Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Wireless Networking Communications Hardware

Voice Over IP On Wireless Mesh 109

Posted by timothy from the network-is-the-network dept.
infractor writes "ZDNet is reporting that the Linux based LocustWorld Mesh system now has SIP routing at every node. The LocustWorld boxes have been widely used in community broadband projects where DSL is not available, so successfully that they have been seen as a threat to next generation mobile networks. With the addition of VoIP support, these mesh networks can now compete with the telcos on voice as well as data services. More details here."
This discussion has been archived. No new comments can be posted.

Voice Over IP On Wireless Mesh More

Voice Over IP On Wireless Mesh

Comments Filter:

  • Wireless VoIP isn't feasible yet... (Score:5, Insightful)

    by mindless4210 ( 768563 ) * on Wednesday April 14, 2004 @03:21PM (#8862890) Homepage Journal
    With the addition of VoIP support, these mesh networks can now compete with the telcos on voice as well as data services.

    I would have to disagree with that comment. Yes, these networks can now provide voice services, but they cannot effectively compete. In reality, wireless VoIP is still being developed and will most likely not be of acceptable quality for another year or so. Mainly, latency is the biggest issue [zdnet.com] to be conquered at this time. I think until they are able to reduce latency times significantly in these applications, it won't be widely accepted. It's just too frustrating when theres a couple seconds in between speaking and hearing a response from the other person.

    Furthermore, while a mesh network can still carry a high data rate, the high number of hops to a wired connection from some locations along the network could make talking over VoIP rather unbearable. I imagine that on a larger mesh network you could experience latency upwards of 1000 ms.

    • Re:Wireless VoIP isn't feasible yet... (Score:5, Informative)

      by LOL WTF OMG!!!!!!!!! ( 768357 ) on Wednesday April 14, 2004 @03:25PM (#8862929) Journal
      Mainly, latency is the biggest issue to be conquered at this time.

      I live in Los Angeles and communicate with an FWD [pulver.com] SIP with which I call a conference in Japan almost daily. Latency with that is very low, and that's with a free service!

      I really don't latency is the problem as much as it is making the technology easier to use for the average joe ( X-Lite is NOT easy to set up if you have router ).

      • Re:Wireless VoIP isn't feasible yet... (Score:4, Insightful)

        by JoScherl ( 228091 ) on Wednesday April 14, 2004 @03:36PM (#8863035) Homepage

        I really don't latency is the problem as much as it is making the technology easier to use for the average joe ( X-Lite is NOT easy to set up if you have router ).

        Does Joe have a router? I think not. Ok, thanks to DSL-Lines, at least here in Germany, many people get routers, but still I don't think Joe Average has one. The greater problem is that a) Joe dosn't know about it and b) he doesn't know anybody else who uses the same VoIP system. To make use from VoIP it would imho need one big company advertising these services, but I think the ISPs do not like VoIP 'cause it creates huge amount of traffic

        • I agree with you on most of that. However, MANY people have routers. Essentially anybody who has a broadband line and more than one computer.

          And routers these days are generally easy to use. CompUSSR sells one for $20 with a nice web interface and very easy instructions.

          However, the fact remains that most VoIP software has horrific problems when working with a router. Whether this is problems with most routers handling UDP, or just bad programming is something that's beyond me.

        • Skype (Score:1, Informative)

          by Anonymous Coward
          I have a router. Everyone I know with a net connection has some type of router. Probably because we all have more than 1 computer, but it's not uncommon.

          I've tried quite a few VoIP programs, and all of them have problems with routers. Last week I ran across Skype. All I can say is wow. Crystal clear sound, works through the router / firewall without changing a thing. No studder, "CB" effect, etc. and the sound quality is better than my phone.

          It's currently in beta, and will most likely have a fee associat

          • I have a router. Everyone I know with a net connection has some type of router. Probably because we all have more than 1 computer, but it's not uncommon.

            People who use their computer more for working etc. have routers, that's true. But still I think Joe Averange, in most cases, doesn't have a router.

        • I work for a cable company, I'd say about 70% of the people that call have routers even if they only have one computer. Most people with routers dont know exactly what they do, in fact that's probably the reason there are so many unsecure access points.

          VoIP has companies advertising and it's becoming more popular as well as usable.

