Net Optics 10_100_1000 Copper Port Aggregator - Manual (Page 9)

10/100/1000 Copper Port Aggregator Tap
5
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 ..One.gigabyte.of.data.from.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.gigabyte.of.capacity.is.available,.or.another.until.another.
burst.in.excess.of.the.NIC's.capacity.requires.additional.memory .
. The.following.three.diagrams.illustrate.a.simple.example.of.a.1000.Mbps.NIC..
. moving.from.80%.utilization,.to.140%.utilization,.then.back.to.80%.
. utilization .
State 1: Side A + Side B is less than or equal to 100%
of the NIC's receive capacity.
State 2: Side A + Side B becomes greater than 100%
of the NIC's receive capacity.
State 3: Side A + Side B is once again less than 100%
of the NIC's receive capacity.
10/100/1000 Copper Port Aggregator
Memory Operation
Copyright © 1996-2008 Net Optics, Inc.
Example: On a 1000 Mbps link, Side A is at 300 Mbps and Side B is at 500 Mbps.
The NIC receives 800 Mbps of traffic (80% utilization), so no memory is required
for the monitoring device NIC to process all full-duplex traffic.
Example: There is a burst of traffic, so Side A is now at 900 Mbps, while Side B
remains at 500 Mbps. The NICʼs utilization is at 140%, requiring the use of
memory to help prevent data loss.
Example: Side A is again at 300 Mbps and Side B remains at 500 Mbps. The
NICʼs utilization is again at 80%.
Router
Side A
300 Mbps 10/100/1000 Copper
Port Aggregator
Firewall
Side B
500 Mbps
Side A
900 Mbps
Side B
500 Mbps
Side A
300 Mbps
Side B
500 Mbps
Monitoring Device
Side A + Side B
800 Mbps
1 Using a single NIC, the monitoring device
receives all combined traffic from Side A and
Side B, including physical layer errors.
2
Monitoring Device
The monitoring device receives 1000 Mbps
of combined traffic from Side A and Side B,
including physical layer errors.
The traffic to the 1000 Mbps
monitoring device is limited
to 1000 Mbps. The extra 400
Mbps of traffic is stored in a
one gigabyte memory buffer.
Memory continues to fill until
the giggabyte capacity is
reached or the burst ends.
10/100/1000 Copper
Port Aggregator
Firewall
Router
Side A + Side B
limited to 1000 Mbps
1
Memory
The Tap applies a first-in,
first-out process to all
packets. Once the burst has
ended and the NICʼs utilization
is again below 100 percent,
the Tap processes the packets
that were stored in memory.
As long as the NICʼs utilization
remains below 100 percent,
this process continues
uninterrupted until the
memory clears.
Once the memory has cleared, the monitoring
device begins receiving new data directly
from the link. The monitoring device
continues to receive all traffic from Side A
and Side B, including physical layer errors.
1
10/100/1000 Copper
Port Aggregator
Firewall
Router
Monitoring Device
Side A + Side B
800 Mbps
2
Memory
Network
2
1
A
LINK ACT
B
LINK ACT
2
LINK ACT
1
LINK ACT www.netoptics.com
Network
2
1
A
LINK ACT
B
LINK ACT
2
LINK ACT
1
LINK ACT www.netoptics.com
Network
2
1
A
LINK ACT
B
LINK ACT
2
LINK ACT
1
LINK ACT www.netoptics.com
Figure_2._80% Utilization