Mitel 5560 IPT none Specifications download pdf (Page 185)

Bandwidth, Codecs and Compression

171

Bandwidth availability

The advertised rate for a particular link is the speed at which the data travels; it is not necessarily

the available data rate. In practice, a percentage of this bandwidth is lost due to communications

between end devices because the data is asynchronous and requires certain guard bands. In a

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.

Table 49: 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 50: 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

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