      • Re:Wireless VoIP isn't feasible yet... (Score:5, Informative)

        by mc6809e ( 214243 ) on Wednesday April 14, 2004 @03:42PM (#8863103)
        I live in Los Angeles and communicate with an FWD SIP with which I call a conference in Japan almost daily. Latency with that is very low, and that's with a free service!

        But your situation is unlikely to be the most common.

        Being on the west coast, you're probably just a few hops from a trans-Pacific link directly to Japan. You have what amounts to a nearly direct link from one place to another.

      • Latency on the wireless part of a connection and latency on the wired part of a connection are much different issues, and the whole VOIP and Video-over-IP world is riddled with mythology about latency. If you've got an ISP connection with decent trunking and your uplink isn't heavily loaded, the biggest components of your latency between LA and Japan are the distance to Japan (which regular phone calls also have) and the sampling time of your codec. But if you're sharing an overloaded community wireless
    • And on top of that, the idea of technically free VoIP calls won't go down well with the sevice providers. I can't imagine them NOT lumping enough service charges on top to make it totally unfeasible to home users, whereas the 'read more' article seems to be aimed at just those people.

      Let me stick with my MSN (*awaits flames*) voice conversations with people I know
      • So long as this is internet to internet there is no service fee.

        However, this sort of thing, if it becomes common, could quite possibly lead to a tragedy of the commons. If everyone actually started using all the bandwidth they had available, the networks would become jammed quickly enough.

        Free VOIP is great in the short-term, but there is *not,* at this point, an unlimited amount of free bandwidth available.
        • Well, it's not like VOIP takes up any more bandwidth
          than PSTN. If I'm calling you on a VOIP phone,
          I'm *not* calling you on a PSTN phone. The difference
          in backbone traffic on the fiber is negligible, but
          the difference to my wallet is significant.
    • Great! Now find me a way to get my electricity via wireless and I can be totally independant!
      • Great! Now find me a way to get my electricity via wireless and I can be totally independant!

        Oh, wireless electricity isn't really that difficult... it can be acheived through a microwave beam.

        The real trick is coming up with wireless electricity that doesn't fry anyone alive who wanders into the path of that beam...
        • Okay, this is off topic, but actually, while I wouldn't recommend STANDING in the path of a wireless power transmission, walking through the path shouldn't affect a person too much. The cell phone, PDA, digital watch, pager, digital camera, laptop, pocket calculator or other nifty gadget might have issues if they're not well shielded, but the human body shouldn't.

          This link [permanent.com] is a summary paper of information from a variety of sources on Solar Power Satellites. This one [permanent.com] has a couple pictures of a test in Ca

      • Well, if you're near some powerlines, you can always roll up a fatty...er...I mean a really huge inductor coil. :-) Otherwise, I think that guy Tesla had some ideas on that.

    • Re:Wireless VoIP isn't feasible yet... (Score:5, Informative)

      by kennybain ( 770451 ) on Wednesday April 14, 2004 @03:51PM (#8863167) Homepage Journal
      In the real world, this isn't the case. You have multiple uplinks into the "wired" interent, so you are only going 3 or 4 hops into the mesh. Ping times to the internet never exceed 100ms on a properly designed mesh network. I use Packet8 over my network... http://www.fastlineinternet.com , we are the first US deployment of the LocustWorld system. So this is a voice of experience.

  • Where's the beef? (Score:5, Informative)

    by Brento ( 26177 ) * <brento.brentozar@com> on Wednesday April 14, 2004 @03:25PM (#8862931) Homepage
    If it supports SIP, it's not obvious from their downloads. Their ISOs haven't been updated since 2002...

  • Quality (Score:5, Insightful)

    by lukewarmfusion ( 726141 ) on Wednesday April 14, 2004 @03:28PM (#8862952) Homepage Journal
    Compete? Maybe not. Remember when NPR discussed this and one of the callers started having problems - right in the middle of his praise for VoIP?

    That said, I'm anxious to find an inexpensive way to replace my $90 cell, $50 broadband cable, and $40 landline. If I can cut these bills down significantly (by using my broadband to provide my landline) I'd be happy. And I'd bet that most bill-paying consumers would be too.

    • Re:Quality (Score:3, Insightful)

      by YanceyAI ( 192279 ) *
      They manage to allow us to consolidate those, along with the idea of the single multimedia device, then I'm happy. Very.
      • The only thing being consolidated is ownership of the pipe. There is no competition. The phone company buys the cable company which buys the ISP. Pretty soon GE (General Electric) owns it all.
        • Dont you mean "The Network." While Running Man scencarios are scary, whats scary is the tempation for totally consolidated systems.

