Abstract:
Communication links with high data throughput capacity (bandwidth) and low latency are
the prime requirements to support multimedia applications such as voice on demand
services, video conferencing and virtual reality. These applications require a particular
Quality of Service (QoS) defined by the delivery of voluminous continuous media (audio
or video) data packets over the network with a certain delay and jitter bound. Best-effort
service is unsuitable for all the above-mentioned requirements because all packets
compete equally for network resources. The necessity to develop better QoS solutions to
address these issues of multimedia transmission has led Internet Engineering Task Force
(IETF) to develop Integrated Services (Intserv) architecture with Resource Reservation
Protocol (RSVP) and Differentiated Services (Diffserv) architecture. In Intserv
architecture, RSVP is used to set up paths and reserve resources towards receiver before
sending data. But in large networks it enjoys the drawbacks of scalability.
In this thesis a new flow-based admission control algorithm has been proposed for routing
the multimedia traffics with a predefined QoS through a Diffserv-Aware ATM based
MPLS network. The routers in the networks work as distributed admission controllers to
find a particular path satisfying a particular QoS. A scheme of rerouting multimedia flows
during the congestion in a particular part of the network is also presented.
Admission controlling would be done by the router connected to the source of the
multimedia traffic by observing the current delay and jitter of the calculated path for the
multimedia request. Virtual Circuits (Ve) in an ATM-based MPLS network are used to
reduce end-to-end delay and router load and for higher throughput. In the proposed
technique, QoS of a multimedia session can be violated if congestion occurs in a router
on its path. Diverting traffic towards low congested path is a common technique used by
the routers to avoid congestion in the network. Consideration has been given in one
particular rerouting option during congestion, to guarantee the overall QoS. However, this
rerouting decision would be made by the source of the multimedia traffic. Unlike the
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traditional routing of data packets, the intermediate routers on the flow of a multimedia
session have nothing to do with this routing scheme.
Based upon the knowledge of the customers' Service Level Agreements (SLAs),
simulation results are also presented that show the improvement of session success rate
by rerouting the multimedia traffic to relatively under-utilized links during congestion.
