4-68
Cisco VISM Installation and Configuration Guide
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter4 Configuring VISM Features
Configuring Additional VISM Features
RTP Connection Statistics
Real-Time Transport Protocol (RTP) connection statistics are collected for individual endpoints and sent
to the call agent. Use the new dsprtpconnstat command to display collected RTP connection statistics.
Jitter delay data collection at call completion is on a per call basis. Jitter delay data and number of
packets sent and received, and numbe r of o ctets sent and received, are reported to the call ag en t through
MGCP.
CAS Immediate Start and Ground Start Glare Handling
CAS Immediate Start—The CAS variants immediate start and immediate start, multifrequency are
supported. Use the addcasvar command to configure CAS variants.
Note The immediate start protocol does not define glare handling procedures—do not use the imm ediate
start protocol on incoming or outgoing endpoints only. Endpoints are added as b i dire ction al by
default. To make them incoming or outgoing, use the cnfcasglarepolicy command. If the endpoints
are left as bidirectional, configured for immediate start operation, and glare occurs, the results may
be unpredictable.
Ground Start Glare Handling—This release supports CAS glare condition handling according to
RFC 3064. The VISM sends a NACK message in response to the call agent’s request for ringing with
error code 401 (off hook) in the event of a glare condition.
On receiving the request for ringing from call control, CAS transmit s a seize signal to the PBX and starts
the glare timer, returning a provisional response code to call control indicating that CAS is still
processing the request. If the timer expires (normal case) or an inco mi ng se izu re i s observed on t he
endpoint, CAS generates an asynchronous response code to call control that is comparable to an MGCP
response code of 200 or 401, respectively.
Grooming for Local Traffic
VISM supports the call agent controlled grooming feature. Grooming allows VISM to avoid routing
local traffic through the IP network. Voice packets from a local connection are switched locally in the
ATM switch.
A call agent determines if a call needs to be setup as local. To set up a local call, the call agent selects
an ATM connection over a VoIP connection. The VISM card, as a gateway, receives the connection
request message from the call agent for an ATM connection. The VISM card allows VoIP calls and
VoAAL1 SVC calls to coexist and allows provisioning of VoIP and ATM simultaneously.
To achieve this, VISM uses VoIP and Switched ATM AAL1 SVC as local switching mode. VISM
receives an ATM AAL1 SVC call setup request from the call agent for local calls.
You must use the cnfvismmode command and select the VoIP and switched ATM AAL1 SVC operating
mode to use the grooming feature. Using this mode does not ch ange any other settings on your card. The
type of connection for a call is determined by the connection request (CRCX) from the call agent or by
the bearer type configuration.