Mitel MiVOICE BUSINESS, Engineering Manualline

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Bandwidth, Codecs and Compression
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synchronous telecom link, these issues are resolved through mechanisms such as framing data
into fixed timeslots. The following table contains some simple guidelines for LAN and WAN links.
LAN bandwidth
The following table contains some simple guidelines for LAN connections (assuming that all
the available bandwidth is used for voice traffic only).
“LAN connections guidelines” reflects the maximum usable bandwidth based on the physical
connection. Other factors in the network must also be considered, including:
• the percentage of data traffic shared with the voice on a common connection.
• the percentage of broadcast traffic; a “flatter” LAN will result in more traffic.
• the percentage of data traffic allowed in the egress queues even under congestion.
• whether the uplink from a switch is blocking in terms of possible data input, e.g. a 1 Gbps
uplink may not be enough for a 24 port switch running 100 Mbps on each input link.
• whether the switch backplane can handle the data throughput in terms of available band-
width and packet per second rate.
The LAN connection guidelines table also shows the maximum capability of a LAN link assuming
that the link is used purely for voice traffic. If the link is shared with other devices such as PCs,
then some priority mechanism is required to ensure that the voice gets the available bandwidth
when needed. Also, in a busy network with multiple broadcasts, the available bandwidth is
reduced by this percentage. For example, in a network with 10% broadcast traffic (at 10 Mbps),
Table 48: LAN and WAN Link Guidelines
DATA CONNECTION TYPE
PERCENTAGE OF
BANDWIDTH AVAILABLE
EXAMPLE
LAN – 10BaseT Half Duplex 40% 10 Mbps => 4 Mbps available
LAN – 10BaseT Full Duplex 80% 10 Mbps => 8 Mbps available
LAN – 100BaseT Half Duplex 40% 100 Mbps => 40 Mbps available
LAN – 100BaseT Full Duplex 80% 100 Mbps => 80 Mbps available
WAN – 1.5 Mbps Frame Relay without QoS
mechanism in router 40% 1.5 Mbps => 600 kbps available
WAN – 1.5 Mbps Frame Relay with QoS
mechanism in Router 70% 1.5 Mbps => 1.05 Mbps available
Table 49: LAN Connections Guidelines (based on a 20 ms packet rate)
CABLE CAPACITY BANDWIDTH
PHONE USAGE
AT G.711
VOICE
CHANNELS
G.711 VOICE
CHANNELS
G.729A (X 2.5)
10BaseT Half Duplex 40% 2% 20 50
10BaseT Full Duplex 80% 1% 80 200
100BaseT Half Duplex 40% 0.2% 200 500
100BaseT Full Duplex 80% 0.1% 800 2000