142 lines
4.6 KiB
Groff
142 lines
4.6 KiB
Groff
.\" $NetBSD: ec.4,v 1.13 2003/08/07 10:31:11 agc Exp $
|
|
.\"
|
|
.\" Copyright (c) 1983, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" from: @(#)ec.4 8.1 (Berkeley) 6/5/93
|
|
.\"
|
|
.Dd June 5, 1993
|
|
.Dt EC 4 vax
|
|
.Os
|
|
.Sh NAME
|
|
.Nm ec
|
|
.Nd 3Com 10 Mb/s Ethernet interface
|
|
.Sh SYNOPSIS
|
|
.Cd "ec0 at uba0 csr 161000 vector ecrint eccollide ecxint flags 0"
|
|
.Sh DESCRIPTION
|
|
NOTE: This driver has not been ported from
|
|
.Bx 4.4
|
|
yet.
|
|
.Pp
|
|
The
|
|
.Nm ec
|
|
interface provides access to a 10 Mb/s Ethernet network through
|
|
a 3Com controller.
|
|
.Pp
|
|
The hardware has 32 kilobytes of dual-ported memory on the
|
|
.Tn UNIBUS .
|
|
This memory
|
|
is used for internal buffering by the board, and the interface code reads
|
|
the buffer contents directly through the
|
|
.Tn UNIBUS .
|
|
The address of this memory is given in the
|
|
.Ar flags
|
|
field
|
|
in the configuration file.
|
|
The first interface normally has its memory at UNIBUS address 0.
|
|
.Pp
|
|
Each of the host's network addresses
|
|
is specified at boot time with an
|
|
.Dv SIOCSIFADDR
|
|
.Xr ioctl 2 .
|
|
The
|
|
.Nm ec
|
|
interface employs the address resolution protocol described in
|
|
.Xr arp 4
|
|
to dynamically map between Internet and Ethernet addresses on the local
|
|
network.
|
|
.Pp
|
|
The interface normally tries to use a
|
|
.Dq trailer
|
|
encapsulation
|
|
to minimize copying data on input and output.
|
|
The use of trailers is negotiated with
|
|
.Tn ARP .
|
|
This negotiation may be disabled, on a per-interface basis,
|
|
by setting the
|
|
.Dv IFF_NOTRAILERS
|
|
flag with an
|
|
.Dv SIOCSIFFLAGS
|
|
.Xr ioctl 2 .
|
|
.Pp
|
|
The interface software implements an exponential backoff algorithm
|
|
when notified of a collision on the cable. This algorithm uses
|
|
a 16-bit mask and the
|
|
.Tn VAX-11 Ns 's
|
|
interval timer in calculating a series
|
|
of random backoff values. The algorithm is as follows:
|
|
.Bl -enum -offset indent
|
|
.It
|
|
Initialize the mask to be all 1's.
|
|
.It
|
|
If the mask is zero, 16 retries have been made and we give
|
|
up.
|
|
.It
|
|
Shift the mask left one bit and formulate a backoff by
|
|
masking the interval timer with the smaller of the complement of this mask
|
|
and a 5-bit mask, resulting in a pseudo-random number between 0 and 31.
|
|
This produces the number of slot times to delay,
|
|
where a slot is 51 microseconds.
|
|
.It
|
|
Use the value calculated in step 3 to delay before retransmitting
|
|
the packet.
|
|
The delay is done in a software busy loop.
|
|
.El
|
|
.Sh DIAGNOSTICS
|
|
.Bl -diag
|
|
.It ec%d: send error.
|
|
After 16 retransmissions using the
|
|
exponential backoff algorithm described above, the packet
|
|
was dropped.
|
|
.Pp
|
|
.It ec%d: input error (offset=%d).
|
|
The hardware indicated an error
|
|
in reading a packet off the cable or an illegally sized packet.
|
|
The buffer offset value is printed for debugging purposes.
|
|
.Pp
|
|
.It ec%d: can't handle af%d.
|
|
The interface was handed
|
|
a message with addresses formatted in an unsuitable address
|
|
family; the packet was dropped.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr arp 4 ,
|
|
.Xr inet 4 ,
|
|
.Xr netintro 4
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
driver appeared in
|
|
.Bx 4.2 .
|
|
.Sh BUGS
|
|
The hardware is not capable of talking to itself. The software
|
|
implements local sending and broadcast by sending such packets to the
|
|
loop interface. This is a kludge.
|
|
.Pp
|
|
Backoff delays are done in a software busy loop. This can degrade the
|
|
system if the network experiences frequent collisions.
|