Yes, 1xEV-DO really is CDMA. The details are very different from IS-95 and CDMA 2000 1x because EV-DO was redesigned from the ground up specifically to carry IP rather than voice, but it still uses many of the same basic features as the voice CDMA systems.
Strictly speaking, even IS-95 is "true" CDMA only on the reverse (mobile to base station) link. Although the forward (base-to-mobile) link is spread spectrum, technically it's not CDMA because there's no "MA" (multiple access); the mobile only listens to one transmitter at a time. The other base stations on the same channel are just unwanted interference that spread spectrum helps suppress. (Soft handoff on the forward link isn't really multiple access either, because both base stations carry the same data stream.)
The 1xEV-DO reverse channel still has multiple users transmitting to the same base station on the same RF channel at the same time, so it's still CDMA.
You can think of the two receive antennas on the tower as something like a (very) simple 2-element phased array. Because the antennas are physically separated, they see slightly different versions of your mobile's randomly fading signal. Even if you fade out completely on one antenna, you may still be strong on the other. The receiver combines the signals from the two antennas and demodulates their sum, giving weight to the stronger of the two.
It's not a true phased array because the two signals are independently tracked and combined at baseband without regard to their individual RF carrier phases.
The cell transmitter uses a single antenna which is not steered. (Remember that it's transmitting to many users at the same time.) The system can, of course, switch you to a different cell site or to a different antenna on the same cell site if that will provide you with a better signal.
There's a lot of research currently going on into Multiple In, Multiple Out (MIMO) schemes in which an array of physically fixed antennas and receiver chains effectively synthesizes a set of phased arrays, one for each of several simultaneous incoming signals. Some serious heavy-duty DSP is required, but the potential is considerable. The big win comes in being able to construct each virtual phased array so as to null out all the transmitters but one, and to do that simultaneously for each of the incoming signals. This greatly increases the achievable signal-to-interference ratio, allowing the use of much higher data rates.
The exact numbers depend on circumstances. An isolated sector (one with no adjacent transmitters on the same RF channel) can use all of its traffic channels. But real-world sectors are usually immersed in a sea of interference from other cells. A typical number might be 25-30 simultaneous calls per sector per RF channel.
The other traffic channels are still available for soft and softer handoff. That's when two or more cells (or sectors within a cell) carry a single call simultaneously. The mobile combines the two cells' signals just as it would the multipath components from a single cell.
Also, the limits of the forward (base-to-mobile) and reverse (mobile-to-base) links may not be reached at the same time. CDMA 2000 1x introduced coherent modulation with a pilot on the reverse link, and this produced a significant improvement in real-world reverse link capacity.
That figure is a little misleading. 61 (not 62) is the number of available traffic channels per sector and per RF channel for the original mid-1990's IS-95 CDMA standard. The number 61 comes from having 64 Walsh code channels, minus three for overhead: pilot, sync and paging.
Sectorization refers to the practice, common with all cellular technologies, of dividing up the area around a cell site into regions, or sectors, each served by its own set of directional antennas. Three sector cells are extremely common; that's why so many towers have triangular platforms with a set of antennas on each side. There are usually three antennas on each side: one for transmit and two for receive, with the extra receive antenna providing spatial diversity.
Most CDMA cell sites in built-up areas have three (or six) sectors, operate on more than one 1.25 MHz RF channel, and use the newer CDMA 2000 1x standard. That can easily provide a total cell capacity of considerably more than 61 calls.
CDMA 2000 1x doubles the number of Walsh code channels (to 128) by adding a second set of traffic channels in quadrature to the original 64. Virtually all CDMA phones sold over the past few years do 1x.
Because of CDMA's inherent robustness, the same RF channel can be reused in adjacent cells and even adjacent sectors, greatly increasing the overall capacity of the spectrum in a given area. Because no careful frequency reuse plan is required, CDMA is also very well suited to the rapid deployment of cells in "hot spots" as described in this article.
Wrong. It is well established law that the US federal government, through the FCC, pre-empts all state and local regulation of the airwaves. It doesn't matter if a particular radio signal doesn't cross state borders; it still falls under exclusive federal jurisdiction.
So far this has actually been a Good Thing, as FCC pre-emption generally works to block local restrictions on radio communications that are almost always unnecessary, heavy-handed, misguided or in outright bad faith. Just ask any ham radio operator. This ruling shows that the FCC is still doing its job.
