ISDN Signaling Link 63
because the NTAK02BBSDI/DCH card does not suppor t QSIG protocols
for ISL. The DCH interface uses these protocols and their variants, as they
have the following advantages:
•ISL configuration support
•symmetry (incoming and outgoing call messaging is the same)
•near H.323 standard
QSIG GF Name Display is the only supported QSIG supplementary service.
The ITG feature complies with H.323 Basic CallQ.931 signaling. This part
of the H.323 standard (H.225) defines the messaging used to setup and
release basic calls. A mechanism is implemented to enable the passing
of ISDN messaging through the IP network between the two endpoints.
The call is set up using the H.323 standard signaling with encapsulated
ISDN-specific information. This mechanism allows interworkings with other
gateways.
The DCHIP card provides the tandem between the ISDN signaling and the
H.323 protocol. If the DCHIP functionality is combined with the Follower
card, messages are sent between the DCH Processor and the H.323
Processor. Most configurations split this functionality between the DCHIP
and Followercards. Figure18 "Signal flow from the DCH to the H.323 stack"
(page 63) shows the signal flowfrom the DCH to the H.323 stack.
Figure 18
Signal flow from the DCH to the H.323 stack
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
.