          Imagine:

          You're watching the game. Your mother-in-law buzzes in. A little picture-in-picture appears. She thinks she's got your full attention, but in reality you're glued to the last play of the game! Brilliant. Hell maybe you've got another 'lindow' open where you're updating your online wager. Evil, but sexy.

    • I use my cable for my landline and it work great. I have a little white box that sits behind my TV that plugs in to my phone jack. Works just like a regular line and cost half the price of the bells. And my cable company cuts me a deal; I get digital cable, phone, and cable Internet for $90 dollars a month. I love having 1 bill and a small one at that!!

    • Re:Quality (Score:2, Insightful)

      by ytseschew ( 562867 ) *
      You also need reliability. My cable modem usually goes out for a couple hours every couple months. This past week it was out 3 times while they did "service upgrades." On the other hand my phone line has been out exactly 1 time in 4 years and only because a telephone pole was knocked down right near my house. My power has gone out a number of times but that never knocked out the phone service. I can't even remember having the phone service going out at my previous location. Having my landline phone go
    • How 'bout Vonage [vonage.com]? I'm thinking about trying 'em out.
      • I used Vonage for about a year and a half when i lived in the UK and I was VERY impressed.

        I had a job and fiancee in the USA, and vonage gave me a local number there and unlimited calling for about the same a british telecom charged for an hour long call each month.

        Now the situation is flipped, I'm in the USA and need to call family and friends in the UK. I just converted my old vonage hardware to run with mywebcalls.com and i can get cheap calls the other way.

        I called my mom yesterday using voip for the

    • QoS (Score:2)

      by div_2n ( 525075 )
      Quality of service is a concern for almost any type of service you get. I have seen people have extreme problems with their landline phone only to discover much later that it was water getting in their line. For a while I could hear other conversations on my landline (not a cordless phone) everytime I placed a call. I could still manage a call but it was hard to ignore.

      Any type of wireless service (regardless of type) is subject to serious issues. On my cellphone, I occasionally place or receive calls

  • This is precisely (Score:5, Interesting)

    by iminplaya ( 723125 ) on Wednesday April 14, 2004 @03:38PM (#8863064) Journal
    the kind of "wireless internet" that I have been babbling about in other threads. This is what can liberate us from corporate control of internet access. I want to see this "wireless cloud" cover the planet. The latency issues will be worked out. In the meantime, this is great for "little" community internets where latency is not that bad. Even if they can't access the net at large, they can communicate, completely free from interference from the gov't, with each other. Maybe (hopefully) it can bring about completely anonymous, untracable communications. Just because it's not codified into law, anonymity is a right, and anything that can bring it about is a good thing.
    • Wireless clouds are cute and friendly and don't have really huge bandwidth (though I'm one of those old-timers who remembers when 56kbps *was* really huge bandwidth :-). Fiber optic pipes *do* have really huge bandwidth, and most of the locations you want to talk to are connected to them, and if you want your community wireless network to do anything useful, you're going to need to tie them together, typically using the wireless for local access and maybe cross-town access and using ISPs for long-haul bac
    • Just because it's not codified into law, anonymity is a right

      Really?
      Justify this statement, please.
    • cache... smart cacheing systems... your local node, the nodes that route info, all over. A smart cacheing system will largely make up for lag on a very large mesh network....

      Also, zerconf(apple's rondezvous) does a lot of thigns we should be using... auto-assigning ips, and discovery, easy setup...

      IPv6, more addresses, better inherit security....

      TCP: that competition that made TCP uber-fast by tweaking it's algorythm... fastTCP, that has articles on /. every once in a while....

      The next version of TCP/IP

    • I want to see this "wireless cloud" cover the planet.

      Okay then... Are YOU going to be the one sailing one of the boats needed, in the middle of the Pacific Ocean, with nothing but an 802.11 access point onboard to relay signals from contient to contient?

      Even if they can't access the net at large, they can communicate, completely free from interference from the gov't, with each other.

      Yeah! They couldn't do that before with telephones, postal mail, wireless radios, smoke signals, et al., right?

      Maybe (

      • Are YOU going to be the one sailing one of the boats needed...

