Posts by Matthew Poole
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Benjamin F wrote:
wireless networking (ie 802.11n) can already transmit super fast speeds and is only going to get better
Ben, wireless isn't the answer. It's got several problems that don't afflict even copper connections, never mind fibre ones.
1) The latency is very average. For voice services, latency is everything. Wireless latency pushes the outer bounds for voice on a good connection, so if you've got a connection that's not so flash you can have problems. Latency in fibre is tiny, maybe 1/4 the speed of light. Copper is worse, and Telecom did its best for a long time to make DSL here absolutely crippling in terms of latency, but it's still better than wireless.
2) Wireless speeds are extremely theoretical. You might have a dot11n connection that says it can do 248Mb/s, but the typical data rate is more like 70Mb/s. That's a big difference, and a very significant problem. With terrestrial links, the theoretical maximum and the typical maximum are usually within 10%, mostly determined by the quality of the equipment in use. People have recorded transfer rates in excess of 900Mb/s on a 1000Mb/s connection. Wireless can't even get close, and almost certainly never will, because of the limitations associated with a shared, ethereal medium.
3) Wireless is shared bandwidth. The more people using a repeater, the less bandwidth available to everyone on that repeater. Thankfully the days of everyone on a repeater being dropped to the speed of the slowest client are gone, but the shared nature of the medium remain. Can't be resolved, either, because you can't physically separate wireless connections like you can with wired ones. With fibre, the full bandwidth of the connection is all yours between your device and the terminating device. -
Rich, that's interesting. Makes sense. The whole near-end cross-talk vs far-end cross-talk problem hadn't occurred to me, but it's a logical (and very significant) impediment to having "standard" and reverse-asymmetric DSL connections bonded to give a fast bi-di link. True symmetric DSL is very, very speed limited, with the "high speed" variant giving a hot 5.69Mb/s to a distance of 2.7km. Pretty lousy, really.
If we want to look beyond low speeds (10Mb/s is fast-ish now, but won't remain so for too much longer) we need to go fibre.
When Telecom was in the process of removing the downstream speed cap, there was a discussion on the NZ Network Operators' Group mailing list about the limitations that upstream speed imposes on downstream. Namely, a 128kb/s upstream will limit the usable downstream to about 4Mb/s for some types of TCP traffic because of the need to send acknowledgement packets. That problem persists at higher data rates, and there's only so much capacity available in the upstream before the downstream must be reduced to minimise cross-talk (as per that link you posted). Fibre has no such problem, even though consumer FTTH connections in the US are frequently installed with asymmetric upstream/downstream speeds to discourage running servers at home. That's purely an ISP policy decision, not a technical limitation as it is with DSL. -
Rich wrote:
Just a thought - it should be technically possible to have ADSL that favours upstream over downstream
Sure, it's "technically possible" to do that. But to the best of my knowledge there's no variant of DSL that actually does that. So you'd have to write the spec, test it, get it approved by IEEE, get someone to make the kit for the telco end, and get consumer equipment manufacturers to produce stuff that could use it. It's not just a matter of twiddling some settings, it's a whole new specification with all the attendant development work. Figure three-to-five years if you start tomorrow before it's actually possible to get it deployed into homes.
in which case you could have two phone lines, one for up and one for down
That'd work if you had equipment that could bond the links. Since a reverse-asymmetry variant of DSL would require completely new consumer kit, it would actually be fairly easy to cope with this concept in hardware. Then you'd just have to set things up on the ISP end to allow two links to be bonded, but link bonding is old hat now.
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Yes, employers are proving to be remarkably obtuse about the whole thing. Proper telecommuting setups are also a good business continuity plan in the event that H5N1 actually fully mutates into a human-human transmissible virus and the world gets struck by a flu pandemic. And if that doesn't eventuate, at some point there will be a pandemic, with consequent impacts on social interaction. Adequate facilities for staff to work from home will mitigate greatly the adverse economic fallout.
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The "we" of a direction set by our glorious elected representatives. AKA, the Polly Tubbies.
