1. (Slide set by Norvald Stol/Steinar Bjørnstad
2013)

2. Outline
Introduction
Enhancements to signaling - Hierarchical LSP setup - The suggested label - Bidirectional LSP setup - Notify messages
GMPLS protection and Restoration techniques - Protection mechanisms (Span/Path protection) - Restoration mechanisms
Conclusions

3. Introduction
IP -> MPLS => Datagram to Virtual Connection (VC) (point-to-point)
Explicitly routed label switched paths (LSPs) established before information transport – independent of actual routing paradigm
Label swapping used as forwarding paradigm
Forwarding equivalence classes (FECs)
Label hierarchy / Label stacking

4. Introduction (2)
Constraint based routing - traffic engineering (QoS differentiation) - fast reroute (after failure) - diversity routing (disjoint alternative paths for protection)
Routing protocols (e.g. OSPF) must exchange sufficient information for ”constraint”
Resource reservation protocol with traffic engineering (RSVP-TE) is used to establish LSP/label forwarding states along path. (The alternative CR-LDP is not used any more)

5. Introduction (3) Generalized MPLS:
Extensions to handle e.g. optical network resources (OXC’s) (e.g. extensions of OSPF, RSVP-TE).
Common control plane for packet and optical network
New Link Management Protocol (LMP) for optical links.
Support for (label) switching in time, wavelength and space domains – and a label hierarchy.
Additional functionality to handle bidirectional links and protection/restoration.

6. RSVP-TE and OSPF enhancements
RSVP-TE (CR-LDP)
Initiate optical channel trails
For optical networks and other connection oriented networks
OSPF (IS-IS)
Advertise availability of resources
Bandwidth of wavelengths
Interface types
Other network attributes and constraints

7. Enhancements to signaling
Control plane may be physically diverse from the data plane.
Hierarchical LSPs  (Study the example in the article to see what establishing a new LSP may entail, start with LSP1)
The suggested label:
An upstream node suggests an optimal label (fast)
May be overridden by its downstream node (slower)
- In optical networks with limited wavelength conversion
Suggested wavelength (-label) to use is very useful

9. Enhancements to signaling (2)
Bidirectional LSP setup (New in GMPLS):
Bidirectional optical LSPs (lightpaths) are important for network operators
Fate sharing
Protection and restoration
Same QoS in both directions, same resource demands
Problems with two independent LSPs in MPLS:
Additional delay in set-up (problem in protection)
Race conditions for scarce resources => lower probability of success for both directions simultaneously
Twice the control overhead
In GMPLS: Single set of Path/Request and Resv/Mapping messages used to establish LSPs in both directions at once.

10. Enhancements to signaling (3)
Notify messages:
Added to RSVP-TE for GMPLS
Provides a mechanism for informing nonadjacent nodes of LSP-related failures.
Inform nodes responsible for restoring connection
Avoid processing in intermediate nodes
Speed up
Failure detection and reaction
Re-establishment of normal operation

11. GMPLS Protection and Restoration
Four primary steps of fault management:
Detection - should be handled at layer closest to failure, i.e. optical layer. E.g. ”Loss-of-light” (LOL), Bit Error Ratio, ..
Localization - requires communication between nodes. LMP includes procedure for fault localization.
Channel fail message over separate control channel
Notification - Notify message added to RSVP-TE signaling
Mitigation
“Repairing the failure”

12. GMPLS Protection and Restoration (2)
Path switching (End-to-end)
Failures addressed at path end-points
Line switching (local)
Action at intermediate transit nodes where the failure is detected
Prot and rest. Terms not precisely defined: In practice used for fault handling in different time frames.
”Protection”
Fast
usually pre-allocated resources to handle failures quickly,
e.g. SDH/SONET: 50 ms – 100% extra resources and simultaneous transmission. (1+1 protection)

13. GMPLS Restoration When fault is handled after a failure has occurred
Dynamic resource allocation
Usually at least one order of magnitude higher delay than protection
Different levels of ”preparedness”
Pre-calculated routes or not;
Some resources reserved or not

14. GMPLS Protection and Restoration (3)
Protection mechanisms:
1+1 protection: simultaneous transmission of data on two different paths.
M:N protection: M preallocated back-up paths shared by N connections. (1:N is most usual; 1:1 also relevant).
Span protection – between adjacent nodes (NB! Avoid ”fate sharing”):

15. GMPLS Protection and Restoration (4)
1+1 Path protection (disjoint paths):
For M:N Path protection: back-up paths may be used for lower priority traffic in normal operation – preemption (Supported by GMPLS)

16. GMPLS Protection and Restoration (5)
Restoration mechanisms:
Alternative paths may be computed beforehand, but resources are seldom allocated before they are needed.

17. Conclusion
GMPLS is a good idea and do have a lot of nice functionality to handle the networks of the future!