About 20 years ago, I remember an attempt by my local town council in New Jersey to effectively ban all private satellite TV dishes. The claimed reason was RF safety -- from receive-only antennas! But outside the hearing room, the town attorney told me a different story; they didn't want satellite TV taking business away from the local cable TV operation because said cable operation was a significant source of cash to the town in the form of franchise fees. Not long afterwards, the FCC squashed this sort of nonsense in no uncertain terms.
You are absolutely right. Congress screwed up big time in the 1996 Telecommunications act when they failed to realize that there is simply no way you can let a monopoly like a local telco into an unregulated business like DSL without said company thoroughly abusing its monopoly position against its competitors.
No amount of oversight can keep these abuses from happening. For a brief and shining moment, the US had a vibrant and competitive DSL market. Then almost overnight, it was pretty much just Covad and the local telcos. And I wonder how much longer Covad will be around.
Just look at how the telcos (and the cable companies for that matter) have managed to snow the FCC, the courts, the regulators, legislatures and the public with their propaganda that requiring them to provide competitive access to their wires is tantamount to socialism, and they'd have no incentive to improve their networks. Horse puckey! They might have a point if they were being required to provide access to their wires for free, but that ain't the case. Competitors are required to pay (often substantial) fees to use those wires. But the mere notion of being required to sell their wires to competitors is anathema to the phone and cable companies who are salivating at what they can do with their monopoly positions.
I see only two ways out. Municipalities could set up utility departments that would lay new wire and/or fiber along public rights of way and sell access on a nondiscriminatory basis. Or the telcos and cable companies could be required to divest their outside wire and cable plants into financially independent entitites banned from actually selling any switched services based on those wires. The outside plant companies would be required to market access to those wires, on a tariffed and non-discriminatory basis, to resellers who would compete in offering actual services to the public.
This is hardly a radical proposal, based as it is on a century of experience with common carrier regulation and antitrust law.
Well, if you want to cut off your own inbound email and create problems for people that you might actually want to hear from, that's your personal choice. I won't object.
What I do strenuously object to are ISPs who unilaterally make that choice for all their customers (or, in the case of an outbound port 25 block, for everyone else's customers) without giving the affected parties a choice in the matter. That is simply wrong.
If an individual user wants his ISP to filter on his behalf, that's fine. As long as it only applies to that user, and he retains control.
I also don't have a problem with blocking known spammers in response to recipient complaints, as long as there is due process, a chance to appeal, etc. That seems to be what Comcast is doing, but I fear it may change because this is just too rational and enlightened a policy for that outfit.
Okay, let's say the ISPs block outbound port 25. The spammers and virus authors will quickly adapt by routing their outbound traffic through the ISP's mail relay, and/or they will start trying port 587 in addition to port 25. (Port 587 is increasingly widely used for MUA->MTA SMTP traffic precisely to evade heavy-handed blocks on port 25, and many admins set it up to be functionally identical to port 25.)
Before you claim that the ISPs' mail relays can magically block all outbound viruses and spam, presumably by some method other than simply dropping most of the mail presented to it because of the resulting extreme overload, consider that virus authors are already morphing their viruses and spam frequently enough to evade these filters; encrypted zip archives are just the beginning.
So once again, how can this stop viruses and spam more effectively than receiver-side filtering? It can't. In fact, it makes things even worse because it deprives the remote targets of the ability to selectively blackhole the individual IP addresses of known spam sources. Since both spam and real mail all come from the same (or a small set) of IP addresses belonging to the ISP's mail relays, the targets are forced to either refuse all mail from that ISP, or accept it all and sort it out after receipt. Personally, I believe that spam and virus filtering can only be properly done by examining entire messages with something like a Bayesian filter, but I still wouldn't want to deny someone else the ability to blacklist the individual IP addresses of known major-league spammers.
The basic problem with those who advocate draconian anti-spam measures like blanket port blocking for spammers and non-spammers alike is that they never seem to learn from history. They never seem to realize that any benefit will be temporary but the collateral damage is permanent. When the cycle repeats, things get even worse.
It's a lot like the Bush Administration's approach to Iraq, now that I think about it.
Why would I want to do that? The main reason people like me run our own mail servers is to avoid having to rely on our ISPs' perenially overloaded and unreliable mail servers. A secondary reason is to be able to monitor and manage our own delivery queues. And yet another reason is to take advantage of the STARTTLS command to transparently encrypt each SMTP transfer.
