Apart from UWB, I'm not sure that any of the technologies that increase bandwidth are incompatible with 'current spectrum usage'- you can always allocate some spectrum for these techniques.
I don't really believe that UWB can increase bandwidth.
Re:Universal expansion doesn't mean *we* expand!
on
The Big Rip
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· Score: 1
Any reasonably dense collection of matter (like a planet, our solar system, and our galaxy) is gravitationally bound and stays together... Shame on New Scientist.
Uh. No.
As the expansion rate increases, the size of the observable universe shrinks i.e. the point of the universe that is moving away faster than the speed of light comes ever closer.
Once the Sun 'falls' over that edge- you are no longer gravitationally bound to the Sun.
Finally the 'observable' universe is smaller than a nucleus; then it's game over.
Re:so, in other words....
on
World of Ends
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· Score: 1
There might be. It could be as simple as a single bitflag for "normal/fast". We'll never know unless we try.
It's not as simple as that though; otherwise I would hack my protocol stack to stick 'fast' on all my packets. My ftp downloads will fly;-).
No. The only solution is to have some way of rationing of fast packets. I suspect a good way would be for the ISP to allow a certain percentage of your packets to be 'fast'. For example, allowing no more than the contention ratio of your pipe to be fast; either up or downstream. That way if you're rich- you buy a better contention ratio, and you can run all of your packets fast.
One problem is what happens if somebody with a low ration of packets is talking to somebody with a high ration. Do you allow a 500kBit/s fat pipe to connect to a 50kBit/s thin, that is burstable to 500kBit/s? I think the answer is no- any packets that are above 50kBit/s should have been sent 'slow' and so would be thrown away by the ISP (I did consider dropping the priority down, but by the time it reaches the ISP, it has already used up the bandwidth of the ISP, but chucking packets away causes the sender to slow down due to the anticongestion algorithms in the IP protocol). The upstream guy with the 500kBit/s pipe should send 50kBit/s 'fast' and the other 450kBits/s 'slow' to avoid this problem. This would introduce problems to some protocols in some cases, but atleast there is a floor to the number of bits/second that can be carried, and both ends should be able to negotiate before they start.
I think that this article ignores the fact that bandwidth is not an unlimited resource.
I'm not sure I agree; well technically you're right of course. But the amount of bandwidth on the internet available for each of us is growing exponentially. Beyond a certain point, there ought to be so much bandwidth sloshing around that nobody can easily use it all. Which isn't to say we won't try;-)
This especially applies to the airwaves. While new technologies (e.g. wireless mesh, ultrawideband, etc.) promise to deliver massively more bandwidth/MHz than the old analog broadcast methods, that doesn't necessarily mean that we have the right to summarily revoke the incumbant telco/broadcasters' rights to use their alloted spectrum without interference.
Yes. Well, they've paid for it. You can't take it away without compensation. I don't think you could take it away legally or morally.
These companies deserve to at least be compensated for the massive amounts of money they spend secureing their specturm licences, and for the infrastructure improvements they're going to have to make to take advantage of the new technologies.
No. I definitely don't agree with this. I mean look at WiFi, nobody paid for the WiFi bandwidth. The users pay for the equipment; and that pays for the R&D. Everyone wins.
Unless you are saying that because of techniques like WiFi, other data carriers should be given a huge compensation from the government? If so- you're nuts.
When the vessel approaches a planet, e.g. the moon, it speeds up, then it travels with very high speed around it, like a slingshot - but: When it leaves the orbit, it gets slower again until it reaches the original speed.
That's true in a 2 body scenario. But there are more options in a 3 body situation.
You write: "least energy" - so, where does this energy come from?
You arrange for the energy to be dumped/removed from some other body.
For example, if a satellite was reentering the earth-moon system, it can arrange for the moon's gravity to suck away some of the kinetic energy it has by going behind the moon; relative to the earth the satellite would have lost energy- and the moon would have gained energy.
Re:assume it is true...
on
The Big Rip
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· Score: 1
The universe being ripped apart would leave what in its place?
It's kind of like the universe would consist of lots of fundamental particles like electrons, photons and so forth, individually being dragged apart by the expanding space; so there's no way they could ever meet.
Perhaps the resulting emptiness could then undergo another big bang and create yet another universe? Wouldn't that be neat.