        Buoys? Bouys? Those little floaty things used for navigations...

        They couldn't do that before with telephones, postal mail...

        Yes, but now encryption is easier. Actually, with all the noise already in the system, it's getting even easier to hide messages, and with wireless, it can be made harder to trace(think constantly changing IP addy's, in a spread spectrum kind of way, and the simple fact that you're mobile, like a scud launcher)

        It does

        • Buoys? Bouys? Those little floaty things used for navigations...

          And how do you plan to power these buoys? Solar isn't powerful enough yet, and if you run a generator, somebody is going to have to go refuel them all the time.

          It doesn't matter if people agree that anonymity is a right. Screw them. I just want to see it made technically possible.

          I think most everyone will agree that postal mail can be as anonymous as you want it to be. You could even use PGP to encrypt the contents if you like.

          so that

          • And how do you plan to power these buoys?

            Those things roll around a lot. Something like the self winding mechanism in a watch, only big?

            Anybody can spend a few bucks and build a powerful signal jammer that will just destroy all wireless networks in the area.

            Curses...foiled again...back to the lab, pinky...I'll get back to you on that. I hope jammers will be easy to find, even in the cloud. Maybe, due to it's power level? or how the signal is modulated? All that work they're doing with active noise can

            • Those things roll around a lot. Something like the self winding mechanism in a watch, only big?

              It's been tried, it just doesn't provide enough power for much more than a dim lightbulb.

              You also have wind power generation, which would be good on the sea where there's no obstructions, but I still don't believe it would be windy enough to provide (just) several dozen watts of power all day.

              I hope jammers will be easy to find, even in the cloud. Maybe, due to it's power level?

              Well, jammers will be like spam

              • Heh...just after posting that, I was thinking that all that crap on Star Trek about shield "frequency and modulation" actually has a meaning or purpose here. We will encounter more RF weaponry as time goes on, and we're going to need more than tin foil to protect ourselves.

                Cops aren't going to be interested in comming out to find who is responsible...

                The cops will probably most likely be the people responsible for putting UP the jammers. The gov't doesn't like P2P communications without going through on
                • If the jammer can be "masked out", could that work?

                  About the only possible way to block all types of signal jammers is to build an aluminum dome around them, that is connected to a large groundind rod with high gauge cables. Good luck!

  • my greatest dream (Score:5, Interesting)

    by ericbrow ( 715710 ) on Wednesday April 14, 2004 @03:38PM (#8863065) Journal
    I've always thought that this should be. Wouldn't it be great if wireless networking were as easy to come by as electricty, but without the wires.

    I know it's a little communistic in thinking, but I really believe that to gain true freedom of information, we need to make the information superhighway free to use.

    While I know many problems would have to be worked out, like security, but it would change everything. Imagine every student being able to turn in assignments anywhere. Imagine doctors being able to monitor patients real-time, as they were being rushed to the emergency room. Yes it would put the telcos and cable companies in an uproar. But I think that would be the price of progress.

  • Queue up Lawyers and Lobbyists (Score:4, Funny)

    by rock_climbing_guy ( 630276 ) on Wednesday April 14, 2004 @03:38PM (#8863071) Journal
    Let's set up a queue for all the lawyers and lobbyists for Cingular and Nokia to try to get a bunch of stupid laws passed to tariff / cripple this technology.

  • So.. (Score:3, Interesting)

    by bigattichouse ( 527527 ) on Wednesday April 14, 2004 @03:41PM (#8863092) Homepage
    question is, will it "all" eventually be one big mesh out there? I imagine the telcos will do what they can to stop it, but I could see mass mesh adoption as an incredible force to recon with.

    • question is, will it "all" eventually be one big mesh out there?

      I can't imagine how. It's just too fragile. Anyone can knock-out a large segment of a wireless network, and without some money behind it, who is going to try and make sure it doesn't happen, or that it's stopped right away?

      And then there's the question of who is going to be the one to pay to setup and operate the relays in the middle of long hauls where you won't find any computers otherwise.

      And there's always the fun part of having the o

  • Dell use VoIP for their Indian call centers (Score:4, Funny)

    by Anonymous Coward on Wednesday April 14, 2004 @03:46PM (#8863132)
    5 second pause...

    Hello, my name is Bob Thandushepatindiar how may I help you?

    5 second pause....

    My computar's borken! Help.