Besides, direct end-to-end delivery is exactly how the Internet was designed to work. And no one has explained to me exactly how forcing everyone to relay their mail through their ISP's mail relay will somehow stop spam.
I suppose it may slow it down simply because the ISP's mail relay will be a single point of failure, underpowered and overloaded, and this will throttle or drop a good fraction of all the outbound mail from that ISP, spam or not.
What about those who don't have the luxury of access to a server in a co-lo?
And what if Comcast decides next that ordinary residential peons like you don't really need to use SSH, and unilaterally blocks port 22, even in the outbound direction? I mean, it's not like SSH is something Microsoft built into Windows XP, the only operating system in the universe that matters and people should be allowed to use. Unlike SSL, SSH isn't needed to buy stuff online from big companies, and we all know that's the only legitimate use of the Internet, right? Every other use of the net is potentially subversive, especially if it's encrypted, so what do you care if they block it?
I hope you can see where this port-blocking crap is leading. It's a very dangerous slippery slope, and it must be stopped now. I have no problem with selective port blocks made after due process in response to direct end-user complaints, but "proactive" blocking will ultimately destroy the Internet architecture and its usefulness without really solving the problems it claims to solve.
GPS One overcomes your first two problems by augmenting the GPS satellite signals with timing and data from local CDMA cells. It is possible to get accurate fixes inside buildings and in urban canyons where conventional 3- or 4- satellite GPS fixes would not be possible. This stuff is now being widely deployed in CDMA systems primarily to meet E911 requirements, but it will also be available for general positioning applications.
"Essentially zero"? How is that? Somebody has to route the lines through a filter and make the high-pass port available to the CLEC. It's certainly reasonable to let the telco recover that cost. The CLECs require space and power for their equipment. It's certainly reasonable to let the telco recover that cost.
What isn't reasonable is for a telco to charge wholesale prices to CLEC DSL providers that are higher than the retail prices for the telco's own DSL services, and/or to drag their feet in providing competitive access, yet this is exactly what the telcos routinely do. And they get away with it.
The old AT&T -- The Bell System -- was fully regulated for many years, yet they still spent a lot of money on "upgrading the lines". They even poured a lot of money into basic research at Bell Labs. Remember who invented the transistor?
Properly done, regulation still provides plenty of incentives for the regulated company to expand and improve its business.
Is a regulated monopoly more efficient and innovative than a true, competitive free market economy? Of course not, but that's an apples-vs-oranges comparison. If there were true competition in the provision of local transmission to my house, we wouldn't need much (if any) regulation. But while the local telcos would like us to believe otherwise, we just don't have that kind of free-market competition, at least not yet. And until we can get it, regulation will be a necessary evil.
The reason the 1996 act isn't working out is obvious to everybody but Congress and the lobbyists who pled with them not to be thrown into the briar patch.
The boundary lines were drawn in all the wrong places.
After a promising start, competition in the DSL market has nearly dried up because the local telcos that own the wires in the streets have absolutely no incentive to cooperate in good faith with CLECs that compete with the telcos' own DSL services. Look at how they always phrase the subject in public. They get indignant and act as if the government is trying to make them give away their wires to their competitors for free when that is not the case at all! Every CLEC pays the local telco for the use of their wires, and no one has ever suggested that they not.
If the boundary lines had been drawn where they belong -- right at the ends of the wires that run along public streets -- things would have turned out differently. The wires would be owned by a fully regulated entity that would be barred from any business other than renting access to those wires to any service provider able to pay a standard tariff. While they would still have an incentive to inflate their costs in order to inflate their tariffs, regulators have a lot of experience in scrutinizing the books of common carriers. And since the only part of the path that would be regulated are the actual wires, regulatory overhead would be kept to an absolute minimum.
Everything but the wires themselves would be the province of competitive, unregulated carriers that would set up the DSLAMs and routers and market their services to customers.
It's a simple and obvious way to do things, but this is not what Congress in its wisdom decided to do in 1996. Why is anybody surprised at how things turned out?
Solar radiation pressure is another factor. As you point out, very small objects have a high ratio of surface area to volume, so solar radiation pressure affects them greatly. Eventually their orbits are perturbed enough that they intersect the atmosphere and re-enter, or achieve escape velocities and go away.