Yeah, that's probably possible, or atleast there are theorists that claim that this may already happen; in blackholes for example.
Or not. I guess we'll never know!
Maybe we can tell, by studying the universe closely enough we may be able to work out the rules, and if the rules allow subuniverses we may be able to experimentally show it happening.
Re:Don't Panic!
on
The Big Rip
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· Score: 4, Funny
so I take it like all such with a grain of salt.
Yes, a large one; and getting larger all the time;-)
I'll be very impressed if they invent a machine which can repeatably toss pancakes. There are an awful lot of variables, which he seems to ignore. But then he is a physicist, not an engineer.;-)
Yeah, but that means he will be more accurate by roughly 5% because he won't be assuming that pi is 'nearly' 3;-)
Well, nickel-iron asteroids are about 80% solid metal. That doesn't need a whole lot of treating to separate.
(I think) You've missed the point of the original post - it still needs to be treated. The fact it is more concentrated makes the economic return greater, but it doesn't (usually) change the treatment process, or negate the need for it.
Nickel iron material might be useable if you just melt down the material- the raw metal should just run out. High temperatures are easily available using solar furnaces. Then pour into a mold.
In the case of aluminium (I'm not from the US so don't try and correct my spelling on that one!), extraction and purification requires a lot of water, which is something of a problem on the moon.
It's unclear that this is necessarily so, although that is the technique used on earth. There are other possibilities, such as possibly the carbothermal process. The carbon can be largely recycled; but there is some carbon on the moon anyway.
This article demanding a troll because/.'ers don't understand mineral industries is becoming as challenging as dynamiting fish in a barrel.
Yeah? The thing you've failed to consider is that:
a) there's a market for materials in LEO (particularly propellent)
b) the cost of any material in LEO currently starts at $2600/kg, even water, due to transport costs. With that kind of markup; even if the material was 100x more costly to mine off-earth, it's still going to be worth doing off-earth mining.
c) the transport cost of moving materials from elsewhere to LEO is likely to be very much lower than that.
d) therefore the likely cost of materials has little to do with how much they cost to mine and purify. Certainly mining would be different, and possibly more difficult in space and on the moon, but it's not going to be hundreds of times more difficult and expensive.
Oh yeah, we are going to centrifuge solids. Get a clue, that works with fluids (liquids and gasses).
Get a clue back again. It also works on solids. Why on (or off!) earth wouldn't it?
only those that pick a minute sulfide grain in a large matrix show any significant concentration of gold or PGEs.
Yes, but the concentrations are higher than found on earth as I understand it. It's probably not worth it enough on it's own, but if you are mining anyway, it might well be worth doing as a sideline.
How can you convince someone who thinks they have an engineering background based upon watching too much deeply deluded TV pseudo-science.
I don't know, I'm an engineer. My question is how you can convince someone that knows about earth mining, that they don't know anything about the off-earth mining? Because nobody is an expert anyway in this area, because it has never been done; yet.
Extraterrestrial mining will not be economical under foreseeable conditions.
You're not very good at this foreseeing lark I think.
Mineral resources require extensive treatment to recover anything of value.
Well, nickel-iron asteroids are about 80% solid metal. That doesn't need a whole lot of treating to separate.
For instance, we mine gold that goes 0.04 onces per ton.
Some other metals (gold, and particularly platinum group metals that sell at $400/oz) are known to be particularly rich in asteroids; far richer than on the earth.
Second, you have to crush it, requiring energy and large mechanical equipment. Ever seen a rod mill? Oh yeah, the rods rely upon weight -- gravity -- to have the force to crush rock.
Amazing that. The rods float up into the sky cos they are incredibly light, apparently, and then somehow become incredibly heavy and destroy rocks all over the place. On the moon you just have to lift it higher. In zero gravity, I don't know off hand, springs, or electric motors, or even a large centrifuge where you just 'drop' the rocks would work.
Or you could set up a shaker table and hope gravity seperation is effective.
It's pretty much bound to be. If it isn't because of the moons low gravity, you can always build a centrifuge.
The moon also lacks active geology, which is responsible for most of the concentration processes that for economic ore on earth.
