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Communicating Even When the Network Is Down

Posted by Zonk on Thu Nov 16, 2006 06:11 PM
from the with-science dept.
Wireless Networking IT Hardware
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.
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  • Wait a minute... (Score:5, Insightful)

    by J05H (5625) on Thursday November 16 2006, @06:17PM (#16877662) Homepage
    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?

    • Re:Wait a minute... (Score:5, Informative)

      by m94mni (541438) on Thursday November 16 2006, @06:26PM (#16877742)
      "But all that breaks down when the network ruptures because of repeated disconnections and long delays. BBN has developed a network protocol and code that moves information from node to node as connections become available, and can hold information in persistent storage until a connection is available. " They are solving the case when at each point in time, there is *no* end-to-end path. ARPANET assumes there is at least one path, though the path can vary over time.

    • Re: (Score:3, Interesting)

      by jmorris42 (1458) *
      > 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?

      Not really, the Internet assumes nodes can change but there is an end to end link possible, if not instantly within a couple of seconds of reconfiguring or outage. This is more like reinventing packet radio or meteor scatter. Mebe they should go talk to some old hams to get some ideas instead of spending millions to r

    • I'm sorry... (Score:5, Funny)

      by rmdyer (267137) on Thursday November 16 2006, @07:20PM (#16878344)
      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, that was packet switching (Score:4, Informative)

      by Capt. Skinny (969540) on Thursday November 16 2006, @07:46PM (#16878624)
      Wasn't that the point of the original ARPANET? To route around broken parts of the network?
      ARPANET was never about sustaining communication in the event of network failure. That goal belongs to the development of packet switching - a separate government funded project by the RAND corporation at about the same time. Sorry, I'm too lazy to dig through my e-mail to find my references.
      • So the messages carry, what, domain names? (It's probably in the article, and I did read the first page, but just wasn't going to click four more times in hopes that maybe it was there if I could just ask you.)

        • Re: (Score:2, Informative)

          by strstrep (879828)
          They carry endpoint IDs, which achieve a similar functionality to IP addresses and TCP/UDP ports, but are also human-readable. DTN protocols are fairly high-level, so they can do that.
      • I thought routing tables and what not meant you don't need to know the route from source to destination. (trunk servers are supposed to have links with weight costs etc etc, where packets take a non-ideal route when a line is down for example.) Of course, it's very true that in practice this is rarely the case. No one seems to build reliable networks these days.

        Sure, doing it with 0% packet loss might be new, but how important is that when you've got TCP to handle that?
        • The point is that you have a route from point A to point B, but at any given time not all of the links on that route will be up. In fact they come up only intermittently (this technology is an offshoot of SCPS--Space Communication Protocol Standard--which had to deal with satellites that were behind the planet for some percentage of the time).

          TCP requires a complete end-to-end connection in order to send data, if you never get that, then you will never send bit 1 with TCP. DTN uses a store-and-forward
      • Back before Algore invented it. . .

        Hey, is that who they named "algorethms" after?!?

        • Re: (Score:3, Informative)

          by DeadChobi (740395)
          No, they named algorithms after an Arabic mathematician named Al-Khwarizmi(Algorismus). He translated a lot of greek works too. Check him out. Some of his translations and original work form the basis of what has become algebra, which is another etymological contribution from him.

          • No, they named algorithms after an Arabic mathematician named Al-Khwarizmi(Algorismus).

            OMFG, you still got the joke though, right? Right...?
                  [sob]

  • Zonk... (Score:3, Insightful)

    by Anonymous Coward on Thursday November 16 2006, @06:17PM (#16877664)
    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.
  • The article is on five small pages, with no option to see a linkable, printable version.

    Yea, except for maybe the link at the bottom of the article that says "Print".

