For designing a good voice network you should have to aware the following voice control issues:
Packet Loss and Packet Delay:
As a network engineer for better voice communication you need to minimize the packet loss and packet delay. Normally for a voice network 150ms one way delay is acceptable, but anything above 400ms is unacceptable and cause problems for your voice network. You also need to focus and control the following fixed delays:
Propagation Delay is delay of sending and receiving data from transmitter to receiver, this delay is fixed and normally building delay of the networking devices.
this delay is occurring when you send the voice data on the interface of a network device. This delay is directly related to interface or link bandwidth and speed and you can minimize this delay by increasing your bandwidth.
processor delay is the delay of compressing, decompressing and encoding of data by device.
This delay is related to your input/output queuing of data at each router or network device, for voice enabled router you have many queuing techniques. You can minimize this delay by QoS.
Jitter is a variation in delay of received packet, when you continuing sending packet in a stream, they are spaced in even fashion but because of congested network and improper queuing techniques other causes jitter is occur.In voice enabled router you can control the jitter by dejitter duffers and playout delay buffer.
Echo:Echo is small delay in voice packets and you can minimize this by echo canceller.
Designing QoS for Voice Traansport:
Here are some guidelines for designing QoS for voice network.
- You can apply the QoS techniques for WAN having E1/T1 connection or lower.
- QoS is most effective on bursty WAN connections, where you are having large traffic and have to send large data over the WAN, dealing with replication on certain part of day.
- You can implement QoS for delay sensitive applications and traffic like stock exchange, web training or video conferencing.
- If you have congestion in your network then for congestion management you can apply and enable QoS for your voice Network.
- For better voice design and QoS you need to implement earlier goals and need to have a proper plan for your all type of data, far this you can implement content networking.
- You want to design your voice network with Cisco then for best QoS you need CCNP and CCIElevel professionals.
- Also make sure that your routers are configured properly for QoS and for best practice before configuration list all the QoS features of your routers, switches and other network devices and enable them.