4.1.4 Port bandwidth control

The port bandwidth control functionality shapes the traffic to the send bandwidth specified for the relevant port after scheduling is performed. You can use this control to connect to wide-area Ethernet services.

For example, if the line bandwidth is 1 Gbit/s and the contract bandwidth with the ISP is 400 Mbit/s, you can use port bandwidth control to suppress the bandwidth to 400 Mbit/s or less when sending frames.

Port bandwidth control uses the leaky bucket algorithm, which is based on the model of a bucket that has a hole in the bottom.

Set the bandwidth so that it is equal to or smaller than the line speed. If setting is not possible, the operation log is displayed, and the port bandwidth control setting is disabled.

The following table describes the burst size characteristics based on the properties of the leaky bucket algorithm.

Table 4-3: Features of burst size

Burst size	Features
Smaller	The dropping of burst traffic is relatively easy. If traffic is sent while communication is not being performed, the send bandwidth fluctuations are relatively small.
Larger	The dropping of burst traffic is relatively difficult. If traffic is sent while communication is not being performed, the send bandwidth fluctuations are relatively large.

For the setting range of port bandwidth control and the setting range of burst size, refer to the explanation of traffic-shape rate command in the Configuration Command Reference.

The part of a frame to which port bandwidth control applies is from the MAC header to the FCS. The following figure shows the part of the frame to which port bandwidth control applies.

Figure 4-2: Scope of port bandwidth control