A droplet of NaK, being a silvery metal that reflects photons, would experience twice the radiation pressure as a same-sized black object that absorbs photons. On the other hand, being liquid they assume spherical shapes that minimize surface area. I wonder what the net effect is on orbital lifetime.
I see what you mean. In this reference:
http://www.basf.com/inorganics/pdf/bulletin/NaK_bu lletin.pdf it says that eutectic NaK (78% K, 22% Na) is liquid from -12.6C to 785C. That's a pretty wide range that helps explain its utility as a reactor coolant, and it also suggests a pretty low vapor pressure. Oh well.
The article correctly emphasizes the hazard (from collisions) to orbiting spacecraft, and (correctly) says very little about the radiation hazard to us on the ground.
In no way will I excuse the extreme sloppiness of the Russians in all things nuclear, but the radiation hazard from these things has been greatly exaggerated to sell newspapers, books and TV spots. Several of these orbiting Soviet reactors failed to go into their disposal orbits and have already fallen back to earth -- and we're still here. Yes, you could say we were lucky that they fell in relatively remote areas. But most of the earth's surface is still sparsely populated (such as the 70% that's covered by water).
Another thing to remember about spent reactor fuel is that its radioactivity falls rapidly with time. While a reactor operates, a significant fraction of the generated power comes from the decay of short-lived fission products. This radioactive decay heat continues even after the chain reaction has been shut down; that's why emergency core cooling is so important in terrestrial reactors. Depending on the reactor design and the fuel, a few hundred years may be enough for its radioactivity to decay to that of the uranium ore from which it was originally made. This point is often lost in the shrill criticism of permanent high-level waste disposal sites.
I do have one question about the physical properties of the NaK coolant: what is its vapor pressure? This particular alloy was chosen partly because it's a liquid at or just above room temperature, so it must have some vapor pressure that would cause it to slowly sublime in the vacuum of space. That sublimation would occur much more quickly for small droplets than large. Anybody have numbers?
I agree, it reads like the guy knows just enough about computing and networking, and may have enough influence, to be dangerous.
Many of the things he complains about are not the fault of IP, and cannot be fixed in IP. Like more reliable packet delivery, for example. If he's running IP over crappy radio modems, then there's nothing you can do to IP to make those crappy modems work better. You need better modems.
He is obviously unaware that the Internet does not really follow the 7-layer OSI Reference Model; it has its own, much simpler 4-layer model. From top down, they are: application, transport (end-to-end), Internet and subnetwork. It is often drawn as a wineglass, because there are many application and subnetwork protocols but very few transport and Internet protocols. This is by explicit design.
The application layer is populated with protocols like SMTP, HTTP, Telnet, FTP and many others, some public and some proprietary. By design, Internet applications are implemented only at the endpoints. This makes it quite easy to create, experiment and deploy new applications. As a result, thousands of flowers now bloom at this layer, so many that the old-school powers that be (like the RIAA, MPAA, and law enforcement) are now contemplating a Cultural Revolution.
The transport or end-to-end layer is either TCP or UDP. Others have been proposed from time to time, but TCP and UDP work so well for just about everybody's needs that none of these other proposals have ever caught on. Still, people are free to try.
The Internet layer is traditionally IPv4; now it has been joined by IPv6. This layer is the core of the Internet and cannot be changed lightly. Despite many compelling advantages of IPv6 over IPv4, the transition will take many years so IPv4 and IPv6 will have to coexist more or less indefinitely. Although much effort has gone into facilitating this coexistence and transition, our experience with IPv6 has only underscored the brilliance of the original Internet architects who argued for a single protocol at this layer.
The subnetwork layer is deliberately unspecified. It can be anything that can pass an IP packet from point A to point B. It can be an entire network in its own right, such as the old ARPANET or the cellular telephone network. Ethernet, 802.11, dialup phone links, carrier pigeons, even tin cans and string all qualify as IP subnetworks if they can be made to work with the right modems.
The Internet model has evolved over decades of research and practical application by a cast of thousands, and it has shown its strength and versatility. I don't think it's going to be replaced overnight just because one DARPA guy doesn't understand why it is the way it is. It will simply continue to evolve.
Most of what this guy really seems to want are general improvements in software engineering and better subnetwork technologies. Subnetworks were deliberately left unspecified in the Internet reference model precisely so it wouldn't have to change to accomodate the radical improvements that were anticipated and have occurred. There's absolutely no need to change the Internet reference model to accomodate new subnetwork designs that use better modems, incorporate automatic configuration, ad-hoc routing algorithms or even quality-of-service mechanisms. That's exactly what the Internet model was designed to do.
