Olicom 8600, 8605 manual Low Latency, Address Management

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conversations, the switch creates 160 Mbps throughput in half-duplex mode, or 320 Mbps throughput in full-duplex mode.

A single segment can be dedicated to a single host or shared by several. To optimize throughput, high-speed servers can be given dedicated switch ports.

By transporting multiple Token-Ring packets simultaneously, it boosts overall network throughput.

Low Latency

When operating in cut-through mode, the switch minimizes latency—the time it takes to forward a packet from one Token-Ring segment to another—by beginning switching immediately after looking at the first six bytes of the destination address in the packet. If the packet needs to be switched to another LAN segment, its data begins flowing through the destination port before the entire packet has been received. The result: packets can appear at the output port 35 microseconds after entering the input port. Network devices that use store-and-forward technology introduce much longer delays because they wait to receive the entire packet before forwarding it.

By minimizing delay, the switch can move more packets freely throughout the LAN without degrading performance.

Address Management

At power up, the system address tables do not contain any information. Whenever a switch receives a packet with an unknown source or destination address, it learns the new source address and stores its location in coming port in the address table. If the destination address is unknown it sends the packet to all ports that can receive data from the incoming port. When the response packet comes back, the switch will learn the responder’s location and adds it to the address table. Once the address table entries are created, the switch uses these learned address to switch all subsequent packets to the port where the destination address is located.

The system address table maintains up to 10,000 entries, and each port address table maintains 5,500 active Token-Ring addresses (each port address table is shared by four ports, using the following: 1-4, 5-8, 9-12, 13-, etc.). If an address has not been active for a configurable aging time, it is removed from the tables. This ensures that the port’s address table is populated only by the most recently used address.

This capability allows users to transparently connect to high-volume backbone networks.

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