    5 second pause...

    I understand your unhappiness.

    5 second pause....

    I said my COMPUTAR'S BORKEN!

    5 second pause...

    Thank you, come again.

  • Latency my ass (Score:4, Informative)

    by www.fuckingdie.com ( 759660 ) on Wednesday April 14, 2004 @03:46PM (#8863135) Homepage
    Latency is not a problem as far as I am concerned. I use FWD on a regular basis, and have never ran into a major issue making even ultra long distance calls. (This includes peak time calling, which has never given me trouble.)

    • Re:Latency my ass (Score:1, Informative)

      by Anonymous Coward
      Every wireless hop adds a bunch of latency to the connection. Not so bad if you're 2-3 away, but if you're 10 away, it'll be hell.
  • I've been thinking about this same thing just recently. From what I understand http://ask.slashdot.org/article.pl?sid=04/04/13/20 43202&mode=nested&tid=126&tid=137&tid= 215 [slashdot.org] that VoIP still isn't the most reliable thing in the world. There are a few things from a business stand point that will keep WVoIP from overtaking the mobile market, although this is perfectly tempting.

    Here are a few of the reasons:
    • The number of flaws and hacks that are readily available for switches, routers, and
    • To counter your arguments

      Hacks do exist for VoIP systems but these dont seem to be any more widespread than other network applications. People still use FTP and SMTP despite their atrocious security records

      An open standardized system is one of the best things about it. I can take my stock VoIP hardware and (in theory) make it work with any number of providers

      Cisco make nice little boxes which have CAT5 in and Telephone out, Grandstream make real phones with CAT5 connections, someone even makes phones

      • Good point to each of those items.

        What about hardware? I'm talking about load balancers, servers, and phone sets? Let's suppose you roll something like this out to a community, what would they have to have to support it? Probably a server with a 1Gb backbone right? Something to handle all of the traffic too. Then they'll need hardware for the phone replacement.
        Or it could be offered as a notebook/PDA based software that you use to make your calls.

        • Well each device can be set to periodically configure itself by TFTP. That can then balance the load just by dividing the users up across your servers.

          Typically you need somewhere between 32 (cell phone like) and 96 kbit/s (better than pots) quality call. However that's the peak bandwidth, at least half the call will be silence (while the other party talks) so you can survive with as little as 16kbit/s average.

          A T3 should be able to support about 2800 low fi calls or almost 1000 hi fi calls. But not every

  • voip in actual use (Score:1, Interesting)

    by Anonymous Coward
    VOIP is great, but outside the cities it really
    doesn't cut it. That's where the market is though.

    I've used some VOIP implementations in less than
    ideal conditions and there is a lot of work to
    be done before this is ready for prime time.

    Not a coder ? Want to help spread Linux ? Click here ! [lp2p.com]

  • Injecting harsh realities (Score:4, Insightful)

    by PureFiction ( 10256 ) on Wednesday April 14, 2004 @04:23PM (#8863460)
    The code is there, the actual performance is going to be lackluster at best.

    Mesh networks suffer from scaling problems due to the overhead associated with ad-hoc protocols. All that flexibility and adaptability come at a price: efficiency, latency and throughtput all decrease as the size of the mesh increases (and even more so when you have popular / power law nodes attracting routes)

    Voice is notoriously sensitive to delay and to some degree packet loss. Sure, delay effects can be overblown (ATM anyone?) but you get a saturated mesh network trying to route voice and those multi-second round trip times are going to make your cable modem look like a T3.

    [You get losses due to interference, transient link problems, mobile nodes, sun spots, whatever, that cause delays at the physical layer (an ethernet frame takes a while to traverse the ether) which then affects all higher layer protocols: UDP packets can't be reassembled because a fragment is lost. TCP starts backing off too agressively. Retransmission timers get triggered adding to inefficiencies, the list goes on]

    Wireless and mesh networking in particular are very promising and useful technologies, but they are no where near the utopia that is often presented.

    Trivial DoS attacks, scalability problems, and compounded complexity all add up to make it a very volatile environment.

    Sure, this stuff will work, but only in very constrained configurations / environments.

