| 9.1 |  | Transport Protocols |
| 9.1.4 |  | UDP features and interaction with PIX |

| As previously discussed, UDP is a connectionless protocol. The PIX Security Appliance must take other measures to ensure its security. Applications using UDP are difficult to secure properly because there is no handshaking or sequencing. It is difficult to determine the current state of a UDP transaction. It is also difficult to maintain the state of a session, as it has no clear beginning, flow state, or end. However, the PIX Security Appliance creates a UDP connection slot when a UDP packet is sent from a more secure to a less secure interface. All subsequent returned UDP packets matching the connection slot are forwarded to the inside network.

When the UDP connection slot is idle for more than the configured idle time, it is deleted from the connection table. The following are some UDP characteristics:

- UDP is an unreliable but efficient transport protocol.
- UDP has no handshaking or sequencing.
- UDP has no delivery guarantees.
- UDP has no connection setup and termination.
- UDP has no congestion management or avoidance.

| Media Activity Demonstration Activity: UDP Initialization Inside to Outside In this activity, students will learn about UDP initialization inside to outside.