As Sonnen proved, taking Silva down is pretty much the only way to put it to him. But even then you risk getting caught in a triangle. However, it's better than standing and getting your nose crushed like a pepsi can.
Bonnar is a HUGE LHW...in fact he might be the biggest LHW in the UFC. He needs to use his size to his advantage, take Silva down, put his weight on him, control and work the ground & pound.
If this fight stays on the feet Bonnar will inevitably get knocked out.