An ethernet switch has a number of ethernet ports, usually [10BaseT], [100BaseT], and [1000BaseT]. A switch receives ethernet frames on every port and based on the destination MAC address, forwards them out another port. Switches of these type tend to be store-and-forward devices, receiving the entire frame and doing a lookup against the MAC table for destination ports.
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The MAC table is updated on reception of packets from a source [MAC] address, for each MAC address an entry in that ports MAC forwarding table is added.
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The quality of a switch usually depends on a number of factors.
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!!Manageability is a key factor.
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Managed switches allow the administrator to use [SNMP]/Telnet/[WWW]/etc. to configure and monitor a particular switch. This enables fine tuning of the switches performance and bandwidth graphs to be generated for each port, etc.
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!!Switch Fabric Bandwidth.
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The amount of bandwidth on the switch fabric dictates how much data can be switched in any one second. If data cannot be switched, it will be stored in a (small) buffer on the incoming port. If this buffer fulls up the packet is dropped.
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!!Per-Port Buffer Size
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If the switch is blocking packet due to high demand, the [FIFO] buffer on the incoming port may be used. The larger this buffer is - the less likely the packet is to be dropped.
This is not usually a problem, a ethernet [MAC] is 6 bytes, most switches claim 4k [MAC] addresses per port, this is only 24kB of [RAM] per port - the buffer size (up to multiple MB) is much more important.
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