Abstract:
Quality of Service (QoS) refers to the ability of a network to provide better, more
predictable service to selected network traffic over various underlying technologies,
including IP-routed networks. QoS in a voice network includes logical issues such as
noise and echo. QoS of Voice over Internet Protocol (VoIP) is of growing importance
for research and study. This work investigates the performance of VoIP and the
impact of resource limitations in the performance of Access Networks. The impact of
VoIP performance in access networks is particularly important in regions where
Internet resources are limited and the cost of improving these resources is prohibitive.
Many factors affect voice quality: the broadband connection, bandwidth, hardware,
software and the technology itself. The bandwidth, hardware and software factors are
in control; so when we speak of voice quality in VoIP, we often point a finger to the
underlying technology itself, something which is beyond our control as users. Issues
of interest include the choice of coding rate, dynamic variation of coding rate, packet
length, methods of controlling echo, and the use of Active Queue Management
(AQM) in Access Network routers. Methods for analyzing the impact of the access
network on VoIP performance are surveyed and reviewed. Also, some approaches for
improving performance of VoIP are considered and enriched by scenario work using
NS2 simulation software. By utilizing the Traffic Trace function in ns2, the simulated
VoIP traffic is fed into ns2, packet loss is calculated for different scenarios. Three
simulation scenarios are performed. These three simulations are based on the same
basic model and performed by changing the traffic control methods in the network. In
scenario 1, the normal Drop tail, AQM is used. In scenario 2 RED algorithm is used,
finally a scenario is conducted using Diffserv system. Two additional scenario,
scenario 2B and scenario 3B have also been conducted in sequence of Scenario 2 and
