Someone Comes to Town, Someone Leaves Town

by Cory Doctorow

with the server. There's a key exchange that we use to makesure that rogue APs don't sneak into the mesh, and a self-healingroutine we use to switch routes if the connection drops or we start tosee too much packet loss."

  The graybeard looked up. "It izz a radio vor talking to Gott!" hesaid. Lyman's posse laughed, and after a second, so did Kurt.

  Alan must have looked puzzled, for Kurt elbowed him in the ribs andsaid, "It's from Indiana Jones," he said.

  "Ha," Alan said. That movie had come out long before he'd come to thecity -- he hadn't seen a movie until he was almost 20. As was often thecase, the reference to a film made him feel like a Martian.

  The graybeard passed his unit on to the others at the table.

  "Does it work?" he said.

  "Yeah," Kurt said.

  "Well, that's pretty cool," he said.

  Kurt blushed. "I didn't write the firmware," he said. "Just stuck ittogether from parts of other peoples' projects."

  "So, what's the plan?" Lyman said. "How many of these are you going toneed?"

  "Hundreds, eventually," Alan said. "But for starters, we'll be happy ifwe can get enough to shoot down to 151 Front."

  "You're going to try to peer with someone there?" The East Indian womanhad plugged the AP into a riser under the boardroom table and wasexamining its blinkenlights.

  "Yeah," Alan said. "That's the general idea." He was getting a littleuncomfortable -- these people weren't nearly hostile enough to theirideas.

  "Well, that's very ambitious," Lyman said. His posse all nodded asthough he'd paid them a compliment, though Alan wasn't sure. Ambitiouscould certainly be code for "ridiculous."

  "How about a demo?" the East Indian woman said.

  "Course," Kurt said. He dug out his laptop, a battered thing heldtogether with band stickers and gaffer tape, and plugged in a wirelesscard. The others started to pass him back his access points but he shookhis head. "Just plug 'em in," he said. "Here or in another room nearby-- that'll be cooler."

  A couple of the younger people at the table picked up two of the APs andheaded for the hallway. "Put one on my desk," Lyman told them, "and theother at reception."

  Alan felt a sudden prickle at the back of his neck, though he didn'tknow why -- just a random premonition that they were on the brink ofsomething very bad happening. This wasn't the kind of vision that Bradwould experience, that far away look followed by a snap-to into the now,eyes filled with certitude about the dreadful future. More like a goosewalking over his grave, a tickle of badness.

  The East Indian woman passed Kurt a VGA cable that snaked into thetable's guts and down into the riser on the floor. She hit a button on aremote and an LCD projector mounted in the ceiling began to hum,projecting a rectangle of white light on one wall. Kurt wiggled it intothe backside of his computer and spun down the thumbscrews, hit abutton, and then his desktop was up on the wall, ten feet high. Hiswallpaper was a picture of a group of black-clad, kerchiefed protesterscharging a police line of batons and gas-grenades. A closer lookrevealed that the protester running in the lead was probably Kurt.

  He tapped at his touchpad and a window came up, showing relativestrength signals for two of the access points. A moment later, the thirdcame online.

  "I've been working with this network visualizer app," Kurt said. "Ittries to draw logical maps of the network topology, with false coloringdenoting packet loss between hops -- that's a pretty good proxy fordistance between two APs."

  "More like the fade," the graybeard said.

  "Fade is a function of distance," Kurt said. Alan heard the dismissal inhis voice and knew they were getting into a dick-swinging match.

  "Fade is a function of geography and topology," the graybeard saidquietly.

  Kurt waved his hand. "Whatever --sure. Geography. Topology. Distance. It's a floor wax and a desserttopping."

  "I'm not being pedantic," the graybeard said.

  "You're not just being pedantic," Lyman said gently, watching the screenon which four animated jaggy boxes were jumbling and dancing as theyreported on the throughput between the routers and the laptop.

