Net Optics PA-CU-AR - Manual (Page 10)

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.
Firewall Router
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 2 A
Application Diagrams: Memory Operation
All traffic that passes through the Tap is sent to the monitoring device NIC on
a first-in, first-out basis, including traffic that is temporarily stored in memory.
(If.two.packets.enter.at.the.same.time.then.one.packet.is.processed.while.the..
other is stored briefly in memory, preventing collisions.)
When there is a burst of data, traffic 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 fill until its capacity is
reached, or the burst ends – whichever comes first.
In both cases, the Tap applies a first-in, first out procedure, processing stored
data before new data from the link. If memory fills before the burst ends, the
memory stays filled as the stored data is processed – data that leaves the buffer
is immediately replaced. If the burst ends before the memory fills, 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