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.\"	Fraunhofer Institute for Open Communication Systems (FhG Fokus).
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.Dd August 11, 2003
.Dt NATMIP 4
.Os
.Sh NAME
.Nm natmip
.Nd IP over ATM PVCs
.Sh SYNOPSIS
.Cd "device atm"
.Cd "options NATM"
.Sh DESCRIPTION
The NATM protocol stack includes support for IP over ATM.
Without any
additional signalling stacks or other modules it is possible to build
a CLIP (classical IP over ATM) network based on PVCs.
.Pp
An ATM network card
.Li ( en0
in this example) is configured for IP by something
like:
.Pp
.Dl "ifconfig en0 128.252.200.1 netmask 0xffffff00 up"
.Pp
IP routing is done with special interface routes (routes with directly
reachable destinations) with a link layer gateway address.
The link layer address specifies the ATM interface through which the
destination can be reached, the virtual channel that connects to the
destination and the ATM characteristics of this channel.
The address part of the link layer address (see
.Xr link_addr 3 )
consists of a fixed part (the first 5 bytes) and a part that
depends on the kind of the PVC (UBR, CBR, VBR, ABR).
Multi-byte values
are big-endian encoded: the bytes with the lower numbers contain the
higher order bits.
.Bl -tag -width "bytes 12...12" -offset indent
.It byte 0
Is a flag byte.
Currently only flag 0x20 is used.
When set, all IP frames are LLC/SNAP encapsulated before putting them into
an AAL5 frame.
Setting this flag is recommended and allows interoperability with other
CLIP implementations.
Note that BPF works only with LLC/SNAP encapsulation.
.It byte 1
This is the VPI of the channel.
.It bytes 2...3
VCI of the channel.
Must not be zero.
.It byte 4
Traffic type.
One of 0 (UBR), 1 (CBR), 2 (ABR), 3 (VBR).
.El
.Pp
The variable part for UBR connections may be either empty or three bytes:
.Bl -tag -width "bytes 12...12" -offset indent
.It bytes 5...7
Specifies the peak cell rate for UBR.
.El
.Pp
The variable part for CBR connections must be three bytes:
.Bl -tag -width "bytes 12...12" -offset indent
.It bytes 5...7
Specifies the peak cell rate for CBR.
.El
.Pp
The variable part for VBR connections must be 9 bytes long and specifies three
values:
.Bl -tag -width "bytes 12...12" -offset indent
.It bytes 5...7
Specifies the peak cell rate for VBR.
.It bytes 8...10
This is the sustainable cell rate.
.It bytes 11...13
The maximum burst size.
.El
.Pp
The variable part for ABR connections must be 19 bytes long and specifies the
following values:
.Bl -tag -width "bytes 12...12" -offset indent
.It bytes 5...7
Specifies the peak cell rate for ABR.
.It bytes 8...10
The minimum cell rate.
.It bytes 11...13
The initial cell rate.
.It bytes 14...16
The transient buffer exposure.
.It byte 17
The NRM value.
.It byte 18
The TRM value.
.It bytes 19...20
The ADTF value.
.It byte 21
The rate increase factor (RIF).
.It byte 22
The rate decrease factor (RDF).
.It byte 23
The cutoff decrease factor (CDF).
.El
.Pp
To add a PVC the
.Xr route 8
utility can be used:
.Bd -ragged -offset indent
.Nm route Cm add
.Fl iface Aq Ar "remote\ IP\ address"
.Fl link Ao Ar iface Ac : Ns Aq Ar lladdr
.Ed
.Pp
The
.Ar iface
is the ATM interface through which
.Ar "remote\ IP\ address"
can be reached and
.Ar lladdr
is the link layer address as a string of dot-separated, hexadecimal bytes.
.Pp
NATM also supports the old, original format.
This consists of 4 byte
link layer addresses (and the channels are implicit UBR):
.Bl -tag -width "bytes 12...12" -offset indent
.It byte 0
Flags:
.Bl -tag -width "0x02" -offset indent -compact
.It 0x01
use AAL5.