Yeah, actually the moon wouldn't be my first choice to mine. Still, it's got quite a bit of aluminum and iron, and they are very useful. But there are advantages of being on the moon though. For one thing solar energy is available for 2 weeks straight; there's no weather and creating high temperatures are pretty straightforward in a vacuum. Some processes that are difficult/expensive on the earth are likely to be cheaper on the moon (like fractionally distilling off iron oxide for example).
There's one thing that is probably on the moon that is very useful however- ice! Steam is an adequate fuel for going to and from mars in fact, and for taxiing around in low earth orbit. If ice can be mined- it's probably worth $2000/kg in LEO.
But I actually think asteroids are a better bet for mining. Solar furnaces can run 24x7 at an asteroid; and the nickel-irons are kinda tasty looking.
I remember reading once that even if the moon were made of solid gold, any mining effort would still lose quite a bit of money due to tremendous launch/return costs that are between $7000 and $20000 per pound.
Yeah, I'd heard that. It's complete bullshit of course. You wouldn't build a rocket, send it to the moon mine the moon and then return in the rocket all the way back to the earth's surface.
No, you'd go to the moon with a load of equipment, mine it for whatever, AND rocket fuel. Launch the ore from the surface and then use the rocket fuel to put it on a reentry trajectory to the earth. The fuel cost is tiny for that, but then burn some more fuel to return the ferry vehicle back to the moon for more ore.
You get a continuous stream of ore returning to the earth- if the moon really did have a lots of gold, you'd make an enormous profit.
My mail servers collectively move about 500,000 messages a day. The most scarce resources is # of processes and # of connections. If I deliberately throttle any of them by any noticeable amount, I'm going to double or triple my requirement for those resources.
Not necessarily. For those IPs you are throttling, you can restrict the number of processes you allocate and send a 'try again later' message to any beyond that.
Your relay spammer will never notice that you're throttleing him. You'll throttle the relay he's abusing, but so what?
The point is that the relay has limited resources; by holding the connection open you are helping to DOS the relay. If the relay is DOSed then the spammer may not be able to use it at all, it won't accept any more mail if its disk is full or it has run out of processes; and in any case the quantity of spam carried by it will go down. The relay is unlikely to be engineered for a high number of connections; so this strategy is likely to help.
So, by throttling you're setting up a situation where he'll open one connection for each message he wants to send and sit there like that until you're done throttling him.
Yes, but *you* control how many connections *you* accept from any one source.
Your modern direct-spammer uses optimizing software which adds parallel connections to the limit of his bandwidth. He wants to push the maximum amount out before his account gets canned. Check your logs for the direct-spammer. His message already arrives slowly because he's saturating his link.
The idea is that *you* get less spam because you throttle it way back. If it hurts the spammers; that's great, but that's not the primary idea. As more people use these techniques, that changes the payback equation to the point where it isn't worth it to spam anymore.
Re:Not quite Re:but still not effectively because.
on
Wireless Mesh Networks
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· Score: 1
Yes, but: 'In contrast, wireless mesh networks are multihop systems in which devices assist each other in transmitting packets through the network, especially in adverse conditions. You can drop these ad-hoc networks into place with minimal preparation, and they provide a reliable, flexible system that can be extended to thousands of devices.'
We're clearly talking about 'wireless mesh networks' in general not the subset of: "
ad hoc 802.11b/a"
How do you propose this whisper?
Physically, it's 'merely' a question of minimising the transmitter power when transmitting a packet.
However, as you say all of this would have to be factored into the routing and of course this implies that the nodes have to occasionally do a search for all the nodes it is within range of and update the routing tables accordingly in its self and its neighbours.
Ideally, each node would have electronically steerable antennas; and multiple antennas, and filtering to make use of multipath. The more sophisticated the nodes are, the more bandwidth there is.
I might be missing something here, but isn't "lots of parallel connections" about as inconspicuous as an elephant amont kittens?
The multiple connections won't typically be attached to your server, they'll usually be scattered all over the internet- you'd have to correlate across the internet to count the connections. Tricky...
Re:Not quite Re:but still not effectively because.
on
Wireless Mesh Networks
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· Score: 1
How? When c = maximum capacity per radio, c+c+c > 3c?
Consider 4 nodes, A, B, C, D in a line.
