50-Series Buffers and Queues

Buffer and queue management relieves congestion in a network. Adding gigabit speeds to existing networks means that there can be a huge disparity between link speeds. For example, anything more than a 1-percent load on a gigabit link could easily overwhelm a 10 Mb/s Ethernet link.

Each switch employs the following buffer and queue management techniques:

• Configurable active backpressure:
• Half-duplex ports use active backpressure to jam input ports when their frame buffers are full.
• Full-duplex links use IEEE 802.3z pause control frames to pause traffic when buffers are full.
• Packed frame buffers for optimal memory utilization. The memory management allows virtually 100% utilization of buffer memory.
• Two CoS priority queues for 50-Series modules and eight CoS priority queues for 80-Series modules provide flexible queue management algorithms to meet application requirements.
• Configurable queue depth for each prioritized packet queues.
• Configurable priority threshold.
• Configurable service ratio tunes queue priority.

For more information on 50-series buffers and queues, see Chapter 24:�Managing Buffers and Queues on 50-Series Modules.