Wendell Odom says:
"Finally, IOS uses queuing only when congestion occurs. IOS considers congestion to be occurring
when the hardware queue is full; that generally happens when the offered load of traffic is far less
than the clock rate of the link. So, a router could have a service-policy out command on an interface,
with LLQ configured, but the LLQ logic would only be used when the hardware queue is full."
Nothing new here but in pages before he said:
"! The class map matches on UDP/RTP header and RTP port numbers.
class-map match-all voip-rtp
match ip rtp 16384 16383
! Next, the policy map uses the bandwidth command to reserve 64 kbps for the class
! voip-rtp. Class-default gets some of the leftover bandwidth by default.
! The interface?s bandwidth 128 command is used as the basis for the limit on the
! amount of bandwidth that can be allocated in the policy map queue-voip.
! The load-interval command sets how often counters are updated. Also, note
! that the policy-map is enabled for output; input is not allowed on routers for
! policy maps that perform queuing.
service-policy output queue-voip"
Note the "bandwidth command is used as a basis for the limit..." This indicates that the queueing would be active at 128k well below the interface tx-ring capability. Am I missing something? The way I see it these two things as they read on the page, cannot be true at the same time. If the queueing mechanisms are engaged only after tx-ring is congested, how can this "bandwidth reference" thing work?