SMC Networks 10/100 manual HOL Blocking Prevention Commands, Queue hol-prevention

COMMAND LINE INTERFACE

HOL Blocking Prevention Commands

If head-of-line (HOL) Blocking Prevention is enabled it prevents the forwarding of data to a port transmit queue that is blocked. This allows for a more efficient transfer of packets across the network. Normally, when the switch sends traffic to a port it goes to the port's transmit queue and is then sent out. If the port's transmit queue is already busy trying to send out data then the switch will keep the waiting traffic in the queue until the port is ready to send it out.

However, if the port remains busy, the switch will fill up more of the transmit queue with traffic waiting to be sent out that port. HOL Blocking Prevention works on the assumption that it is better to randomly drop traffic waiting in the queue than to continue using more memory and impacting performance across all the ports.

The switch controls the maximum number of frames that can be accumulated in the transmit queue before frames are dropped.

Note: If HOL Blocking is enabled on this switch, priority tags cannot be processed.

Command	Function	Mode	Page
queue	Enables HOL Blocking Prevention	GC	3-86
hol-prevention
show queue	Configures the query count	PE	3-87
hol-prevention

queue hol-prevention

Use this command to enable HOL Blocking Prevention. Use the no form of this command to disable it.

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