  • wow, a press release from 1983! (Score:4, Funny)

    by toby (759) * on Thursday November 16 2006, @06:21PM (#16877704) Homepage Journal
    Anyone else feel like they're time travelling when they're reading this?
    • You missed the point of DTN (available when you RTFA) - at any instant in time, no end-to-end connectivity is needed. Standard network protocols (including those developed back in '83) cannot function without end-to-end communication.
        • There is already a web browsing proxy available. I'm not sure if the dtnrg.org link to it is obvious yet (you used to have to be a genius to find it), but it's there. Admittedly, it's just a hack of wwwofled that is designed to work over DTN (basically, when you request a page that isn't in the cache and there is no good end-to-end connectivity, it brings up a webpage asking you how much of the remote page you want (images, scripts, spider down a level or two, perhaps with some keywords to search for, up

  • Hmm, a... DARPA-net? (Score:3, Funny)

    by dfay (75405) on Thursday November 16 2006, @06:29PM (#16877776)
    I'm glad DARPA funds stuff like this. They should perhaps call it DARPA-net or something like that. Also, perhaps this research will result in really cool new inter-networking technology that the public can make use of. Perhaps universities might be the first big users.

    Of course, if that happens, I hope this new inter-networking thing doesn't get privatized... 'cause then all kinds of crazy things might happen.

    (For the uninitiated or those who like things spelled out, see: http://en.wikipedia.org/wiki/History_of_the_Intern et [wikipedia.org])
  • Yes, SMTP is an amazingly strong example of redundancy. However, we installed redundant fiber at a school I work for within a few days, and just for fun we'd pull plugs randomly and monitor the response time while a alternate link was used. I think 10ms was about average... Then it stopped being fun after a while. We even tested load balancing.

    So my question is.. why are we treating this like its a new thing? This seems like another one of the frequent quasi-ads which seem to be more common lately here
  • In related news, the DoD has awarded RoundCo Inc. a 100 million dollar contract to develop a circular structure to facilitate the movement of objects with maximum efficiency. RoundCo is currently investigating deploying rubber-based, air-filled rings to fit this need. "This new technology could revolutionize logistics.", says RoundCo CEO David Goodyear-Wheeler.

  • Reliable networks with malicious components (Score:3, Insightful)

    by G4from128k (686170) on Thursday November 16 2006, @07:14PM (#16878258)
    Although this research is nice, it does not address the worst vulnerabilities of the current internet. Botnets, ARP poisoning, DNS poisoning, pwned routers seem to be a more dangerous risk than mere unreliable components. Cyberterrorism and criminal exploitation of the internet means subverting the system rather than just breaking pieces of it.

    The original internet design carried the naive assumption that all the devices on the net could be trusted -- all the devices assumed the validity of all control data, responses to protocols, etc. In the original model, devices had two primary states -- "unavailable" and "available" where "unavailable" might cover both damaged or overloaded components (a slightly more sophisticated version assesses capacity or latency as gradations between the binary unavailable/available dichotomy). In this one dimensional two-state model, disruption tolerance means routing around "Unavailable" or overloaded components.

    Yet the rising threat is from malicious entities that want to subvert the network's functioning, not just disable it. Spam, phishing, click fraud, and extortion depend on twisting a functioning network, not just poking holes in the network -- all the parts remain "available" but their data and responses become deceptive. Thus future fault-tolerant networks will need to distinguish between trustworthy and untrustworthy components. This suggests employing techniques such as cryptographic signatures, polling systems, blacklisting, FOAF, firmware integrity checks, and device-to-device secret questions.

    Designing a more robust internet is a laudable task but we need to spend more effort on securing against the true threat of untrustworthy components rather than unavailable components.

  • This is not simply OSPF, this is a new layer 3 net (Score:4, Informative)

    by thanasakis (225405) on Thursday November 16 2006, @07:19PM (#16878332)
    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 [ipnsig.org], this article reminded me of it.

