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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
•The ability for VISM to perform as either the network or user side of the LAPD protocol for PRI
backhaul
•CCS/PRI backhaul between VISM and a call agent in VoIP mode
•Support VoIP G.729ab compression
•Idle channel suppression
•Support for setting the IP precedence bit
•Support for Q.50 CAS signaling variant
•Negotiable packetization period
•AAL2 subcell multiplexing
•E1 back card support in AAL2 trunking mode
•E1 back card support (VoIP mode only)
•Provides 8 standard T1 interfaces with B8ZS, AMI and HDB3 line coding
•Support for voice over ATM using AAL2 cells (multiplexing only, no LLC/SNAP encapsulation.
•VoIP using AAL5 cells to RFC 1889
•Support for both PCM a-law and u-law
•Programmable 24, 32, 48, 64, 80, 96, 112, 128 ms near end e cho c an cell ation
•Voice compression to G.711 and G.726-32k standards
•Nx64 clear channel (N = 1 only) support
•Voice activity detection (VAD) and comfort noise generation (CNG) using variable threshold energy
(Cisco proprietary)
•Support for call agent Simple Gateway Control Protocol (SGCP) Version 1.0, SGCP 1.1+, and
Media Gateway Control Protocol (MGCP) 0.1
•Support for CCS signaling transport across an AAL5 trunk
•Support for Fax and modem VoIP bearer transmissions
•Support for dual (redundant) virtual circuits across the packet network
•Support for full continuity testing (COT). Supports origination and termi nat ing lo opb ac k an d
transponder COT towards the packet bearer and the TDM sides
•Support for loop timing, payload and line loopbacks
•1:N cold redundancy using SRM-3T3 capabilities (bulk mode support for T1 lines only) for
switched calls
•1:N hot redundancy for trunking applications only
•Courtesy downing of ongoing voice calls when the VISM is taken out of service for main tenance or
other reasons