A key feature of the Sun eri FastEthernet driver is auto-negotiation. The auto-negotiation protocol, as specified by the 100BASE-T IEEE 802.3u Ethernet Standard, selects the operation mode (half-duplex or full-duplex), and the auto-sensing protocol selects the speed (10 Mbps or 100 Mbps) for the adapter.
The auto-negotiation protocol does the following when the system is booted:
Identifies all link partner-supported modes of operation
Advertises its capabilities to the link partner
Selects the highest common denominator mode of operation based on the following priorities (in decreasing order):
Priority |
Line Speed and Mode |
---|---|
First |
100 Mbps, full-duplex |
Second |
100 Mbps, half-duplex |
Third |
10 Mbps, full-duplex |
Fourth |
10 Mbps, half-duplex |
The link partner is the networking device (system, Ethernet hub, or Ethernet switch) at the other end of the link or cable.
If the SUNW,eri device is connected to a remote system or interface that is not capable of auto-negotiation, your system automatically selects the correct speed and half-duplex mode.
If the Sun eri FastEthernet is connected to a link partner with which the auto-negotiation protocol fails to operate successfully, you can configure the device so it does not use this protocol. This forces the driver to set up the link in the mode and speed of your choice.
The internal transceiver also supports a forced mode of operation. This is where the user selects the speed and mode using the ndd utility, by editing the /etc/system file, or by creating an eri.conf file in the kernal/drv/ directory. The ndd utility makes calls to the eri driver to choose the speed and mode.
Click this link to return to the chapter, Chapter 1, The eri Device Driver