    • Re: (Score:3, Insightful)

      by ebyrob (165903)
      The problem is, discarding extraneous packets is actually a VERY GOOD THING when it comes to the internet. Several store and forward systems pre-dated the current TCP/IP stack, but guess what. They weren't as efficient in terms of required hardware resources or latency. This is because in a store and forward network, certain problems (like network cards going nuts and spewing tons of garbage) can cause lots and lots of data to accumulate in the network, and then you have to wait for every single packet t
      • Right, but only if you've got end-to-end connectivity. If you don't, TCP breaks, and you get zero delivery. There are situations (see data mules and wireless sensor networks in disconnected environments) where you simply cannot have a complete end-to-end link, but periodic links within the larger path are still possible or even predictable. DTN can take advantage of single TCP connections without requiring the entire set of nodes from source to destination to be up at one time, and, if this project works
  • Routing around holes in a network... Sounds like the basic functionality of routing protocol to me. So they're getting paid big bucks to re-invent IGPs like IS-IS [wikipedia.org], OSPF [wikipedia.org], RIP [wikipedia.org] (though this POS creates more holes than it routes around), IGRP [wikipedia.org], EIGRP [wikipedia.org] or an EGP like BGP [wikipedia.org]? Hell when it comes right down to it good ole IEEE 802.1D [wikipedia.org] is a layer-2 routing protocol (when you think about how it actually works and not the generic description you read about in references). Hello, wheel.
  • Are we talking outages of 20ms or 5 minutes or 3 days or what?

  • DTN (Score:2, Informative)

    by Anonymous Coward
    No, this has not been done before in this manner. The internet does not communicate when disconnected. Try to send a file to a machine that is turned off or not connected to the net and see what you get?

    This type of network, DTN (Disruption tolerant network - which btw, is similar to DTN - delay tolerant network - (see IETF working group)) is oriented towards disconnected operation, mobile nodes and ad-hoc environments.

    BBN is not the only participant (though it is a big one). The project includes various
    • Try to send a file to a machine that is turned off or not connected to the net and see what you get?

      What you get is called "Usenet", and it's been doing just that quite successfully for a few decades now. ;-)

      Usenet originally ran mainly on top of UUCP, invented at Bell Labs back in the 1970s. UUCP implemented the same sort of scheme some years before the Internet came into existence. The general term is "store-and-forward".

      It's all covered in many "intro to networking" courses.
  • ... some kind of DARPAnet birthday celebration ?
  • Of course, alot of people/ISPs do this already (not at the internet level but within their network), trouble is when one of the links go down, the 'failover' route gets it's own traffic and the traffic from the broken route. AND there's not enough bandwidth over this route to handle both sets of traffic.

    Happened to me many many times...as a customer of lots of different ISPs.
  • that gives you a one-page format of the article. Counter-intuitive? yeah, that's right.

    Not as bad as the macromedia paged website the other week. Sheesh!!!!!

    • Re: (Score:2, Informative)

      by daiichi (888740)
      This isn't SMTP. SMTP is a layer built atop of TCP/IP for sending of very specialized messages. Apparently BBN's protocol is generic enough to conceivably cache HTTP requests (e.g. the reference to a "google earth map.") So I would give them the benefit of the doubt until more information is forthcoming.

      A real criticism of what BBN is doing is that, heck, my cell phone is low enough on memory already--and I would be very put out having to share that meager space in order to persist that scoutmaster r

      • There is already a HTTP proxy for DTN. You hit the nail right on the head that this isn't SMTP, it's far more generalized.

        As for storage requirements on the routing nodes, it is up to them to know how much storage they have and the status of their links. If they have no storage available (or if they are configured not to store that kind of data), then they can refuse to take custody of the DTN bundle. If that happens, there are several options available to whoever does have custody of the bundle. The
    • Don't you mean FLA?
    • BBN has developed a network protocol and code that moves information from node to node as connections become available, and can hold information in persistent storage until a connection is available.

      Wow... what can I say ? - over 8 million bucks to re-discover or re-invent SMTP...

