Overview of the P220 Gigabit Switch Family

Figure 2-4.Spanning Tree

Single 802.1D Spanning Tree

One Spanning Tree

Longer convergence

One path to and from root for all VLANs Improper configuration

can shut down Trunk Links

Multi-layer Spanning Tree Backbone terminates 802.1D STP

Smaller STP Domains

Quicker Convergence

VLAN Load Balancing

Interoperates w/ existing Bridge/Routers

Buffer and Queue Management

Adding gigabit speeds to existing networks means that there can be a huge disparity between link speeds. For example, anything more than a 1% load on a gigabit link could easily overwhelm a 10 Mb/s Ethernet link.

Without queue and buffer management, gigabit links might only move congestion in a network, rather than relieving it. The 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 Class of Service priority queues that provide flexible queue management algorithms to meet application requirements.

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Cajun P550/P220 Switch Operation Guide