TELECOM Digest OnLine - Sorted: Re: Using Two ADSL Internet Connections Simultaneously

Re: Using Two ADSL Internet Connections Simultaneously

James Carlson (james.d.carlson@sun.com)
23 Dec 2005 13:56:04 -0500

bonomi@host122.r-bonomni.com (Robert Bonomi) writes:

> The rest of the problem description that you chose not to quote gave a
> concrete example of the problem -- using a first user with a streaming
> audio stream, and a bunch of other people then doing something as
> simple as having multiple HTTP requests ("keepalive" protocol option)

Of course there are pathological cases. That wasn't at issue. Here's
the original question, in full:

> I have two telephone lines. I want to make both of these lines ADSL
> connections to the internet and use these connections to provide
> internet access to several wireless laptop computers. A maximum of
> about 20 laptops would be connected to the system at once. I would
> like the laptops to be able to use both lines simultaneously so that I
> don't have one line overloaded and one underloaded (ie: I want to
> balance the traffic on the lines at any given time).

> Anyone have any suggestions on how to set up something like this?

The answer is yes, you can do that. In fact, there are commercial
products designed to solve exactly this problem. E.g.:

http://www.xrio.co.uk/product-c800.asp

Unsplittable flows are certainly a hazard with *any* network layer
load balancing scheme, including one like this. There's nothing much
you can do about it as long as the links are independent.

If you want to avoid that problem, you'll need to use an L2 mechanism
that fragments datagrams across multiple links, such as MP (RFC 1990)
or IMA. Doing this requires cooperation with your ISP and you
certainly can't do it across two separate ISPs.

James Carlson, KISS Network <james.d.carlson@sun.com>
Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677

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