3Com 3C13636 Configuration Manual page 1313

3Com Router 3000 Ethernet Family
Configuration Guide
Table 3-1 Congestion management technologies
Type
FIFO
PQ
CQ
Queue
Advantages
No.
No need for configuration,
easy to use
1
Easy operation, low delay
Provide service of absolute
preference to data of different
applications, and capable of
ensuring the low delay for
real-time applications (VoIP)
4
Provide absolute preference
to the packets of preferential
business
bandwidth-occupying
Capable of assigning the
bandwidth-occupying
proportion
packets
applications
17
If packets of certain classes
do not exist, it can increase
the bandwidth for existing
packets
3Com Corporation
Chapter 3 Congestion Management
on their
according to
with different
Need to be configured,
generate
overhead
3-7
Disadvantages
All packets are treated
equally. The available
bandwidth, delay and
drop probability are
decided by the arrival
order of the packets.
No restriction on the
unmatched data sources
(that is, flows without
flow control mechanism,
UDP for example),
resulting bandwidth loss
of matched data sources
such as TCP.
No guarantee to the
delay of time-sensitive
real-time application,
such as VoIP
Need to be configured;
generate great system
overhead
If there are no restriction
on bandwidth-occupying
of packets with high
preference, the packets
with low preference
won't obtain the required
bandwidth
great system