Net Optics PA-CU-AR Switch User Manual


 
10/100 Port Aggregator Tap
6
Each using a single NIC, the monitoring
devices both receive all combined traffic
from Side A and Side B, including physical
layer errors.
State 1: Side A + Side B is less than or equal to 100%
of the NIC's receive capacity.
Example: On a 100 Mbps link, Side A is at 30 Mbps and Side B is at 50 Mbps.
The NIC receives 80 Mbps of traffic (80% utilization), so no memory is required
for the monitoring device NIC to process all full-duplex traffic.
FirewallRouter
Monitoring
Device 1
1
Active Response Dual
Port Aggregator Tap
Monitoring
Device 2
Side B
Side A
Side A +
Side B
®
www.netoptics.com
B 1 2A
Application Diagrams: Memory Operation
All trafc that passes through the Tap is sent to the monitoring device NIC on
a rst-in, rst-out basis, including trafc that is temporarily stored in memory.
(If two packets enter at the same time then one packet is processed while the
other is stored briey in memory, preventing collisions.)
When there is a burst of data, trafc in excess of the NIC's capacity is sent to
the Tap's memory. Up to one megabyte of data per side of the full-duplex
stream can be stored in memory. Memory continues to ll until its capacity is
reached, or the burst ends – whichever comes rst.
In both cases, the Tap applies a rst-in, rst out procedure, processing stored
data before new data from the link. If memory lls before the burst ends, the
memory stays lled as the stored data is processed – data that leaves the buffer
is immediately replaced. If the burst ends before the memory lls, memory
clears until the full megabyte of capacity is available, or until another burst in
excess of the NIC's capacity requires additional memory.
The following three diagrams illustrate a simple example of a 100 Mbps NIC
moving from 80 percent utilization, to 140 percent utilization, then back to 80
percent utilization. If you have PA-CU-AR model, there is only one monitor
port.
Figure 4: 80% Utilization