Introduction

IP telephony is something that is growing up very fast and the main reason is that phone calls can be cheaper because we are using a well-known infrastructure (Internet).

However, if we have to say something against VoIP it is that the quality of PSTN (public switched telephone network) is still higher. The problem of this low quality is due to the network (Internet and low bandwidth networks) and could be solved in the future. Meanwhile, if we know the quality problems and the possible solutions we could have a good quality of service.

The main problems of a VoIP QoS (quality of service) are latency, jitter, packet loss and echo. In the following pages you could see some techniques to solve these problems.

The problems of VoIP QoS are due to two main factors:

a) Internet is a packet-switched network and therefore the information do not travel always by the same path. This causes packet loss and jitter problems.

b) The VoIP communications are in real time This means that echo, packet loss and latency are annoying and must be solved