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Managing the Hub 2-41
The SmartSwitch 2000 Chassis View
The following operational modes can be speciÞed:
Speed
This Þeld speciÞes a port speed of 10MB, 100MB, or 1000MB.
Duplex
This Þeld speciÞes Half Duplex or Full Duplex mode for the port.
Flow Control
Flow control allows Ethernet devices to notify attached devices that congestion is
occurring and that the sending device should stop transmitting until the
congestion can be cleared. There are two commonly used methods of ßow control:
Frame-based (operates on Full Duplex links) and Backpressure (operates on Half
Duplex links).
Ports set to Full Duplex mode have frame-based ßow control, using pause
control frames. Frame-based ßow control options are:
Symmetric The port is able to both receive and transmit pause control
frames.
Asymmetric RX This option appears only for Gigabit Ethernet ports. The port
will receive pause control frames, but will not transmit its own.
Asymmetric TX This option appears only for Gigabit Ethernet ports. The port is
capable of sending pause control frames, but will not
acknowledge received pause control frames.
Disabled Disables ßow control on the port.
Auto Negotiate Ports conÞgured to operate in auto negotiation mode will only
use pause control frames if the negotiation process determines
that the link partner supports them. Both ends of the link must
support auto negotiation and a common mode of operation.
Ports set to Half Duplex mode use Backpressure ßow control. Backpressure ßow
control simply asserts the carrier sense signal out the port causing the device
transmitting to detect a collision, stop transmitting data, and send the jam signal.
Backpressure ßow control options are enabled or disabled.
Setting the Desired Operational Mode
For any 100Base-TX port, you can conÞgure operational modes, or you can select
Auto Negotiate mode, which allows the port to negotiate with its link partner to
Þnd the highest mutually available bandwidth and ßow control. If you select
Auto Negotiate mode, you must also choose which of the portÕs bandwidth and
ßow control capabilities you wish to advertise to the link partner (refer to Auto
Negotiation Technologies, page 2-42).