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combining two internet connections to one...

M

MetroRider

Senior member
my friend has both a DSL modem and cable modem (don't ask why... you'd think one broadband connection would be enough). he can reach 120 kb/sec downloads with his cable modem, and 80 kb/sec modem.

he wants to know if there was a way to combine them so he would get a total download speed of 200 kb/sec with both of them in action. if so, would it be as simple as needing to have two NICS, and the OS doing the work? Would he need a special router or box that would do this, and then filter its way down to his machine?

thanks in advance!
 
It's not possible with that sort of configuration. To bond connections they both must go through the same ISP, same type of connection, and actually even connect to the same router on the other end, with one IP address configured to be routed over both lines (load sharing).

With two different connections, the remote servers see two different IP addresses, so the traffic can't be sent back partially over one line and partially over the other, because a server can only communicate with one machine per connection. With a bonded service (such as dual T1s, dual DSL, or even dual dialup), your IP address is used on both lines, so when it gets to your ISP, the traffic is considered one connection to the remote site.

Even if he had two connections from different ISPs and managed to have a single block of IPs on his side, routed through both ISPs (something reserved for high-paying business class connections), that would only result in a multi-homed service, so that remote networks would have two possible return paths, in case an ISP along the way considers one path better than the other. The traffic would still not be split between the two paths.
 
interesting and detailed response there.

so i guess that even if i had two T1's available, but being of different networks, i would still be out of luck. is this also the same reason why when behind a NAT routed broadband connection, when connecting with a dial-up, the dial-up takes precendence due to the fact that you are getting a real IP with it?

thanks!
 
The computer doesn't look at IP's as "real" or not. To it, all IPs are valid (except certain ones that are considered unusable by design). The IPs that most people use behind routers are simply a range assigned at the beginning of the use of IP as reserved for private use, meaning no one could use them as their public IP addresses, only for an internal network or one not connected to the Internet. The reserved IPs can sometimes be useful for troubleshooting things like NAT setups, as well as making it easier to distinguish parts of the visible and non-visible network, and avoiding accidentally allowing traffic from your network to reach anyone else (since all other routers automatically ignore traffic from those IPs), and to avoid accidentally using IPs assigned to someone else and then trying to connect to the Internet with them.

I've never had both a dialup account and a network card installed on a machine, so I don't know how the preference is determined. It can easily be changed of course in most applications. You're given a choice of which connection to use in all web browsers and email clients for example, and most other applications use the browser settings to determine how they work.

That of course has nothing to do with how bonded lines work. There's no technical reason that a modem connection should be chosen automatically by anything, it may just be automatic when you setup the dialup account that it's assigned as the primary connection. You can technically use either connection for traffic, because they both can be active at the same time. The computer doesn't just have a "network access" function that can only have one IP at a time; each network card, modem, wireless card, whatever can have its own IP address, on entirely different networks. That's how Internet Connection Sharing and other gateway software works -- the "inside" network card uses one IP network, and the "outside" card uses whatever network and IP your ISP assigns. In fact that's pretty much how a router works.
 
couldn't he bridge them together?

it wouldn't give 200mbs downloads but would let him use the full capacity of both at the same time.
 
Those devices don't actually combine traffic the way a true bonded service would. A bonded line sends every other packet over each line (or 2 packets and 1 packet, et cetera, whatever ratio you want based on their speeds).

The FatPipe and Nexland devices only send packets from one connection over each line. If your web browser opens 4 connections to a server to get a page, then the device will send 2 requests over each line in order to allow them both to share the load. However if you're just doing a download from a server, only one connection is opened, and it will only use one line for it. It might even end up being the slower line, since the device can't actually know the available speeds of each line (though they may have a way to set a "preference" but I'm not sure how that would work reliably).

Whether they'd be of value would depend on how much spare money you've got to throw around. With both cable and DSL services, maybe this guy could do it, but I wouldn't bother with it myself.

The most noticeable difference might be seen when downloading a single file, while browsing the web at the same time. If the devices are able to avoid sending the web connections over the fully utilized line carrying the download, then the web browsing won't be slowed down like it would be with a single connection. But normal web browsing probably wouldn't seem any different, and single downloads won't be any faster.

Theoretically, software could do the same thing with two NICs, but I haven't heard of anything like that.
 
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