Final answer:
The 'insufficient-data' application on a Palo Alto Firewall indicates that the firewall lacks enough information to identify the application in the network traffic, possibly due to non-standard ports, insufficient initial packet data, or encryption.
Step-by-step explanation:
The application "insufficient-data" on a Palo Alto Firewall refers to a situation where the firewall does not have enough information to accurately identify the application running on the network. In the context of Palo Alto Networks firewalls, this means that the traffic being inspected does not match any of the application signatures known to the device, and the firewall cannot associate it with any of the predefined applications within its database. This scenario can occur if the traffic is using non-standard ports, there is insufficient data in the first few packets for the firewall to make a decision, or if the application is encrypted and cannot be decrypted for inspection. To resolve this, administrators may need to create custom application signatures, update the firewall's application database, or investigate the traffic to understand its nature better.