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Cisco VISM Installation and Configuration Guide
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter 4 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 echo cancellation
• 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 terminating loopback and
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 maintenance or
other reasons