REALITY: The PCoIP protocol optimizes the user experience to the available bandwidth
The PCoIP encoding algorithms attempt to deliver a perfect, high-frame rate display experience whenever possible. Think of this like a high-performance sports car that will easily exceed 200kph on the open Autobahn, but slows down when driving on local roads or in congested traffic. Because the PCoIP algorithms can deliver a superior experience to Citrix ICA/HDX, when using them both in a single session on a 1Gbs network, the PCoIP session will deliver a superior image quality and frame rate, but will also use more bandwidth much like the high-performance sports car will go faster on the Autobahn than the average family car. In fact, in Citrix’s own bandwidth sizing presentations, they state, “Single session bandwidth testing is invalid”. We agree with this statement and suggest that Citrix follow their own guidelines.
The more relevant way to benchmark the two protocols is compare the user experience delivered when the network is constrained to say 5Mbs or 1Mbs or 200Kbs. In these constrained networks, the PCoIP user experience is equal to or better than that delivered by ICA/HDX under the same network constraints. This means that no matter the network conditions, the PCoIP protocol will optimize the user experience to the available bandwidth. Many customers are successfully deploying PCoIP solutions across WANs with high latency and limited bandwidth and are very satisfied with their experience.
For some additional clarification, the 10x bandwidth numbers that Citrix cites in their literature is based on comparing HDX-3D at it lowest quality and frame rate to a PCoIP session operating at a perception-free experience. This is because the two protocols have completely different philosophies on quality settings. For HDX-3D, the image quality settings are used to limit the maximum bandwidth by explicitly limiting the maximum quality and frame rate that the user can experience. This is like forcing a car to drive at 20kph no matter what the current road conditions are. In contrast, the PCoIP image quality settings represent the minimum image quality that the user will experience. If more bandwidth is available, the encoder is allowed to use more bandwidth to deliver a better experience. Thus, even on the lowest quality setting, a PCoIP session on an unconstrained 1Gbs network will still operate at the maximum frame rate and image quality it can deliver. In this case, the PCoIP sports car is driving over 200kph on the Autobahn while the HDX-3D sedan is only going 20kph even though the road is completely clear. Obviously, user experience must be factored into any benchmarks comparing virtual desktop protocols.