TechScape: Vint Cerf on the InterPlanet
To Mars and beyond...
Interview In the second of TechScape’s three exclusive interviews with Vint Cerf, Bill Robinson investigates the story of the InterPlanet (or Interplanetary Internet as it is sometimes called).
The first time I met Vint Cerf was about five years ago when he was speaking at Cambridge University. Being a Yank over here, I decided I should hear him speak, particularly given the topic: The InterPlaNet.
What, I wondered, was this guy smoking? It all sounded so bizarre, so surreal. An internet out in space?
I told him years later of my initial cynicism, and he replied simply: “Yes, I get a lot of that.”
When he first began speaking at Cambridge that day, there was an auditorium full of skeptics like me who wanted to see a scientist meltdown publicly.
But no such meltdown was forthcoming, only a man articulately describing his vision for projecting a communications network into outer space.
“In late 1997,” Cerf began during his recent interview with TechScape, “I began thinking about how the internet started 25 years earlier and what I could get working on that might be important 25 years later.”
Hmmm, this is already beginning to get scary, I thought, recalling an interview I did with interview of Sir Arthur C. Clarke. Here, Cerf is trying not only to predict the future as Sir Arthur would undoubtedly try to do, but also how he could contribute to it.
“My mind wandered into the possibility of expanding the internet out into the solar system,” Cerf boldly went where no other man has gone. He knew an engineer working at JPL (Jet Propulsion Labs in Pasadena, California) which is a close partner of NASA’s in all of its space missions and this man was a very willing and enthusiastic partner for laying out the blueprint for this extraterrestrial creation.
And the InterPlaNet’s visionaries knew that NASA was sending missions to Mars. This seemed like a natural opportunity to begin laying the railroad tracks, infrastructure or IP backbone for the solar system’s first human communications system.
But where to start technologically?
Initially, “flow control”, or the time it takes for a signal to reach and return from an exploratory mission in space, was Cerf’s challenge to overcome. If he could reduce or minimize this crucial “downtime” period, he could vastly improve the efficiency of interplanetary communications just as he did with the internet and intra-planetary communications here on Earth.
Also essential, surprisingly, were the availability of domain names for the space communications network. “At the outset, we thought the domain-name system may not work,” Cerf said, “but we realized that not using it meant one might spend 40 minutes looking up an IP address for a certain location in space. We didn’t want that. We also worried that due to the popularity of the internet, Earth may use up all possible domain names. This is why ICANN set aside the .mars and other planetary domains for this initiative.”
The next key issue was satellites and how to position them.
The time astronomical and physics complexities of sending data (and instructions) to and from Mars are infinite and most often involve reception-quality issues such as we Earthlings experience terrestrially on our mobile phones. “If you’re transmitting data to Mars, Mars is spinning of course. If your receptor is on the far side, you have to wait until it comes back to the close side again; or have a satellite to bounce it back from the dark side,” Cerf declared.
The challenge, according to Cerf, was an extension of communications reception problems here amongst us humans. “Think about mobile operation and connectivity here which is not great - when we go under a bridge for instance.” Going under a bridge is one thing; trying to call Mum from Mars another thing entirely.
“It can take 40 minutes round trip for data to/from Mars,” Cerf said, “and there’s a minimum of six minutes even when Mars is at its closest to Earth.” So any reduction in wait time can be important particularly if you’re remote-controlling a Mars rover.
Imagine sending an instruction through the joystick only to find out 12 minutes later that you’ve just sent your $60m Mars rover into a two-mile-deep Martian chasm.
“To overcome some of these issues, we created a new protocol we called Delay & Disruption-Tolerant Networking (DDTN) which we believed would offer ways around some of these communications problems,” Cerf explained.
Shortly thereafter, Cerf contacted his old friends at DARPA (Defense Advanced Research Projects Agency). He told them of his idea to create an interplanetary communications system and they sat up and took notice.
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