NEC Univerge SV9100 Manual page 327

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This description discusses voice and data. These terms are commonly used when describing QoS, although in the

case of VoIP, the voice is actually converted to IP and transmitted as data. Therefore, everything transmitted on a

Data Network is data, but logically we think of this as voice and data traffic.

SV9100 Networking Manual

Figure 5-3 Network Bottleneck Example

Switched Hub

For this example, each end of the network has only.one host Typically, many hosts

are sending data over the narrow bandwidth. The routers buffer packets and

transmit them over the WAN lines as efficiently as possible. When this occurs,

certain packets are dropped by the router and some packets are delayed.

For most data applications this packet loss/delay is not critical.For example, a

delay of one to five seconds to transmit an email is imperceptible. When VoIP is

implemented, this loss/delay has a massive impact on the voice quality. The

resulting gaps in speech, distortion and delay are unacceptable for voice traffic.

To avoid this problem, it is possible to prioritize the VoIP packets. The router

examines all packets received, determines the priority level of the packet, and

forwards it accordingly. The data

transmitted before the data. This can have a negative impact on the data network

if a lot of voice is transmitted.

Private Circuit

(Leased Line)

is assigned lower priority and the voice is

Switched Hub