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Configuring Session Bandwidth

From the AWI Bandwidth page (shown next), you can control the bandwidth that your PCoIP Remote Workstation Card uses during a PCoIP session. The following parameters display on the AWI Bandwidth page:

AWI Bandwidth Page
AWI Bandwidth page

Three settings found on the AWI Bandwidth page—Device Bandwidth Limit, Device Bandwidth Target, and Device Bandwidth Floor—help the PCoIP protocol use the available network bandwidth effectively.

Device Bandwidth Limit

Enter the maximum bandwidth peak for hosts or clients. When configuring hosts, this setting defines the bandwidth from the host to the client (e.g., graphics data). When configuring clients, it defines the bandwidth from the client to the host (e.g., USB data).

The usable range of the device bandwidth is 1000 to 900000 kbps for Tera2 devices.

The PCoIP processor only uses the required bandwidth up to the Device Bandwidth Limit maximum, and dynamically adjusts the bandwidth in response to network congestion. Setting this field to 0 configures the PCoIP processor to use the maximum rate available in the network at any time.

We recommend setting this field to the limit of the network connected to the client and host.

Device Bandwidth Target

Enter the temporary limit on the network bandwidth during periods of congestion. When the host or client detects packet loss, the device bandwidth is rapidly reduced to this value, and then more slowly reduced below it. This allows for a more even distribution of bandwidth between users sharing a congested network link.

Device Bandwidth Floor

Enter the minimum bandwidth when congestion is present and bandwidth is required. This allows you to optimize performance for a network with understood congestion or packet loss. If the bandwidth is not required, the bandwidth used drops below the floor.

When configuring hosts, this setting defines the minimum bandwidth from the host to the client (e.g., graphics data).When configuring clients, it defines the minimum bandwidth from the client to the host (e.g., USB data).

A setting of 0 configures the PCoIP processor to reduce bandwidth to 1000 Kbps during these network impairments. You should have a good understanding of the network topology before setting this to a non-zero value.

PCoIP Algorithm behavior

The firmware implements a slow-start algorithm that increases the bandwidth used until the required bandwidth is reached, network congestion is detected, or the Device Bandwidth Limit is met. It begins at the lesser of the Device Bandwidth Limit and 8000 Kbps, and increases the bandwidth used within seconds. The slow-start algorithm allows a graceful session startup for low bandwidth scenarios (e.g., WAN scenarios). After initiating a PCoIP session, users may temporarily notice low bandwidth video artifacts as the algorithm ramps up bandwidth use.

You can avoid the slow-start algorithm by setting the bandwidth floor higher than 8000 kbps, but you must ensure your network capacity is large enough or you will create severe session degradation.

Bandwidth Floor incorrectly configured

If the bandwidth floor is accidentally set above the actual capacity of the network, then massive packet loss will result since the device will never drop it's active limit below the floor. This will result in severe session degradation. This is why care must be taken when choosing an appropriate bandwidth floor.