Title page for ETD etd-08062002-125435

Type of Document

Master's Thesis

Author

Adhikari, Akshay Arun,

Author's Email Address

aaadhika@unity.ncsu.edu

URN

etd-08062002-125435

Title

Voice Over IP Performance Diagnosis

Degree

Master of Science

Graduate Program

Computer Networking

Advisory Committee

Advisor Name	Title
Dr. Douglas S. Reeves	Committee Chair
Dr Wushow Chou	Committee Member
Dr. George N. Rouskas	Committee Member

Keywords

SNMP
Voice over IP
self-similarity
clock synchronization

Date of Defense

2002-08-05

Availability

unrestricted

Abstract

We investigate a framework for assessing the readiness of a network
to support Voice over IP (VoIP) at the pre-deployment
stage. In this framework, VoIP traffic is synthesized on the network, while
simultaneously monitoring the health of network devices and links using the
Simple Network Management Protocol(SNMP). Using this framework, we try to
understand whether SNMP can be used to detect which network links or devices,
if any, cause poor VoIP quality.

First, we investigate the limitations of the end-to-end VoIP quality
measurement, and SNMP measurement framework used in lab experiments. We
quantify the errors in end-to-end VoIP quality measurements, and in SNMP
measurements, so that these errors can be taken into account depending on
the application at hand.

Next, we use our lab experiments to understand how VoIP performance
metrics like delay and loss are affected by offered load on a link. From
our initial experiments with faulty synthetic traffic generators, we find
that even at low utilization, bursty network traffic can significantly
degrade VoIP quality, and small timescale measurements, which are
impractical with SNMP, are required to detect the problems. However,
using realistic emulation of network traffic in the lab, we find that when
network problems are severe and last for long periods of time, they can be
easily detected using SNMP. We also present a case study of VoIP
assessment data collected from a real network, where we again
successfully used SNMP to detect the network links that caused poor quality

Files

Filename		Size	Approximate Download Time (Hours:Minutes:Seconds)
Filename		Size	28.8 Modem	56K Modem	ISDN (64 Kb)	ISDN (128 Kb)	Higher-speed Access
	etd.pdf	2.76 Mb	00:12:45	00:06:33	00:05:44	00:02:52	00:00:14