Guy Kewney  01-04-2006
03:07 PM ET (US)
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Gosh. Do you know anybody who can talk to me about that? Just a name or a phone number would do to guy dot kewney at gmail dot com
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AH
01-02-2006
12:06 PM ET (US)
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If anyone is still reading this thread, Newmarket has now been "rewired".
This was not due to any problems with the Locust mesh systen, which is superb (IMO) but the way it had been installed by the provider, massively unrealistic expectations set by the provider which were never able to be realised.
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Guy Kewney 11-09-2004
05:47 PM ET (US)
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I shall give it a nudge, and find out...
:-)
Nice to see you back...
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PhilT 11-09-2004
10:19 AM ET (US)
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How did it all pan out in the end then ?
My contention point was that N businesses supplied over a 1M leased line will see more contention in practice than the same number of businesses on 20:1 contended ADSL from BT.
If there is a 1M line only one person can get 1M, and then with no other traffic. Add one guy streaming radio and nobody can get 1M. On a BT exchange there is say 10M of backhaul serving the 20:1 users, so you can have 10 people getting their full 1M worth before the 11th guy slows everyone down a bit.
The contention may be the same at 20:1, but the probability of seeing that contention rises exponentially as the service supplied approaches the backhaul capacity.
Phil
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Guy Kewney 10-21-2003
06:37 AM ET (US)
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I think the problem is exactly as your link says; lack of professionalism. The question of "community broadband" doesn't have to imply a bunch of amateurs waiting for each other to do it, and I think Comtralis is worth a closer look, frankly. It's using a community mesh, yes; but it's offering a professional service.
As to the contention, well... we'll see. I was talking with someone who used to install switch gear for BT (he worked for Marconi) and he has a very, very good knowledge of how they manage contention.
According to him, there's substantially no difference between the way they manage contention at 50:1 and 20:1 and when the lines get busy, they'll have to re-configure their system. I found his argument pretty compelling.
But until both networks are running at full chat, it's pointless hand-waving to speculate on which will run out of steam first.
For what it's worth, my DSL service is already showing signs of heavy contention; I can no longer stream 128 kbit internet radio except off peak. Spending a little while doing streaming benchmarks shows that my DSL throughput hovers around the 350 kbit mark and frequently drops below 200K - and every now and then, gives me 60K or so.
Not sure about your point about local networking. For example, in Newmarket, the vet will be using a VPN tunnel back through the mesh from Tattersalls, to the surgery LAN. No need to go back through the Internet for that. Then there's VoIP calling locally...
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Andrew Glossop
10-20-2003
03:27 AM ET (US)
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What you've said about BT's method is basically correct.
Really all I'm saying is that you will see the effects of contention far sooner than BT's customers will. It is generally accepted that BT's current 50:1 contention ratio will be unworkable when the number of customers and bandwidth usage grows.
You might find this interesting:
http://bbs.adslguide.org.uk/showthreaded.p...essbb&Number=934842
Personally speaking, unless you want to P2P with you neighbour, bandwidth "inside the mesh" isn't going to be a lot of use.
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Guy Kewney 10-19-2003
06:45 PM ET (US)
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As to whether Comtralis's claim to be "number one" is right or wrong, is up for debate, of course!
:-)
As to the performance of broadband, it's an area I'm happy to admit I'm no expert in. Nor, I think, do many people understand the way it works.
Yes, I'm pretty sure that /m4 is right, and Zen would have to have bandwidth enough in their own network to cover all their customers logging in at full speed simultaneously. That can happen!
What is less clear, is that it will happen as a rule, any more than on any other broadband network. Here's how I understand it (correct me if I have it badly wrong!)
1) BT provides a link from you, the ADSL customer, to its exchange. That goes into a DSLAM, the access module that takes your data and feeds it back into the network.
2) The Internet connection from the DSLAM is, for our purposes, unmeasurable unless we have access to BT's ATM network logs. It is assumed to be "sufficient" and BT has promised to ensure that it is.
3) BT routes your data link from its DSLAM to your ISP - say, Zen. When it gets to Zen, Zen has to be able to accept the data at the rate guaranteed by its contract with you, and it has to be able to feed it back at contract rate, too. If it has five customers with a one megabit service, it has to be able to cope with five megabits in its own network and forward it on to the next hop.
4) However, the link into the DSLAM is shared. Business lines are (typically) shared with 19 other users; home lines with 49 other users. There are also 7:1 contention ratios available.
5) In these early days for broadband, most people don't use their broadband most of the time. But already, there are starting to be issues. Some stream music at 48K for hours at a time; they'd rate as "heavy" data users. You can work out that this uses about 10% of your share of the DSLAM's capacity; that means that if ten of you are using it for this purpose, you've used up all your group's download capacity. There are, however, 50 of you on home, and 20 of you on the typical business contention group...
To me, it means that if you have about a megabit per second, and you share it with 20 people, then ordinary Web access is going to work quite well. But if several of you start using big chunks of bandwidth continuously, it falls apart.
The advantage of the Mesh approach is that all traffic inside the Mesh is free. It isn't contended at all, except for the mesh overhead, which is small; the more nodes you have, the more bandwidth you have between members of the mesh.
Thoughts?
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Andrew Glossop
10-19-2003
02:48 PM ET (US)
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FirstNet have the odd 1 or 2 customers.
Mesh have a few too (and taken over Invisible's business)
Also there's several "community" wireless broadband systems, who have more than 50 customers.
On that basis, can you still claim Comtralis to be No 1
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Andrew Glossop
10-19-2003
02:46 PM ET (US)
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Contention is quoted as 20:1, but you would never expect to actually receive only 1/20 of the service you pay for.
As an example, ZEN state that they provision for 100% of their customers bandwidth. That's how they can sustain high speeds.
OK, when tings are busier, contention will be a factor, not it's not affecting anyone on ADSL yet.
With only 1Mb leased line backhaul, you will get unhappy customers.
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Guy Kewney 10-19-2003
02:23 PM ET (US)
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I'm not sure I follow your maths.
Yes, the businesses would install their own DSL line - and indeed, they might ask for a megabit! - but the contention ratio on a DSL line (business rate) is 20:1 not 1:1 as is the case over a leased line.
At 25:1 contention ratio, I'd have thought the typical customer will get a very similar service. Or am I missing an important factor?
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PhilT 10-19-2003
11:21 AM ET (US)
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Well Newmarket isn't exactly rural, though it has taken them forever to get to the same trigger as we had for a cluster of 5 villages. (Newmarket used to have a Digital - DEC - office and has a number of other Cambridge type businesses).
BT will be providing ADSL in Newmarket from early January 2004. I believe it is an untruth to say that BT has ruled out providing ADSL in any specific town - the recent "unviables" will be subject to continuing review.
If BT were to rule out provision it would make it easier for wireless providers to move in, however "25 businesses sharing a 1Mb leased line" sounds like a crime rather than a service :)
If that's his viable business model I look forward to hearing what the customers think of it. They would probably install a 1 Mb/s ADSL line *each* so sharing should be fun.
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Guy Kewney 10-17-2003
03:29 PM ET (US)
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Now that Invisible Networks has vanished, is Comtralis the UK's biggest provider of rural broadband over WiFi?
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