Now D can talk direct to A direct by maxing out it's power and shouting over nodes B and C. But if it does that then A's conversation with B, gets drowned out, likewise B and C, and C and D, because they go momentarily deaf with all the shouting.
If instead D whispers to C, C whispers to B, B whispers to A, then the other conversations aren't affected. The overall bandwidth is 3 links, whereas if you just shout all the time, the bandwidth is one link shared between everyone. (I'm glossing over some complications, but that's the basic idea).
Not quite Re:but still not effectively because...
on
Wireless Mesh Networks
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· Score: 1
and each hop increases the bandwidth used. In contested, quite limited spectrum.
No, that's not so. Each hop increases the bandwidth, not the bandwidth used. This is so because each node can whisper to the node next door rather than shout and take up everyone's bandwidth. The bandwidth scales UP with the number of nodes; since you then have multiple independent ways to route from A-B through the mesh.
There is fundamentally only so much bandwidth in the air, and it is not enough to support ubiquitous wireless use.
No. Actually the bandwidth is not finite. In fact it scales up proportional to the number of nodes if the nodes are reasonably smart.
The idea of a fixed pie of bandwidth is based on the Shannon limit and the idea that radio waves go infinite distance.
In real life the radio waves get absorbed, attenuate with distance and the Shannon limit only applies between any two nodes in the network- it does not represent a fundamental limit for the network.
It's a bit like sound in an office. If there's lots of walls around the sound gets absorbed and everyone can talk to each other and pass messages around.
The failure here seems to be not appreciating that people will all want to connect to certain nodes, as they supply the (wired) bandwidth.
Yeah, but that's a problem we have already on the internet, and the protocols already divide the bandwidth up fairly.
And if the cells get smaller, the amount of routing hops increases
Yeah, but not much. The number of hops goes up with the square root of the number of nodes; so a network with a thousand nodes has 30 hops; and that's a huge wireless network. 30 hops might be a lag of 60ms.
All this will accomplish is to tie up resources on YOUR mail server.
The spammer already IS tying up 30-50% of the resources on the mail server; if you throttle the bastards back they'll end up using less. What would you prefer a few hundred megs of spam on your hard disk or a few kilobytes of spam that trickled in over a few days till they eventually kill the run. This way you save both bandwidth AND disk space.
Either they use their own server, in which case they're easy to spot. Or they use someone else's- in which case chances are, it isn't engineered for lots of parallel connections.
Yes, the big issue isn't the fusion reactor itself (although a half life of 37 years is problematic because it tends to be radioactive enough to be an issue, and can remain significantly radioactive even 100 years later.)
No, the big issue is the fissioning of the lithium. That's the dirty step- and the fission reactors are rather more awkward.
Patents are a tool for creating temporary, artificial monopolies.
Yeah, I agree. Still not all monopolies are bad; I guess it depends on the character of the company that has the monopoly; or what they do with it, or don't do with it. In the US, monopolies aren't illegal, although some of the freedoms that you have if you aren't a monopoly are removed. This seemed to upset Microsoft no end: "we've done nothing wrong, we aren't really a monopoly. Yeah right. Or actually, no, wrong.
...aren't even those examples better than fission?
Not really. The hazards are about identical- the lithium reactor can still melt down, the fusion reactors certainly become radioactive in and of themselves, and have a finite life due to radiation damage. It's not clean, it may very well not be cheap either.
The tritium-tritium reaction is a different beast though; that's potentially pretty clean, and pretty safe- no fission reactors need be involved. But very much more difficult to ignite.
Slashdot Mirror
I don't really believe that UWB can increase bandwidth.
Uh. No.
As the expansion rate increases, the size of the observable universe shrinks i.e. the point of the universe that is moving away faster than the speed of light comes ever closer.
Once the Sun 'falls' over that edge- you are no longer gravitationally bound to the Sun.
Finally the 'observable' universe is smaller than a nucleus; then it's game over.
It's not as simple as that though; otherwise I would hack my protocol stack to stick 'fast' on all my packets. My ftp downloads will fly ;-).
No. The only solution is to have some way of rationing of fast packets. I suspect a good way would be for the ISP to allow a certain percentage of your packets to be 'fast'. For example, allowing no more than the contention ratio of your pipe to be fast; either up or downstream. That way if you're rich- you buy a better contention ratio, and you can run all of your packets fast.
