Packet Flow Sampling

The Packet Flow Sampling mechanism carried out by each sFlow instance ensures that any packet observed at a Data Source has an equal chance of being sampled, irrespective of the Packet Flow(s) to which it belongs.

Packet Flow Sampling is accomplished as follows:

• When a packet arrives on an interface, the Network Device makes a filtering decision to determine whether the packet should be dropped.
• If the packet is not filtered (dropped), a destination interface is assigned by the switching/routing function.
• At this point, a decision is made on whether or not to sample the packet. The mechanism involves a counter that is decremented with each packet. When the counter reaches zero, a sample is taken. When a sample is taken, the counter that indicates how many packets to skip before taking the next sample is reset. The value of the counter is set to a random integer where the sequence of random integers used over time is the Sampling Rate.

To access the sFlow Sampler Configuration page, click System > Advanced Configuration > sFlow > Sampler in the navigation menu.

Click Refresh to refresh the page with the most current data from the switch.

Use the buttons to perform the following tasks:

• To add an sFlow sampler instance, click Add and complete the required information.
• To edit an existing sFlow sampler instance, select the appropriate checkbox or click the row to select the sFlow sampler instance and click Edit. Modify the sFlow sampler configuration information as needed.
• To delete an sFlow sampler instance, select one or more table entries and click Remove.

The Add Sampler page lets you configure the sampling rate for ingress/egress/flow based sampling. After successful configuration, the sFlow packet sampling is performed based on sampling rate.