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Chapter 3
Configuring the Cisco IPVC 3500 Series Gateway
Table 3-8
Field or Check Box
Conceal caller ID
Enable T.120 capabilities in incoming IVR and
TCS4 calls.
Support sub-address at Call Setup
IP Options section
Support H.323 Fast Start in voice-only call
setup
Administrator's Guide for Cisco IPVC 3521 BRI Gateway, Cisco IPVC 3526 PRI Gateway, and Cisco IPVC 3540 PRI Gateway
OL-7995-01
Advanced Settings
Configuring Gateway Settings
Description
Select to have the gateway hide the identifier of
the calling endpoint on the ISDN network,
regardless of whether or not the Support
Presentation Restriction advanced setting is
selected. The callerID field of the Q.931 message
is sent over the IP network containing the string
"0000."
Select to enable the gateway to send T.120
capabilities messages to the ISDN endpoint upon
receiving a call at the IVR-internal or TCS4 stage.
The gateway sends the T.120 messages before
connecting to the IP network endpoint.
Sub-addressing is a one-stage Direct Inward
Dialing (DID) dialing mechanism in which a
phone sends two numbers. One number is for
routing on the circuit switched network. The other
number is forwarded to the gateway inside a
Q.931 sub-addressing information element for IP
address resolution by the gatekeeper.
Sub-addressing can also be used for implementing
ISDN fallback when not enough bandwidth is
available for routing an IP-oriented call over IP.
Select for the gateway to take the E.164 number
from the Q.931information element sub-address
field and forward it to the gatekeeper for address
resolution. Sub-addressing requires gatekeeper
support.
The H.323 fast start functionality enables
endpoints that support the feature to join a voice
conference in the gateway more quickly.
Standard call setup requires four round trips of
messages between endpoints before the first
media stream is exchanged between peers. The set
of messages includes Setup/Connect (Q.931
procedure), Master/Slave Determination (H.245
procedure), Capability Exchange (H.245), and
Open Logical Channel (H.245).
H.323 fast start shortens the time it takes to start a
call by skipping the H.245 phase and combining
the call setup procedure into a single H.225
transaction.
Select to encapsulate H.245 capabilities exchange
and negotiation messages within Q.931 setup
messages.
3-27
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