Troubleshooting guide

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Cisco Broadband Local Integrated Services Solution Troubleshooting Guide
OL-5169-01
Chapter 4 Troubleshooting with Call Flows
Understanding SS7
Step 8 Any call-progress indications (or other signals that can be carried in-band) are cut through the voice path
as soon as an end-to-end audio channel is established. Signaling that can be detected by the voice ports
(for example, in-band dual tone multifrequency [DTMF] digits after the call setup is complete) is also
trapped by the session application at either end of the connection and carried over the IP network
encapsulated in RTP Control Protocol (RTCP), using the RTCP APP extension mechanism.
Step 9 When either end of the call hangs up, session ends. Each end becomes idle, waiting for the next off-hook
condition to trigger another call setup.
ISUP Signaling Messages
ISUP defines the protocol used to set up, manage, and release trunk circuits that carry voice and data
between terminating line exchanges (for example, between a calling party and a called party). ISUP is
used for both ISDN and non-ISDN calls. However, calls that originate and terminate at the same switch
do not use ISUP signaling. Table 4-7 displays ISUP messages.
Table 4-7 ISUP Messages
Message Description
IAM Initial Address Message
ACM Address Complete Message
SAM Subsequent Address Message
ANM Answer Message
REL Release Message
RLC Release Complete Message