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Doubling or tripling dialup connections

  1. May 26, 2005 #1
    I learned that someone can increase the dialup connection speed by using two modems, two phonelines and a special program that makes it work as one connection. Has anyone ever tried or heard of this?
  2. jcsd
  3. May 26, 2005 #2


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    I think I have, it's how ISDN works.
  4. May 26, 2005 #3


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    It's fairly similar, however, the key difference is that dialup modems are analog devices. ISDN is a digital, two channel (sometimes four), connection. The difference between a commericial connection, like a T1, and ISDN, is that a T1 uses many more channels (12 alone for data if I recall). So, a T1 and ISDN line are very similar technologies.

    Bottom line, ISDN is still much better than a dialup connection using multiple modems.

    Edit: On a sidenote, ISDN does not require you to have multiple "lines" per every 64kbps channel, unlike the dialup solution to having multiple "channels."
    Last edited: May 26, 2005
  5. May 26, 2005 #4


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    Yes, ISDN is digital. BRI (basic rate interface) utilizes two 64k lines. PRI (Primary Rate Interface) is provisioned over a T1 and delivers 23 (64k) channels ("B" bearer channels) and one signaling ("D" data channel).

    ISDN (Integrated Services Digital Network) is a type of service that can be delivered over either dial-up lines (2 line max) or T1. ISDN utilizes out of band signaling, which means that the 8k per channel (normally allocated for signalling ANI, DNIS, trouble shooting, etc...) can be used for traffic. A T1 in the telecom industry is just a 1.544Mb span, services like ISDN can be added to enhance functionality. An ISDN T1 normally has 23 B channels and 1 D channel, however, you can bond a small number of these together and designate 1 D channel to handle multiple T1's. The drawback to this is that if you lose the T1 with the D channel, you lose all T1's. This is where I would recommend a backup D channel.


    Actually, the telephone company does deliver one phone line per ISDN 64k channel (BRI), but the end user doesn't usually know this because we assign a fictitious telephone number, so they may not realize that they are getting two phone lines. Remember, BRI is only 128k max (two phone lines), the next jump is to provisioning ISDN over a T1 span (PRI).
    Last edited: May 26, 2005
  6. May 27, 2005 #5
    ISDN BRI is 3 channels not 2 or 4...
    1 signaling
    2 data/voice

    T1 is ONLY applicable in USA. In Europe we use E1 as a standard, and it consists of 30 channels

    Why do you say that? You can have as many ISDN BRI's as you like coupled together?
  7. May 27, 2005 #6


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    Correct, 3 channels for BRI (2B+D) B1 & B2, for 128k (most common and the maximum BRI is delivered at) there would be 2 phone lines. There is 64k BRI which is 1B+D, not ordered very often anymore, but I still have clients using it. ISDN BRI isn't used much anymore, PRI T1 is used mainly for PBX feature functionality, not for data transmital much anymore, it's too cost prohibitive

    ISDN BRI is designed and delivered with 128k max. The next step up is ISDN PRI T1. You can purchase equipment that can "bond" multiple BRI's, but that doesn't change the BRI itself. Tying a bunch of water hoses together can deliver more water, but you are not changing the individual capacity of a single hose.

    Also, for practical and financial reasons T1 is a better solution if you're needing significantly more bandwidth.

    Edit: to clarify further, PRI bundling (NFAS) is done by the phone company and the circuits are engineered to have a single master D channel for multiple PRI's. Bonding of multiple BRI's is an equipment "fix" that the end user does himself on premise, the BRI circuits are not re-engineered into a "fat pipe".
    Last edited: May 27, 2005
  8. May 27, 2005 #7
    Not for teleco its not, if you only need approx 5 voice conversations at the same time you arent going to buy 1 T1/E1 you will typically buy 5 BRI and spread a DID range over them, so the person dialing in will only hit you on 1 number... and be round robined on the trunks...It is seamless

    Large corporate companies still use T1/E1 becuase it is typically more rubust than other technologies. There are newer more robust technologies like MPLS but it's even more expensive than T1/EI (Do you have this state side yet?)... Dsl wont cut it when you have 2000 People trying to connect to WAN services

    I understand what you are getting at now tho.. You can only provision BRI or PRI... You cant get delivered 1/2 a T1 or something
  9. May 27, 2005 #8


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    There is no way to give a short answer. :smile: Depends on what you are trying to do. You typically wouldn't want to use ISDN BRI for voice calls because you pay a lot more for ISDN usage than regular voice usage. But there are a lot of "ifs" it depends if local use is metered or flat rate. It depends on how your provider bills, if the call is sent out as ISDN or not. In this part of the US we will not provide DID's over ISDN BRI, it's not a tariffed offering, or if it is, it is so outrageously expensive, it's never sold. (I will look into the tariffs if i have time) (our non T1 offering for DID's is $100/mo per trunk, with a limit of 1 DID per trunk at a time, so if you want it to roll over to another trunk, it's another $100/mo) I actually have a client that has this on Plexar and I am moving him to a T1 for a huge savings.

    Long distance ISDN usage is much more expensive than normal long distance, ballpark 47 cents per minute per channel as opposed to 2.5 cents per minute over regular long distance. Here in the US, the most common application for ISDN is videoconferencing.

