NEC SL1100, Networking Manual

Page: 77 / 292

NEC SL1100 Issue 6.0
Networking Manual 6 - 15
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
1
is assigned lower priority and the voice is
transmitted before the data. This can have a negative impact on the data
network if a lot of voice is transmitted.
Figure 6-4 Voice and Data Network Implementation shows how a voice and
data network can be implemented.
1. 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.
Figure 6-4 Voice and Data Network Implementation
256Kbps
Private Circuit
(Leased Line)
Data Switch Router
Host A
Router Data Switch
Host B
100Mbps 100Mbps
100Mbp
s
100Mbp
s
100Mbp
s
100Mbp
s
Telephone
System A
Telephone
System B