OpenStack Compute supports VNC consoles to guests. The VNC protocol is fairly limited, lacking support for multiple monitors, bi-directional audio, reliable cut-and-paste, video streaming and more. SPICE is a new protocol that aims to address the limitations in VNC and provide good remote desktop support.
SPICE support in OpenStack Compute shares a similar architecture to the VNC implementation. The OpenStack dashboard uses a SPICE-HTML5 widget in its console tab that communicates to the
nova-spicehtml5proxy service by using SPICE-over-websockets. The
nova-spicehtml5proxy service communicates directly with the hypervisor process by using SPICE.