Joint-layer restoration in packet-over-optical networks
A joint “packet-optical” layer restoration mechanism protects against single, packet-layer router failures by managing network resources from both the packet layer and the optical transport layer in a synergistic manner. It reuses packet-layer router service-ports and/or transport-layer service wavelengths associated with optical switch-ports instead of reserving additional standby packet-layer router service-ports. It can reuse resources from primary paths that are unaffected by router failures and paths that exist for link-failure protection at the optical layer. Embodiments feature a modified node structure that includes both an IP router and a dynamically reconfigurable OXC, which dynamically establishes connectivity between IP-router ports and transport-layer optical fibers. The joint-layer router provides fine-granularity grooming at the IP layer and full-fledged wavelength networking via dynamic wavelength switching and/or wavelength translation at the optical layer. The latter can change the wavelength cross-connections on-demand to perform restoration or to modify the connectivity between IP routers in the network.
1. A method for restoring service after a failure in a multi-layer network capable of operating at two or more different network layers, the network comprising a plurality of nodes, at least one node capable of operating at more than one network layer, the method comprising the steps of:
detecting the failure; and
modifying the operations of one or more of the nodes at two or more different network layers to restore at least some portion of the service affected by the failure by routing around the failure, wherein:
the multi-layer network is a packet-over-optical network having a packet layer and an optical layer;
one or more nodes operate at both the packet and optical layers;
each node operating at both the packet and optical layers comprises an optical cross-connect (OXC) and a packet router;
the step of modifying the node operations comprises the steps of:
modifying optical-layer processing of at least one of the OXCs; and
modifying packet-layer processing of at least one of the packet routers;
prior to the failure, first and second packet streams are transmitted within a single optical channel to a transit packet router that demultiplexes the single optical channel for further transmission of each packet stream within a different optical channel; and
when the failure is a failure of the transit packet router, the step of modifying the node operations comprises the steps of:
modifying the packet-layer processing of an other packet router to cause that other packet router to generate two different optical channels for the first and second packet streams; and
modifying the optical-layer processing of one or more OXCs to route the two different optical channels.
2. The invention of claim 1 , wherein the one or more OXCs comprises an OXC that is part of the node having the failed transit packet router.
3. The invention of claim 1 , wherein the step of modifying the operations of one or more of the nodes comprises the step of modifying node operations to use network resources already reserved for pure single-layer service restoration.
4. The invention of claim 3 , wherein the pure single-layer failure recovery is pure optical-layer service restoration.
5. The invention of claim 4 , wherein the modifying is a function of a solution to a mixed-integer optimization problem.
6. The invention of claim 5 , wherein the optimization problem includes at least one of the variables: number of IP ports, number of smart optical ports, and number of optical channels.
7. A multi-layer network capable of operating a two or more different network layers, the network comprising a plurality of nodes, at least one node capable of operating at more than one network layer, wherein the network is adapted to:
detect a failure; and
modify the operations of one or more of the nodes at two or more different network layers to restore at least some portion of the service affected by the failure by routing around the failure, wherein:
the multi-layer network is a packet-over-optical network having a packet layer and an optical layer;
one or more nodes are adapted to operate at both the packet and optical layers,
each node adapted to operate at both the packet and optical layers comprises an optical cross-connect (OXC) and a packet router;
the node operations are modified by modifying optical-layer processing of at least one of the OXCs and modifying packet-layer processing of at least one of the packet routers;
prior to the failure, first and second packet streams are transmitted within a single optical channel to a transit packet router that demultiplexes the single optical channel for further transmission of each packet stream within a different optical channel; and
when the failure is a failure of the transit packet router, the node operations are modified by:
modifying the packet-layer processing of an other packet router to cause that other packet router to generate two different optical channels for the first and second packet streams; and
modifying the optical-layer processing of one or more OXCs to route the two different optical channels.
8. The invention of claim 7 , wherein the one or more OXCs comprises an OXC that is part of the node having the failed transit packet router.
9. The invention of claim 7 , wherein the modification of the node operations results in the reuse of optical wavelengths that were reserved for link or path restoration at the optical layer.
10. The invention of claim 7 , wherein the node operations are modified to use network resources already reserved for pure single-layer service restoration.
11. The invention of claim 10 , wherein the pure single-layer failure recovery is pure optical-layer service restoration.
12. The invention of claim 11 , wherein the network resources include at least one of optical-layer optical channels and packet-layer ports.
13. A first node for a multi-layer network, the network being capable of operating at two or more different network layers, the network comprising a plurality of nodes, at least one node capable of operating at more than one network layer, wherein the network is adapted to:
detect the failure; and
modify the operations of one or more of the nodes at two or more different network layers to restore at least some portion of the service affected by the failure by routing around the failure, wherein:
the multi-layer network is a packet-over-optical network having a packet layer and an optical layer;
one or more nodes are adapted to operate at both the packet and optical layers,
each node adapted to operate at both the packet and optical layers comprises an optical cross-connect (OXC) and a packet router;
the node operations are modified by modifying optical-layer processing of at least one of the OXCs and modifying packet-layer processing of at least one of the packet routers;
prior to the failure, first and second packet streams are transmitted within a single optical channel to a transit packet router that demultiplexes the single optical channel for further transmission of each packet stream within a different optical channel; and
when the failure is a failure of the transit packet router, the node operations are modified by:
modifying the packet-layer processing of an other packet router to cause that other packet router to generate two different optical channels for the first and second packet streams; and
modifying the optical-layer processing of one or more OXCs to route the two different optical channels.
14. The invention of claim 13 , wherein the first node is the at least one node.
15. The invention of claim 14 , wherein the first node comprises an optical cross-connect (OXC) and a packet router.
16. An apparatus for restoring service after a failure in a multi-layer network capable of operating at two or more different network layers, the network comprising a plurality of nodes, at least one node capable of operating at more than one network layer, the apparatus comprising:
means for detecting the failure; and
means for modifying the operations of one or more of the nodes at two or more different network layers to restore at least some portion of the service affected by the failure by routing round the failure, wherein:
the multi-layer network is a packet-over-optical network having a packet layer and an optical layer;
one or more nodes operate at both the packet and optical layers;
each node operating at both the packet and optical layers comprises an optical cross-connect (OXC) and a packet router;
the means for modifying the node operations comprises:
means for modifying optical-layer processing of at least one of the OXCs; and
means for modifying packet-layer processing of at least one of the packet routers;
prior to the failure, first and second packet streams are transmitted within a single optical channel to a transit packet router that demultiplexes the single optical channel for further transmission of each packet stream within a different optical channel; and
when the failure is a failure of the transit packet router, the means for modifying the node operations:
modifies the packet-layer processing of an other packet router to cause that other packet router to generate two different optical channels for the first and second packet streams; and
modifies the optical-layer processing of one or more OXCs to route the two different optical channels.
17. The invention of claim 1 , wherein, prior to the failure, the first and second packet streams share a single wavelength in the single optical channel.
18. The invention of claim 7 , wherein, prior to the failure, the first and second packet streams share a single wavelength in the single optical channel.
19. The invention of claim 13 , wherein, prior to the failure, the first and second packet streams share a single wavelength in the single optical channel.
20. The invention of claim 16 , wherein, prior to the failure, the first and second packet streams share a single wavelength in the single optical channel.