Host Link Failure Detection

Introduction

If the Excel platform detects a failure in the host link, all spans/channels are brought out of service with the Host Link Failure Detection feature.

Determining HLF

The Excel platform determines the integrity of the host link by monitoring host acknowledgments to Poll messages. You must enable polling to use the Host Link Failure Detection feature.

If the host does not acknowledge two consecutive Poll messages, the Excel platform initiates a timer. If the Excel platform does not receive an acknowledgment from the host before the timer expires, the Excel platform resets its Ethernet receiver.

Configuration

You configure Host Link Failure options using the System Configuration message.

Data[1] configures the Excel platforms response to Host Link Failure:

0x00 - Bring all channels out of service

0x01 - Bring all channels and spans out of service

Data[2,3] configures the Failure Confirmation Timer.

Process

When the Excel platform detects a host link failure, it responds according to one of two options set by the host and sends an Alarm message to the host to report the failure (Alarm Type: Card 0x02, Alarm Number: 0x10).

If the host link failure is related to Excel platform hardware, it is resolved when the Ethernet receiver is reset. If the host link failure is not related to Excel platform hardware, it may have been caused by slow host processing.

If this is the case, you should consider increasing the polling interval. Slow host processing is most evident during the boot-up cycle. This alarm may also indicate that the host is not sending messages to the Excel platform. If this is the case, the Excel platform will have stopped sending responses (because there are no host messages to respond to).