Overview
8
Each ATM MAC address is created by adding the port number to the basic
AT-4016F MAC address.
Since the AT-4016F has 16 ports there are 16 MAC addresses:
Port #1 - [basic MAC a 01]
Port #2 - [basic MAC a 02]
*
**
***
Port #16 - [basic MAC a16]
Two Modes of Ethernet Switching
There are two popular methods to forward information: cut-through and
store-and-forward. Although your AT-4016F employs store-and-forward as
the default, you can also choose cut-through.
Cut-Through
In a cut-through system, the device starts to forward the incoming packet
while the packet is still being received on the inbound link.
Cut-through switching requires software that can both look at the start of
the packet and determine which outbound link is to be used to forward the
packet. Cut-through does not check for Cyclic Redundancy Check (CRC)
errors before forwarding a packet.
Store-and-
Forward
Store-and-forward means that your AT-4016F stores the incoming packet
as it receives it until it has the entire packet and then forwards it.
Store-and-forward switching, performed at the MAC layer, not only checks
for a valid CRC before forwarding a packet, but allows your AT-4016F to
temporarily store packets until network resources, typically an unused
link, are available for forwarding. This allows complete error checking
until the entire packet is received correctly and limits the amount of time
between when a device requests access to the network and when it is
granted permission to transmit. Full store-and-forward switching,
therefore, ensures data integrity, thus preventing network error
conditions from being generated throughout the network.
On the other hand, in a store-and-forward system, every device in the
path from the sender of the packet to the packet’s receiver adds a small
delay due to the time spent storing the packet before forwarding it.
