- Differences Between Acceleration Decisions and Traffic Shaping Policies
- Configuring Service Class Definitions
To make an acceleration decision, the CloudBridge appliance examines the initial SYN packet of each TCP connection to determine whether the connection is a candidate for acceleration. The SYN packet contains no payload, only headers, so the acceleration decision must be based on the contents of the SYN packet's headers, such as the destination port or destination IP address of the connection. Acceleration, once applied, lasts for the duration of the connection.
Unlike acceleration decisions, traffic-shaping policies can be based on the contents of the connection's data stream. Depending on how long it takes for the application classifier to receive enough data for a final classification, a connection might be reclassified during its lifetime.
For example, the first packet in an HTTP connection to http://www.example.com is a SYN packet that contains a header but no payload. The header has an IP destination port of 80, which matches the HTTP: Internet service class definition, so the acceleration engine bases its acceleration decision, in this case, none (no acceleration) on that service class.
The traffic shaper uses the traffic-shaping policy from the HTTP: Internet service-class, but this decision is temporary. The first payload packet contains the string GET http://www.example.com, which matches the example application definition in the application classifier. The service class that includes the example application is selected by the traffic shaper, instead the service class that includes HTTP: Internet, and the traffic shaper uses the service-class policy named in that service-class definition.