Why buffers in switching systems do not essentially improve QoS: An analytical case study for aggregated On-off traffic

Document type: Conference Papers
Peer reviewed: Yes
Full text:
Author(s): Gerhard Hasslinger, Markus Fiedler
Title: Why buffers in switching systems do not essentially improve QoS: An analytical case study for aggregated On-off traffic
Translated title: Varför buffertar i switch system inte förbättrar tjänstekvalitén på avsevärd sätt: En analytisk fallstudie för trafik från On-off källor
Conference name: Internet Performance Control of Network Systems
Year: 2002
Pagination: vol. 4865, pp 47-58
Publisher: SPIE
City: Boston
Organization: Blekinge Institute of Technology
Department: Department of Telecommunications and Signal Processing (Institutionen för telekommunikation och signalbehandling)
Department of Telecommunications and Signal Processing S-372 25 Ronneby
+46 455 38 50 00
Authors e-mail: markus.fiedler@bth.se
Language: English
Abstract: Traffic models with a rate varying according to a Gaussian distribution are commonly used to evaluate statistical multi-plexing
in telecommunication systems. The superposition of a sufficient large number of homogeneous Markovian On-Off
sources asymptotically approaches an Ornstein-Uhlenbeck process (OUP) which represents a Gaussian process with ex-ponential
autocorrelation function. We derive a simple expression for the bandwidth demand under QoS constraints which
is close to numerical OUP/D/1 analysis results over the entire parameter region with relevance to applications. In com-parison,
results of the fluid flow method for fixed aggregation level are used to verify the OUP/D/1 asymptotics and to
estimate its accuracy depending on the number of aggregated flows.
Moreover, the OUP/D/1 asymptotics provides a useful check of the accuracy of bounds and approximations proposed
in the literature in order to improve the effective bandwidth principle. Based on analytical evaluation, the efficiency of
buffers for voice traffic is finally shown to be very limited, i.e. no more than 2% of bandwidth can be saved owing to
buffers with regard to real time constraints and a predefined loss probability as QoS demands for voice.
Summary in Swedish: Pappret visar att man tjänar inte mycket på bandbredden genom att buffrar rösttrafik i ett nätverk.
Subject: Telecommunications\Modelling of Bursty Traffics
Telecommunications\Fluid Flow Models
Keywords: On-off sources, Gaussian traffic, Ornstein-Uhlenbeck process, dimensioning, statistical multiplexing gain
Note: COST Technical Document 279TD(02)013. Presented at the Leidschendam meeting (Feb. 2002). See http://www.lx.it.pt/cost279