Dell PowerEdge M420 Dell PowerConnect M8024-k User's Configuration Guide - Page 692

Table 24-1. Port-Based Traffic Control Features Feature Protected ports LLPF Description Prevents traffic from flowing between members of the same protected port group. Filters proprietary protocols that should not normally be relayed by a bridge. What is Flow Control? IEEE 802.3x flow control allows nodes that transmit at slower speeds to communicate with higher speed switches by requesting that the higher speed switch refrains from sending packets. Transmissions are temporarily halted to prevent buffer overflows. Enabling the flow control feature allows PowerConnect M6220, M6348, M8024, and M8024-k switches to receive pause frames from connected devices. Flow control is available for ports that are configured for full-duplex mode of operation. Since ports set to auto negotiate may not be added as LAG members, LAG member ports cannot have flow control configured to auto. Flow control is incompatible with head of line (HOL) blocking prevention mode. The switch can operate in either mode, but not at the same time. If flow control is enabled, HOL blocking is disabled. What is Priority-Based Flow Control? NOTE: PFC is supported only on the PCM8024-k. The PCM6220, PCM6348, and PCM8024 switches do not support PFC. Ordinarily, when flow control is enabled on a physical link, it applies to all traffic on the link. When congestion occurs, the hardware sends pause frames that temporarily suspend traffic flow to help prevent buffer overflow and dropped frames. PFC provides a means of pausing individual priorities within a single physical link. By pausing the congested priority or priorities independently, protocols that are highly loss-sensitive can share the same link with traffic that has different loss tolerances. 692 Configuring Port-Based Traffic Control