bcm(7)
NAME
  bcm - DEGXA Gigabit Ethernet interface

SYNOPSIS
  config_driver	   bcm

DESCRIPTION
  The bcm interface provides access to Gigabit Ethernet (1000Mbs) through the
  DEGXA 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 -ibcm0 -a0

       Note that you may add this command to the /etc/inet.local file to
       preserve the setting of Link Autonegotiation across system restarts.

    ·  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 bcm0 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 supports 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 DEGXA-SX, we recommend that you use the auto-negotiation 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 DEGXA-SX setting must match
  perfectly, otherwise you might encounter interoperability problems. The
  DEGXA-SX (fiber optic version) runs at 1000Mbps only.

  For the DEGXA-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 DEGXA-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:

  CPU speed/utilization
      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.

  PCI Bus speed/arbitration
      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).

  Application/Transport factors
      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 information
  provided by the bcm interface, and are displayed to the console.  Each
  message begins with the adapter identification, including the number of the
  adapter.

  No dense or linear space available on this system
      The bcm interface could not find adequate I/O addressing on this system
      to operate.  This is a fatal error, and the DEGXA-SA will not operate
      on this system.

  Link up via auto-negotiation (1000 Mbps, full duplex)
      Indicates that the Gigabit Ethernet link is up, and the autonegotiation
      protocol was used to set the speed and duplex mode.  Note, this will
      only appear if autonegotiation is enabled.

  Link up via manual configuration (1000 Mbps, full duplex)
      Indicates that the Gigabit Ethernet link is up, and was manually
      configured.

  Link down
      Indicates that the link is no longer established.	 No communication
      will occur over the link while it is down.

SEE ALSO
  Commands: ifconfig(8), lan_config(8)

  Files: inet.local(4)

  Network information: arp(7), inet(7), netintro(7)