On the 7210 SAS-D, each queue provides the user with the following options:
option to configure three slopes per queue - high-priority RED slope, low-priority RED slope, and a non-TCP RED slope
option to use two slopes per queue - high-priority RED slope and a low-priority RED slope
The high-priority RED slope manages access to the shared portion of the buffer pool for high priority or in-profile packets. The low-priority RED slope manages access to the shared portion of the buffer pool for low-priority or out-of-profile packets. The non-TCP slope manages access to the shared portion of the buffer pool for non-TCP packets.
By default, the high-priority, low-priority, and non-TCP RED slopes are disabled.
When queue depth exceeds the queue CBS, packets received on that queue must contend with other queues exceeding their CBS for shared buffers. To resolve this contention, two RED slopes are used to determine buffer availability on a packet-by-packet basis. A packet that is either classified as high-priority or considered in-profile is handled by the high-priority RED slope. This slope should be configured with RED parameters that prioritize buffer availability over packets associated with the low-priority RED slope. Packets that are classified as low priority or out-of-profile are handled by the low-priority RED slope. When the queue is configured with option to use non-TCP Slope, non-TCP packets are handled by this slope.