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The Design Process—Planning. Understanding Bandwidth Provisioning Issues. What Codecs Are Supported by Cisco Unity?. About G.711. Standard format for digital voice delivery in the PSTN
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The Design Process—Planning Understanding Bandwidth Provisioning Issues
About G.711 • Standard format for digital voice delivery in the PSTN • Supported by Cisco, Intel Dialogic, all versions of Microsoft, and many other hardware and software platforms • Best-quality codec • Highest bandwidth—64 kbps and headers
About G.729a, G.726, and GSM 6.10 • G.729a • Compressed voice to 8 kbps • Can be used on WAN links where limited bandwidth exists • Not supported natively in Windows • Support can be added manually • G.726 • Used with VPIM • GSM 6.10 • Smart phones
Codec Task List • Choose a codec for recording and storage. • Choose one or more codecs for message retrieval. • Match Cisco Unity prompts and greetings to the codec chosen for recording and storage. • If necessary use the Set WAV Format utility to change the format of recorded .wav files.
Network, Hardware, and Software Considerations for Choosing a Codec
WAN Cisco Unified Call Manager1 Cisco Unified Call Manager2 Workgroup Cisco Unity and Bandwidth Issues Headquarters Branch DC DDNS Exchange 2000 G.729a DC/GC DDNS DC/GC DDNS CiscoUnity
WAN Cisco Unified Call Manager1 Cisco Unified Call Manager2 Workgroup Example: Branch Office Client Access • User at the branch office uses TUI to access Cisco Unity. • Cisco Unity contacts domain controller to authenticate caller. • Message is streamed from Exchange to Cisco Unity to the TUI. • In ViewMail for OutLook, message is streamed to ViewMail client or downloaded first. Branch Headquarters Region 2 DC DDNS Exchange 2000 Region 1 G.729a CiscoUnity DC/GC DDNS DC/GC DDNS Region 1
Transcoding Considerations for Choosing a Codec • Minimize transcoding when possible to preserve audio quality. • Use Cisco hardware resources for transcoding. Cisco Unity should not do all transcoding.
WAN Cisco Unified Call Manager1 PSTN Cisco Unified Call Manager2 Workgroup What Is the Cisco SRST Fallback Support for Branch Offices? • Cisco SRST can be used to enable IP phones if connectivity is lost to the Cisco Unified CallManager. • When in Cisco SRST mode, branch-to-headquarters calls use the PSTN. • Voice-mail access must be explicitly configured on the router. Headquarters Branch Cisco Unity Cisco SRSTEnabled If WAN is down, messages button can access Cisco Unity via the PSTN.
Summary • There must be adequate bandwidth to enable good-quality audio between all endpoints in the network. • The codec selection guideline is that, if there is adequate bandwidth, G.711 is recommended. • If compression is required to save bandwidth, G.729A is used. Intel Dialogic codecs are used with voice cards for PBX integrations. G.726 is used with VPIM integrations. • Minimize transcoding when possible to preserve audio quality. • If bandwidth is an issue, ViewMail for OutLook messages can be downloaded first and played back later. • Cisco SRST can send and receive voice-mail messages from Cisco Unity and other voice-mail systems during Cisco Unified CallManager fallback.