flow-control negotiation receive

Usage Scenario

Flow control prevents packet loss caused by network congestion. Received flow control auto-negotiation enables a device to determine whether to enable received flow control by negotiating with the peer device. On a unidirectional communication network, you can run the flow-control negotiation receive command on the Ethernet interface functioning as the outbound interface at the transmit side to enable received flow control auto-negotiation, and run the flow-control negotiation command on the inbound interface at the receive side to enable flow control auto-negotiation. After received flow control auto-negotiation is enabled on the Ethernet interface, if congestion occurs on a device, the device sends a message to request the peer device to stop sending packets, which prevents packet loss.

Prerequisites

The Ethernet interface has been configured to work in auto-negotiation mode using the negotiation auto command.

Precautions

• Electrical interfaces support this configuration.

• Received flow control auto-negotiation can be implemented only if flow control auto-negotiation is enabled on the interface of the peer device.

• Flow control, received flow control, flow control auto-negotiation, and received flow control auto-negotiation can be configured on Ethernet interfaces, but cannot be configured together. For example, if received flow control auto-negotiation has been enabled on an Ethernet interface using the flow-control receive command, you need to run the undo flow-control receive command to disable received flow control and then run the flow-control negotiation receive command. Otherwise, the flow-control negotiation receive command fails to be executed.

• The XGE interfaces of the S5720-32C-HI-24S-AC, the first 12 XGE interfaces of the S6720-50L-HI-48S, and the XGE and last eight GE interfaces of the S5720-56C-HI-AC, S5720-56C-PWR-HI-AC, and S5720-56C-PWR-HI-AC1 do not support received flow control auto-negotiation.

• XGE optical interfaces support this command after GE copper modules are installed on them.

• GE optical interfaces support this command after GE optical or GE copper modules are installed on them.
• This command can be used on an 25GE optical interface that has a GE copper module installed. Before installing a GE copper module on a 25GE optical interface, you need to run the port mode ge command to configure the interface to work at the rate of 1 Gbit/s.

For the S2720-52TP-EI and S5720-52P-LI-AC, if received flow control auto-negotiation is configured on the interfaces 0 to 23 that work as inbound interfaces and flow control auto-negotiation is configured on the interfaces 24 to 47 that work as outbound interfaces, received flow control auto-negotiation and flow control auto-negotiation do not take effect.

For the S5735-L, S5735S-L, S5735S-L-M, S5735-S, S5735-S-I, and S5735S-S, the multicast functions (both Layer 2 and Layer 3 multicast functions) conflict with the flow control function.