Flow Control - Huawei OptiX OSN 550 Configuration Manual

OptiX OSN 550 Multi-Service CPE Optical Transmission
System
Configuration Guide

4.2.4 Flow Control

When the data processing/transferring capability of the equipment fails to handle the flow
received at the port, congestion occurs on the line. To reduce the number of discarded packets
due to buffer overflowing, proper flow control measures must be taken.
The half-duplex Ethernet port applies the back-pressure mechanism to control the flow. The full-
duplex Ethernet port applies PAUSE frames to control the flow. Currently, the half-duplex
Ethernet function is not widely applied. Hence, the flow control function realized by Ethernet
service boards is used for the full-duplex Ethernet ports.
The flow control function realized by Ethernet service boards is classified into two types: auto-
negotiation flow control and non-auto-negotiation flow control.
Auto-Negotiation Flow Control
When the Ethernet port works in the auto-negotiation mode, you can adopt the auto-negotiation
flow control function. The auto-negotiation flow control modes include the following:
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Non-Auto-Negotiation Flow Control
When the Ethernet port works in a fixed working mode, you can adopt the non-auto-negotiation
flow control function. The non-auto-negotiation flow control modes include the following:
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Issue 02 (2011-06-30)
Enable dissymmetric flow control
The port can transmit PAUSE frames in the case of congestion but cannot process the
received PAUSE frames.
Enable symmetric flow control
The port can transmit PAUSE frames and process the received PAUSE frames.
Enable symmetric/dissymmetric flow control
The port has the following abilities:
– Transmits and processes PAUSE frames.
– Transmits PAUSE frames but cannot process the received PAUSE frames.
– Processes the received PAUSE frames but cannot transmit PAUSE frames.
Disable
Disables the auto-negotiation flow control function.
Send only
The port can transmit PAUSE frames in the case of congestion but cannot process the
received PAUSE frames.
Receive only
The port can process the received PAUSE frames but cannot transmit PAUSE frames in
the case of congestion.
Send and receive
The port can transmit PAUSE frames and process the received PAUSE frames.
Disable
The port does not support the auto-negotiation flow control function.
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4 Configuring Ethernet Services
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