User Manual - Configuration Guide (Volume 3)
Versatile Routing Platform Chapter 3
Congestion Management
3-4
Table QC-3-1 Comparison table of congestion management policies
No. of
queue Advantages Disadvantages
FIFO 1
1.No configuration is needed, and easy
to use.
2. Simple processing with less
processing delay
1. All packets are treated equally, and the
arriving sequence of packets determines the
packet occupied bandwidth, delay and loss of
the packets.
2. It has no restriction on mismatched data
source (for example, UDP packet sending),
while the mismatched data source will affect the
bandwidth of the matched data source (for
example, TCP packet sending).
3. Delay of the real-time application that is
sensitive to time can not be ensured (for
example VoIP).
PQ 4
It provides absolute priority for the data of
different services, and delay is ensured
for real-time applications (for example,
VoIP) that are sensitive to time. The
packet of priority service has absolute
priority to occupy the bandwidth.
1. Configuration is needed, and processing
speed is slow.
2. If the bandwidth for packets with higher priority
is not restricted, packets with lower priority may
not acquire the bandwidth.
CQ 17
1. Bandwidth can be allocated in
proportion for the packets of different
services.
2. If no specific types of packets exist, the
bandwidth can be increased
automatically for the existing packet
types.
Configuration is needed, and processing speed
is slow.
WFQ
Specified
by the use
r
(256 by
default)
1. Easy to configure.
2. The bandwidth can be protected for
coordinated (interactive) data source (for
example, TCP packet sending).
3. Capable of reducing the jitter of the
delay.
4. Small packet is sent with priority.
5. Different bandwidths can be allocated
for the flows with different priorities.
6. When the number of the flows is
reduced, the bandwidths for the existing
traffic can be increased automatically.
The processing speed is slower than FIFO.
3.1.4 Working Principle of Congestion Management Policy