The guy's comments about the Von Neumann architecture are just bizarre. It's as if he has never heard of hardware memory management and memory protection.
The latency is higher than I'd like, but it can be improved. Do a traceroute over 1xEV-DO and you'll see that much of the latency isn't in the airlink, but in the backhaul.
I'm not up on 1xEV-DV, so I'm afraid I can't answer your questions about it.
Actually, the latency associated with even an ideal code is dictated by Shannon. The closer you want to approach the Shannon limit, the larger the code block must be. The larger the code block, the longer it takes to transmit. So at low data rates, you can wait a long time just sending the encoded block even if you can instantly decode it once you get it.
These large block sizes are not a problem at high data rates or on very long deep space links where the propagation delay still exceeds the block transmission time, but they are a problem with heavily compressed voice where low latencies are required.
One way to decrease the average latency associated with a forward error correcting code is to attempt a decode before the entire block has been received. If the signal-to-noise ratio is high, the attempt may succeed; if not, you wait, collect more of the frame and try again, and you've only lost some CPU cycles. This is called "early termination", and it's one of the tricks done in Qualcomm's 1xEV-DO system, now deployed by Verizon as BroadbandAccess. 1xEV-DO is probably the first widespread commercial application of turbo codes. A 128-byte code block is used to get good coding gain. This relatively large block size is practical because 1xEV-DO is primarily designed for Internet access rather than voice.
Slashdot Mirror
It's kind of hard to respond to your message if you won't identify yourself nor explain your claimed reasons...
Strictly speaking, even IS-95 is "true" CDMA only on the reverse (mobile to base station) link. Although the forward (base-to-mobile) link is spread spectrum, technically it's not CDMA because there's no "MA" (multiple access); the mobile only listens to one transmitter at a time. The other base stations on the same channel are just unwanted interference that spread spectrum helps suppress. (Soft handoff on the forward link isn't really multiple access either, because both base stations carry the same data stream.)
The 1xEV-DO reverse channel still has multiple users transmitting to the same base station on the same RF channel at the same time, so it's still CDMA.
It's not a true phased array because the two signals are independently tracked and combined at baseband without regard to their individual RF carrier phases.
The cell transmitter uses a single antenna which is not steered. (Remember that it's transmitting to many users at the same time.) The system can, of course, switch you to a different cell site or to a different antenna on the same cell site if that will provide you with a better signal.
There's a lot of research currently going on into Multiple In, Multiple Out (MIMO) schemes in which an array of physically fixed antennas and receiver chains effectively synthesizes a set of phased arrays, one for each of several simultaneous incoming signals. Some serious heavy-duty DSP is required, but the potential is considerable. The big win comes in being able to construct each virtual phased array so as to null out all the transmitters but one, and to do that simultaneously for each of the incoming signals. This greatly increases the achievable signal-to-interference ratio, allowing the use of much higher data rates.
The other traffic channels are still available for soft and softer handoff. That's when two or more cells (or sectors within a cell) carry a single call simultaneously. The mobile combines the two cells' signals just as it would the multipath components from a single cell.
Also, the limits of the forward (base-to-mobile) and reverse (mobile-to-base) links may not be reached at the same time. CDMA 2000 1x introduced coherent modulation with a pilot on the reverse link, and this produced a significant improvement in real-world reverse link capacity.
Sectorization refers to the practice, common with all cellular technologies, of dividing up the area around a cell site into regions, or sectors, each served by its own set of directional antennas. Three sector cells are extremely common; that's why so many towers have triangular platforms with a set of antennas on each side. There are usually three antennas on each side: one for transmit and two for receive, with the extra receive antenna providing spatial diversity.
Most CDMA cell sites in built-up areas have three (or six) sectors, operate on more than one 1.25 MHz RF channel, and use the newer CDMA 2000 1x standard. That can easily provide a total cell capacity of considerably more than 61 calls.
CDMA 2000 1x doubles the number of Walsh code channels (to 128) by adding a second set of traffic channels in quadrature to the original 64. Virtually all CDMA phones sold over the past few years do 1x.
Because of CDMA's inherent robustness, the same RF channel can be reused in adjacent cells and even adjacent sectors, greatly increasing the overall capacity of the spectrum in a given area. Because no careful frequency reuse plan is required, CDMA is also very well suited to the rapid deployment of cells in "hot spots" as described in this article.
