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STRIP(4) NetBSD Kernel Interfaces Manual STRIP(4)
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strip -- Metricom Ricochet packet radio wireless network device
The strip driver takes outbound network packets, encapsulates them using
the Metricom "star mode" framing, and sends the packets out an RS-232
interface to a Metricom Ricochet packet radio. Packets arriving from the
packet radio via the serial link are decapsulated and then passed up to
the local host's networking stack.
strip is an acronym for STarmode Radio IP.
The strip interfaces can be created by using the ifconfig(8) create com-
mand. Each strip interface is a pseudo-device driver for the Metricom
Ricochet packet radio, operating in peer-to-peer packet mode.
In many ways, the strip driver is very much like the sl(4) SLIP pseudo-
device driver. A strip device is attached to a tty line with
slattach(8). Once attached, the interface is configured via ifconfig(8).
The major difference between the sl(4) SLIP pseudo-device driver and the
strip driver is that SLIP works only between two hosts over a dedicated
In contrast, strip sends packets to a frequency-hopping packet radio,
which can address packets to any peer Metricom Ricochet packet radio,
rather than just to a single host at the other end of a point-to-point
line. Thus, one strip pseudo-device is usually sufficient for any ker-
In other respects, a strip interface is rather like an Ethernet inter-
face. Packets are individually addressed, and subsequent packets can be
sent independently to different MAC addresses. However, the "star mode"
framing and MAC addressing are not in any way compatible with Ethernet.
Broadcast or multicast to more than one packet radio is not possible, due
to the independent frequency-hopping operation of the packet radios. The
interface flags IFF_POINTOPOINT and IFF_BROADCAST are not supported on
the strip interface.
In other words, strip implements a multiple-access, non-broadcast device,
accessed via an RS-232 serial line, using a proprietary packet framing
This version of the strip driver maps IP addresses to Metricom Ricochet
packet radio addresses using statically configured entries in the normal
routing table. These entries map IP addresses of peer packet radios to
the MAC-level addresses. The exact syntax of this mapping and an example
are discussed below. The Internet Assigned Numbers Authority (IANA) has
allocated an ARP type code for use with STRIP. A future version of this
driver will support arp(4) to obtain the IP address of reachable peer
packet radios dynamically.
This version of the STRIP driver requires static pre-configuration of the
mapping from IP addresses to packet radio MAC addresses. The route(8)
command should be used to bind a peer STRIP host's packet radio IP
address to the peer's link-level packet radio address.
Radio addresses are encoded using the hex equivalent of the packet
radio's decimal ASCII address. For example, the following route command
will configure a routing entry to a packet radio with a MAC address of
1234-5678, and an IP address 10.11.12.13, reachable via the strip0 inter-
route add -host 10.11.12.13 -link strip0:1:2:3:4:5:6:7:8
Generalising from this example to other IP addresses and to other 8-digit
MAC addresses should be clear.
The Metricom Ricochet packet radios can auto-baud at speeds up to 38.4K
baud. At higher speeds -- 57600 or 115200 -- the packet radio cannot
autobaud. When running at high speeds, the packet radio's serial port
should be manually configured to permanently run at the desired speed.
Use a terminal emulator and the Hayes command ATS304=115200 to set the
serial baudrate to the specified number (or 0 for autobaud). The command
AT&W will then save the current packet radio state in non-volatile mem-
Metricom Ricochet packet radios can operate in either ``modem-emulation''
mode or in packet mode (i.e. "star mode"). The strip driver automati-
cally detects if the packet radio has fallen out of "star mode", and
resets it back into "star mode", if the baud rate was set correctly by
arp(4), inet(4), sl(4), ifconfig(8), route(8), slattach(8)
strip was originally developed for the Linux kernel by Stuart Cheshire of
Stanford's Operating Systems and Networking group, as part of Mary
Baker's MosquitoNet project.
This strip driver was ported to NetBSD by Jonathan Stone at Stanford's
Distributed Systems Group and first distributed with NetBSD 1.2.
Currently, strip is IP-only. Encapsulations for AppleTalk and ARP have
been defined, but are not yet implemented in this driver.
strip has not been widely tested on a variety of lower-level serial driv-
The detection and resetting of packet radios that crash out of "star
mode" does not always work in this version of the driver. One workaround
is to kill the slattach(8) process, ifconfig(8) the strip interface down,
and then start a new slattach and rerun ifconfig to enable the interface
NetBSD 9.0 December 5, 2004 NetBSD 9.0