One solution is to get both to increase your reliability.
There are several companies now that make Dual Wan Routers.
They let you use a cable modem and DSL at the same time.
I had a problem back in 1996 where T1 Lines where very unreliable.
Any given line was down for about 1 day per month. It would take a call in the internet provider and telco, sometimes even sending technicians out to test the lines.
It was painful. And nearly impossible to provide internet service over a T1.
After setting up T1's and T3's for many customers and having done 3 offices previously, in the next one I was determined to avoid all of the problems.
In my previous office a someone actually went in to the telco closet down in the underground parking garage in Beverly Hills and cut our T1 and phone lines! It didn't take me more then a few minutes to repair, but tought me a lesson.
So in the new office on La Cieniga Blvd & Pico in Los Angeles we found a cheap building that straddled the line between both phone companies GTE & Pac Bell.
I was able to set up 2 de-mark's (demarcation point) these are the big plywood board on the wall where all the phone connections come in from the street and get wired in to the building. One was in the back from GTE was locked behind a steel fence gate and then behind a discreet solid oak door and looked like a broom closet. The other in the corner of our servers room, with 2 more telco's coming in Pac Bell and MFS. It was very impressive intended for show and tell for visitors.
Not even the employees knew about the one in the back closet.
These had 3 T1 lines to 3 different ISP, Cerfnet, World Site and Softaware, all of which went in to different backbones.
John Sokol with 3 T1 Routers and CSU/DSU,
at Internet Broadcast System in 1996
at Internet Broadcast System in 1996
These also had different IP blocks.
I had a pair of PC's below then that would connect to my Co-Located servers, and provide a non-encrypted VPN link in and out of the office to all of the remote servers out on the internet.
It worked very effectively.
The seed money from the company came from a brutal "Do or Die" contract with one customer. One in which we had bet everything in return for a million dollar advance on services. If we had any down time at all in a year we would loose our companies and the rights to all of our video source code for the "Livecam" product.
Well towards the end a year, we had proven we could indeed keep things running with 100% uptime, something unheard of in the industry. Two people who posing as telco employee's showed up to work on our lines, I was out of the office along with all of the engineers. So our receptionist ignoring strict orders was all to happy to be helpful after a little social engineering and unlock our server room and let them in. I don't even know how she had a key even.
The whole tech team and me were out meeting with this customer, I could sense something was wrong the whole time.
He had been stalling us.
When we returned from a meeting, the whole server room had been trashed.
Every wire cut, servers destroyed. The demark, torn to shreds.
The shock of it was gut wrenching.
Moments after I arrive, the customer who's office I had just left, called.
Gloating he said "Your video feed seems to be down.".
I replied "Really? Why would you think that? Everything is just fine."
All I heard was the clicking of his keyboard then "Ahhuuooo- Click" as he hung up his phone.
I could just imagine the look that must have been on his face to see everything was working perfectly. I guess he never stopped to think about the fact that our main phone number was still working too.
All of the vital systems were hidden in the drop ceiling bolted to the roof and in that back closet.
Before I had wonders if I was being too paranoid. Spending too much money and time going through all these tricks to hide the cables and servers.
After that, I felt so vindicated. What a bitter sweet victory. What a mess to clean up.