With all the bitching and griping and moaning about how terribly NZ does in the OECD, National cannot ignore this opportunity to actually improve our standing in some way. Labour's already said they want our ranking to shift, and National's agreed. Ergo, "we" have been told by the residents of the Beehive that this is something we want.
Personally, I, like you, don't much care about the OECD stuff I just want it to work at speeds and prices comparable to other countries.
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tussock: You said it far better than I ever could.
Rich: You seem to be quite confident of the quality of the copper that feeds most of NZ. Lots of people aren't, and for good reason. Also, you're still thinking small. You see 10Mb/s as the baseline, but where to from there? 10Mb/s isn't even particularly fast now, and by the time it's available to a large majority (80%+) of the population we'll be standing in the same place we are now, relative to the speeds available to the rest of the world.
Don't forget, we're trying to get into the top half of the OECD, and stay there! Which means we have to be running faster than the people who're a) already there, and b) not there but want to be. And we have to keep running faster, even if we make it there, because everyone else is running too. Saying that 10Mb/s is a perfectly acceptable speed, for now and for evermore, loses sight of the fact that we'd barely make it into the top half of the OECD now if we had 10Mb/s to every home. In a couple of years' time, we'd be back in the bottom half and we'd have lost that couple of years in which we could've been building an infrastructure that would let us keep delivering ever-faster speeds to consumers in the same way that our "competitors" are.You want some examples of things that we could do with FTTH, that are difficult now. OK, here's a couple. 1) Video-on-demand. That's where things are heading, and it's been observed more than once in the MSM in the last year that as things stand in NZ, it's not going to happen. Even 10Mb/s is pushing it, especially for high-def content. 2) Proper telecommuting. I'm not just talking about being able to fire up a Citrix session and use Word/Excel/Outlook, I'm talking about full-on video conferences, with multiple home-based participants, using quality cameras and without jerking or voice-sync issues. Can't do that currently, either, because our up-stream speeds are shit. They can't improve much with ADSL, either, because of that whole asymmetric thing.
So there's two examples, both here-and-now, and both really stretching the capabilities of even VDSL2 never mind ADSL or ADSL2+. Fibre has better latency, meaning that voice-based applications work better, and it scales beyond anything possible with copper. You seem to be fixated on us being "good enough" for "right now", but the Government (and National) have said that they want us in the top half of the OECD. That means being better than we are now, and if we want to stay there it means staying better than no fewer than 15 other countries who will also be trying to improve the services available.
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Why do people constantly require justification against today's concepts when faster 'net to the home is discussed? Seriously, who'd have thought of YouTube five years ago? It requires broadband as an enabler, and in the absence of that nobody was going to really think of it. There will be other ideas out there that just require someone to view it as viable before they try it out. You don't try ideas that are doomed to failure because the market is inaccessible.
The short version is, the ideas follow the technology. Cart, horse, etc. Demanding that the ideas be around to justify the technology is a nonsense.
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Rich said:
But wouldn't it be cheaper to make a clean copper connection the basic standard than to go to fibre?
*choke* You mean re-lay the copper to every home in the country? Buy tens-of-thousands of kilometres of high-quality copper wire and run it down every street, back-road and goat-track in the country? Can I please have some of what you're smoking?
Seriously, if you're going to do that you really should just future-proof and lay fibre. Fibre is dramatically cheaper than copper (in those kind of quantities, maybe 1/6th the cost of the equivalent quantity of copper), and the biggest argument against running FTTH is the cost of actually getting it to the end-user. If the plan is just to rip everything and start again anyway, then fibre would be the choice of all the people who make such decisions.
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Rich said:
Which begs the question, since one can get 24Mbit with current DSL copper technology, and VDSL2 is even faster, why do we need fibre to the home? Is this a subsidy for a small minority that want HDTV movies in the time in takes to make a cuppa?
Did you actually read anything more about VDSL2 than just the headline speed? Such as, maybe, VDSL2 deteriorates quickly from a theoretical maximum of 250 Mbit/s at 'source' to 100 Mbit/s at 0.5 km and 50 Mbit/s at 1 km, but degrades at a much slower rate from there, and still outperforms VDSL. Starting from 1.6 km its performance is equal to ADSL2+? Most NZers are a lot more than 1km from the exchange. Phonelines aren't run in a straight line, they're full of bends and joins and other things that both lengthen the run and lower the quality of the connection. Those speeds are very much reliant on a "clean" connection, and there aren't very many homes in NZ that actually have one. The copper's been spliced and joined and repaired and generally fucked with so much that in a lot of cases it struggles to give people even ADSL speeds never mind VDSL2.
