3Com OfficeConnect 3CDSG8 - 11 QoS Quality of Service; 11.1 QoS Configuration

QoS 61
11 QOS
11.1 QoS Configuration
QoS (Quality of Service) is a mechanism which is used to prioritize certain traffic as it is moves
through the switch. Traffic can be classified as High, Medium, Normal or Low priority. This
switch features both strict priority-based and weighted round-robin (WRR) forwarding, with
guaranteed bandwidth allocation for the different QOS classes. The queueing method can be
selected using the Queue Mode drop-down list:
• Strict priority - Higher priority frames take precedence over lower priority frames during
forwarding. In case of congestion, the lowest priority traffic is dropped before higher
priority frames. Head-of-queue blocking maybe encountered by using this mode.
• WRR - In this mode, all priorities can be guaranteed a share of the bandwidth when the
system is overloaded. The bandwidth sharing percentage can be adjusted by specifying
the four QOS class with different ratio in WRR Weight, which appears after WRR is
enabled in Queue Mode.
Note: WRR is selectable when Jumbo Frame is disabled in Ports > Settings.
You can select how traffic is prioritized by using one of the three QoS modes which is selected
using the QoS Mode drop-down list:
• QoS Disabled - QoS is turned off and all packets have equal priority.
• 802.1p - Packets are prioritzed using the content of the VLAN-tag.
• DSCP - Packets are prioritized using the DSCP (Differentiated Services Code Point) value.