alt(7)alt(7)NAMEalt - DEGPA Gigabit Ethernet interface
SYNOPSIS
config_driver altDESCRIPTION
The alt interface provides access to Gigabit Ethernet (1000Mbs) through
the DEGPA device. The interface supports full-duplex operation in a
switched or point-to-point configuration, and provides the following
features: The interface has Link Autonegotiation enabled by default.
Some switches do not support Link Autonegotiation. To turn Link
Autonegotiation off, use the following command:
# lan_config -ialt0 -a0
Note that you may add this command to the /etc/inet.local file
to preserve the setting of Link Autonegotiation across system
restarts.
If you manually set the speed by using the ifconfig or lan_con‐
fig commands, autonegotiation is automatically disabled. If you
then want to enable autonegotiation (for example on interface
alt0), use the following command:
# lan_config -ialt0 -a1 JUMBO packets are disabled by default.
JUMBO packets provide a non-standard larger packet size. This
enables the interface to carry more data with less CPU overhead.
To enable JUMBO packets, use the following command:
# ifconfig alt0 ipmtu 9000
Note that there are several interoperability issues with using
JUMBO packets (for example, if your switch goes from 1000Mbps to
a 100Mbps client, JUMBO packets will not work on a 100Mbps LAN).
In order to use JUMBO frames, you will need a switch that sup‐
ports JUMBO frames or a point-to-point configuration with a
partner that supports JUMBO frames. Receive flow control is
enabled. There is currently no way to turn this off.
For the DEGPA-SX, we strongly recommend that you use the auto-negotia‐
tion protocol. This protocol has been thoroughly tested, and works
reliably with many different switch vendors over Gigabit Ethernet. If
you disable auto-negotiation, the switch port setting and the DEGPA-SX
setting must match perfectly, otherwise you might encounter interoper‐
ability problems. The DEGPA-SX (fiber optic version) runs at 1000Mbps
only.
For the DEGPA-TX (the copper version of the Gigabit Ethernet NIC), you
must enable auto-negotiation. This is a mandatory requirement of the
IEEE 802.3ab auto-negotiation protocol. The DEGPA-TX can run at 1000,
100, or 10 Mbps.
Gigabit Ethernet performance with TCP/IP depends on several factors.
Some of the influencing factors are as follows: The speed at which data
can be delivered to the interface influences throughput. If your
CPU(s) are busy doing several tasks, the task using Gigabit Ethernet
may not get enough run time to deliver packets. In general, faster
CPUs will deliver better throughput. Fast access to the PCI bus is
critical for high throughput. Using a 64-bit PCI slot will give you
better performance and use less PCI resources than a 32-bit PCI slot.
Putting the interface on the same PCI bus as other peripherals will
degrade throughput. Each system type may also have different PCI-to-
host speed considerations (the speed at which the PCI-to-host hardware
allows the device to operate). The standard TCP/IP applications (for
example, ftp and rcp) are not designed to run at Gigabit speeds. TCP
applications that expect performance should use a message size of 65000
bytes and a window size of 128000 bytes. Even when an application is
modified to use these settings, high throughput may not be attainable.
This is particularly true when an application is waiting for data to
send (data from a disk, for example).
ERRORS
The following diagnostic and error messages contain relevant informa‐
tion provided by the alt interface, and are displayed to the console.
Each message begins with the adapter identification, including the num‐
ber of the adapter. The alt interface could not find adequate I/O
addressing on this system to operate. This is a fatal error, and the
DEGPA-SA will not operate on this system. There was a memory alloca‐
tion problem or the device initialization has failed. This indicates a
hardware problem. Indicates that the Gigabit Ethernet link is up. The
Autonegotiated keyword indicates that the link was autonegotiated.
Note, this will only be on if autonegotiation is enabled. The Receive‐
FlowControl keyword indicates that Receive Flow control is enabled on
the link. Indicates that the link is no longer established. No commu‐
nication will occur over the link while it is down.
SEE ALSO
Commands: ifconfig(8), lan_config(8)
Files: inet.local(4)
Networkinformation: arp(7), inet(7), netintro(7)alt(7)