One problem is what happens if somebody with a low ration of packets is talking to somebody with a high ration. Do you allow a 500kBit/s fat pipe to connect to a 50kBit/s thin, that is burstable to 500kBit/s? I think the answer is no- any packets that are above 50kBit/s should have been sent 'slow' and so would be thrown away by the ISP (I did consider dropping the priority down, but by the time it reaches the ISP, it has already used up the bandwidth of the ISP, but chucking packets away causes the sender to slow down due to the anticongestion algorithms in the IP protocol). The upstream guy with the 500kBit/s pipe should send 50kBit/s 'fast' and the other 450kBits/s 'slow' to avoid this problem. This would introduce problems to some protocols in some cases, but atleast there is a floor to the number of bits/second that can be carried, and both ends should be able to negotiate before they start.
I'm not sure I agree; well technically you're right of course. But the amount of bandwidth on the internet available for each of us is growing exponentially. Beyond a certain point, there ought to be so much bandwidth sloshing around that nobody can easily use it all. Which isn't to say we won't try ;-)
This especially applies to the airwaves. While new technologies (e.g. wireless mesh, ultrawideband, etc.) promise to deliver massively more bandwidth/MHz than the old analog broadcast methods, that doesn't necessarily mean that we have the right to summarily revoke the incumbant telco/broadcasters' rights to use their alloted spectrum without interference.
Yes. Well, they've paid for it. You can't take it away without compensation. I don't think you could take it away legally or morally.
These companies deserve to at least be compensated for the massive amounts of money they spend secureing their specturm licences, and for the infrastructure improvements they're going to have to make to take advantage of the new technologies.
No. I definitely don't agree with this. I mean look at WiFi, nobody paid for the WiFi bandwidth. The users pay for the equipment; and that pays for the R&D. Everyone wins.
Unless you are saying that because of techniques like WiFi, other data carriers should be given a huge compensation from the government? If so- you're nuts.
That's true in a 2 body scenario. But there are more options in a 3 body situation.
You write: "least energy" - so, where does this energy come from?
You arrange for the energy to be dumped/removed from some other body.
For example, if a satellite was reentering the earth-moon system, it can arrange for the moon's gravity to suck away some of the kinetic energy it has by going behind the moon; relative to the earth the satellite would have lost energy- and the moon would have gained energy.
It's kind of like the universe would consist of lots of fundamental particles like electrons, photons and so forth, individually being dragged apart by the expanding space; so there's no way they could ever meet.
Perhaps the resulting emptiness could then undergo another big bang and create yet another universe? Wouldn't that be neat.
Yeah, that's probably possible, or atleast there are theorists that claim that this may already happen; in blackholes for example.
Or not. I guess we'll never know!
Maybe we can tell, by studying the universe closely enough we may be able to work out the rules, and if the rules allow subuniverses we may be able to experimentally show it happening.
Yes, a large one; and getting larger all the time ;-)
Um. Actually...
The space elevator is only feesible in the minds of those who have read TOO MUCH Heinlein.
Heinlein? Not as far as I know. Clarke, yes.
Yeah, but that means he will be more accurate by roughly 5% because he won't be assuming that pi is 'nearly' 3 ;-)
(I think) You've missed the point of the original post - it still needs to be treated. The fact it is more concentrated makes the economic return greater, but it doesn't (usually) change the treatment process, or negate the need for it.
Nickel iron material might be useable if you just melt down the material- the raw metal should just run out. High temperatures are easily available using solar furnaces. Then pour into a mold.
In the case of aluminium (I'm not from the US so don't try and correct my spelling on that one!), extraction and purification requires a lot of water, which is something of a problem on the moon.
It's unclear that this is necessarily so, although that is the technique used on earth. There are other possibilities, such as possibly the carbothermal process. The carbon can be largely recycled; but there is some carbon on the moon anyway.
Yeah? The thing you've failed to consider is that:
a) there's a market for materials in LEO (particularly propellent)
b) the cost of any material in LEO currently starts at $2600/kg, even water, due to transport costs. With that kind of markup; even if the material was 100x more costly to mine off-earth, it's still going to be worth doing off-earth mining.
c) the transport cost of moving materials from elsewhere to LEO is likely to be very much lower than that.
d) therefore the likely cost of materials has little to do with how much they cost to mine and purify. Certainly mining would be different, and possibly more difficult in space and on the moon, but it's not going to be hundreds of times more difficult and expensive.
