Summary
Flow control is the process of managing the rate of data transmission between two nodes (switch, router, computer, etc.) to prevent a fast sender from outrunning a slow receiver. It provides a mechanism for the receiver to control the transmission speed, so that the receiving node is not overwhelmed (congested) with data from the transmitting node. Pause frames are the control mechanism used between two nodes to control the transmission rate. The receiving node element can send a PAUSE frame, which halts the transmission of the sender for a specified period of time. This will allow the receiving node time to recover from the congestion state. At the end of the specified time period, the transmitting node will resume normal transmission of frames.
Details
TippingPoint IPS Devices Some devices allow pause frames to pass through transparently while other devices drop the pause frames. If "Flow Control" is turned on, the device will drop the pause frames causing the network to experience latency and jitter. If this problem presents itself on your network, you will have to contact your ISP and request to turn off Flow Control.
The following platform behaviors have been verified:
Note: Putting the IPS device into L2FB does not change the behavior as the pause frames are dropped at the Broadcom chip which is where the L2FB is performed. The only way of troubleshooting this is by physically removing the device from the network.
The following platform behaviors have been verified:
| Device | Pause Frames |
| S-Series devices (S10, S110, S330) | PASS |
| N-Platform (660N, 1400N, 2500N, 5100N, 6100N) | DROP |
| NX-Platform (2600NX, 5200NX, 6200NX, 7100NX, 7500NX) | DROP |
| TPS (440T, 2200T, 8200TX, 8400TX, vTPS) | DROP |
Note: Putting the IPS device into L2FB does not change the behavior as the pause frames are dropped at the Broadcom chip which is where the L2FB is performed. The only way of troubleshooting this is by physically removing the device from the network.
