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Re: [RE] On worst-case latency for Ethernet networks and alternative shaping concept

At 16:40 28/09/2005, Gross, Kevin wrote:


>The whole ATM experience is an interesting reference point. The objectives were technically and practically sound. They got off to a good start - Reducing all data streams to a series of 53 byte cells does make traffic engineering a tractable problem. ATM is no more complex than it needs to be. And yet the complexity turns out to be untenable and cost prohibitive in most non-telecom applications.

I agree with all that except for the penultimate sentence; ATM actually is quite a bit more complex than it needs to be. There's a whole lot of baggage which is a legacy of its history in telecoms, plus I personally think they only need two of the eight combinations of class of service and connection configuration (UBR unicast and CBR multicast -- so no VBR or ABR) and most switches don't implement CBR in the most efficient way.

I've just become aware of which has a lot of good stuff on this topic, for instance at the bottom of page C-8 of the document at pointing out that circuit switching is inherently cheaper and more scalable than packet switching. An ATM CBR service done properly is more like circuit switching.

John Grant
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