Troubleshooting PCoIP packet loss on the LAN and WAN networks?

Problem

Packet loss impacts real-time protocols, like PCoIP, as the time to resend lost packets will negatively impact desktop performance - including:

Imaging

• Reduced display frame rate (choppy motion)
• Slicing of the display image (a slice of the previous imaging remains visible for a period of time)
• Increased display compression (fuzzy imaging)
• Momentary black screens

Audio

• Can result in gaps or pops in the audio. 

USB

• Longer transmission times for USB data.

Keyboard and mouse

• Stutter in the input.
• Long pauses in input followed by rapid input playback

All these are symptoms of potential packet loss.

Cause

After reviewing the logs, packet loss was identified at the times when the PCoIP session experienced poor performance. 

Resolution

There are several possible causes of packet loss over the LAN/WAN in a PCoIP deployment including:

Faulty link

• Random packet loss caused by a faulty network link (network interface, connector, SFP transceiver, cable etc).

• On WAN links, this type of loss is typically quickly identified and fixed by service providers. 

Congestion management algorithms

• Network device packet drops due to congestion or intrusion detection/protection.
• Traffic shaping, policing, and congestion avoidance policies in network devices.
• QoS turned on but not configured for PCoIP. UDP is at the bottom of the priority list by default.
• May be due to an overload of general traffic, or a heavy load of high-priority traffic.
• Router or switch maybe overloaded if it can't handle all layer 3 traffic between VLANs.
• See Network checklist for PCoIP protocol LAN and WAN deployments

Client

• Anti-virus / intrusion detection software.  (note this does not affect PCoIP zero clients)

Wireless

• Similar to a faulty link, packet loss in a wireless network is random in nature. While a proper wireless network architecture can help minimize packet loss, it will be unlikely to eliminate the loss. For this case, consider adjusting the bandwidth floor setting. 

• Ensure WAN/MAN wireless links are full duplex.

Packets considered as lost by the PCoIP protocol

• PCoIP packets may be considered lost if they are sufficiently out-of-order causing the data to be stale.  This loss will not show up in network logs (since the packets were delivered), but will show up as packet loss in the PCoIP event logs. 

In depth diagnostics

The following section provides some brief guidance as to how to troubleshoot in more detail. If you require assistance, in depth diagnostics can be performed by the HP Anyware Processional Services Team.

Packets can be dropped at multiple points in the system. Using wireshark to perform packet captures can help track down what network device, network segment or software appliance is contributing to the issue.

When performing a wireshark capture of the issue it is suggested that the following be done.

1. Perform an initial capture on or next to each PCoIP end point. This serves as a reference point to ensure the packets are indeed leaving and getting dropped along the way. (Note wireshark is not perfect and can fail to capture all packets.) Analysis of the packet capture should show the dropped packets.
2. After the issue is confirmed, perform additional captures at various points throughout the network where you believe the packets could potentially be dropped. Analysis of each capture should show if the issue occurs before or after the point of capture.
3. Repeat the captures until the network device, network segment for software applicance has been isolated.
4. Reconfigure the device or consult the OEM's technical support.