Performance of WR-OBS and TCP in OBS Networks

1. Performance of WR-OBS and TCP in OBS Networks UCL Benn Thomsen, Adam Burke

2. Introduction • This work applies to two-way reservation schemes such as WR-OBS or APSON • Features of two-way reservation: • Provides a guaranteed end-to-end lightpath • Removes the need for contention resolution in the optical core • All buffering is done electronically at the edge. • Here we develop an analytical model to estimate the upper bounds on the performance of two-way reservation OBS schemes compared to the static case

3. Holding Time Idle Time WR-OBS overview Edge router Traffic aggregation and multiplexing 1 2 tuneable lasers burst aggregation Core router Burst Aggregation Control node Lightpath Request Request Processing Ack. Propagation Transmission New Burst

4. WR-OBS Performance • Generalized performance analysis of WR-OBS architecture • Provides upper bounds within which operation is limited • Wavelength reuse factor (RUF): • Quantifies the advantage of WR-OBS over a static WRON achieved by using a single wavelength for multiple end-to-end connections • Utilization: • The efficiency with which any one lightpath can be used • Network performance: • Product of wavelength reuse factor and utilization • Provides means for optimization of operational parameters • Effect on network performance of: • Round trip time (network diameter) (10ms equiv. 1500km) • Edge (aggregation) delay (Determined by required QoS) • Ratio of core bit rate to input bit rate

5. Summary of WR-OBS Performance WR-OBS WRON Network Performance = RUF • Utilization • Wavelength idle time (tRTT) induced by connection setup limits utilization • Wavelength reuse (RUF) can cancel out the effect of this • E.g. Consider edge delay 50ms, with bcore/bin=10, tRTT=10ms gives Utilization=33% and RUF=3.33