Why does everyone assume that faster speeds are simply for downloading movies? What about graphics artists who work from home? Some of these small companies us DVDs to ship work to clients, because it's too damn slow to try and use what passes for "broadband" here. Some even send DVDs to the US, for crying out loud!
Also, copper has real limits. We keep pushing them out, but every increase in speed has shorter operating distances. Fibre runs at high speeds for the length of the connection, not diminishing with distance. Run FTTH and we could get "at source" VDSL2 speeds to everyone regardless of how far they are from the exchange. Even if they're high country farmers.Not to mention that while copper seems to be very versatile, I'm not convinced that fibre can be upgraded as easily. It certainly seems that any upgrade would need new subscriber equipment in every home in an area. I'm happy to be proved wrong on that, though?
And it doesn't require an upgrade of subscriber equipment for every new variant of DSL that comes out? You have to buy a new modem, usually, to go from ADSL to ADSL2 to ADSL2+ to VDSL, and so on. How is fibre any different? Plus, fibre's expansion capacity is virtually unlimited and over much longer distances. You can run 100Mb/s for certain over several km using fibre, but there's no way in hell to do that using copper. Also, if the roll-out is done with some foresight (yes, yes, I know, foresight in NZ telecommunications, I must be off my rocker), people could be attached with equipment capable of doing 1Gb/s right from the get-go. The cost is very, very similar to 100Mb/s (go have a look at the price of fibre-based network cards), and gives a lot of future-proofing.
Also, fibre termination doesn't change. Like you don't need to get new phone jacks in order to use new variants of DSL, you can continue to use existing fibre terminations if there are upgrades to the transmission equipment. In the same way that you can connect a 10Mb/s NIC to a Gig-E switch, and it'll work, you can plug an old fibre NIC into a higher-speed network. They just negotiate a common speed and run with it. I believe my home exchange has been upgraded to ADSL2+, but we're still using an ADSL router. Works fine. No upgrade required, but if I want higher speeds I'm going to have to fork out. No different to fibre.
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Jarno said:
For example, a million households at 100mb/s is roughly 100Tb/s of bandwidth. Currently the total capacity of the Southern Cross cable network is less than 1Tb/s.
I'm slightly concerned this is going to lead to giving everyone a super-duper driveway, connecting to the main dirtroad.
It doesn't work like that, though. At no point in the history of consumer Internet has the upstream pipe been even half the size of the sum of the connections it serves. If you're lucky, your ISP only over-subscribes the connection by 10:1, meaning for every 10Mb/s of connection speed they've sold to customers they have 1Mb/s of connection to their supplier. Suddenly your 100Tb/s is down to 10Tb/s, and that's if ISPs are over-sub'ing to a very, very low level. In reality the SCC could support 100Mb/s to every home in the country as it is now.
Why? Three reasons:
1) Not everyone will buy a connection that's actually 100Mb/s. Some will want only 10Mb/s, and pay correspondingly less for it. Far fewer users will want 100Mb/s than would be quite happy with 10 or 20.
2) Not everyone saturates their connection. In fact, very few people do. Even fewer saturate their connection constantly. The reason over-subscription is viable is that most users don't use most of their connection most of the time. They use a bit of their connection most of the time, a lot of their connection a little bit of the time, and all of their connection very infrequently. And the bigger the connection, the smaller the period of time in which they use most or all of it because they get the data so much quicker.
3) Akamai and other proxying services bring the content to NZ. You aren't connecting via the SCC to get stuff, you're just connecting to boxes on our shores, so the size of the SCC is irrelevant. Toss in peering, and there's actually a lot of content available without a single bit having to depart NZ. Fatter pipes encourage local content, which improves the ratio of domestic:international even further, encouraging more local content, rinse and repeat.