L-ET4148-50C-DB LSI, L-ET4148-50C-DB Datasheet - Page 32

• Manufacturer Part Number: L-ET4148-50C-DB
• Manufacturer: LSI

Specifications of L-ET4148-50C-DB

• Lead Free Status / RoHS Status: Supplier Unconfirmed

ET4148-50
Single-Chip 48 x 1 Gbit/s + 2 x 10 Gbits/s Layer 2+ Ethernet Switch
Functional Description
Storage
During the storage process, packet buffer storage space is allocated to a receive packet. References to the packet
are deposited onto the queues identified by the bridging and ACL processes.
The first step in storing a receive packet is to ensure that sufficient storage resources are available to accommo-
date a maximum length packet. If insufficient resources are available, then the packet is discarded.
If sufficient storage space is available, the space is allocated to the packet. This allocation may result in the packet
buffer entering into a congested state, either globally or locally. If either condition is true, the appropriate indication
is provided to the ingress policers and/or Ethernet MACs.
The remainder of the storage process entails the actual storage of the packet into the allocated buffers, mapping
the packet’s priority level (16 levels) to one of the eight queues that exist per transmit port. Finally, the queue map-
ping and the destination map are used to identify the various individual queues into which a reference to the stored
packet is deposited.
32
DEPOSIT STORAGE REFERENCES
(continued)
ONTO DESTINATION QUEUE(S)
ALLOCATE STORAGE SPACE
MAP PRIORITY TO QUEUE
STORE PACKET
CONGESTION
CONGESTION
THRESHOLD
THRESHOLD
AVAILABLE?
CROSSED?
STORAGE
CROSSED?
GLOBAL
SPACE
START
LOCAL
DONE
Figure 12. Storage Process
Agere Systems - Proprietary
Y
N
N
N
Y
Y
DECLARE CURRENT
PORT CONGESTED
DISCARD PACKET
PORTS CONGESTED
DECLARE ALL
DONE
Preliminary Data Sheet
Agere Systems Inc.
April 2006