Remoting experiance?

Namely, I have n-tier(exactly 4-tier) win application. Communication between layers is thru remoting. Application runs on 3-4 machines in LAN (all machines is in same room, I mean local network works fine). Clients applications also runs fine, but sometime is too slow (request to server and server response), and when again do same operation everything is fine.
Maybe this explanation is general and unintelligible, but really I don't know where is a problem. Like I said, sometimes application is too slow, but mostly it runs fine.
Did anybody have same or similar problem in remoting?

regard j

Could it be from the network load - especially when the user is making a request that needs to hit all 4 tiers?

Oh, and what formatter are you using? Should be using Binary.

Actually, I didn't use any formatter. I just register tcp channel, and I think, by default tcp channel use binary formatter. Is it true?

regard j