The effectiveness of protection strategies that use a photonic layer and a synchronous digital hierarchy (SDH) layer is experimentally investigated in an IP-over-optical overlay model. With SDH-layer protection, the path alarm-indication signal that reports upstream failures is able to hold the link states of customer edge (CE) routers and establish interworking operation between the SDH layer and the IP layer. However, photonic-layer protection requires guard-time setting for CE routers in order to avoid IP-layer restoration. When we apply a guard time that is longer than the photonic-layer protection time, interworking operation can be achieved. On the basis of these experimental results on the fault-recovery operation, the appropriate guard-time setting for photonic-layer protection is discussed.
© 2003 Optical Society of AmericaPDF Article