This is one of my favorite submisssions, and it's the same/variation of the choke that Antonio Rodrigo Nogueira applied on Randy Couture at UFC 102. I have enclosed a couple of .gifs after the jump.
Notice the 'Gator Roll" and Nogueira turning into Hirotaka Yokoi for leverage.
Notice the same thing against Heath Herring.
HT: MMACore for the .gifs