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Among the current applications for the dynamic circuit network, Internet2 expects to facilitate the transfer of data from CERN's large hadron collider to researchers at other institutions, and it has done trials in which circuits are opened between the collider and the University of Nebraska. In the future, Summerhill says, the researchers hope that commercial applications develop from the technology. "Think of a network that provided hundreds or thousands of high-definition channels and also provided on-demand video capabilities," he says. He foresees a commercial network that needs both high bandwidth and high quality of service, like some current academic requirements. "The methods for supporting that network are under investigation," Summerhill says. Although right now, there are no commercial implementations, he notes that Internet2 works with commercial partners that might eventually be a conduit to bringing the technology into the ordinary Internet.
Clive Davenhall worked on software for academic circuit-switched networks in the United Kingdom, as part of his role as an engineer at the National e-Science Centre, in Edinburgh, which works to improve methods for conducting large-scale science research over the Internet. Davenhall says that, although people have been talking about dynamic circuit networks for a long time, this type of network hasn't had much of an impact on the commercial Internet, partly because of concerns about how it might function in an environment less controlled than academia. For example, if the average person could set up a dedicated circuit on demand, it might be possible to hog resources that could interfere with other users' experience.
Summerhill says that the dynamic circuit network is still in its early stages, and "still has some evolution to do." He recalls the time that IP wasn't considered ready for commercial applications. So far, four universities in four different regional networks are connected to the dynamic circuit network, says Lauren Rotman, public relations manager for Internet2. Rotman adds that it will be easy to add universities in regions that are already connected. The organization hopes to increase the dynamic circuit network's reach significantly in the coming year.
ESNet and Internet2 have built a networking test bed for ideas that are too disruptive for the networks that people actually use.
With unprecedented access to network hardware, researchers have the chance to remake the Internet.
Didn't Enron have a similar business unit? They couldn't make it work, but it was probably not just the technology.
One size technology does not fit all
The hype of the marketplace often overshadows technological common sense. Every time some new technology comes along, it's hyped as the one solution to all problems, and it's NOT! Never!
Twenty (and more) years ago, we had a digital switched phone system using time division multiplexing, a broadcast TV system, and a packetized protocol computer network.
As LANs became more popular, Ethernet, Token Ring and other less popular networks were told they were obsolete, to be replaced by ATM, the backbone protocol of the digital phone system, to interface with dial up communications access. ATM killed off some very powerful networks like FDDI with false promises - then fell by the wayside when everyone realized a 53 byte ATM packet would have about 30% overhead, compared to a few percent for a 1000 byte Ethernet packet.
Recently, we have had media wars - copper, fiber, wireless, with each saying it's the best, when what smart users are doing is combining the three to create networks that support users with different needs.
I've never understood IPTV. Sure, it can be done, but it makes no sense to packetize a broadcast network. Hollywood is working on a better solution, a video backbones connecting studios to sound stages and eventually theaters. Keeping the video separate enhances quality and reduces overhead.
Even VoIP causes problems for data networks, as latency causes problems, forcing higher bandwidth solutions at higher costs.
In truth, we need several Internets, running on the same fiber using WDM (wavelength division multiplexing), data as IP traffic, switched voice and streaming video.
The model of Verizon's FiOS fiber to the home using PON and WDM is a model for what can be done cheaply.
I'll bet that optimizing traffic on different "carriers" saves more $ than trying to force all traffic on one backbone.
Re: One size technology does not fit all
You are absolutely right. My group did studies 29 years ago, comparing three types of networks (circuit switched -- then already in widespread use for five years, datagram, and virtual circuit) and three types of traffic (voice, interactive data, and bulk data/video). Two things we found were:
(1) If you have a small amount of one kind of traffic added to a large amount of another kind, then one size does fit all. "Fit in" the small amount onto a network designed for the large amount, and let the small traffic reap the benefits of economy of scale.
(2) If you have comparable amounts (same order of magnitude) of different kinds of traffic, none of the network types is best taken by itself. The best solution is a hybrid of multiple networks for different kinds of traffic.
The study was done for WAN traffic, where transmission costs are a significant percentage of total costs. The answer may be different for LANs.
Applying this to some of the history that you mention, VOIP was a wonderful, inexpensive, effective service as long as it was a tiny fraction of the bits flowing over the Internet. But, as it grows to a visible fraction, the traffic characteristics of voice are starting to affect the flow of traffic, and datagrams (IP) are not the best answer to a voice-only network.
The study was done for WAN traffic. The answer may be different for LANs.
Almost 30 years has flown under the bridge since then, and the technology has changed. The best choices for each kind of traffic could be different. But I'm sure that #1 and #2 above remain true.
Cheers!
DaveT
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dtutelman
117 Comments
Dynamic circuit switching is really old
In the early 1970s, when the Internet (actually ARPAnet) was in its birth pangs, there were lots of debates as to which was the better way to go for packet switching. The debate was generally expressed as "datagrams" (lone packets, like IP) and "virtual circuits" (dynamic circuit switching).
I'm surprised by the assertion that the big network providers are wary of dynamic circuit switching because they don't know how it will perform outside an academic environment. That was actually the rap on datagrams in the 1970s. The academic community was pushing datagrams for a variety of reasons (some technical and some not), but there was no experience with a heavily-loaded datagram network for about a decade after datagrams became the ARPAnet standard. The network providers favored dynamic virtual circuits; again, not all the reasons were technical, but the ability to control a heavily-loaded network was the major one.
There are quite a few examples of dynamic circuit switching (think of it as pre-routed packet switching), both in history and the present. A couple of examples:
(1) In 1976, about the time the Internet standards started, the CCITT (now the ITU, the standards body for the network providers) adopted its own packet switching standard, X.25, which used virtual circuits rather than datagrams. Several networks were implemented with X.25 before the Internet got big enough to dominate packet switching.
(2) Asynchronous Transfer Mode (ATM) is a common way for Internet backbone providers to derive circuits between nodes. Those circuits are pre-routed packet circuits.
Hope this gives a little background for the discussion.
Cheers!
DaveT
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Erica Naone
70 Comments
Re: Dynamic circuit switching is really old
Thanks very much for adding the background. I should note that the people at Internet2 are aware that circuit switching is an old idea. Summerhill told me during our conversation: “What we’re doing is looking at ideas that were used in the past to see how we might enhance the existing network.”
However, the dynamic circuit network itself, as built by Internet2, does seem to apply this idea in a new way, with new technology. For example, their control plane software, which sets up optical circuits across a variety of regional networks, is one of the things Summerhill told me is still in development.
-- Erica Naone
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samfwood
1 Comment
Re: Dynamic circuit switching is really old
I am interested in your comments on dynamic circuit switching as I have been working in this area and view that these systems are the only ones that can scale to infinity. I have been working on a layer 4 technology that will solve the problems of layer 3. Please see my site: www.fluidnetworking.net.
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dtutelman
117 Comments
Re: Dynamic circuit switching is really old
I pretty much agree, based on studies my group did in the 1970s.
If you're interested in the origins of Label-Switched Paths and hardware packet switches, A.G. (Sandy) Fraser invented Datakit at Bell Labs in the early 1970s. Different protocol and shorter packets and, of course, smaller and slower because of technology and lower demand. But all the fundamental concepts were there.
Dave Tutelman
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