User`s guide

FX-16NW

Switching scheme

Most switching hubs support one of the following switching schemes: Cut

Through or Store & Forward. In Cut Through switching, any received

packet is sent to one of the ports immediately after its destination address is

discerned. Since packets themselves are not inspected, some error packets

may leave the switch among normal packets. In contrast, Store & Forward

technology first stores the received packet in an internal packet buffer and

checks for length and CRC. Error packets are dropped at this stage, and

only normal packets are transmitted. The FX-16NW Switching Hub

supports the Store & Forward switching scheme.

Resets the Limitations on Cascading Hubs

Generally, repeater hubs can cascade only up to four stages for 10BASE-T

and two stages for 100BASE-TX. This limitation does not apply to a

switching hub because each port on the switch has its own collision domain.

For this reason, switching hubs can expand an existing network without

using relatively more expensive routers or bridges.

This number is also required for all technical support services.

How Switching Hubs differ from Repeater Hubs

Ordinary repeater hubs transmit data to all ports, even when only one port

needs the data. Consequently, the overall network traffic increases, slowing

down communications on the network itself. Moreover, repeater hubs

require that all ports share the same bandwidth; a collision occurs when

multiple packets are transmitted simultaneously. To counter these problems,

the switching hub learns the destination address and sends data only to the

port that leads to the destination node. This scheme prevents the data from

being sent to other ports, thereby reducing network load. A switching hub

thus allows more efficient communication among computers on the

network.

Switching Technology

Figure 1-4