    Maybe someday further in the future these dreams can be realized when we have robust MIMO software radios and intelligent network stacks that can adapt to such harsh conditions. :-)
    • Actually, you are only partially right. Traditional mesh networks, such as the one that MIT has been working on, require routing tables that grow (exponentially) each time a new node is added to the mesh. However, you should read up how LW has solved those issues. From the LW website: "As each mesh node is autonomous, discovering routes on demand, there is no central control to act as a bottle neck. As the network grows the routing task for each node does not grow exponentially, as they only build routes to
      • Indeed, the biggest problems with adhoc mesh routing protocols are unidirectional links and routes needing to be reformed due to mobile nodes. Fortunatly the kind of mesh networks locustworld are dealing with will be fixed so there are no mobile nodes, and unidirectional links can probably be dealt with.
    • Er, no.

      Mesh networks aren't perfect, but the extreme low bandwidth of voice (8kbps for G.729) relative to the channel capacity makes up for quite a bit. Voice is way more sensitive to packet loss than delay, because almost nobody's implemented error concealment*. You notice the dropped signal on your cell phone way before you notice the absolutely atrocious latency you chug through.

      Multisecond RTT doesn't happen on anything but GPRS, and that's because the actual core bandwidth is so slow (well, it's fo

      • Re:Reality Check (Score:3, Informative)

        by PureFiction ( 10256 )
        Good points. What I meant by latency is that losses in the physical layer result in large latencies at the transport layer (i.e. the 802.11 MAC).

        And RTP wont fragment as you mention because of MTU (unless you were doing something really odd with fragmentation at the 802.11 MAC?). I was thinking along the lines of long setup delays for the sessions due to SIP over TCP with larger payloads.

        I was a bit harsh on mesh networks. The combination of AODV, DSR, and DSDV is a huge shift in the style of ad-hoc or

      • Re:Reality Check (Score:4, Interesting)

        by PureFiction ( 10256 ) on Thursday April 15, 2004 @01:43AM (#8866522)
        I'll shut up after this, promise. :-)

        Multisecond RTT doesn't happen on anything but GPRS

        I've seen it far too often on congested wifi networks. you easily get into a congested state with a crowded AP that forces lots of client waits for the DCF (i.e DIFS + padding, each in turn) and also induces lots of retransmission at the physical level due to collision with so many clients trying to talk to the same AP. Low power clients associated at the 1 or 2 Mbps rates drive this contention over the DCF even higher, severely punishing everyone associated.

        The big conference venues are notoriously bad about this, as you often end up with 10-20+ people associated with a single access point. That is just too many, and the 802.11 MAC was never meant to handle that kind of load efficiently. It is a pretty good solution for the general case that simply can't cover all the edge cases (long shots, high client loads, noisy RF environments).

        This type of situation results in really weird ping times, for example. I've seen fluctuations myself that go from 80ms, 120ms to 3s!, 2s!, etc. then back down to a few score milliseconds. That is the 802.11 MAC trying to cope with scenario's it was never designed to encounter.

        I mentioned software radios in the first post because having access to timing and congestion control in the MAC would allow mesh boxes, clients, and AP's to make very significant performance enhancements for situations where they were needed. Why be forced to use a static, inflexible, proprietary hardware layer when you can have the open flexibility associated with software radio? (It's coming, just not soon enough :-) There are also extensions to the ad-hoc routing protocols (like passive monitor of route info between other clients in DSR) that could be supported if only the hardware was open enough to do so.

        I don't want to bitch too much; we have come a long way from sub-megabit data via FHSS over 900Mhz. I just want the really good stuff to hurry up and get here already so that things like mesh networks, low latency/loss voice over IP, and highly available multipath/redundant network configurations can be enjoyed to their full potential. (software radio + multiple input / multiple output + intelligent network stacks that can handle a diverse and volatile network environment). ... and a pony!

        Gratuitous links:
        congestion problems at TechEd conference [newswireless.net]

        congestion melt down at CeBIT [newswireless.net]

        GNU Radio's software defined radio (SDR) [comsec.com]

        software defined radio on $2,000 of 'roids [xilinx.com] [it's a dev kit, but would work very well for almost any kind of project]

        • Re:Reality Check (Score:3, Interesting)

          by Effugas ( 2378 )
          Wow. Very cool. I was unaware of this particular failure mode for 802.11. I would have assumed that the exponential TCP backoffs would have slowed down the incoming packet rates enough for the system to eventually slow down to some reasonable rate ... I bet, to some extent, hidden node played a _big_ factor here too.

