TR:How does this new protocol, the delay- and disruption-tolerant networking system, work?
VC: We are using store-and-forward methods [routing information through hosts that hold on to it until a communications link can be established] similar to the TCP/IP design in order to service space-communication requirements. But our new bundle protocol is based on DTN principles. We have to cope with the fact that there is a really high potential for delay and disruption in the system. For example, Pluto is a long ways away, on the order of three to five billion miles and about 12 hours round-trip time. Using the DTN bundle protocol allows us to design more-complex mission configurations involving many devices on the surface of planets and in orbit around them. At Mars, for example, there are four orbiters and three landed and operational spacecraft. We expect to be able to use the standard TCP/IP protocols on the surface of planets and inside spacecraft, but we will use the DTN protocols for interplanetary distance communications.
TR: Is this going to require putting new infrastructure in space?
VC: The answer is yes and no. For example, the Deep Impact spacecraft [now called EPOXI] is already in orbit around the sun. It was used to launch a probe into a comet to examine its interior. EPOXI is being temporarily repurposed to test the new DTN protocols. The spacecraft has processing, memory, radio equipment, and solar panels for power so we don’t have to put new hardware up. We just have to upload new software. We are lucky to not have to field any new equipment yet, but the DTN protocols eventually have to show up in a fairly significant number of devices in the system to create the kind of network that can serve space-communication needs. Some specialized spacecraft could become store-and-forward routers. Each time a new mission is launched, using the standard bundle protocol, previous mission assets that are still in operation could be used to support the communication requirements of the new mission. In this way, we hope to accrete a kind of interplanetary backbone network.
TR: How are you handling security issues?
VC: There are security concerns, and we have been very careful to build defenses into the basic design. Each bundle-aware node will verify the identity of any other nodes that it is communicating with, and it will refuse to forward data from any nodes that it does not recognize. We will be using strong authentication methods, cryptographic communication methods, to ensure that the parties that are using the resources are authorized to do so.
TR: What is the biggest advantage of building new protocols for space communication?
VC: The important part here is that we have standardized protocols that will allow internetworking of various spacecraft launched by all the spacefaring nations. Over time, as new missions are launched, you start to build up a backbone capability. Every time you put up a new mission, you basically are putting up another potential node in the network. Our hope in the near term is to start putting DTN/bundle-protocol applications up on the Internet terrestrially, and also put them up on the International Space Station for testing. Eventually, we hope to have this capability running all the time, and then, when new deep-space missions are launched using these standard protocols, they will become part of the interplanetary communications system.