NEC Electra Elite IPK II Features And Specifications Manual page 484

Document Revision 1
Back Pressure
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For congestion on a half-duplex port, back pressure flow control is supported. Back pressure
generates collision-detection signals in the CSMA/CD MAC-layer (media access control) protocol
of Ethernet when a port is overloaded. These collision-detection signals from the congested port
trick the sending port into believing a collision is imminent, and cause it to back off. This, in turn,
forces a throttling back of the LAN segments experiencing congestion. When the sending ports try
to transmit after the standard Ethernet delay time, the congested port may again send
collision-detection signals or accept the incoming frames if ready.
Flow Control
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For congestion on a full-duplex port, the ETU supports IEEE 802.3x flow control that allows a
device to momentarily stop the flow of traffic from a transmitting device, by sending a pause frame.
Port Mirroring
For troubleshooting network issues with a protocol analyzer, port mirroring can be enabled to have
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traffic on a source port reflected to the target port.
Conditions
r When Auto Negotiation is denied and port speed is set to 100Mbps, the yellow LED
(located on the RJ45 connector) is ON. When port speed is set to 10Mbps, this LED is
OFF.
Only one HUB(8)-U( ) ETU can be assigned and installed per cabinet.
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Default Setting
None
System Availability
Terminals
None
Required Components:
HUB(8)-U( ) ETU
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Electra Elite IPK II
Internal Hub