      Funny, but maybe a bit mistargeted. The idea behind SMTP really was to do email via a direct end-to-end TCP link. Caching when the destination couldn't be reached was a "temporary" kludge that was grudgingly added because the Int
      • I was thinking of a network where the node between every link could has an SMTP host. That way there are no path / routing issues. If a SMTP host that's nearer the destination comes online, then send the message.

        How do you determine if the host is nearer ?
        Use the DNS LOC Resource Records : Location information, code 29. Associates a geographical location with a domain name. Defined in RFC 1876.

        See : http://en.wikipedia.org/wiki/LOC_record [wikipedia.org]

        • Geography is not necessarily related to the best data links to choose from. Sometimes it pays to go out of your way to hit a backbone instead of trying to jump through a thousand mom and pop ISPs to get to your destination.

      • So can SMTP. (Score:3, Interesting)

        by khasim (1285)
        The spec provides for "intermediate" servers receiving the message and passing it on.

        Years ago this was duplicated with the old BBS's and phone lines. I'm talking about the single user at a time boards. One phone line. Lots of waiting.

        The boards had the numbers of different boards that they would call as the lines were free (their's and the recipient's). Messages would be passed along whatever route was available until they were received at the destination.

        This model is heavily dependent upon storage, thoug
        • The DTN routing community is very active. As it turns out, in a Disruption Tolerant Network a lot of the assumptions you make about normal routing can be wrong. For instance, Routing Loops are not necessarily bad (and sometimes necessary). Finding the best path through the network (especially if it's an ad-hoc network) is a hard (in just about every sense of the word) problem.

    • Re:What, AGAIN? (Score:5, Informative)

      by xyzzy (10685) on Thursday November 16 2006, @06:57PM (#16878090) Homepage
      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.

      See: Where Wizards Stay Up Late
      http://www.amazon.com/Where-Wizards-Stay-Late-Inte rnet/dp/0684832674 [amazon.com]

      and
      http://www.businessweek.com/1996/38/b349359.htm [businessweek.com]

      • What you're describing is NSFnet, which was based on the arpanet. NSFnet, proposed in the early 80's, proposed to expand the connectivity of the arpanet via several high-speed backbones, for the purpose of scientific data exchange. I collaborated on several projects using NSFnet.

        The arpanet (and I was a registered arpanet user prior to the installation of the NSFnet backbones), was developed for military purposes -- (a fun trick was to send packets all the way around the world via, for example, a node cal

    • See, the problem is that first thing, the "Internet" thing, got away from the powers that be. They let the peasants behind the castle walls, and now it's all spoilt for the really "important" people and their really "important" business.

      So now, see, they've got to start from scratch, and this time, boyo, there's gonna be none of this "Net Neutrality" stuff mucking up the works. And you best believe there won't be any dirty-necked hacker types or dot.com money-for-nothing strivers in the picture. This ti

    • Re: (Score:2, Informative)

      by strstrep (879828)
      Actually, a planned convergence layer for the DTN project is sneakernet.

      DTNs work by storing packets (well, "bundles," really) at the router, until an opportunistic connection is available. Bundles move from hop to hop, until they arrive at their destination.

      This is accomplished over a variety of "convergence layers," such as TCP and UDP, with UDP being the most commonly used for transmitting bundles currently in research. However, other convergence layers for other uses are being planned. One of these i
      • Remember, this is Slashdot. We would gladly pay $8.5M in research to allow the computers to do the talking for us.

        --------------
        From: John Smith
        To: Jane Doe
        Subject: Thnx

        thnx 4 ppt. wnt g00d lol.

        JS
        University in NZ
        --------------
        Come to think of it, forget the network. I think our communication is down.
    • First off, the article headline is bullshit. "Has holes in it" is not the same as "down".

      Secondly, dynamic rerouting to overcome partial failure or congestion is as old as digital backbone telephony and predates the internet by many years.

      • Re: (Score:3, Insightful)

        by strstrep (879828)
        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.

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