Disclaimer: I work for Qualcomm.
So far this has actually been a Good Thing, as FCC pre-emption generally works to block local restrictions on radio communications that are almost always unnecessary, heavy-handed, misguided or in outright bad faith. Just ask any ham radio operator. This ruling shows that the FCC is still doing its job.
About 20 years ago, I remember an attempt by my local town council in New Jersey to effectively ban all private satellite TV dishes. The claimed reason was RF safety -- from receive-only antennas! But outside the hearing room, the town attorney told me a different story; they didn't want satellite TV taking business away from the local cable TV operation because said cable operation was a significant source of cash to the town in the form of franchise fees. Not long afterwards, the FCC squashed this sort of nonsense in no uncertain terms.
So has your DMCA bot-killer generated any takedown notices yet?
No amount of oversight can keep these abuses from happening. For a brief and shining moment, the US had a vibrant and competitive DSL market. Then almost overnight, it was pretty much just Covad and the local telcos. And I wonder how much longer Covad will be around.
Just look at how the telcos (and the cable companies for that matter) have managed to snow the FCC, the courts, the regulators, legislatures and the public with their propaganda that requiring them to provide competitive access to their wires is tantamount to socialism, and they'd have no incentive to improve their networks. Horse puckey! They might have a point if they were being required to provide access to their wires for free, but that ain't the case. Competitors are required to pay (often substantial) fees to use those wires. But the mere notion of being required to sell their wires to competitors is anathema to the phone and cable companies who are salivating at what they can do with their monopoly positions.
I see only two ways out. Municipalities could set up utility departments that would lay new wire and/or fiber along public rights of way and sell access on a nondiscriminatory basis. Or the telcos and cable companies could be required to divest their outside wire and cable plants into financially independent entitites banned from actually selling any switched services based on those wires. The outside plant companies would be required to market access to those wires, on a tariffed and non-discriminatory basis, to resellers who would compete in offering actual services to the public.
This is hardly a radical proposal, based as it is on a century of experience with common carrier regulation and antitrust law.
What I do strenuously object to are ISPs who unilaterally make that choice for all their customers (or, in the case of an outbound port 25 block, for everyone else's customers) without giving the affected parties a choice in the matter. That is simply wrong.
If an individual user wants his ISP to filter on his behalf, that's fine. As long as it only applies to that user, and he retains control.
I also don't have a problem with blocking known spammers in response to recipient complaints, as long as there is due process, a chance to appeal, etc. That seems to be what Comcast is doing, but I fear it may change because this is just too rational and enlightened a policy for that outfit.
Okay, let's say the ISPs block outbound port 25. The spammers and virus authors will quickly adapt by routing their outbound traffic through the ISP's mail relay, and/or they will start trying port 587 in addition to port 25. (Port 587 is increasingly widely used for MUA->MTA SMTP traffic precisely to evade heavy-handed blocks on port 25, and many admins set it up to be functionally identical to port 25.)
Before you claim that the ISPs' mail relays can magically block all outbound viruses and spam, presumably by some method other than simply dropping most of the mail presented to it because of the resulting extreme overload, consider that virus authors are already morphing their viruses and spam frequently enough to evade these filters; encrypted zip archives are just the beginning.
So once again, how can this stop viruses and spam more effectively than receiver-side filtering? It can't. In fact, it makes things even worse because it deprives the remote targets of the ability to selectively blackhole the individual IP addresses of known spam sources. Since both spam and real mail all come from the same (or a small set) of IP addresses belonging to the ISP's mail relays, the targets are forced to either refuse all mail from that ISP, or accept it all and sort it out after receipt. Personally, I believe that spam and virus filtering can only be properly done by examining entire messages with something like a Bayesian filter, but I still wouldn't want to deny someone else the ability to blacklist the individual IP addresses of known major-league spammers.
The basic problem with those who advocate draconian anti-spam measures like blanket port blocking for spammers and non-spammers alike is that they never seem to learn from history. They never seem to realize that any benefit will be temporary but the collateral damage is permanent. When the cycle repeats, things get even worse.
It's a lot like the Bush Administration's approach to Iraq, now that I think about it.
Besides, direct end-to-end delivery is exactly how the Internet was designed to work. And no one has explained to me exactly how forcing everyone to relay their mail through their ISP's mail relay will somehow stop spam.
