Well I suppose the first step is to see how Ivan feels. Has he ever shown strong prey drive?
First step would be to allow the kitty to settle into a "safe" room and feel comfortable in there. That'll take a couple of days usually (if it's a kitten then perhaps faster). Then I'd get a baby gate in the doorway and let Ivan see the cat through the gate. Gage his reaction. If he simply seems curious then try leashing him and bringing him in. I'd personally work on a really solid sit or down so that the cat can come sniff him without the dog's big head getting shoved into his back end, that would likely result in a face slap or bite on Ivan's face. if he wants to eat the kitty through the gate (or seems that way) then you'll have to go a different route but don't worry about that unless you have to.
If the cat is way too scared to meet Ivan up close you can start with swapping scent on blankets, then put on in a crate and let the other sniff, then put the other in a crate and let sniff.
You really need to judge how fast the intro can go based on their reactions, it's hard to put a solid plan in place without knowing if anyone is petrified or wants to eat the other. For my dog and cats it was as simple as several meetings in the cat's safe room. Max was very excited but he layed down when I asked and I fed him treats to distract him while the cat sniffed him all over. Then I let him sniff the cat while still laying, started feeding treats again if the cat got irritated. Once I felt Max was perfectly safe I let him up and he followed the cat around for a while but eventually got over the novelty and they were best buds.
Oh and a word of caution, don't let anyone hold the cat when he sees the dog for the first few times, if the cat freaks out it could be very painful for the person.