Alcatel Carrier Internetworking Solutions 6648 - Manual (Page 336)

Source Learning
page -12 OmniSwitch Troubleshooting Guide September 2005
Source Learning
Coronado ASIC is a ingress classifier that performs Layer 2 hardware table lookups to the VLAN Id corre-
sponds to the incoming packets.
In principle, Coronado will perform a Layer 2 Source Address (L2 SA) lookup based on whether the
incoming port is a tagging or non-tagging port, a copy of the packet is re-queued to the Source Learning
queue for processing if the lookup fails. Coronado then performs a L2 Destination Address (L2 DA)
pseudoCam lookup to find out the destination Queue Identifier (QID) to queue the packet to the egress
port. Coronado always put the packet in the flood queue if the L2 DA lookup fails until Source Learning
updates DA entry.
Source Learning is responsible for managing (creation, update, deletion) MAC address entry in Layer 2
pseudoCam hardware source and destination address tables and communicating other interested entities
(QOS, Layer 3,...) regarding the new learned mac address.
By taking advantage of the Coronado hardware processing capabilities, Source Learning is distributed on
every Coronado in the switch. The processing load is spread among all the Coronados, thus performance is
increased. On the other hand, Address Learning is independent from the presence of CMM.
Each Coronado sends an event to the CMM to update the filtering database on CMM whenever there is an
operation on its Source Address pseudoCam. As a result, each Coronado has a local view of layer 2
pseudoCam information of its own slot/slice, and the software filtering database on the CMM has global
view of the layer 2 pseudoCam information in the switch.