Digital Circuits
Multi-Channel connectivity on a single port
Typically 4-23 channels (bearer or voice)
1 channel signalling
channel associated signalling (CAS)
common channel signalling (CCS)
T1 US, E1 Europe
Voice Codec’s
Codec | G.711 (SD) | G.722 (HD) | G.729 | iLBC | iSAC |
Bandwidth | 64Kbps | 64Kbps | 8K | 13.3K | 10-32K |
w/overhead | 82K+ | 80K+ | 26K+ | 28K+ | 16-64K+ |
MOS | 4.3/5 | ㅤ | 3.92/5 | 4.14/5 | ㅤ |
DSP Modules
- Convert TDM and Analog voice calls into IP Packets
- Sampling, encoding, and quantization
- Transcoding
- Conferencing
RTP
RTP uses even ports UDP range 16384-32767
RTCP offers out of band statistics and control information
SRTP is used for encrypted voice calls
Layer 2 header | IP Header | UDP Header | RTP Header | Voice Payload |
VoIP Signalling Protocols
Protocol | Description |
H.323 | ITU standard protocol for interactive conferencing. Evolved from H.320 ISDN. Flexible Complex |
MGCP | IETF standard for PSTN gateway control |
SIP | IETF protocol for interactive and non-interactive conferencing. Simpler than H.323 |
SCCP (Skinny) | Cisco proprietary protocol used between Cisco Unified Communications Manager and Cisco VoIP phones |
Latency < 150ms
Jitter < 30ms
Loss < 1%
Collaboration Call Control
Cisco Unified Communications Manager (CUCM)
- SIP based signaling
- VoIP and Telepresence endpoints
- Alphanumeric / numeric dial plans
- Cisco End Game Controller
- ≤ 30,000 phones per cluster
- Uses IBM Informix database
- Customised Red Hat Kernel (not accessible)
- GUI management and administration
Unified Communications Manager Express
- Router (IOS) based call control platform
- Fully featured IP telephony
- Support for up to 450 phones
- Video calling support
- Voice conferencing
- Advanced call routing and voice gateway
- Licensed feature of Cisco IOS routers
Cisco Video Communication Server (VCS)
- H.323 and SIP based signalling
- Video / Telepresence endpoints
- Firewall traversal capabilities
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