A better comparison with X is the RDP protocol, which too is an API level protocol (its basically forwarding large parts of the windows GDI interface). OTOH, t

A better comparison with X is the RDP protocol, which too is an API level protocol (its basically forwarding large parts of the windows GDI interface). OTOH, the big strength of RDP is the async stream requests. This gives it a much lower apparent latency than X, but it can also do the VNC thing and render/compress parts of the UI on the remote machine.