I suppose it may slow it down simply because the ISP's mail relay will be a single point of failure, underpowered and overloaded, and this will throttle or drop a good fraction of all the outbound mail from that ISP, spam or not.
By your reasoning, I suppose that we should just shut down email entirely. This would be 100% effective in stopping all spam!
And what if Comcast decides next that ordinary residential peons like you don't really need to use SSH, and unilaterally blocks port 22, even in the outbound direction? I mean, it's not like SSH is something Microsoft built into Windows XP, the only operating system in the universe that matters and people should be allowed to use. Unlike SSL, SSH isn't needed to buy stuff online from big companies, and we all know that's the only legitimate use of the Internet, right? Every other use of the net is potentially subversive, especially if it's encrypted, so what do you care if they block it?
I hope you can see where this port-blocking crap is leading. It's a very dangerous slippery slope, and it must be stopped now. I have no problem with selective port blocks made after due process in response to direct end-user complaints, but "proactive" blocking will ultimately destroy the Internet architecture and its usefulness without really solving the problems it claims to solve.
GPS One overcomes your first two problems by augmenting the GPS satellite signals with timing and data from local CDMA cells. It is possible to get accurate fixes inside buildings and in urban canyons where conventional 3- or 4- satellite GPS fixes would not be possible. This stuff is now being widely deployed in CDMA systems primarily to meet E911 requirements, but it will also be available for general positioning applications.
What isn't reasonable is for a telco to charge wholesale prices to CLEC DSL providers that are higher than the retail prices for the telco's own DSL services, and/or to drag their feet in providing competitive access, yet this is exactly what the telcos routinely do. And they get away with it.
Properly done, regulation still provides plenty of incentives for the regulated company to expand and improve its business.
Is a regulated monopoly more efficient and innovative than a true, competitive free market economy? Of course not, but that's an apples-vs-oranges comparison. If there were true competition in the provision of local transmission to my house, we wouldn't need much (if any) regulation. But while the local telcos would like us to believe otherwise, we just don't have that kind of free-market competition, at least not yet. And until we can get it, regulation will be a necessary evil.
The boundary lines were drawn in all the wrong places.
After a promising start, competition in the DSL market has nearly dried up because the local telcos that own the wires in the streets have absolutely no incentive to cooperate in good faith with CLECs that compete with the telcos' own DSL services. Look at how they always phrase the subject in public. They get indignant and act as if the government is trying to make them give away their wires to their competitors for free when that is not the case at all! Every CLEC pays the local telco for the use of their wires, and no one has ever suggested that they not.
If the boundary lines had been drawn where they belong -- right at the ends of the wires that run along public streets -- things would have turned out differently. The wires would be owned by a fully regulated entity that would be barred from any business other than renting access to those wires to any service provider able to pay a standard tariff. While they would still have an incentive to inflate their costs in order to inflate their tariffs, regulators have a lot of experience in scrutinizing the books of common carriers. And since the only part of the path that would be regulated are the actual wires, regulatory overhead would be kept to an absolute minimum.
Everything but the wires themselves would be the province of competitive, unregulated carriers that would set up the DSLAMs and routers and market their services to customers.
It's a simple and obvious way to do things, but this is not what Congress in its wisdom decided to do in 1996. Why is anybody surprised at how things turned out?
Great resource! Thanks for the pointer.
A droplet of NaK, being a silvery metal that reflects photons, would experience twice the radiation pressure as a same-sized black object that absorbs photons. On the other hand, being liquid they assume spherical shapes that minimize surface area. I wonder what the net effect is on orbital lifetime.
I see what you mean. In this reference: http://www.basf.com/inorganics/pdf/bulletin/NaK_bu lletin.pdf it says that eutectic NaK (78% K, 22% Na) is liquid from -12.6C to 785C. That's a pretty wide range that helps explain its utility as a reactor coolant, and it also suggests a pretty low vapor pressure. Oh well.
In no way will I excuse the extreme sloppiness of the Russians in all things nuclear, but the radiation hazard from these things has been greatly exaggerated to sell newspapers, books and TV spots. Several of these orbiting Soviet reactors failed to go into their disposal orbits and have already fallen back to earth -- and we're still here. Yes, you could say we were lucky that they fell in relatively remote areas. But most of the earth's surface is still sparsely populated (such as the 70% that's covered by water).
