NAME
bah —
ARCnet network driver for SMC
COM90C26 based boards
SYNOPSIS
bah* at zbus0
DESCRIPTION
The
bah interface provides access to the 2.5 Mb/s ARCnet
network via the SMC COM90C26 + COM90C32 ARCnet chip set.
Each of the host's network addresses is specified at boot time with an
SIOCSIFADDR
ioctl(2). The interface MTU is
507 for protocols that do not use link level fragmentation and 60480 bytes for
the others. The routing layer may specify additional limits.
Currently supported protocols are IPv4(+ARP), and IPv6.
IP VERSION 4 CONSIDERATIONS
When the NOARP flag is set on the
bah interface, it does not
employ the address resolution protocol described in
arp(4) to dynamically map
between Internet and Ethernet addresses on the local network. Instead, it uses
the least significant 8 bits of the IP address as hardware address, as
described in RFC 1051 and RFC 1201.
With the IFF_LINK0 flag cleared, IP and ARP encoding is done according to the
deprecated, but popular among Amiga users, RFC 1051 encoding (that is, with
simple header, packet type 240 / 241), and the MTU is 507.
With the IFF_LINK0 flag set, IP/ARP/RARP encoding is done according to RFC 1201
(that is, with Packet Header Definition Standard header and packet type
212/213). The MTU is normally 1500.
When switching between the two modes, do a
ifconfig interfacename
down up to switch the MTU.
When the IFF_LINK2 flag is set, ARP packets are sent with the protocol type
encoded as it would be in the ARCnet header, and decoded to the right protocol
encoding on reception. According to "assigned numbers", this is
wrong, but some legacy software (namely, AmiTCP 3.0beta) shows this bug.
HARDWARE
The
bah interface supports the following Zorro II expansion
cards:
-
-
- A2060
- Commodore's ARCnet card, manufacturer 514,
product 9
-
-
- AMERISTAR
- Ameristar's ARCnet card, manufacturer 1053,
product 9
SEE ALSO
amiga/intro(4),
arp(4),
inet(4),
ifconfig(8)
P.A. Prindeville,
Standard for the transmission of IP datagrams and ARP
packets over ARCNET networks., RFC,
1051, March 1988.
D. Provan,
Transmitting IP traffic over ARCNET networks.,
RFC, 1201,
February 1991.
I. Souvatzis,
Transmission of IPv6 Packets over ARCnet Networks.,
RFC, 2497,
January 1999.
ARCnet Packet Header Definition Standard, Novell Inc., 1989
STANDARDS
RFC 1051/RFC1201 with ARP, or without, using direct mapping of lower 8 IP
address bits instead.
HISTORY
The Amiga
bah interface first appeared in
NetBSD 1.1. ARP support was added in
NetBSD 1.3.
AUTHORS
Ignatios Souvatzis