Nortel Modular ICS 7.1, Инструкция по установке

Страница: 56 / 700

56
/ Welcome to ISDN
Modular ICS 7.1 Installer Guide N0130943 02
Layer 1: A physical connection that supports fundamental
signaling passed between the ISDN network (your service
provider) and the Norstar ICS. When a DTI card configured as
BRI or PRI is used for a network connection, the LED for the
loop on the card is lit when the layer 1 is functioning.
Layer 2: A logical connection between the ISDN network
(your service provider) and the Norstar ICS. Norstar has two
of these connections for each BRI line, one for each of the
logical lines. Without Layer 2, call processing is not possible,
and there is no dial tone.
Layer 3: Also a logical connection between the ISDN network
(your service provider) and the Norstar ICS. For BRI lines,
layer 3 is where call processing and service profile identifier
(SPID) information is exchanged. This controls which central
office services are available to the connection. For example, a
network connection can be programmed to carry data calls.
The system of layers is important when you are installing,
maintaining, and troubleshooting an ISDN system. See
Problems with BRI service on page 615 for more information
about working with the layers.
ISDN bearer capability
Bearer capability describes the transmission standard used by
the BRI or PRI line that allows it to work within a larger ISDN
hardware and software network.
The bearer capability for BRI and PRI is voice/speech at
3.1 kHz audio, and data at unrestricted 64 kbps, restricted
64 kbps, 56 kbps.