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Chapter 3
VISM Functional Description
Use the CLI PRI/backhaul commands to do the following:
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•
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•
Refer to
CAS Processing in AAL2 Trunking Operating Mode
CAS signaling is extracted from the voice data and is transported across the packet network in AAL2
trunking operating mode. The signaling is transported across the same trunk (VC) and the same channel
identifier (CID) as its associated voice stream, using AAL2 Type 3 messages in accordance with ITU-T
I.366.2. The messages are used for CAS (A,B,C, and D) robbed bits, fax/modem tones, and digits and
are transported with triple redundancy.
CCS Processing in AAL2 Trunking Operating Mode
CCS signaling is maintained as Q.931 messages and transported across the packet network using an
AAL5 PVC in AAL2 trunking operating mode. The local and remote ends of the PVC are the same as
those for the AAL2 PVC trunk carrying the associated voice data.
ATM Voice Data Processing Function
The VISM DSPs process incoming voice data (for compression, ECAN, etc.) and then the data is
prepared for transport over the ATM network. Voice samples are processed into ATM packets and then
into ATM cells in preparation for transport. VISM then transports the cells to Voice over ATM (VoATM)
networks with the following supported operating modes:
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•
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Transporting Voice Cells with VoIP
The VoIP switching operating mode processes voice cells in the following order to transport them over
ATM networks:
1.
2.
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Create and delete session sets
Create, delete, configure, and display sessions and sessions groups
Create, delete, configure, and display D channels for CCS
Display PRI/backhaul statistics
Chapter 5, "CLI Commands,"
VoIP
Switched AAL2 PVC
AAL2 trunking
AAL1 SVC
Formatted into Real-Time Transport Protocol (RTP) packets.
RTP allows time-stamping of the voice samples, which permits dejittering of the samples
Note
transmitted to the destination TDM line.
Encapsulated in a UDP packet.
for more information on CLI commands.
Cisco VISM Installation and Configuration Guide
ATM Voice Data Processing Function
3-11
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