MOS Rating
Compression Method Bit Rate (Kbps) MOS Score
G.711 PCM 64 4.1
G.726 ADPCM 32 3.85
G.728 LD-CELP 16 3.61
G.729 CS-ACELP 8 3.92
G.729a CS-ACELP 8 3.7
G.723.1 MP-MLQ 6.3 3.9
G.723.1 ACELP 5.3 3.65
Cisco voice DSP modules are 72-pin Single In-line Memory Modules
(SIMMs) from Texas Instruments (TI). Cisco uses TI DSPs, C542 and C549.The
C542 DSP is supported on the AS5300 Voice Feature Card (VFC), 2600/3600/
VG-200 Voice Network Modules: NM-1V and NM-2V, and MC3810 Voice
Compression Module (VCM).The Cisco AS5800,AS5300 double-density VFC,
2600/3600/VG-200 High Density Voice Network Module (NM-HDV), 7200/
7500 Digital T1/E1 High Capacity Voice port adapter (PA), 175x Series router, and
MC3810 High-density Compression Module (HCM) utilizes the C549 DSP
module. DSP SIMM modules are also in Catalyst 4000 and 6000 blades,WSX4604-
GWY and WS-X6608-T1/E1, respectively.This chapter will focus on the
DSP modules in the Catalyst 4000 and 6000, and NM-HDV modules used as DSP
resources or a DSP farm in CallManager deployments.The Catalyst 4000 and 6000
switches serve as DSP farms.A DSP farm is a pool or group of DSP SIMMs
located in Cisco switch and router modules. Prior to CallManager 3.1, DSP
resources were provisioned to individual Cisco CallManagers—in other words, the
DSP resources could not be shared between servers. CallManager 3.1 allows
resource sharing between servers in the cluster. DSP provisioning is the process of
allocating DSP resources for Cisco CallManager clusters to provide hardware conferencing
and transcoding functions. CallManager also supports software-based
conferencing and transcoding. Just as with planning and designing your AVVID
network in regards to what switches, routers, and gateways should be used, you
should consider early on what DSP resources will be needed for a successful
AVVID installation.To help in the planning of DSP resources and provisioning, you
must consider all the applications and users that will be communicating with G.711
applications, such as voice messaging and interactive voice response (IVR) packages
and IP WAN conferencing.We will discuss next what conferencing and transcoding
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means to your AVVID network, as well as some possible scenarios and hardware
solutions.