Oh yeah, we are going to centrifuge solids. Get a clue, that works with fluids (liquids and gasses).
Get a clue back again. It also works on solids. Why on (or off!) earth wouldn't it?
only those that pick a minute sulfide grain in a large matrix show any significant concentration of gold or PGEs.
Yes, but the concentrations are higher than found on earth as I understand it. It's probably not worth it enough on it's own, but if you are mining anyway, it might well be worth doing as a sideline.
How can you convince someone who thinks they have an engineering background based upon watching too much deeply deluded TV pseudo-science.
I don't know, I'm an engineer. My question is how you can convince someone that knows about earth mining, that they don't know anything about the off-earth mining? Because nobody is an expert anyway in this area, because it has never been done; yet.
You're not very good at this foreseeing lark I think.
Mineral resources require extensive treatment to recover anything of value.
Well, nickel-iron asteroids are about 80% solid metal. That doesn't need a whole lot of treating to separate.
For instance, we mine gold that goes 0.04 onces per ton.
Some other metals (gold, and particularly platinum group metals that sell at $400/oz) are known to be particularly rich in asteroids; far richer than on the earth.
Second, you have to crush it, requiring energy and large mechanical equipment. Ever seen a rod mill? Oh yeah, the rods rely upon weight -- gravity -- to have the force to crush rock.
Amazing that. The rods float up into the sky cos they are incredibly light, apparently, and then somehow become incredibly heavy and destroy rocks all over the place. On the moon you just have to lift it higher. In zero gravity, I don't know off hand, springs, or electric motors, or even a large centrifuge where you just 'drop' the rocks would work.
Or you could set up a shaker table and hope gravity seperation is effective.
It's pretty much bound to be. If it isn't because of the moons low gravity, you can always build a centrifuge.
The moon also lacks active geology, which is responsible for most of the concentration processes that for economic ore on earth.
Yeah, actually the moon wouldn't be my first choice to mine. Still, it's got quite a bit of aluminum and iron, and they are very useful. But there are advantages of being on the moon though. For one thing solar energy is available for 2 weeks straight; there's no weather and creating high temperatures are pretty straightforward in a vacuum. Some processes that are difficult/expensive on the earth are likely to be cheaper on the moon (like fractionally distilling off iron oxide for example).
There's one thing that is probably on the moon that is very useful however- ice! Steam is an adequate fuel for going to and from mars in fact, and for taxiing around in low earth orbit. If ice can be mined- it's probably worth $2000/kg in LEO.
But I actually think asteroids are a better bet for mining. Solar furnaces can run 24x7 at an asteroid; and the nickel-irons are kinda tasty looking.
Yeah, I'd heard that. It's complete bullshit of course. You wouldn't build a rocket, send it to the moon mine the moon and then return in the rocket all the way back to the earth's surface.
No, you'd go to the moon with a load of equipment, mine it for whatever, AND rocket fuel. Launch the ore from the surface and then use the rocket fuel to put it on a reentry trajectory to the earth. The fuel cost is tiny for that, but then burn some more fuel to return the ferry vehicle back to the moon for more ore.
You get a continuous stream of ore returning to the earth- if the moon really did have a lots of gold, you'd make an enormous profit.
Not necessarily. For those IPs you are throttling, you can restrict the number of processes you allocate and send a 'try again later' message to any beyond that.
Your relay spammer will never notice that you're throttleing him. You'll throttle the relay he's abusing, but so what?
The point is that the relay has limited resources; by holding the connection open you are helping to DOS the relay. If the relay is DOSed then the spammer may not be able to use it at all, it won't accept any more mail if its disk is full or it has run out of processes; and in any case the quantity of spam carried by it will go down. The relay is unlikely to be engineered for a high number of connections; so this strategy is likely to help.
So, by throttling you're setting up a situation where he'll open one connection for each message he wants to send and sit there like that until you're done throttling him.
Yes, but *you* control how many connections *you* accept from any one source.
Your modern direct-spammer uses optimizing software which adds parallel connections to the limit of his bandwidth. He wants to push the maximum amount out before his account gets canned. Check your logs for the direct-spammer. His message already arrives slowly because he's saturating his link.
