G-MPLS mesh protection sans penalties

To capitalize on these benefits, one must acknowledge the barriers to deployment of G-MPLS-enabled solutions. The current standards tracks for G-MPLS are making solid progress but are in the early phases of development. Network-based control plane intelligence turns the current service-provider management paradigm upside down. Significant effort will be required to create a secure operational model for service creation delivered by the interaction of the control and management planes. The G-MPLS-enabled solutions will require simplification of their perceived and real operational complexities from a provisioning, fault-isolation and performance perspective. SONET/SDH fault detection (1+1 Link Access Protocols for SDH or LAPS, Unidirectional Path-Switched Ring or UPSR) must also be combined efficiently with G-MPLS path-restoration and equipment-protection schemes to provide a fault-tolerant environment.

To provide robust protection and restoration capabilities, one must have a flexible set of Sonet 1+1 LAPS, UPSR and Path protection mechanisms combined with G-MPLS path signaling based upon RSVP protocols. Fault detection and isolation are typically handled by transport plane monitoring of Sonet and equipment alarms. The third phase of G-MPLS protection mechanisms is failure notification and may be signaled via RSVP or transport plane notification messages or both. The protection path may be already established with a protection mode when it is created to enhance recovery times. Alternatively, the protection path is not created until failure notification and does not gain the benefit of the underlying Sonet protection mechanisms.

Speeding G-MPLS recovery

G-MPLS-enabled paths may be provisioned as shared-risk link groups (SRLG) to allow the traffic to share the desired protection and routing diversity. Combining multiple paths into an SRLG will reduce the number of paths that must be signaled in the event of a particular failure scenario. A primary factor in recovery time is path creation based upon signaling messages that may be shared across the creation of a G-MPLS protection group, or SRLG.

For service providers to deploy intelligent transport infrastructure that independently makes the decision where paths should be routed takes a leap of faith. The business benefits of deployment must be clearly understood in detail before that leap is made. For a G-MPLS-enabled network to fully demonstrate its benefits, equipment must support the necessary interactions across any of the multivendor divides. Network migrations will have to ensure zero disruption to existing services and operational capabilities. We should expect much more experimentation by the service providers as the technology matures to ensure that the vendors have got it right.

GMPLS signaling is shown across existing optical network signaling across existing Sonet infrastructure.

So where initially will we see this technology being deployed and by whom? G-MPLS-enabled transport infrastructure is inherently suited for data-networking applications and specifically for leased lines carrying IP traffic. Many data services can accommodate larger restoration and recovery times, and single path failures do not have an impact on the ability to meet the desired SLAs. Service providers that wish to enhance their in-territory service offers while significantly improving their operational cost model will be the early adopters of this technology. The faster turn-up of services and reduced operational cost of this type of equipment will also be a strong factor for service providers that are considering expansion to compete in new territories.

Traditional Sonet/SDH architectures have served carriers well for decades, but with the growth in demand for high-capacity circuits and the drop in bandwidth pricing driven by competitive pressures, carriers will move to G-MPLS to improve their cost models — as long as they can be convinced that the network's survivability and recovery times won't suffer unduly. By employing G-MPLS protection groups, carriers can greatly streamline their network operational models, optimize bandwidth and speed provisioning without risking a network meltdown.

Ian Hood is senior product line manager and Colm O'Brien is director, product line management, at Mahi Networks Inc. (Petaluma, Calif.).