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Is QoS a con job?

Thursday, 08 August 2013 18:24

The principle of quality of service is that some IP packets our prioritised over others. The analogy is letting some cars into the fast lane so they get there quicker.

The problem is, says Geoff Huston, Chief Scientist at APNIC, that creates congestion in the other lanes. Instead, build another lane – add extra capacity and let everyone go fast.

But you can’t always add extra capacity, says Layer 10’s Paul Brooks, making a repeat appearance on CrossTalk. Access networks tend to be the bottleneck and the point where traffic has to be prioritised.

So, does this mean the slower speeds promised by the coalition’s broadband plan make QoS more important for the delivery of video and interactive apps like teleconferencing? Perhaps. Although Geoff Huston says fibre to the premises is the real answer, there. It adds a lot of extra lanes to his highway.

The need for QoS on the Internet is given some rigorous discussion this week – along with a quick look at the Murdoch conspiracy that’s doing the rounds at the moment. And the Prime Minister is amongst the theorists. Ho hum!

Listen to the podcast to hear their views – and let us have your thoughts too. Leave a message on our feedback line: 02 9304 5198.

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Last modified on Thursday, 29 August 2013 21:06

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0 #1 Rod Dines 2013-08-09 18:33
Gee what a load of dribble...
Of course the ISP's do QoS on their VoIP.
Geoff Huston obviously has no need for torrents and kids watching YouTube while the wife watches a QuickFlix video on the SmartTV and your trying to download the latest OS ISO.
Try looking at a recently recognised problem called "BufferBloat" (many people are unwaware of this but will recognise the symptoms as it happens a lot) if your trying to understand the significance of this issue and the ability of QoS to fix it.

http://www.youtube.com/watch?v=-D-cJNtKwuw
http://queue.acm.org/detail.cfm?id=2071893
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0 #2 Evan Stanbury 2013-08-18 14:04
I think the Crosstalk session on QoS may have had your two guests speaking at cross purposes?
- Geoff Huston seemed to be mostly talking about a "Resource Reservation" style of QoS (eg the RSVP protocol), which is a "heavyweight" form of QoS - expensive, and rarely used. Indeed it is easier to add capacity!
- Paul Brooks seemed to be mostly talking about a "Differentiated Services" style of QoS (eg the DSCP field in IP), which is a "lightweight" form of QoS - so cheap that it is already built into all modern switch chips "for free" - noone would buy a chip that didn't support these everyday standards.

This discussion is reminiscent of the debate between traditional telcos and the IP world:
- Traditional telcos provide lots of intelligence in their network core, and expect that the customer premises equipment will be relatively "dumb".
- The IP world assumes that the intelligence is in the end-devices and that the network is relatively "dumb".

Where these worlds collide is:
- Complete resource reservation requires large servers in the network core which have an omniscient view of the entire network state. They are expensive, and are a potential source of network failure. And they could be used to identify end-parties and charge them. A classic telco model.
- Differentiated Services requires that end-devices mark each packet with its priority, and the network is able to process each packet independently while maintaining minimal data about the communicating parties. A classic IP model.

Configuring QoS is probably beyond the average end-user, and so Windows effectively hides these settings away in the Windows Registry. However, these settings will be familiar to IP engineers, and they are usually configured in IP Routers, Residential Gateways and telco core switches.
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