natmip(4)

NAME

natmip - IP over ATM PVCs

SYNOPSIS

device atm
options NATM

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.

An ATM network card (en0 in this example) is configured for

IP by something like:

ifconfig en0 128.252.200.1 netmask 0xffffff00 up

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 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.

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 in

teroperability
with other CLIP implementations. Note

that BPF
works only with LLC/SNAP encapsulation.

byte 1 This is the VPI of the channel.

bytes 2...3 VCI of the channel. Must not be zero.

byte 4 Traffic type. One of 0 (UBR), 1 (CBR),

2 (ABR), 3

(VBR).

The variable part for UBR connections may be either empty or

three bytes:

bytes 5...7 Specifies the peak cell rate for UBR.

The variable part for CBR connections must be three bytes:

bytes 5...7 Specifies the peak cell rate for CBR.

The variable part for VBR connections must be 9 bytes long

and specifies
three values:

bytes 5...7 Specifies the peak cell rate for VBR.

bytes 8...10 This is the sustainable cell rate.

bytes 11...13 The maximum burst size.

The variable part for ABR connections must be 19 bytes long

and specifies
the following values:

bytes 5...7 Specifies the peak cell rate for ABR.

bytes 8...10 The minimum cell rate.

bytes 11...13 The initial cell rate.

bytes 14...16 The transient buffer exposure.

byte 17 The NRM value.

byte 18 The TRM value.

bytes 19...20 The ADTF value.

byte 21 The rate increase factor (RIF).

byte 22 The rate decrease factor (RDF).

byte 23 The cutoff decrease factor (CDF).

To add a PVC the route(8) utility can be used:

route add -iface <remote IP address> -link

<iface>:<lladdr>

The iface is the ATM interface through which remote IP

address can be
reached and lladdr is the link layer address as a string of

dot-separated, hexadecimal bytes.

NATM also supports the old, original format. This consists

of 4 byte
link layer addresses (and the channels are implicit UBR):

byte 0 Flags:

0x01 use AAL5.
0x02 if using AAL5, use an

LLC/SNAP header.

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.

byte 1 VPI for the channel

bytes 2...3 VCI for the channel

EXAMPLES

Suppose you have 3 hosts 128.252.200.1, 128.252.200.2 and

128.252.200.3
connected by ATM through PVCs:

between 128.252.200.1 and 128.252.200.2: 0xc9 UBR
between 128.252.200.1 and 128.252.200.3: 0xca VBR
between 128.252.200.2 and 128.252.200.3: 0xcb CBR

The parameters for the VBR channel are: PCR 50000, SCR

10000, MBS 10.
The peak cell rate for the CBR channel is 100000.

To enable the links use the following commands:

on host 128.252.200.1:

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

on host 128.252.200.2:

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

on host 128.252.200.3:

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

This can also be done in rc.conf(5):

on host 128.252.200.1:

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"

on host 128.252.200.2:

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"

on host 128.252.200.3:

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"

SEE ALSO

en(4), fatm(4), hatm(4), natm(4), patm(4)

AUTHORS

Chuck Cranor of Washington University implemented the NATM

protocol layer
along with the EN ATM driver in 1996 for NetBSD.

BSD August 11, 2003

BSD