  "Not just pedantic," the graybeard said. "If you have a *lot* of theseboxes in known locations with known nominal throughput, you can use themas a kind of sensor array. When throughput drops between point foo andpoint bar, it will tell you something about the physical world betweenfoo and bar."

  Kurt looked up from his screen with a thoughtful look. "Huh?"

  "Like, whether a tree had lost its leaves in the night. Or whether therewere a lot of people standing around in a normally desolate area. Orwhether there are lots of devices operating between foo and bar that areinterfering with them."

  Kurt nodded slowly. "The packets we lose could be just as interesting asthe packets we don't lose," he said.

  A light went on in Alan's head. "We could be like jazz critics,listening to the silences instead of the notes," he said. They alllooked at him.

  "That's very good," Lyman said. "Like a jazz critic." He smiled.

  Alan smiled back.

  "What are we seeing, Craig?" Lyman said.

  "Kurt," Alan said.

  "Right, Kurt," he said. "Sorry."

  "We're seeing the grid here. See how the access points go further up thespectrum the more packets they get? I'm associated with that bad boyright there." He gestured to the box blinking silently in the middle ofthe board room table. "And it's connected to one other, which isconnected to a third."

  Lyman picked up his phone and dialed a speed-dial number. "Hey, can youunplug the box on my desk?"

  A moment later, one of the boxes on the display winked out. "Watchthis," Kurt said, as the remaining two boxes were joined by acoruscating line. "See that? Self-healing. Minimal packetloss. Beautiful."

  "That's hot," Lyman said. "That makes me all wet."

  They chuckled nervously at his crudity. "Seriously."

  "Here," Kurt said, and another window popped up, showing twenty or moreboxes with marching ant trails between them. "That's a time-lapse of theKensington network. The boxes are running different versions of thefirmware, so you can see that in some edge cases, you get a lot moreoscillation between two similar signals. We fixed that in the newversion."

  The graybeard said, "How?"

  "We flip a coin," Kurt said, and grinned. "These guys in Denmark ransome simulations, proved that a random toss-up worked as well as anyother algorithm, and it's a lot cheaper, computationally."

  "So what's going on just to the northeast of center?"

  Alan paid attention to the patch of screen indicated. Three accesspoints were playing musical chairs, dropping signal and reacquiring it,dropping it again.

  Kurt shrugged. "Bum hardware, I think. We've got volunteers assemblingthose boxes, from parts."

  "Parts?"

  Kurt's grin widened. "Yeah. From the trash, mostly. I dumpster-dive for'em."

  They grinned back. "That's very hot," Lyman said.

  "We're looking at normalizing the parts for the next revision," Alansaid. "We want to be able to use a single distro that works on all ofthem."

  "Oh, sure," Lyman said, but he looked a little disappointed, and so didKurt.

  "Okay, it works," Lyman said. "It works?" he said, nodding the questionat his posse. They nodded back. "So what can we do for you?"

  Alan chewed his lip, caught himself at it, stopped. He'd anticipated aslugfest, now he was getting strokes.

  "How come you're being so nice to us?" Kurt said. "You guys are TheMan." He shrugged at Alan. "Someone had to say it."

  Lyman smiled. "Yeah, we're the phone company. Big lumbering dinosaurthat is thrashing in the tarpit. The spazz dinosaur that's soembarrassed all the other dinosaurs that none of them want to rescueus."

  "Heh, spazz dinosaur," the East Indian woman said, and they all laughed.

  "Heh," Kurt said. "But seriously."

  "Seriously," Lyman said. "Seriously. Think a second about the scale of atelco. Of this telco. The thousands of kilometers of wire in thegrou
nd. Switching stations. Skilled linesmen andcable-pullers. Coders. Switches. Backhaul. Peering arrangements. We'vegot it all. Ever get on a highway and hit a flat patch where you can'tsee anything to the horizon except the road and the telephone poles andthe wires? Those are *our wires*. It's a lot of goodness, especially fora big, evil phone