The idea is that *you* get less spam because you throttle it way back. If it hurts the spammers; that's great, but that's not the primary idea. As more people use these techniques, that changes the payback equation to the point where it isn't worth it to spam anymore.
We're clearly talking about 'wireless mesh networks' in general not the subset of: " ad hoc 802.11b/a"
How do you propose this whisper?
Physically, it's 'merely' a question of minimising the transmitter power when transmitting a packet.
However, as you say all of this would have to be factored into the routing and of course this implies that the nodes have to occasionally do a search for all the nodes it is within range of and update the routing tables accordingly in its self and its neighbours.
Ideally, each node would have electronically steerable antennas; and multiple antennas, and filtering to make use of multipath. The more sophisticated the nodes are, the more bandwidth there is.
The multiple connections won't typically be attached to your server, they'll usually be scattered all over the internet- you'd have to correlate across the internet to count the connections. Tricky...
Consider 4 nodes, A, B, C, D in a line.
Now D can talk direct to A direct by maxing out it's power and shouting over nodes B and C. But if it does that then A's conversation with B, gets drowned out, likewise B and C, and C and D, because they go momentarily deaf with all the shouting.
If instead D whispers to C, C whispers to B, B whispers to A, then the other conversations aren't affected. The overall bandwidth is 3 links, whereas if you just shout all the time, the bandwidth is one link shared between everyone. (I'm glossing over some complications, but that's the basic idea).
No, that's not so. Each hop increases the bandwidth, not the bandwidth used. This is so because each node can whisper to the node next door rather than shout and take up everyone's bandwidth. The bandwidth scales UP with the number of nodes; since you then have multiple independent ways to route from A-B through the mesh.
No. Actually the bandwidth is not finite. In fact it scales up proportional to the number of nodes if the nodes are reasonably smart.
The idea of a fixed pie of bandwidth is based on the Shannon limit and the idea that radio waves go infinite distance.
In real life the radio waves get absorbed, attenuate with distance and the Shannon limit only applies between any two nodes in the network- it does not represent a fundamental limit for the network.
It's a bit like sound in an office. If there's lots of walls around the sound gets absorbed and everyone can talk to each other and pass messages around.
The failure here seems to be not appreciating that people will all want to connect to certain nodes, as they supply the (wired) bandwidth.
Yeah, but that's a problem we have already on the internet, and the protocols already divide the bandwidth up fairly.
And if the cells get smaller, the amount of routing hops increases
Yeah, but not much. The number of hops goes up with the square root of the number of nodes; so a network with a thousand nodes has 30 hops; and that's a huge wireless network. 30 hops might be a lag of 60ms.
Thanks for informing us of this vital information Johan, we really appreciate it.
Cue a horde of morons saying otherwise.
No! Don't cue them... too late. What did you have to go and do that for Johan?
The spammer already IS tying up 30-50% of the resources on the mail server; if you throttle the bastards back they'll end up using less. What would you prefer a few hundred megs of spam on your hard disk or a few kilobytes of spam that trickled in over a few days till they eventually kill the run. This way you save both bandwidth AND disk space.
Either they use their own server, in which case they're easy to spot. Or they use someone else's- in which case chances are, it isn't engineered for lots of parallel connections.
This scheme may actually work.
Because they don't know the words?
No, it's because they're happy to be transformers.
No, the big issue is the fissioning of the lithium. That's the dirty step- and the fission reactors are rather more awkward.
Yeah, I agree. Still not all monopolies are bad; I guess it depends on the character of the company that has the monopoly; or what they do with it, or don't do with it. In the US, monopolies aren't illegal, although some of the freedoms that you have if you aren't a monopoly are removed. This seemed to upset Microsoft no end: "we've done nothing wrong, we aren't really a monopoly. Yeah right. Or actually, no, wrong.
Not really. The hazards are about identical- the lithium reactor can still melt down, the fusion reactors certainly become radioactive in and of themselves, and have a finite life due to radiation damage. It's not clean, it may very well not be cheap either.
The tritium-tritium reaction is a different beast though; that's potentially pretty clean, and pretty safe- no fission reactors need be involved. But very much more difficult to ignite.