Optical Networks – Some research topics

(Part 2) Optical Networks – Some research topics Topics to be covered • Fault tolerance • Impairment aware network design • OFDM networks Fault-tolerance in Optical Networks
Faults in Optical Networks  Link failures the most common type of fault, where the fiber constituting a link between two nodes in the network does not permit data transmission.     Node failures Channel failures Software failures Most papers assume single fault scenario. Fault-tolerance in Optical Networks
Reasons behind faults in optical layer  Fiber cut  Noise introduced by optical signal regenerators and amplifiers  Cable inside a site may get disconnected
Importance of Fault management in optical networks  Large amount of traffic carried by optical channels  Each fiber carries many channels, each channel having a capacity of 2.5 to 40 GB/sec  Failure may lead to huge data loss Fault-tolerance in Optical Networks
Categorization of fault management schemes Figure 1 Fault-tolerance in Optical Networks
Protection scheme  Recovery scheme determined at design time  Resources are reserved for each possible failure (link or path).  Faster recovery time and guaranteed recovery
Restoration scheme  Recovery scheme determined after the occurrence of fault  Dynamically search for backup path and available wavelength after failure occurrence.  Efficient in utilizing capacity Fault-tolerance in Optical Networks
Link protection – backup path reserved around each link Primary path: N8N4N6N1 N1 C3 C3 C3 N2 N3 The faulty edge N4N6 is replaced by an alternate route N4N7N6. N4 N5 Backup path: N8N4N7N6N1 N8 Primary path X C3 C3 N6 N7 C3 C3 Backup path Figure 2: Link protection scheme Fault-tolerance in Optical Networks
Path Protection  In the case of a fault, for each primary lightpath using the faulty component, the corresponding backup lightpath will be set up.  All data carried by each primary lightpath affected by the fault will be switched over to the corresponding backup lightpath.  Primary and backup paths must be edge-disjoint. Fault-tolerance in Optical Networks
Path Protection – backup path reserved on a end-to-end basis N1 N2 N3 N4 N5 C3 C3 C1 C2 C1 N6 N7 N8 Primary path C2 Backup path Figure 3: Path protection scheme Fault-tolerance in Optical Networks
Dedicated path protection Dedicated Path Protection The channel used by a backup lightpath is always reserved for a single primary lightpath. Primary 2 3 1 4 6 5 Backup Figure 4: 1:1 Protection