Olicom 8600 Transmission Priority Queues, CrossLink Connections, Spanning Tree Protocol Support

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the same segment. Therefore, the IEEE Spanning-Tree Protocol (STP) must be enabled, which will place one port in forward and the other in blocked mode. If there is a break in the main ring, the STP will place both ports in forward mode, and all MACs on both segments will be relearned.

If a switch port has been configured to RI/RO mode, it will automatically sense whether the port has been connected to RI or RO of the MAU.

➽Note: It is not possible to automatically verify whether an UTP/STP port has been connected according to the configuration. Any errors, such as attaching port 19 or 20 to a normal MAU port when the CrossFire 8600 port has been configured for RI/RO, will cause a complete disruption of the ring to which the port is attached. Therefore, be careful when using the RI/RO feature.

Transmission Priority Queues

To address the needs of delay-sensitive data, such as multimedia, the Token-Ring ports of the switch have two transmit queues, a high-priority queue and a low- priority queue.

The queue for a frame is determined by the value of the priority field in the frame control (FC) byte. If FC priority is above a configurable level (default 3), the frame is put into the high-priority queue. If an output port becomes congested, you can dynamically configure the port to transmit all frames at high priority regardless of the FC byte contents.

CrossLink Connections

Two switch stacks or switches may be interconnected by a number of parallel Token-Ring connections (up to 256 Mbps using eight ports). The traffic between the switches will be shared between the connections.

Spanning Tree Protocol Support

IBM initially supported only Source Route Bridging (SRB) in its bridges, so most networks were built to use it. The main consideration for SRB implementations in switches is the spanning-tree algorithm for spanning tree explorers (STEs). IBM originally implemented a form of the Institute of Electrical and Electronics Engineers (IEEE) spanning-tree algorithm. This algorithm, commonly referred to as the IBM spanning tree, limits the STE frames to one copy per destination ring. Some SRB implementations have also implemented the IEEE Spanning Tree Protocol to be compatible with SRT bridges. The IEEE Spanning Tree Protocol is not compatible with the IBM Spanning Tree Protocol.

The switch supports both the IEEE 802.1D and IBM Spanning Tree Protocols.

CrossFire 8600/8605 Token-Ring Switches v. 1.2, P/N: 710001641 Switch Theory of Operation