.It 0x02
if using AAL5, use an LLC/SNAP header.
.El
.Pp
Thus, parameter 3 means AAL5 and LLC/SNAP encapsulation (this is the required
setting for interworking with other CLIP clients).
Note that BPF works only with LLC/SNAP encapsulation.
.It byte 1
VPI for the channel
.It bytes 2...3
VCI for the channel
.El
.Sh EXAMPLES
Suppose you have 3 hosts 128.252.200.1, 128.252.200.2 and
128.252.200.3 connected by ATM through PVCs:
.Pp
.Bl -item -offset indent -compact
.It
between 128.252.200.1 and 128.252.200.2: 0xc9 UBR
.It
between 128.252.200.1 and 128.252.200.3: 0xca VBR
.It
between 128.252.200.2 and 128.252.200.3: 0xcb CBR
.El
.Pp
The parameters for the VBR channel are: PCR 50000, SCR 10000, MBS 10.
The peak cell rate for the CBR channel is 100000.
.Pp
To enable the links use the following commands:
.Pp
on host 128.252.200.1:
.Bd -literal -offset indent -compact
ifconfig en0 128.252.200.1 netmask 0xffffff00 up
route add -iface 128.252.200.2 -link en0:3.0.0.c9.0
route add -iface 128.252.200.3 -link en0:3.0.0.ca.3.0.c3.50.0.27.10.0.0.a
.Ed
.Pp
on host 128.252.200.2:
.Bd -literal -offset indent -compact
ifconfig en0 128.252.200.2 netmask 0xffffff00 up
route add -iface 128.252.200.1 -link en0:3.0.0.c9.0
route add -iface 128.252.200.3 -link en0:3.0.0.cb.1.1.86.a0
.Ed
.Pp
on host 128.252.200.3:
.Bd -literal -offset indent -compact
ifconfig en0 128.252.200.3 netmask 0xffffff00 up
route add -iface 128.252.200.1 -link en0:3.0.0.ca.3.0.c3.50.0.27.10.0.0.a
route add -iface 128.252.200.2 -link en0:3.0.0.cb.1.1.86.a0
.Ed
.Pp
This can also be done in
.Xr rc.conf 5 :
.Pp
on host 128.252.200.1:
.Bd -literal -offset indent -compact
network_interfaces="lo0 en0"
ifconfig_en0="inet 128.252.200.1 netmask 255.255.255.0"
static_routes="host2 host3"
route_host2="-iface 128.252.200.2 -link en0:3.0.0.c9.0"
route_host3="-iface 128.252.200.3 -link en0:3.0.0.ca.3.0.c3.50.0.27.10.0.0.a"
.Ed
.Pp
on host 128.252.200.2:
.Bd -literal -offset indent -compact
network_interfaces="lo0 en0"
ifconfig_en0="inet 128.252.200.2 netmask 255.255.255.0"
static_routes="host1 host3"
route_host1="-iface 128.252.200.1 -link en0:3.0.0.c9.0"
route_host3="-iface 128.252.200.3 -link en0:3.0.0.cb.1.1.86.a0"
.Ed
.Pp
on host 128.252.200.3:
.Bd -literal -offset indent -compact
network_interfaces="lo0 en0"
ifconfig_en0="inet 128.252.200.3 netmask 255.255.255.0"
static_routes="host1 host2"
route_host1="-iface 128.252.200.1 -link en0:3.0.0.ca.3.0.c3.50.0.27.10.0.0.a"
route_host2="-iface 128.252.200.2 -link en0:3.0.0.cb.1.1.86.a0"
.Ed
.Sh SEE ALSO
.Xr en 4 ,
.Xr fatm 4 ,
.Xr hatm 4 ,
.Xr natm 4 ,
.Xr patm 4
.Sh AUTHORS
.An Chuck Cranor
of Washington University implemented the NATM protocol layer
along with the EN ATM driver in 1996 for
.Nx .