Allied Telesis AT-S41 - Manual (Page 127)

AT-S41 User’s Guide
127
Quality of Service Overview
The AT-8326GB switch supports QoS as specified in the IEEE 802.1p and
802.1Q standards. QoS can be important in network environments
where there are time-critical applications, such as voice transmission or
video conferencing, that can be adversely affected by packet transfer
delays.
Prior to QoS, network traffic was handled in a best-effort manner. File
transfer delays did occur, but were mostly transparent to network users.
But with the introduction of time-critical applications, packet transfer
delays can prove problematic. For example, transfer delays of voice
transmission can result in poor audio quality.
QoS was designed to address this problem. The 802.1p standard outlines
eight levels of priority, 0 to 7, with 0 the lowest priority and 7 the highest.
The AT-8326GB switch has two priority queues, 1 (low) and 0 (high).
When a tagged packet enters a switch port, the switch responds by
placing the packet into one of the two queues according to following
assignments:
IEEE 802.1p AT-8326GB
Traffic Class Queue
0 1
1 1
2 1
3 1
4 0
5 0
6 0
7 0
For example, a tagged packet with a priority tag of 6 is placed in the high
priority queue, while a packet with a priority tag of 1 is placed in the low
priority queue.
These priority-to-queue assignments can be overridden using the
AT-S41 management software on a per port basis.
Note
QoS is disabled by default on the switch.