Figure 6-5 Priority Queuing On Voice And Data Networks - NEC Sl2100 Networking Manual

ISSUE 1.0
Host A
Data Switch
Chassis
Telephone
System A
After the router is configured for QoS, it examines incoming packets and allocates a priority to the
packet. Figure 6-5 Priority Queuing on Voice and Data Networks on page 6-11
priority queuing has on voice and data networks. The packets arrive randomly. They are processed
and output according to the QoS policy. The VoIP traffic is output first.

Figure 6-5 Priority Queuing on Voice and Data Networks

To enable this type of queuing it is necessary to:
1. Configure the VoIP equipment to mark its packets with a specific value so that the switches/
routers can identify that it is voice – Called Marking.
2. Configure the network equipment to recognize the difference between the different Marked
packets – Called Classification. (i.e., informs the router what a voice packet looks like.
3. Configure the network equipment to give priority to the packets that have been classified as voice
– Called Priority Queuing.
6.2 Layer 2 QoS (802.1pq)
QoS is most commonly implemented at Layer 3 of the OSI model. This layer deals with IP addresses,
and is usually handled by Routers. However, sometimes it is necessary to implement Layer 2 QoS –
usually in large LAN environments with many IP phones.
Networking Manual
100Mbps
Router
Figure 6-4 Voice and Data Network Implementation
Packet from VoIP Device
Packet from PC
E h t e n r e t 1 ( 0 0 M b p ) s
Router with QoS
Policy Applied
Direction of IP Traffic
256Kbps
Private Circuit
(Leased Line)
100Mbps
Router
L e a e s d L n i e 2 (
SL2100
Host B
Data Switch
Chassis
Telephone
System B
shows the affect
5 6 K b p ) s
6-11