reply to ipanini
Re: [DSL] Basic question - Can MLPPP be applied with *ANY* ADSL ipanini, you can use the two lines at the same time. For Windows, you just connect the two models to your computer and Windows will use either connection as it will. In Linux, there's a module that allows multiple network interfaces to be bonded and appear as a single virtual network interface called bonding.o for exactly that purpose.
Under the hood however, the two lines will operate independently from one another. Once a [TCP] connection is established, it will be established on one line and cannot hop from one line to the other. That's because each line will have a different IP address. When you send a packet out, the response will always come back on the same line. If you're watching a movie on Netflix for instance, you'll send a request to the Netflix server on one of the two lines saying "Please send me a movie". But the response, the whole ~700MB response, will have to came back the same line the request was sent on. There is no way to tell the server "Please send me half the packets on this IP and the other half on that other IP". At least not with TCP streams. There are however many file download protocols (ftp and http for instance) that can be accelerated on multiple-links using specialized software (Down Them All! extension in Firefox for instance).
To achieve what [I think] you want to do, you'd have to have a server sitting on the net somewhere that consolidates your two network connections into a single IP address and, conversely, splits any incoming traffic on the two lines. That's pretty much what MLPPP does for you.