    Again, there are many flavors of "products" that utilize ISDN over T1. For example on a local T1 (used as a replacement for local phone lines), a company may need ISDN in order for them to receive ANI and utilize DNIS. It may be the only reason they need ISDN signaling. In this case BRI is not an option. They would not actually place ISDN calls from it and instead route over the regular PSTN. Costs change constantly, I price this stuff out every day.

    MPLS is utilized in WAN's here, it is not something ordered on an individual T1. The benefit is full meshing without multiple PVC's and QOS for voice/video/data. But it is over a network. MPLS is the big buzzword in networks, but traditional frame/ATM makes more sense $$ wise if your network is spoke & hub and you're not doing VOIP over the network. Voice over frame works fine and dialtone can be delivered as an FXS line to an old key set by adding a VIC to the router.

    Yes, DSL is too unreliable and doesn't have the same performance SLA's (longer down time in the event of a repair issue)

    You have the best understanding of telecom knowledge here (telecom has it's own weird world and unless you're inside of it, it's not easy to understand. Just because something can "work" doesn't mean that's how it's done, or allowed. I am constantly having to explain to clients the difference between what "can" work and how it can legally be engineered. Some services just are allowed. We stopped selling sub T1 rate private lines, I still have clients with them, but they can't order any new lines.

    You are a network engineer for a telecom company? I'm in technical sales, which is why I know the tariffs (US regulatory nightmare) and costs involved.
  10. May 27, 2005 #9


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    I'm not sure if windows has this but under Linux there is something called Bonding. This basically means you can take all your ethernet interfaces and make it look like one gaint pipe. I don't know if this works with dailup.
  11. May 27, 2005 #10
    wow... They cost us next to nothing here...! :-) In fact a building where we have a remote office gave us an ISDN 10, untill we could get our trunks in...

    True... MPLS is nice tho, very fast, very good QoS, and 'can' deliver you savings in network hardware, but its just too pricey right now, unless you are investing in a furture proof converged network

    Yes we use VIC's ints on Cisco 2600 to deliver PVN to remote offices, we've moved away from FR tho, although the uptime and Garanteed BW (CIR) was good there was to many savings to be had by moving over to a VPN/dsl spoke setup... We still use the PVN and it works ok, as we use Packetshapers on our WAN links to give some sort of QoS... Although its not end to end it is enough..

    Yes I am Network Engineer, and I do a lot of Avaya/Cisco VoIP stuff nowadays also, but mainly data networks
  12. May 27, 2005 #11


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    I think we're hijacking the thread. :redface:

    We do Cisco, Nortel & Avaya for phone systems, mostly Cisco for routers & switches, and some Adtran.

    DID's are $10/mo for a block of 100 if it's on a T1, big difference, doing DID's off a T1 here are intentionally priced high so that people don't buy them.
  13. May 27, 2005 #12
    Well since I can't get ISDN or DSL in my area (I guess if I could have, I would have done it already), is there someway that I can get some ISDN equipment and use it for a dialup connection? I only asked that question because I don't know if on the server's side this is possible/impossible.
  14. May 27, 2005 #13


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    You shouldn't need the ISDN equipment. You can do it with two modems, and two normal phone lines. You just bridge the connections together in Windows (or whatever).
  15. May 28, 2005 #14
    The only way I can think you could do this would be to buy a router with 2 DDI (demand dailing ints) interfaces, and then 50/50 load balance accross them...You would also need a static public IP address on the inside INT of your router... You could get this to work if you were willing to throw lots of money at it... But I dont think it is worth it

    Perhaps on Linux, or more likely freeBSD (configured to route) you could do this with a dual homed box...

    The problem I see to doing this on you PC is that every "session" you open (ie a www site) will have to be sent through only 1 interface on the PC so there wont be any visable difference between having 1 modem or 2 attached to you PC.

    The reason why you cant switch between modems on the same session, is that www server you are connecting to will get confused when the tcp sequence numbers get out of sync and from different IP addresses which will happen. (AFAIK)...
  16. May 28, 2005 #15
    hehe yep ;-)
  17. May 28, 2005 #16


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    I knew I'd read this somewhere, it's called multi-linking. The problem is that a lot of ISP's will not allow this.

    HOW TO: Set Up Multiple-Device (Multilink) Dialing in Windows XP

    This article describes how to configure multiple-device dialing in Windows XP.

    With Windows XP, you can use multiple modems to connect to your Internet service provider (ISP) to increase the total speed of your transfers. Multiple-device dialing (also known as Multilink PPP, modem aggregation, or Multilink) causes multiple physical links to be combined into one logical link. Typically, two or more ISDN lines or modem links are bundled together for greater bandwidth. You might use this feature if you do not have access to DSL or cable services.

  18. May 28, 2005 #17
    well... if your isp will allow 2 dial-ups to be linked to 1 ip address it will work, if not then I cant see how it would be of any use

    Thats what I was getting at in my last post... typically you get 1 IP address per dial up, not 1 accross multiple dial ups
  19. May 28, 2005 #18


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    Yes, your post was spot on...which is why you don't really see anyone doing this.
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