Advantech B+B SmartWorx IMcV-Giga-FiberLinX-III User Manual page 27

DATA PORT
Ingress Bandwidth
Limit (CIR)
Max Burst
Allocation Size (BA)
Ingress Burst
Allocation
Egress Traffic
Shaping
OSI Level Used in
Calculations
(Open Systems
Interconnect, referring
to seven layers for
TCP/IP)
Unit Rate Control
Enable/Disable
OSI NOTES: Bandwidth Limit functions can be adjusted to only count the Layer 1, 2, or 3 portions of the
physical line rate. Layer 1 is used to relate Bandwidth to the physical line rate where a 100BaseT Ethernet line
can carry a MAX bandwidth of 100Mbps. Layer 2 may be more useful when the Ethernet Frame may be carried
over several different physical protocols such as SONET or SDH. Only the bandwidth required by the Ethernet
frame is counted, making this a more consistent number over different protocols. Layer 3 counting could be
Monitors the traffic entering the unit (ingress), discarding
traffic that exceeds a fixed Committed Information Rate (CIR)
plus Burst Allocation (BA). Frames are not held in queue -
they either meet the bandwidth limits and are accepted into
the unit, or they are dropped.
The BA size is specified in bits; the # of bits above the
bandwidth limit before packets are thrown away.
Bandwidth limiting can be set at Ingress of each port
individually by setting the MAX BW Limit in bits/sec. and the
BA in bits. Traffic in excess of the bandwidth limit plus BA for
any time interval will be dropped. This function uses an
advanced "Leaky Token-Bucket" algorithm to provide typical
resolution under 5% of the set values at all data rate and
frames sizes.
Actively controls the transmitter and hard limits the maximum
frame rate that can be sent. Frames can be delayed in the
internal buffers of the unit, waiting their turn to be sent. If the
internal buffers are full, excess traffic will be dropped. The Unit
Rate Control can be used to alleviate this.
Choose Layer 1, 2 or 3 for the counter. This determines how
many bytes from the Ethernet frame are to be included in the
calculations.
Layer 1
Layer 2
Layer 3
Explanations:
Preamble
DA
CRC
IFG
Allows end users to globally configure all Bandwidth settings
when enabling Unit Rate Control (Flow Control). If END device
connected to the port also has Flow Control enabled, this
ensures packets will not be dropped.
27
iMcV-Giga-FiberLinX-III
= Preamble + DA to CRC + IFG
= Frames DA to CRC
= Frames DA to CRC – 18
(- 4 if frame is tagged)
= 8 bytes
= EtherNet Destination Address
= EtherNet Checksum
= 12 bytes