Allied Telesis AT-FS217 - Manual (Page 15)

AT-FS21x and AT-FS212/x Series Installation Guide
5
Functional Description
Frame Processing
The switches support store and forward switching at Fast Ethernet full-wire
speed 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 depending on its destination address and error status. This ensures
that only error-free data packets destined for another segment will be
transferred across the switch, reducing network load. For example, if the
packet entering from Port 1 is destined for 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 for 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 4,000 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, the entry is deleted from the table. The
switch forwards multicast, broadcast, and unicast packets when the MAC
address table size is exceeded.