deployments require design guidelines for other voice services that are being
run at the branch. For example, the branch is a remote Unified CM site
supporting both ACD agent and nonagent phones. This deployment also implies
that the PSTN Gateway is used not only for ingress of Unified CVP calls but for
ingress or egress of the regular non-ACD phone calls.
reliability in WANs may be an issue in a centralized Unified CVP model because
they are typically less reliable than LAN links. The call survivability
function must be considered for both the Unified CVP and non-CVP calls. For
Unified CM endpoint phones, survivability is accomplished by using a Cisco IOS
feature known as Survivable Remote Site Telephony (SRST). For further details
on SRST, see the latest version of the
Communications SRND Based on Cisco Unified Communications Manager,
CVP calls, survivability is handled by a combination of services from a TCL
script (survivability.tcl) and SRST functions. The survivability TCL script
monitors the SIP connection for all calls that ingress through the remote
gateway. If a signaling failure occurs, the TCL script takes control of the
call and redirects it to a configurable destination. The destination choices
for the TCL script are configured as parameters in the Cisco IOS Gateway
called number is in "E164" format, the survivability script removes the "+"
sign from the called number before forwarding it to Unified CVP. This is
because Unified CVP or ICM does not support the "+" sign in the beginning of
destinations for this transfer include another IP destination (including the
SRST call agent at the remote site), *8 TNT, or hookflash. With transfers to
the SRST call agent at the remote site, the most common target is an SRST alias
or a basic ACD hunt group. For further information about these SRST functions,
Communications Solution Reference Network Design (SRND) based on Cisco Unified
and recording servers do not send Real-Time Control Protocol (RTCP) packets in
reverse direction toward the caller (TDM Voice Gateway), which can falsely
trigger the media inactivity timer of the survivability script. It is important
to apply the survivability.tcl script carefully to the dial peers because a
call might drop if it goes to the voice mail or to a recording element. One
method is to use a separate dial peer for voice mail or recording calls, and do
not associate the Unified CVP survivability script for those dial peers.
Another method is to disable the media inactivity on the survivability script
associated with the voice mail or recording dial peers.
information on configuration and application of these transfer methods, see the
latest version of
Configuration Guide for
Cisco Unified Customer Voice Portal,
also refer to
CUBE Deployment with SIP Trunks.
To take advantage
of alternate routing on signaling failures, you must use the survivability
service on all gateways pointing to Unified CVP. Always use this service,
unless you have a specific implementation that prevents using it.
Router requery is
not supported when using SIP REFER with Unified CVP Comprehensive Call Flow
when the survivability service is handling the REFER message from Unified CVP.
Router requery with REFER can be supported in other call flows when Cisco IOS
is handling the REFER without the survivability service or if Unified CM is
handling the REFER. For third-party SIP trunks, the support of router requery
with REFER is dependent on their implementation and support for SIP REFER.