Functional Description; Frame Processing; Address Recognition And Filtering - Allied Telesis at-fs201 Installation Manual

Description

Functional Description

The AT-FS200 family of switches function as unmanaged dual-port switches or
switches with automatic MAC Address Aging.

Frame Processing

The switches support store and forward switching at Fast Ethernet full-wire
speed either in 10 or 100 Mbps, half- or full-duplex mode. Packets entering
each port are stored in buffers. After the full packet is received, it is forwarded
or discarded appropriately depending on its destination address and error
status. This ensures that only error-free data packets destined to another
segment will be transferred across the switch, reducing network load. For
example, if the packet entering from Port 1 is destined to an end station on
Port 2, it will be forwarded if the Frame Check Sequence (FCS) is valid. If the
packet from Port 1 is destined to an end station also attached to Port 1, then
the packet is discarded.
The switch will discard CRC error, misaligned, runt, and under-sized/over-
sized packets. When the packet has dribble bits at the end, the switch will
truncate to octet boundary and check for a good FCS before forwarding.

Address Recognition and Filtering

Up to 8,192 MAC addresses can be stored in the MAC address table. The
switch will learn all new addresses in real-time after power-up with its
address self-learning mechanism. If the source address of an incoming packet
is not found in the Address Table, the switch waits until the end of the packet
to check for good CRC and then updates its MAC Address table. Because the
switch has Automatic Address Aging, if a source address entry in the table is
not updated within five minutes, that entry is deleted from the table. The
switch forwards multicast, broadcast, and unicast packets when the MAC
address table size is exceeded.
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