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UNUSED (1bit).
User can randomly control these fields to achieve some special QoS goals. When bits D, T, R, or M set, the D
bit requests low delay, the T bit requests high throughput, the R bit requests high reliability, and the M bit
requests low cost.
DiffServ DSCP Priority act on DSCP field of IP Header. In the late 1990s, the IETF redefined the meaning of
the 8-bit SERVICE TYPE field to accommodate a set of differentiated services (DS). Under the differentiated
services interpretation, the first six bits comprise a codepoint, which is sometimes abbreviated DSCP, and the
last two bits are left unused.
High Priority Packet streams will experience less delay into the switch. For handing different priority packets,
each egress port has designed up to 4 queues. Each QoS is influenced by two scheduling, WRR (Weighted
Round Robin) and Strict Priority as well. When you finish setting the priority mapping to the queue, WRR
scheduling will distribute the bandwidth according to the weight you set for 4 queues (queue 0 to queue 3).
Another scheduling is Strict Priority dedicated for the function named VIP Port of QoS. While we select some
ports as the VIP Port, these ports will own the highest transmitting priority in egress queue of the switch.
The QoS functions as we mentioned above are able to enable at the same time. But, the following precedence
will decide whether these functions work or not.
z Enable both VIP and TOS --- Choose priorities of VIP and TOS.
z Enable both VIP and DSCP --- Choose priorities of VIP and DSCP.
z Enable both TOS and DSCP --- Choose "DSCP".
z Enable both VIP and DSCP --- Choose priorities of VIP and DSCP.
z Enable both 802.1p and TOS --- Choose "TOS".
z Enable both 802.1p and DSCP --- Choose "DSCP".
z Enable both 802.1p and DSCP and TOS --- Choose "DSCP".
z Enable both 802.1p and DSCP and TOS and VIP --- Choose priorities of VIP and DSCP.
** VIP/DSCP > TOS > 802.1p (Final result)
3.19.1 Global
When you want to use QoS function, please enable QoS Mode in advance. Then you can use MAC Priority,
802.1p Priority, IP TOS Priority, DiffServ DSCP Priority, or VIP Port functions and take effect. In this function,
you can Enable QoS Mode. Choose any of Priority Control, such as 802.1p, TOS, DSCP. Moreover, you can
select Scheduling Method of WRR (Weighted Round Robin) or Strict Priority. Next, you can arrange Weight
values for queue 0 to queue 3.
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