Another thing to remember about spent reactor fuel is that its radioactivity falls rapidly with time. While a reactor operates, a significant fraction of the generated power comes from the decay of short-lived fission products. This radioactive decay heat continues even after the chain reaction has been shut down; that's why emergency core cooling is so important in terrestrial reactors. Depending on the reactor design and the fuel, a few hundred years may be enough for its radioactivity to decay to that of the uranium ore from which it was originally made. This point is often lost in the shrill criticism of permanent high-level waste disposal sites.
I do have one question about the physical properties of the NaK coolant: what is its vapor pressure? This particular alloy was chosen partly because it's a liquid at or just above room temperature, so it must have some vapor pressure that would cause it to slowly sublime in the vacuum of space. That sublimation would occur much more quickly for small droplets than large. Anybody have numbers?
Many of the things he complains about are not the fault of IP, and cannot be fixed in IP. Like more reliable packet delivery, for example. If he's running IP over crappy radio modems, then there's nothing you can do to IP to make those crappy modems work better. You need better modems.
He is obviously unaware that the Internet does not really follow the 7-layer OSI Reference Model; it has its own, much simpler 4-layer model. From top down, they are: application, transport (end-to-end), Internet and subnetwork. It is often drawn as a wineglass, because there are many application and subnetwork protocols but very few transport and Internet protocols. This is by explicit design.
The application layer is populated with protocols like SMTP, HTTP, Telnet, FTP and many others, some public and some proprietary. By design, Internet applications are implemented only at the endpoints. This makes it quite easy to create, experiment and deploy new applications. As a result, thousands of flowers now bloom at this layer, so many that the old-school powers that be (like the RIAA, MPAA, and law enforcement) are now contemplating a Cultural Revolution.
The transport or end-to-end layer is either TCP or UDP. Others have been proposed from time to time, but TCP and UDP work so well for just about everybody's needs that none of these other proposals have ever caught on. Still, people are free to try.
The Internet layer is traditionally IPv4; now it has been joined by IPv6. This layer is the core of the Internet and cannot be changed lightly. Despite many compelling advantages of IPv6 over IPv4, the transition will take many years so IPv4 and IPv6 will have to coexist more or less indefinitely. Although much effort has gone into facilitating this coexistence and transition, our experience with IPv6 has only underscored the brilliance of the original Internet architects who argued for a single protocol at this layer.
The subnetwork layer is deliberately unspecified. It can be anything that can pass an IP packet from point A to point B. It can be an entire network in its own right, such as the old ARPANET or the cellular telephone network. Ethernet, 802.11, dialup phone links, carrier pigeons, even tin cans and string all qualify as IP subnetworks if they can be made to work with the right modems.
The Internet model has evolved over decades of research and practical application by a cast of thousands, and it has shown its strength and versatility. I don't think it's going to be replaced overnight just because one DARPA guy doesn't understand why it is the way it is. It will simply continue to evolve.
Most of what this guy really seems to want are general improvements in software engineering and better subnetwork technologies. Subnetworks were deliberately left unspecified in the Internet reference model precisely so it wouldn't have to change to accomodate the radical improvements that were anticipated and have occurred. There's absolutely no need to change the Internet reference model to accomodate new subnetwork designs that use better modems, incorporate automatic configuration, ad-hoc routing algorithms or even quality-of-service mechanisms. That's exactly what the Internet model was designed to do.
The guy's comments about the Von Neumann architecture are just bizarre. It's as if he has never heard of hardware memory management and memory protection.
I'm not up on 1xEV-DV, so I'm afraid I can't answer your questions about it.
1xEV-DO is designed for Internet access, and I'm sure you're aware you can run voice over the Internet. That's all I meant.
These large block sizes are not a problem at high data rates or on very long deep space links where the propagation delay still exceeds the block transmission time, but they are a problem with heavily compressed voice where low latencies are required.
One way to decrease the average latency associated with a forward error correcting code is to attempt a decode before the entire block has been received. If the signal-to-noise ratio is high, the attempt may succeed; if not, you wait, collect more of the frame and try again, and you've only lost some CPU cycles. This is called "early termination", and it's one of the tricks done in Qualcomm's 1xEV-DO system, now deployed by Verizon as BroadbandAccess. 1xEV-DO is probably the first widespread commercial application of turbo codes. A 128-byte code block is used to get good coding gain. This relatively large block size is practical because 1xEV-DO is primarily designed for Internet access rather than voice.