Not necessarilly if you are only going to do point to point between two devices where you know the ip addresses.

When you get several ip video devices, within your h.323 network, a gatekeeper is becomes a good option for e.164 address resolution. This is where a video endpoint will register and if authorized provide its phone number. The gatekeeper then resolves the phone number into an ip address for all other video endpoints that may want to call it.

In addition, the gatekeeper can provide call admission control, call authorization & bandwidth management between ip video devices registered to it.