Engineering Guidelines
184
Therefore, define the link bandwidth based on the IP throughput.
An alternative method is to determine the physical wire bandwidth and define the number of
voice streams, or “channels”, that are required or achievable across the link, using the physical
wire bandwidth per connection. Once the number of “channels” is defined, multiply this by the
numbers defined in the table above to define the Inter-zone bandwidth limit.
For example, suppose a link has a physical bandwidth of 200kbits/s and running DSL. The
protocol is PPPoEoATM and on such a link, a G.729 call uses ~64kbits/s. With this link it should
be possible to achieve 3 voice streams, albeit with high utilization (200/(3x64)). Therefore, a
bandwidth value of 96 should be defined for the link or maybe 64 in order to maintain usage
below 80%. See Table 55 and Table 56 for more details of wire bandwidth, codec type, frame
rate and WAN protocols.
CODEC – INTRODUCTION
The word CODEC is a concatenation of two words: Coder and Decoder. The CODEC is actually
two functions, coding and decoding, for the conversion of media, in this case, voice, into some
data format that can be returned at the far end into something akin to the original. For voice,
this usually involves converting the analog signals into digital signals and levels and returning
them back to analog.
The most popular CODEC, G.711, has become standardized across large parts of the telephony
network. As such, it has become the baseline for IP devices to perform to. But to make life
interesting, the G.711 CODEC comes in two varieties: A-Law and µ-Law. Typically these coding
laws were kept separated by geographic boundaries, but with increasingly global IP traffic, both
types are regularly encountered. Therefore a G.711 CODEC has to negotiate which coding law
to use as well.
Other coding laws also exist. One that gives good voice quality and is also efficient at coding
is G.729. This also comes in different formats:
•
G.729 - original version—very processor intensive
•
G.729a - reduced processor effort and compatible with G.729
•
G.729b - includes voice activity detection and ability to send background information. Com-
patible with G.729 and G.729a
Wideband audio, up to 7kHz (50Hz to 7.0kHz) of voice bandwidth, is available with the G.722
range of codecs. Although there are a number of wideband codecs under the G.722 banner a
number of these are not compatible with each other, so extra care is needed when specifying
these.
Table 54: CODEC Throughput
CODEC TYPE
IP P %OVERHEAD
G.711
32
G.722.1 (32k)
56
G.729
88
Summary of Contents for MiVOICE BUSINESS
Page 1: ...Mitel MiVoice Business RELEASE 7 2 ENGINEERING GUIDELINES ...
Page 15: ...Chapter 1 ABOUT THIS DOCUMENT ...
Page 16: ......
Page 22: ...Engineering Guidelines 8 ...
Page 23: ...Chapter 2 SYSTEM OVERVIEW ...
Page 24: ......
Page 28: ...Engineering Guidelines 14 ...
Page 29: ...Chapter 3 TYPICAL CONFIGURATIONS ...
Page 30: ......
Page 73: ...Chapter 4 PHONES AND VOICE APPLICATIONS ...
Page 74: ......
Page 95: ...Phones and Voice Applications 81 Figure 9 ICP Connection Paths and Limitations ...
Page 100: ...Engineering Guidelines 86 ...
Page 101: ...Chapter 5 POWER ...
Page 102: ......
Page 128: ...Engineering Guidelines 114 ...
Page 129: ...Chapter 6 PERFORMANCE ...
Page 130: ......
Page 135: ...Chapter 7 APPLICATIONS ...
Page 136: ......
Page 142: ...Engineering Guidelines 128 ...
Page 143: ...Chapter 8 EMERGENCY SERVICES ...
Page 144: ......
Page 151: ...Chapter 9 IP NETWORKING ...
Page 152: ......
Page 167: ...Chapter 10 LICENSING ...
Page 168: ......
Page 183: ...Chapter 11 BANDWIDTH CODECS AND COMPRESSION ...
Page 184: ......
Page 209: ...Chapter 12 NETWORK CONFIGURATION CONCEPTS ...
Page 210: ......
Page 244: ...Engineering Guidelines 230 ...
Page 245: ...Chapter 13 NETWORK CONFIGURATION SPECIFICS ...
Page 246: ......
Page 309: ...Appendix A CAT 3 WIRING ...
Page 310: ......
Page 315: ...CAT 3 Wiring 301 Figure 55 CX MX MXe AX and LX Minimum Cable Standard ...
Page 316: ...Engineering Guidelines 302 ...
Page 317: ...Appendix B INSTALLATION EXAMPLES ...
Page 318: ......
Page 335: ...Appendix C LLDP AND LLDP MED CONFIGURATION EXAMPLES ...
Page 336: ......
Page 347: ...Appendix D VOIP AND VLANS ...
Page 348: ......
Page 353: ...Appendix E VOIP SECURITY ...
Page 354: ......
Page 381: ... ...