Previous research has demonstrated that in a single IP-over-optical burst switched WDM (OBSWDM) node, higher-priority bursts can be successfully isolated from lower-priority bursts according to a certain user-defined isolation degree. This is achieved by allocating longer offset times (i.e., the time between the arrival of the control packet and the burst) to higher-priority bursts where the longer the offset time, the higher the degree of isolation. However, this creates a catch-22 situation in which quality of service (QoS) is achieved at the expense of a serious degradation in system performance. We present what we believe is a novel dual control-packet OBS system that aims to reduce the loss probability of the single control-packet OBS system owing to priority definitions. The dual control-packet scheme maintains the same QoS isolation degree as the single control-packet scheme but with a much reduced drop probability for lower-priority packets. Under 75% loading conditions, the drop probability for low-priority packets in the dual control QoS scheme ranges from 10 to 5 times lower compared with the single control-packet scheme depending on the situation and the presence of fiber delay lines (FDLs). The dual control-packet system is also shown to exhibit a smaller complexity measure compared with the single control-packet system for moderate loading conditions.
© 2004 Optical Society of AmericaPDF Article