Technical data

SunOS 5.5 Ioctl Requests isdnio(7I)
Primary Rate ISDN Primary Rate ISDN (PRI) interfaces are either 1.544Mbps (T1 rate) or 2.048Mbps (E1 rate)
and are typically organized as 23 B-channels and one D-Channel (23B+D) for T1 rates,
and 30 B-Channels and one D-Channel (30B+D) for E1 rates. The D-channels on a PRI
interface operate at 64000 bits per second. T1 rate PRI interface is the standard in the
United States, Canada and Japan while E1 rate PRI interface is the standard in European
countries. Some E1 rate PRI interface implementations allow access to channel zero
which is used for framing.
Channel Types ISDN channels fall into several categories; D-channels, bearer channels, and management
pseudo channels. Each channelhas a corresponding device name somewhere under the
directory /dev/isdn/ as documented in the appropriate hardware specific manual page.
D-channels There is at most one D-channel per ISDN interface. The D-channel car-
ries signaling information for the management of ISDN calls and can
also carry X.25 packet data. In the case of a PRI interface, there may
actually be no D-channel if Non-Facility Associated Signalingis used.
D-channels carry data packets that are framed and checked for transmis-
sion errors according to the LAP-D protocol. LAP-D uses framing and
error checking identical to the High Speed Data Link (HDLC) protocol.
B-channels BRI interfaces have two B-channels, B1 and B2. On a BRI interface, the
only other type of channel is an H-channel which is a concatenation of
the B1 and B2 channels. An H-channel is accessed by openingthe “base”
channel, B1 in this case, and using theISDN_SET_FORMAT ioctl to
change the configuration of the B-channel from 8-bit, 8 kHz to 16-bit,
8kHz.
On a primary rate interface, B channels are numbered from 0 to 31 in Europe and 1 to 23
in the UnitedStates, Canada and Japan.
H-Channels A BRI or PRI interface can offer multiple B-channels concatenated into a
single, higherbandwidth channel. These concatenated B-channels are
referred to as an “H-channels” on a BRI interface. The PRI interface ver-
sion of an H-channel is referred to as an Hn-channels where n is a
number indicating how the B-channels have beenaggregated into a sin-
gle channel.
A PRI interface H0 channel is 384 kbps allowing 3H0+D on a T1 rate
PRI interface and 4H0+D channels on an E1 rate PRI interface.
A T1 PRI interface H11 channel is 1536 kbps (24×64000bps). This will
consume the channel normally reserved for the D-channel, so signal-
ing must be done with Non-Facility Associated Signaling(NFAS)
from another PRI interface.
An E1 PRI interface H12 channel is 1920 kbps (30×64000bps). An
H12-channel leaves room for the framing-channel as well as the D-
channel.
modified 7 Apr 1994 7I-153