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NAME    [Toc]    [Back]

       bcm - DEGXA Gigabit Ethernet interface

SYNOPSIS    [Toc]    [Back]

       config_driver    bcm

DESCRIPTION    [Toc]    [Back]

       The  bcm  interface  provides  access  to Gigabit Ethernet
       (1000Mbs) through the DEGXA device.   The  interface  supports
  full-duplex  operation  in  a switched or point-topoint
 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.

              If you manually set the speed by using the ifconfig
              or lan_config commands, autonegotiation is automatically
 disabled. If you then want to enable autonegotiation
 (for example on interface bcm0), use  the
              following command:

              #  lan_config -ibcm0 -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 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:  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    [Toc]    [Back]

       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.  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.
       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.  Indicates that the Gigabit Ethernet link
       is  up,  and  was manually configured.  Indicates that the
       link is no  longer  established.   No  communication  will
       occur over the link while it is down.

SEE ALSO    [Toc]    [Back]

       Commands: ifconfig(8), lan_config(8)

       Files: inet.local(4)

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

[ Back ]
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