zl50411 Zarlink Semiconductor, zl50411 Datasheet - Page 38

• Manufacturer Part Number: zl50411
• Description: Managed 9-port Fast Ethernet Switch With Private Vlan
• Manufacturer: Zarlink Semiconductor

and CPU ports, to map the 8 transmit priorities into 4 multicast queues, the LSB is discarded. The priority mapping
can be modified through memory configuration command. The multicast queue that is in FIFO format shares the
space in the internal memory block. The size and starting address can also be programmed through memory
configuration command.
During scheduling, the TxQ manager treats the unicast queue and the multicast queue of the same class as one
logical queue. The older head of line of the two queues is forwarded first. The port control requests a FCB release
only after the EOF for the multicast frame has been read by all ports to which the frame is destined.
4.3
Frame forwarding from the CPU port to a regular transmission port is nearly the same as forwarding between
transmission ports. The only difference is that the physical destination port must be indicated in addition to the
destination MAC address.
Frame forwarding to the CPU port is nearly the same as forwarding to a regular transmission port. The only
difference is in frame scheduling. Instead of using the patent-pending Zarlink Semiconductor scheduling algorithms,
scheduling for the CPU port is simply based on strict priority. That is, a frame in a high priority queue will always be
transmitted before a frame in a lower priority queue. There are four output queues to the CPU and one receive
queue.
5.0
5.1
The ZL50411 search engine is optimized for high throughput searching, with enhanced features to support:
•
•
•
•
•
•
•
•
•
•
5.2
Shortly after a frame enters the ZL50411 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 packet’s VLAN ID,
and whether the frame is unicast or multicast or broadcast. Requests are sent to the SRAM to locate the associated
entries in the MCT table.
When all the information has been collected from the 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).
Up to 4 K of Unicast/Multicast MAC addresses and IP Multicast addresses
Up to 4 K VLANs
Private VLAN Edge (protected ports) support
Up to 8 groups of port trunking
Traffic classification into 2 (or 4 for MMAC) transmission priorities, and 2 drop precedence levels
Packet filtering based on MAC address, Protocol or Logical Port number
Security
Up to 4 K IP Multicast groups
Individual Flooding, Broadcast, Multicast Storm Control
MAC address learning and aging
Frame Forwarding To and From CPU
Search Engine Overview
Basic Flow
Search Engine
Zarlink Semiconductor Inc.
ZL50411
38
Data Sheet