L-ET4148-50C-DB LSI, L-ET4148-50C-DB Datasheet - Page 30

• 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
Policing
The ET4148-50 includes a series of policer functions that serve to limit the amount of ingress bandwidth permitted
for any particular packet flow.
Two processes run in parallel for each policer. The first process simply performs the leak function for the accumu-
lator. The second process starts with each receive packet and determines if the receive packet is out of profile and,
if so, which action to take.
The leaky bucket accumulator uses two parameters to regulate the leak rate. The first parameter is a delay interval.
This delay interval is proportional to the operating speed of the associated receive port. i.e., the interval for a 10
Mbits/s port is 100 times that of a 1 Gbit/s port. This automatic proportional behavior means that the delta that is
periodically applied to the accumulator can be reasonably thought of as a percentage of available bandwidth. The
delta is adjusted as desired during configuration to establish the maximum receive bandwidth allowed for the asso-
ciated traffic flow.
30
PROPORTIONAL TO PORT SPEED
LEAKY BUCKET ACCUMULATOR
WAIT FOR PERIOD THAT IS
SUBTRACT DELTA FROM
START
DEMOTE PACKET’S PRIORITY
(continued)
Figure 11. Policing Processes
Agere Systems - Proprietary
LEAKY BUCKET ACCUMULATOR
DELIVER PACKET TO STORAGE
Y
ADD PACKET LENGTH TO
PROFILE TRAFFIC?
DEMOTE OUT OF
ACCUMULATOR >
PACKET BUFFER
OUT OF PROFILE
CONGESTED?
DISCARD ALL
TRAFFIC?
START
LIMIT?
DONE
Y
N
N
N
N
Y
Y
N
PROFILE TRAFFIC WHILE
DONE
DISCARD PACKET
DISCARD PACKET
DISCARD OUT OF
CONGESTED?
DONE
DONE
Y
Preliminary Data Sheet
Agere Systems Inc.
April 2006