3Com 4007, Implementation Manual, Page: 203 / 684

CoS in Your System 203
CoS in Your System
Using the Administration Console on Layer 2 Switching Modules, you
can:
■
Enable or disable CoS (the setting affects all ports), which changes the
number of hardware queues per port from one to two.
■
Modify how the eight priority levels are assigned between the two
queues.
By default, the priority levels are assigned according to
recommendations in the IEEE 802.1p standard. See “Configuring
Priority Levels” later in this section.
■
Set a rate limit on the high priority queue.
See “Configuring a Rate Limit on Queue 1” later in this section.
■
Display a summary CoS configuration.
CoS Architecture When CoS is enabled, a Layer 2 Switching Module uses two CoS queues
per port:
■
Queue 1 is always the high priority queue.
■
Each Fast Ethernet port has a queue-specific buffer of 64 KB.
■
Each Gigabit Ethernet port has a queue-specific buffer of 128 KB.
■
You can affect the flow of queue 1 traffic by configuring a rate
limit. See “Configuring a Rate Limit on Queue 1” later in this
chapter.
■
Queue 2 is always the low priority queue.
■
Each Fast Ethernet port has a queue-specific buffer of 256 KB.
■
Each Gigabit Ethernet port has queue-specific buffer of 512 KB.
When CoS is disabled, the high priority queues and associated buffers are
shut off; all traffic flows through the low priority queues.
CoS settings are stored in non-volatile memory. Thus, in the event of a
power cycle or reboot, user-configured settings are retained.