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Cisco VISM Installation and Configuration Guide
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter1 Overvi ew of the VISM and VISM-PR Cards
VISM and VISM-PR Card Features
The voice bearer path is treated in the same manner as in the VoIP switching and AAL2 PVC modes,
except that only preprovisioned AAL2 PVCs are available for transport of voice over the trunks. The
CAS signaling data is transported over the ATM network in the same AAL2 trunk as Type 3 messages.
The CCS signaling data is transported over the ATM network in a separate AAL5 PVC.
VoIP Trunking Operating Mode
The Voice over IP (VoIP) trunking feature allows the VISM to connect to the PBX, or central office
digital systems, using T1/E1 digi tal interfaces and converts the TDM bit s tream into RTP packets, after
ECAN and compression, and transports it over the IP network.
No call agent is required for setting up and tearing down calls. You must configure the DS0 circuits. The
connection between VISM and the first router will be ATM after which it will be IP only. VISM and the
router can have one or multiple PVCs to transport the data. You have the option to configure PVC for
bearer or control. If the PVC is configured a s be are r an d n o c on t rol P VC exis ts , th en PRI s ign al tr affic
and bearer traffic will go through this PVC. If you configure separate PVCs for contro l and bearer, PRI
signaling will go through control traffic only. You can modify some of the connection parameters after
it is added.
CAS is transported to the far end using a Cisco proprietary format ( not NSE s). PR I is transpo rte d over
RUDP to the far end once the trunk is provisioned between the originating and terminating VISM.
PRI transport is handled in a way identical to PRI backhaul except that the PRI traffic is sent to remote
gateway instead of a call agent. You can configure one line for PRI trunking and another line fo r PRI
backhauling.
You must provision the LAPD trunk when using this feature. You must conf i g u re a line number, remote
gateway IP address, local UDP port, and remote gateway UDP port, an d then op en a tr unk . You must
then configure the D-channel as a trunk or backhaul:
•To configure the D channel as trunk, use the addlapdtrunk command prior to the addlapd
command. If the addlapd command has been previously executed for that line, the command is
rejected.
Note Two D channels on one line are not supported.
•To configure the D channel as backhaul, use the addses command prior to the addlapd command.
If you do not configure either trunk or session, the addlapd command is rejected.
AAL1/AAL2 SVC Operating Mode
Release 3.0(0) supports the AAL1 and AAL2 switched virtual circuit (SVC) operating modes for
VISM-PR cards. VoAAL1 SVC is supported with the G.711 codec and clear channel.
Note VAD is not supported in combination with AAL1 SVCs. CAS is not supported in combination with
SVCs.