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CHAPTER 8 Appendix A: Quality of Service (QoS) Setup
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One thing should be noticed. If the priority mode of ETH4 is set as CoS or ToS, for instance, and then
you go on to configure its Fixed priority, the system will ignore the setting of Fixed Priority. This is
because that if you set the priority mode of an interface as CoS or ToS, the next step is to perform the
VLAN CoS priority setup or ToS field priority setup rather than Fixed Priority, and both CoS and ToS are
introduced in succeeding sections.
8.2.1.2. CoS Priority Setup
If “CoS” is selected as the “Priority Mode”, the next step is to configure the “VLAN CoS Priority Setup”.
The screen is shown as below.
SLOT 2 TDMoE === Vlan Cos Priority Setup === 13:18:47 12/31/2009
ARROW KEYS: CURSOR MOVE, TAB: ROLL OPTIONS
Cos priority Transmission priority
0 P0
1 P0
2 P0
3 P0
4 P0
5 P0
6 P0
7 P0
NOTE: Priority:P3 > P2 > P1 > P0
<< Press ESC key to return to previous menu >>
( VT-100 Terminal Path: Main Menu > (S) System Setup > (C) Qos Setup > (A) Class of Service > (C)
Vlan CoS Priority Setup)
Class of Service (CoS) is a 3-bit field added in the MAC header when applying VLAN tagging. CoS is
adopted to discriminate higher-priority traffic from lower-priority one. CoS determines the relationship
between priorities of ingress Ethernet frame traffic and queues. There are 8 levels of priority values,
ranging from 0 to 7, where 0 is the lowest priority and 7 the highest. By attaching priority value to
frames, users are enabled to classify and place them into different queues. The screen above allows
users to configure the transmission priority (= queue) for packets with different priorities.
Assumed that the priority mode for ETH3 and ETH4 are “CoS”, then both ports should apply the “VLAN
CoS Priority Setup”. Moreover, ETH3 and ETH4 share common settings, rather than have their own.
8.2.1.3. ToS Priority Setup
If “ToS” is selected as the “Priority Mode”, the next step is to configure the “ToS Field Priority Setup”.
The screen is shown as below.
SLOT 2 TDMoE === TOS field Priority Setup === 13:28:23 12/31/2009
ARROW KEYS: CURSOR MOVE, TAB: ROLL OPTIONS
Tos priority Transmission priority
0 P0
1 P0
2 P0
3 P0
4 P0
5 P0
6 P0
7 P0
NOTE: Priority:P3 > P2 > P1 > P0
<< Press ESC key to return to previous menu >>
( VT-100 Terminal Path: Main Menu > (S) System Setup > (C) Qos Setup > (A) Class of Service > (D)
ToS Field Priority Setup)