          Still, I'm amazed you saw not dropped packets, but the MAC hold onto stuff for thousands of ms. Wow.

          You know, the newest Linux wireless drivers have moved _everything_ into software -- thu
          • You know, the newest Linux wireless drivers have moved _everything_ into software -- thus the ability to throw up an AP on demand.


            Where can I find out how to do that? I researched this reccently, hostAP only works with cards that have built in support for being a master. I'd like to use cheap cards in routers made from old PC's to act as access points in mesh networks instead of operating in ad-hoc mode. What about the performance issues, will this work on early pentium hardware?

    • Actual measurement of a LW mesh (Score:4, Informative)

      by Baldrson ( 78598 ) on Wednesday April 14, 2004 @07:40PM (#8864823) Homepage Journal
      Here are ping times from a mesh node that is 3 hops from the gateway:

      PING yahoo.com (66.218.71.114): 56 data bytes
      64 bytes from 66.218.71.114: icmp_seq=0 ttl=52 time=581.611 ms
      64 bytes from 66.218.71.114: icmp_seq=1 ttl=51 time=231.480 ms
      64 bytes from 66.218.71.114: icmp_seq=2 ttl=51 time=381.342 ms
      64 bytes from 66.218.71.114: icmp_seq=3 ttl=51 time=402.864 ms
      64 bytes from 66.218.71.114: icmp_seq=4 ttl=51 time=439.277 ms
      64 bytes from 66.218.71.114: icmp_seq=5 ttl=52 time=412.702 ms
      64 bytes from 66.218.71.114: icmp_seq=6 ttl=51 time=151.642 ms
      64 bytes from 66.218.71.114: icmp_seq=7 ttl=52 time=430.497 ms
      64 bytes from 66.218.71.114: icmp_seq=8 ttl=51 time=444.032 ms
      64 bytes from 66.218.71.114: icmp_seq=9 ttl=52 time=280.485 ms
      64 bytes from 66.218.71.114: icmp_seq=10 ttl=51 time=724.143 ms
      64 bytes from 66.218.71.114: icmp_seq=11 ttl=52 time=92.999 ms
      64 bytes from 66.218.71.114: icmp_seq=12 ttl=51 time=695.740 ms
      64 bytes from 66.218.71.114: icmp_seq=13 ttl=51 time=419.220 ms
      64 bytes from 66.218.71.114: icmp_seq=14 ttl=51 time=737.417 ms
      64 bytes from 66.218.71.114: icmp_seq=15 ttl=52 time=618.897 ms
      64 bytes from 66.218.71.114: icmp_seq=16 ttl=52 time=539.789 ms
      --- yahoo.com ping statistics ---
      17 packets transmitted, 17 packets received, 0% packet loss
      round-trip min/avg/max/stddev = 92.999/446.126/737.417/183.842 ms


      Here are the ping times from the gateway itself:



      PING yahoo.com (66.218.71.114): 56 data bytes
      64 bytes from 66.218.71.114: icmp_seq=0 ttl=52 time=64.234 ms
      64 bytes from 66.218.71.114: icmp_seq=1 ttl=53 time=64.491 ms
      64 bytes from 66.218.71.114: icmp_seq=2 ttl=53 time=64.086 ms
      64 bytes from 66.218.71.114: icmp_seq=3 ttl=52 time=63.948 ms
      64 bytes from 66.218.71.114: icmp_seq=4 ttl=52 time=63.516 ms
      64 bytes from 66.218.71.114: icmp_seq=5 ttl=53 time=65.467 ms
      64 bytes from 66.218.71.114: icmp_seq=6 ttl=53 time=64.871 ms
      64 bytes from 66.218.71.114: icmp_seq=7 ttl=52 time=64.494 ms
      64 bytes from 66.218.71.114: icmp_seq=8 ttl=52 time=64.090 ms
      64 bytes from 66.218.71.114: icmp_seq=9 ttl=52 time=64.252 ms
      64 bytes from 66.218.71.114: icmp_seq=10 ttl=53 time=64.044 ms
      64 bytes from 66.218.71.114: icmp_seq=11 ttl=53 time=67.765 ms
      64 bytes from 66.218.71.114: icmp_seq=12 ttl=53 time=64.428 ms
      64 bytes from 66.218.71.114: icmp_seq=13 ttl=53 time=63.651 ms
      64 bytes from 66.218.71.114: icmp_seq=14 ttl=53 time=64.078 ms
      64 bytes from 66.218.71.114: icmp_seq=15 ttl=53 time=63.852 ms
      --- yahoo.com ping statistics ---
      16 packets transmitted, 16 packets received, 0% packet loss
      round-trip min/avg/max/stddev = 63.516/64.454/67.765/0.967 ms

      A caveat on these numbers. First, I haven't optimized the mesh for VoIP -- I just got my VoIP equipment in and will be getting around to that shortly. Secondly, I'm running on the mesh myself so these were output to my ssh screen simultaneously from the distant box so the traffic was doubled up.

