ZL50418GKC ZARLINK [Zarlink Semiconductor Inc], ZL50418GKC Datasheet - Page 23

• Manufacturer Part Number: ZL50418GKC
• Description: Managed 16-Port 10/100 M + 2-Port 1 G Ethernet Switch
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

5.0
5.1
The ZL50418 search engine is optimized for high throughput searching, with enhanced features to support
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5.2
Shortly after a frame enters the ZL50418 and is written to the Frame Data Buffer (FDB), the frame engine generates
a Switch Request, which is sent to the search engine. The switch request consists of the first 64 bytes of the frame,
which contain all the necessary information for the search engine to perform its task. When the search engine is
done, it writes to the Switch Response Queue and the frame engine uses the information provided in that queue for
scheduling and forwarding.
In performing its task, the search engine extracts and compresses the useful information from the 64-byte switch
request. Among the information extracted are the source and destination MAC addresses, the transmission and
discard priorities, whether the frame is unicast or multicast and VLAN ID. Requests are sent to the external SRAM
to locate the associated entries in the external hash table.
When all the information has been collected from external SRAM, the search engine has to compare the MAC
address on the current entry with the MAC address for which it is searching. If it is not a match, the process is
repeated on the internal MCT Table. All MCT entries other than the first of each linked list are maintained internal to
the chip. If the desired MAC address is still not found, then the result is either learning (source MAC address
unknown) or flooding (destination MAC address unknown).
In addition, VLAN information is used to select the correct set of destination ports for the frame (for multicast) or to
verify that the frame’s destination port is associated with the VLAN (for unicast).
If the destination MAC address belongs to a port trunk, then the trunk number is retrieved instead of the port
number. But on which port of the trunk will the frame be transmitted? This is easily computed using a hash of the
source and destination MAC addresses.
As stated earlier, when all the information is compiled, the switch response is generated. The search engine also
interacts with the CPU with regard to learning and aging.
Up to 64 K MAC addresses
Up to 255 VLAN and IP Multicast groups
3 groups of port trunking (1 for the two Gigabit ports, and 2 others)
Traffic classification into 4 (or 8 for Gigabit) transmission priorities, and 2 drop precedence levels
Packet filtering
Security
IP Multicast
Flooding, Broadcast, Multicast Storm Control
MAC address learning and aging
Search Engine Overview
Basic Flow
Search Engine
Zarlink Semiconductor Inc.
ZL50418
23
Data Sheet