BISSEX: Packet Store
Packets. It all comes down to packets.Every e-mail message you send, every web page you look at, every Internet audio file you listen to gets from place to place on the network in the same unlikely way. They don't get wrapped up in big tidy electronic bundles. Instead, they are torn apart, broken down into packets -- bite-size chunks of information which all travel the Net independently and yet manage to arrive and reconstitute themselves at their destination.At every point in the network, special high-speed computers called routers take care of shipping the packets off in the right direction as they relentlessly pour in.This is quite different from the more familiar "switched-circuit" network, the telephone switchboard model where communication between two points is essentially served by a dedicated line.The ability to break messages and data down into individual packets is a very efficient way to operate. It uses more of the available bandwidth, or channel capacity. It doesn't eliminate congestion, but it softens its effects.A switched-circuit network pushed to its carrying limits is not very forgiving, as anyone who has tried to get on the phone after an earthquake can tell you. There just aren't enough circuits for everyone to be on at once. You get either get a dial tone or the raspberry of the "fast busy" signal. No middle ground.A packet network like the Internet gives more warning as it approaches its carrying limit. When routers under heavy traffic receive more packets than they can handle, the packets start to back up. If the overload is extreme, packets get "dropped" and must be sent again.This is an ordinary occurrence; packets get dropped and re-sent all the time. Messages don't generally get lost, just delayed. (The basic idea of the Net's military architects was, if a bomb takes out part of the network you still want your messages to get through. The routers just do their best to avoid the craters.)In practice, the extreme success of the Net in recent years has kept it too close to the crisis zone. Internet statisticians measuring the percentage of packets dropped at various points in the network offer some alarming figures: during short-term snarls some sites lose over half the packets sent to them.What must gall the scientists studying these traffic crunches is that most of the heavy drain on the Net's capacity is so goofy: real time video chatting, Net radio broadcasts, promotional clips from Hollywood blockbusters. (E-Mail, still the number one application on the Net, accounts for a tiny fraction of the traffic.) A researcher would be understandably irked to see his global warming simulation moving at a snail's pace just because it's lunch time on the East Coast and millions of workers are firing up their web browsers for recreational pornography hunts.A few weeks ago, researchers at Lawrence Berkeley National Laboratory demonstrated a "differentiated services" system that allows for prioritization of packets. They sent two sets of packets (video streams, actually) along the same congested network route from California to Illinois. One set was flagged as high priority, the other was left alone. The prioritized packets poured into their destination eight times faster than the others; the researchers declared their experiment a success. They believe that their techniques can be applied to the Net at large without burdening the already saturated routers further.Other approaches to this problem are also gaining ground. MCI recently announced its support of the Resource Reservation Protocol, which lets people prepay for discrete amounts of guaranteed bandwidth -- to make sure that a live video broadcast doesn't get bogged down at a critical moment, for instance. And the next version of the Internet Protocol, the Net's low-level traffic regulations, accommodates prioritized packets as well.You may wonder what kind of Internet service will be left after the people who can afford to pay for speed have staked their claims. Basic Net service may not seem like much when the rich are having 3D holographic communications via $1,000 virtual reality helmets.Still, these changes are a step in the right direction. Flat pricing for access encourages an all-you-can-eat frenzy among multimedia fanatics, who are being subsidized by the quiet e-mailing masses. If somebody besides me is going to have fun with a $1,000 virtual reality helmet, they damn well better be paying for it.***Sites in my SightsIf you want numbers, one good source is the Internet Weather Report (www.internetweather.com), whose single page of dense figures says more about the state of the Net at any given moment than a dozen pundits. You can learn more about the multimedia craze's burden on the net by reading this proposal from the Internet Society (ftp.isi.edu/in-notes/rfc2309.txt).Are all packets created equal? Send a letter in care of this publication, drop a line via e-mail (email@example.com), or visit the Cyberia website (www.well.com/user/pb/cyb).