56
mentioned to offer powerful QoS capabilities, meeting different QoS requirements of
different applications. Table 9 compares these queuing technologies for efficient use.
Table 9 Congestion management technology comparison
No need to configure, easy
to use
Easy to operate, low delay
All packets are treated equally. The
available bandwidth, delay and
drop probability are determined by
the arrival order of the packets.
No restriction on the uncooperative
data sources (that is, flows without
flow control mechanism, UDP for
example), resulting in bandwidth
loss of cooperative data sources
such as TCP.
No delay guarantee to
time-sensitive real-time
applications, such as VoIP
Provide absolute bandwidth
and delay guarantees for
real-time and mission critical
applications
Need to configure; low processing
speed
If there are no restrictions on
bandwidth assigned to high-priority
packets, low-priority packets may
fail to get bandwidth.
Provide different bandwidth
percentages for different
applications
If packets of certain classes
do not exist, it can increase
the bandwidth for existing
packets.
Need to configure; low processing
speed
NOTE:
If the burst traffic is too heavy, you can increase the queue length to make queue scheduling
more accurate.
Configuring PQ
You can define multiple match criteria for a priority queue list (PQ list) and apply the list
to an interface. When a packet arrives at the interface, the system matches the packet
with each match criterion in the order configured. If a match is found, the packet is
assigned to the corresponding queue and the match procedure is complete. If the
packet cannot match any match criterion, the packet is assigned to the default queue
normal.