Managing the Module 2-57The Device View
routing fields, if present), and then recomputing the Frame Check Sequence (FCS)
appropriately. On receiving such a frame, a tag-aware switch will read the priority from
the tagged portion of the frame, remove the Tag Header, recompute the FCS, and then
direct it to its appropriate transmission queue.
There are eight priority levels — indicated 0 through 7— available to designate user
priority. Frames tagged with a 0 represent the lowest priority level (or normal) traffic, and
frames tagged with a 7 indicate the highest priority level traffic.
The 6000 and Matrix E7 series modules themselves support two transmission queues: one
that is for 0 or normal priority traffic (or any non-tagged traffic), and a second queue that
is reserved for frames that have been tagged with a priority level of 1 or higher. On
receiving any priority-tagged frames, the SmartSwitch 6000 or Matrix E7 will forward
them out of the high priority queue before forwarding any frames in the normal priority
queue. However, the SmartSwitch 6000 or Matrix E7 will tag outgoing frames with the
full range of eight priority levels, so that upon reception, a device that supports the entire
range of priority queuing will forward the frame appropriately.
You can use NetSight Element Manager to configure the criteria that determine the
priority in which frames will be queued for transmission by your SmartSwitch 6000 or
Matrix E7 module. Several different criteria can be used to determine a frame’s
transmission queue order:
• The module and port at which the frame was received.
• The destination and/or source MAC address associated with the frame.
• A combination of destination and/or source MAC address and the frame’s protocol
type.
• The frame’s protocol type.
When you configure the transmission queue for a specific frame, an entry is made in one
of three priority tables maintained by the SmartSwitch 6000 or Matrix E7 module. These
tables are used to determine which transmit queue to use — normal priority or high
priority — when forwarding frames.
•The ctPriorityExtPortTable maintains priority entries based on a frame’s receive port.
•The ctPriorityExtMACTable maintains priority entries based on a frame’s MAC-layer
information.
•The ctPriorityExtPktTypeTable maintains priority entries based on the frame’s
protocol type.
The following sections discuss how to use the Port Priority Configuration window, the
MAC Based Priority Configuration window, and the Frame Priority Configuration
window to make entries in these transmit priority tables.