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Communicating Even When the Network Is Down
coondoggie writes to mention a NetworkWorld article covering efforts to maintain network connectivity even when the network has holes. Building off of the needs of the military, the end goal is to create a service which will route around network trouble spots and maintain connectivity for users. From the article: "Researchers at BBN Technologies, of Cambridge, Mass., have begun the second phase of a DTN project, funded by $8.7 million from the Department of Defense's Defense Advanced Research Projects Agency (DARPA). Earlier this year, the researchers simulated a 20-node DTN. With each link available just 20% of the time, the network was able to deliver 100% of the packets transmitted." The article is on five small pages, with no option to see a linkable, printable version.
Wasn't that the point of the original ARPANET? To route around broken parts of the network? BBN was involved in that, too. What, have they been double-billing the DoD this whole time?
gigantino.tv - Heavy but weighs nothing.
Baby, darling. I appreciate the warning, but you do realize, as a janitor at Slashdot you have a decent amount of power, clout in the nerd world. Even though you're condemning their actions with your comment, you're promoting their site, giving them extra ad revenue with their annoying practices.
If you want to make a difference, make a stand, stop linking to sites like these. Send them a quick letter saying you'd be happy to send X thousand happy clickers their way if they'd give a single page, printable version. With their "Slashdot it" link at the bottom of the page, they obviously care.
Anyone else feel like they're time travelling when they're reading this?
you had me at #!
You must be just as blink as Zonk. The link to the print version is right next to the "Slashdot it" link!
link
This is an old wive's tale that deserves to die. The ARPANet was NOT built as an experiment in resiliant networking; it was built by DARPA to connect scientists so they could share all the large computers that DARPA was funding.
e rnet/dp/0684832674
See: Where Wizards Stay Up Late
http://www.amazon.com/Where-Wizards-Stay-Late-Int
and
http://www.businessweek.com/1996/38/b349359.htm
It is clear from the article that they are aiming for something more than OSPF or other link state routing protocols. If a link is cut inside a network, OSPF adjusts so that traffic is routed through alternative paths. But, until there is convergence (which is quite fast in most cases), packets may be lost. Packet drops do tend to occur if a router cannot find a suitable route to a destination, if it is able to find a route but the link to that route is down, or even if the queue on that link is congested (full). That's the very nature of our present best effort internet.
It appears to me that these guys try to address some of these "shortcomings" by making certain privisions that can guarantee packet delivery, even in a overly late fashion. A routing instability, lost routes or links should not be able to cause packet drops if they have it right.
However, I used the quotes in "shortcomings" because I am not entirely certain that this has not been tried before. If, instead of a best effort packet routing service, you try to invent a "smart" network layer that can guarantee stuff like ordered delivery (packets are delivered in the order they departed), assured delivery (even with great delays) etc, you are basically trying to invent a (gasp!) connection oriented service. Not that connection oriented technologies are inherently bad, but, well, they are certainly an order of magnitude harder to implement. Anyone remembers OSI? It might as well be easier to leave IP simple as it is and try to move some smartness to the upper layers.
Additionally, it would be better to try to build on top of unreliable services like IP and construct stuff like SMTP (as a previous poster very cleverly pointed out), that can function even if parts of the network are mulfunctioning.
Well, anyway, you might want also to take a look at the efforts on the interplanetary internet, this article reminded me of it.
In the new "non" net-neutral(ity) world, routing around trouble spots was not a service you paid for. If you need that service it will be an extra $10.00 a month. We love all our customers and hope your experience with our product is to your satisfaction. Now, if you would please take just a few moments and fill out our survey...
No. Normal routing works through space. Packets move from node to node, avoiding nodes and links that are down. DTNs can route through space and time, delaying packets until they can be routed further along.
If you have two networks that are only intermittently connected, normal routing will drop packets when the connection is down. DTNs will allow the packets to be held until the connection is up.