SMC Networks TIGERSWITCH 10/100 - Manual (Page 228)

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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.
queue hol-prevention
Use this command to enable HOL Blocking Prevention. Use the no
form of this command to disable it.
Command Function Mode Page
queue
hol-prevention Enables HOL Blocking Prevention GC 3-86
show queue
hol-prevention Configures the query count PE 3-87