NOTE

CAUTION

 

 

Configuring Gigabit Ethernet Parameters

 

 

Understanding the Gigabit Ethernet Parameters

 

 

 

 

Speed

Duplexity

Autonegotiation

 

 

 

 

 

 

 

 

 

10

Half

Off

 

 

 

 

 

10

Full

Off

 

 

 

 

 

100

Half

Off

 

 

 

 

 

100

Full

Off

 

 

 

 

 

1000*

N/A*

On

 

 

 

 

 

*When autonegotiation is on, 1000Base-T will autonegotiate with its link partner; then, if its partner also autonegotiates and can attain a speed of 1000 Mbps, 1000Base-T will operate at 1000 Mpbs full-duplex (it is not designed to operate at 1000 Mbps half-duplex).

Partners on a link must be configured to have the same setting, that is, either both must autonegotiate or both must be set to the same manual setting. For example, if the card is set to 100 Mbps full-duplex, the link partner must also be set to 100 Mbps full-duplex. This will help ensure operation without degraded performance.

•Receive flow control

Flow control allows use of flow control negotiation and sending and receiving of pause frames. When the flow control parameter is on, the card receives and manages pause frames sent by the link partner. When the flow control parameter is off, the card will silently discard these pause frames. The card cannot be configured to send pause frames.

Performance Tuning Parameters

•Send Buffer Coalescing Threshold

•Receive Buffer Coalescing Threshold

•Send Interrupt Coalescing Ticks

•Receive Interrupt Coalescing Ticks

These features are for advanced users. If you set these parameters and you do not understand what they do, you may have unpredictable results. It is recommended to use the default settings.

When the card transmits or receives a frame, the system must be notified of the event. If the card interrupts the system for each transmitted and received frame, the result is a high degree of processor overhead. To prevent that, Gigabit Ethernet provides a feature called Interrupt Coalescence. Effective use of this feature can reduce system overhead and improve performance.

Interrupt Coalescence essentially means that the card interrupts the system after sending or receiving a few frames. The number of frames after which the card interrupts the processor can be tuned independently for both send and receive. The tuning can be specified via two parameters each for send and receive, so that there are four parameters

Chapter 2

13