from the BT exchange and so they can partition customers their own bandwidth. However this can be expensive and is only necessary where there is the possibility of network congestion. Select your ISP carefully and this should be unnecessary in most cases.

4. IPStream is not suitable for voice

MYTH there are thousands of customers using IPStream for voice with no problems at all. Many of them use a dedicated IPStream line for voice and a separate IPStream line for data. However, with QoS enabled Engineered Broadband customers can use IPStream for both voice and data. On such a network voice traffic is prioritized in both directions over other traffic. The prioritization applies to both the link between the customer and the BT exchange and the interconnect pipes between the ISP and BT. This has the effect of providing the best possible voice quality, regardless of other applications on the same broadband circuit.

Source Comms Business February 2007.