14
6. XSNet 2800 SW Quality of Service (QoS)
Enabling QoS on the 2800 SW instates two priority levels (high/low) and corresponding queues, used in case of
network congestion. These levels can be defined as follows:
-
Port based: tagged and untagged frames entering a port marked ‘high’ go to the high-priority queue.
-
Priority based: per Q-frame (only priority level 0-7 in tag is important). A TCI lo/hi threshold of 1-7
must be set. Tagged frames with a priority level equal to the TCI-threshold and up go into the high-
priority queue.
(TCI = tag control information)
Fulfilling either of these two conditions (see the arrows in figure 13) will get a frame into the high-priority
queue.
The H-weight and L-weight entries (values allowed are 0-15), defining how fast the queues are handled, must be
set. They are defined as:
-
H-weight =
m
(default 4): after handling maximum of
m
high-priority frames, start with low-priority
frames
-
L-weight =
n
(default 1): after a maximum of
n
low-priority frames, return to handling high-priority
frames.
Figure 13. The example has QoS enabled, weights of 4 and 1, ports 1-3 set to high priority, and a TCI-threshold of 4.