      • Another LW mesh provider is getting vastly better latencies and we're not sure why. The nodes in his mesh have greater distances (miles) between them compared to ours (hundreds of yards).

        Investigating.

        Here are his ping numbers from 3 hops out from the gateway:

        PING yahoo.com (66.218.71.113): 56 data bytes
        64 bytes from 66.218.71.113: icmp_seq=0 ttl=51 time=88.457 ms
        64 bytes from 66.218.71.113: icmp_seq=1 ttl=51 time=79.813 ms
        64 bytes from 66.218.71.113: icmp_seq=2 ttl=51 time=166.744 ms
        64 bytes from 66.21
        • Here is the latest ping measurement to yahoo from 2 hops out from the gateway on my LW mesh (the mesh has reconfigured itself):

          PING yahoo.com (216.109.127.28): 56 data bytes
          64 bytes from 216.109.127.28: icmp_seq=0 ttl=47 time=104.552 ms
          64 bytes from 216.109.127.28: icmp_seq=1 ttl=47 time=167.325 ms
          64 bytes from 216.109.127.28: icmp_seq=2 ttl=47 time=133.283 ms
          64 bytes from 216.109.127.28: icmp_seq=3 ttl=47 time=110.557 ms
          64 bytes from 216.109.127.28: icmp_seq=4 ttl=47 time=107.804 ms
          64 bytes from 216.109.1

  • Like Air Supply, this could be big in Asia (Score:3, Interesting)

    by pangian ( 703684 ) on Wednesday April 14, 2004 @06:11PM (#8863932)
    The only place that my organization considers VoIP is in our offices in developing countries.

    In many developing countries landlines simply aren't a viable option due to underresourced, corrupt and/or incompetent state-owned telecoms. Many of these countries have been able to develop more robust cell and broadband services, as these industries have seen less regulation and are more scaleable.

    For security, convenience and efficiency reasons we like to provide staff in these offices with cell phones, however cell phones plans in may still leave much to be desired in some countries.

    I think that many of our offices would be interested in VoIP cell phones if the coverage was decent (even covering major cities might be > or = to existing cell networks). Latency in phone conversations is already par for the course.

    Could be an interesting microenterprise project.
  • ...but.. I am fresh out of 30,000$ bills for the startup hardware glancing at the page for the suppliers, then the recurring T-1 connection, and even if I had that, I could wirelessly connect to ..myself! There's so little interest in my little locale for even dialup it's amazing. I might be the only one online as far as I know in a mile or so distance up and down the street. So far, I estimate that at least 1/2 or more of my neighbors don't even have a landline phone. I wouldn't even bother trying to drum
  • When 802.16 is deployed, wireless VoIP phones that are also PDAs will take over, allowing both high speed wireless voice and data links.

  • RFC Correction (Score:3, Informative)

    by muonzoo ( 106581 ) on Wednesday April 14, 2004 @07:55PM (#8864957)
    Of course, RFC2543 as referenced in the parent article is deprecated, the current base SIP RFC(s) can be considered:
    1. RFC3261 [ietf.org],
    2. RFC3262 [ietf.org],
    3. RFC3263 [ietf.org],
    4. RFC3264 [ietf.org], and;
    5. RFC3265 [ietf.org].
  • Until now, TCP/IP networks have measured bandwidth in terms analagous to current, the linear impedence. And with traffic and collisions, there have been some measures of viscosity. But these mesh networks' fabric capacity is fractional in dimension: routes are more than linear, but less than areal. What is the fractal capacity of an interconnected network of nodes with certain internode rates? Fractal spaces are enlarged when measured with smaller granularity units. Which protocols developed in the fractal

Slashdot Top Deals

It is easier to write an incorrect program than understand a correct one.

Close