Port Traffic Controls
Guaranteed Minimum Bandwidth (GMB) on the Series 5300xl Switches
13-10
Table 13-1. Per-Port Outbound Priority Queues
802.1p Priority Settings in Tagged VLAN
Packets*
1 (low)
2 (low)
0 (normal)
3 (normal)
4 (medium)
5 (medium)
6 (high)
7(high)
*The switch processes outbound traffic from an untagged port at the "0" (normal) priority level.
You can use GMB to reserve a specific percentage of each port's available
outbound bandwidth for each of the four priority queues. This means that
regardless of the amount of high priority outbound traffic on a port, you can
ensure that there will always be bandwidth reserved for lower-priority traffic.
Since the switch services outbound traffic according to priority (highest to
lowest), the highest-priority outbound traffic on a given port automatically
receives the first priority in servicing. Thus, in most applications, it is neces
sary only to specify the minimum bandwidth you want to allocate to the lower
three priority queues. In this case, the high-priority traffic automatically
receives all unassigned bandwidth without starving the lower-priority queues.
Conversely, configuring a bandwidth minimum on only the high-priority out-
bound queue of a port (and not providing a bandwidth minimum for the lower-
priority queues) is not recommended because it may "starve" the lower-
priority queues. (See the Note, below.)
Outbound Priority Queue for a Given Port
1
2
3
4