Bandwidth, Codecs and Compression
171
BANDWIDTH, BANDWIDTH MANAGEMENT, CODECS
AND COMPRESSION
An IP packet carrying voice information has a number of additional “wrappers” (see graphic
below) so that different network devices know how to route the information (IP address), how
to forward information between physical devices (MAC address), and how to identify when a
packet starts and finishes (Ethernet).
These additional wrappers add overhead to the overall packet. This overhead increases the
bandwidth required to transport a voice packet. To understand the true bandwidth requirements,
this overhead must be taken into account.
Codecs are devices or programs that encode or decode a signal into a digital format, in this
case, the voice payload. Different codecs can provide different sized voice payloads given the
same input information. A reduction in payload is often referred to as compression.
The following sections discuss bandwidth, codecs and compression in further detail.
CALCULATING AND MEASURING BANDWIDTH
Bandwidth can be described in a number of ways:
•
Payload bandwidth, voice: sufficient bandwidth to transfer the usable information.
•
IP bandwidth: bandwidth to transfer the data between the two end devices. Note that this
doesn’t include the transport protocol, which may change between devices and network.
•
Wire bandwidth: This includes all of the bits and timing gaps that are transmitted onto the
media. This includes the payload, the IP address information and the transportation and
synchronization information.
It is important to note which bandwidth is being described when comparing information. For
instance, a G.711 Ethernet connection with 20 ms frames will have the following values:
•
Payload bandwidth: 64 kbps
•
IP bandwidth: 80 kbps
•
Wire bandwidth: 96.8 kbps
Ethernet
MAC
IP
UDP
RTP
Voice
R U I
M E
Notes:
1.
To calculate and measure bandwidth, use the Mitel calculator rather than a
third-party tool. The Mitel calculator uses 802.1p/Q (8100) frames, which ensure the
highest degree of accuracy. Many third-party tools use standard Ethernet (0800)
frames, which are less accurate and do not account for VLANs.
2.
PC-based applications for monitoring IP network traffic often do not indicate the
actual bandwidth being used. These applications usually do not include IP packet
overhead information, and as a result using these applications to try and measure
bandwidth will provide misleading results
Содержание MiVOICE BUSINESS
Страница 1: ...Mitel MiVoice Business RELEASE 7 2 ENGINEERING GUIDELINES ...
Страница 15: ...Chapter 1 ABOUT THIS DOCUMENT ...
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Страница 22: ...Engineering Guidelines 8 ...
Страница 23: ...Chapter 2 SYSTEM OVERVIEW ...
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Страница 28: ...Engineering Guidelines 14 ...
Страница 29: ...Chapter 3 TYPICAL CONFIGURATIONS ...
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Страница 73: ...Chapter 4 PHONES AND VOICE APPLICATIONS ...
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Страница 95: ...Phones and Voice Applications 81 Figure 9 ICP Connection Paths and Limitations ...
Страница 100: ...Engineering Guidelines 86 ...
Страница 101: ...Chapter 5 POWER ...
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Страница 128: ...Engineering Guidelines 114 ...
Страница 129: ...Chapter 6 PERFORMANCE ...
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Страница 135: ...Chapter 7 APPLICATIONS ...
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Страница 142: ...Engineering Guidelines 128 ...
Страница 143: ...Chapter 8 EMERGENCY SERVICES ...
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Страница 151: ...Chapter 9 IP NETWORKING ...
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Страница 167: ...Chapter 10 LICENSING ...
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Страница 183: ...Chapter 11 BANDWIDTH CODECS AND COMPRESSION ...
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Страница 209: ...Chapter 12 NETWORK CONFIGURATION CONCEPTS ...
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Страница 244: ...Engineering Guidelines 230 ...
Страница 245: ...Chapter 13 NETWORK CONFIGURATION SPECIFICS ...
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Страница 309: ...Appendix A CAT 3 WIRING ...
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Страница 315: ...CAT 3 Wiring 301 Figure 55 CX MX MXe AX and LX Minimum Cable Standard ...
Страница 316: ...Engineering Guidelines 302 ...
Страница 317: ...Appendix B INSTALLATION EXAMPLES ...
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Страница 335: ...Appendix C LLDP AND LLDP MED CONFIGURATION EXAMPLES ...
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Страница 347: ...Appendix D VOIP AND VLANS ...
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Страница 353: ...Appendix E VOIP SECURITY ...
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