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Understanding ISDN
BRI Features
•
Circuit Mode Data (CMD): Channels (DS0s or B's) are switched by the CO to the destination
user for the duration of the call.
–
–
•
Permanent B channel support, i.e., 56, 64, 112, 128, or 144 Kbps lease line. Each BRI port can be
configured for CMD or Leased-Line mode of operation.
•
Supported switch types: ETSI for international applications, NI1, 5ESS and DMS100 in North
America and NTT in Japan. Layer 1 activation is initiated by incoming or outgoing calls for
ETSI and NTT switch types.
•
TEI auto-negotiated.
•
Q.921/Q.931 (Layer 2/Layer 3) configuration is set automatically by selection of switch type.
PRI Features
•
Circuit Mode Data (CMD): Channels (DS0s or B's) are switched by the CO to the destination
user for the duration of the call.
–
–
•
Supported switch types: ETSI, NI2, 5ESS, DMS100 and NTT.
•
Handling restart and maintenance modes automatically set.
•
Fixed TEI to 0.
•
Q921/Q931 (Layer 2/Layer 3) configuration is set automatically by the choosing switch type.
•
Not supported on the XSR 1200 Series
Understanding ISDN
Physically, an ISDN line is provisioned via unshielded twisted pair cable which would, in the
absence of ISDN service, be used for regular analog telephone service or a T1/E1 connection.
Typically, numerous ISDN devices connect onto this single line through a device known as an
NT1 provided by the user in North America and by the carrier most everywhere else. PRI service
is terminated in the XSR's T1/E1 NIM the same way as E1 or T1 service. BRI service is connected
to the XSR's BRI-S/T NIM via a interface adapter known as NT1. The NT1 is provided by the
service provider. Only in North America do users have to provide their own NT1. The BRI U NIM
can be connected directly to incoming BRI lines in North America as they include a built-in NT1.
Logically, ISDN consists of two types of communications channels: bearer service B-channels,
which carry data and services at 64 Kbps; and a single D-channel (delta), which usually carries
signaling and administrative information which is used to set up and tear down calls. The
transmission speed of the D-channel depends on the type of ISDN service you've subscribed to.
Available ISDN services include two categories: Basic Rate Interface (BRI) service, which provides
access to two B-channels and a 16 Kbps D-channel; and Primary Rate Interface (PRI) service,
11-2 Configuring Integrated Services Digital Network
0utgoing calls supported for Backup, DoD/BoD.
Incoming calls routed to the correct protocol stack based on called number/sub-address
and calling number/sub-address.
Outgoing calls supported for Backup, DoD/BoD.
Incoming calls routed to the correct protocol stack based on called number/sub-address
and calling number/sub-address.
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Troubleshooting
