What does the link rear suspension do as opposed to direct/no link suspension?

Does it have something to do with the progression?

 

yeap.
What you want is a shock that gets harder when you're close to bottoming. Oil inside has a definite maximum speed (defined by the washers inside) and the closer you get to this moving speed, the harder it gets.
When you hit small bumps, the speed of the shock rod is made slow (by the linkage) so it absorbs it.
When you hit a big bump, it will start slowly, but, for a constant vertical wheel speed, the rod will accelerate (again defined by the linkage)...making the shock harder.
It's not necessary (KTM has supressed it from their bikes now, they plau only with shock angle)), but gives a serious hand to the shock being smooth...and hard, usually when you want it.

 

Thank you. I was wondering if the extra maintenance and weight was worth it. I saw an aftermarket frame that had no link suspension, so I wanted to know if there was an advantage.

 

It looks like the shocks performance has gone up a lot since the 80s (first time linkage came out, if I remeber well, unitrak, on the kx). Now linkage probably isn't as mandatory as it was 15 years ago. KTM has understood it...some others did. within some years, maybe children will laugh at our stone age shock linkage...hehe.

PS...in front there is no linkage, and the shocks still do the job very well.

 

Forgot to mention that the ktm suspension is loved by the competent guys. All journalists say it grips awesome, doesn't bottom, is smooth...etc