A new SONET-based network simulator was designed and implemented to study the performance
of different routing mechanisms on transport networks based on the SONET ring architecture. The simulator
incorporates some unique features of the SONET technology. Three static routing schemes were evaluated
on the simulator at different levels of traffic load. The hop-by-hop routing (HHR) scheme uses the
physical network as a fat bit pipe to transport the data traffic from one node to its neighboring node. Utilizing
the Digital Cross-connect System in the SONET technology, virtual topology routing (VTR) schemes
establish the multiple-hop point-to-point links across a SONET ring in order to reduce overall nodal processing
time. The simulation results show that virtual topology routing schemes have advantage of low network
latency over the hop-by-hop routing scheme only when the bursty traffic load is well below the
network capacity. In medium to high traffic load conditions, increased queuing delay counteracts the
reduced overall nodal processing time in the VTR schemes, resulting in high network latency, while the
HHR scheme have the advantage of high bandwidth utilization and low packet-drop rates.
To overcome the drawbacks of the static routing schemes, dynamic bandwidth-allocation mechanisms
combining VTR and HHR principles were suggested. The mechanisms allocate bandwidth dynamically
between VTR and HHR regions in response to the changes in traffic patterns on a SONET ring. Both
centralized model and distributed model were proposed. For the centralized model, the problem of optimal
effective bandwidth allocation on the Unidirectional Path Switched Ring (UPSR) architecture was formulated
and a solution based on a Greedy algorithm with cost of 0(n²m + mlogm) was provided for
UPSR architecture with n nodes and m flows. A heuristic bandwidth optimization algorithm based on the
solution for UPSR was developed and evaluated numerically for Bidirectional Path Switched Ring (BPSR)
architecture. The possibilities of extending the heuristic algorithms to other SONET-ring-based architectures
were also explored. For the distributed model, a mechanism was proposed to maintain the tension
between bandwidth utilization and network latency in local scope rather than in global scope. By resolving
problem early and locally, intensive computation of global bandwidth optimization and synchronization of
global reconfiguration may be avoided.Science, Faculty ofComputer Science, Department ofGraduat
