Delay Tolerant Networking

Having a network that tolerates delays is like wearing a leather jacket on a moped. In this phase of networking where email is too slow, video streaming is 28% on Internet traffic and Public Switched Telephone Networks are being bypassed with the use of SIP Trunking, delay of any type is the last thing I want on my network. But what if you have to contend with object/node movement? A few years back, I installed optical laser communication units on top of very tall buildings for continuous communications between buildings. The one thing I had to contend with was building sway pulling the lasers out of collimation and thereby breaking the communication pathway. We accomplished this with gimbals and various auto-trackers and never had a problem except the occasional bird turd on the optics. Should have purchased the optional turd burn thru mode, but at 50+ stories who would have guessed? and at that angle too? That’s like Navy SEAL accuracy. What if your communications platform is Outer Space and you now have to contend with orbital mechanics? The entire communications game changes in Space. Milliseconds are no longer a luxury we have. No, we are dealing in minutes, hours and days. For example, for the Mars Sojourner to send traffic back to Earth it takes approx 9 minutes one way. As I get deeper into Space, we use communication windows that may be on Monday at 1:32AM – 2:17AM and then the corridor is closed until Wednesday. But look, we just can’t send folks into Space without the ability to send Tweets or stream Family Guy, that would be cruel and unusual treatment that would have Amnesty International all up in our galactic business. Orbital mechanics are an absolute that we can not change, so how do we deal with it from a protocol level? We call Vint Cerf! Vint, along with a bunch of other scientist-type folks, came up with the idea of Delay Tolerant Networking. DTN (as it is called by the cool in-crowd) is really an overlay network that rides on top of other regional networks. Unlike our terrestrial packet-switched networks (You have to say that in the same tone a Mac user says “You got a virus” to a Windows user), DTN uses a store-and-forward methodology. In this method data is transferred from one router intersection and held until it has a scheduled transfer based on orbital movement (and unbelievably accurate clocks) or an opportunistic transfer based upon a new Space vehicle launch. This is cool stuff, but for an overlay network, what is it that is being overlaid? This is where the new protocol layer called the Bundle Layer comes into play. Looking at the common Internet Layers: – Application – Transport – Network/IP – Link – Physical The Bundle Layer fits between the Application and Transport Layers and ties all regional-specific lower-layer areas together so applications can communicate across multiple regions. This allows multiple types of communications methods to be used across regions without affecting the primary upper-layer applications. That gives DTNs extensibility to use radio (RF), Ultra Wide Band (UWB), Free Space Optical and various acoustic technologies like SONAR and Ultrasound, etc… whatever works BEST in that region or that mission. A packet sample of a Bundle would have three parts: – Source application data. – Control information. This is provided by the application itself and tells how to handle, store, forward and dispose of the data. – A Bundle header inserted by the Bundle layer itself so some messages can be fragmented and reassembled. Because of the delays, DTN is not a chatty protocol at all. As a matter of fact, acknowledgment from the far end is optional and based upon the class of service selected. The one thing I though was different in DTN was the Class of Service options. I immediately thought of QoS, but on DTN it is truly a class of handling with options, from transfer of transmission custody to authentication. Leaving the Bundle Layer and looking more at the DTN Node itself, they actually have implemented a DNS-ish naming system to identify DTN Nodes. The tree looks like this: – . <– root – int <— Interplanetary Internet – sol <—- Solar System – Mars Venus Earth <— Backbone Region if you are looking to connect to Mars at address mars.sol.int techwisetv.com, DTN would handle mars.sol.int to route between regions, then techwisetv.com would routed within the region for normal processing. That’s the power of the overlay. Does it work or is this just an idea? It works GREAT! Last October the Deep Impact probe used DTN on its way to fly by Comet Hartley 2. DTN transmitted 300 pix over 15 million miles with no corrupt or dropped packets. Matter of fact, one of the Earth-based antennas accidentally rebooted (Patch Tuesday, no doubt) and DTN paused, recovered and keep going. The final test is using security this coming October and then it’s ready to go! I am a huge Astronomy geek and can been seen getting chewed up by mosquitoes in the Summer and shivering in the Winter while looking thru my Celestron 15-inch. The ability to combine my two greatest passions – protocols and stars – is just sometimes too much to handle sitting down. If Vint combines a fried chicken component to this I am going to have to go on blood pressure meds! For more information on this amazing protocol, go here. Jimmy Ray Purser Trivial File Transfer Protocol Years ago the transistor changed the world. Now the stage is set for the memristor to do the same thing again. Is this how SkyNet begins….