The GMPLS Control Plane

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To control components outside the standard data packet, a separate control plane was developed for GMPLS. This control plane is the true magic of GMPLS. It allows for the total control of network devices.

The GMPLS control plane provides for six top-level functions:

• Discovery of neighborhood resources

• Dissemination of link status

• Topology link-state management

• Path management and control

• Link management

• Link protection

Neighbor Discovery

The link manager, all switches, and all multiplexers must know every component of a network—all routers and all active components. GMPLS uses a new protocol, LMP, to discover these devices and to negotiate functions (see Figure 6.8).

Figure 6.8: Neighbor Discovery

Dissemination of Link Status

It does no good just to know what hardware is out there if the link is down or having problems. To disseminate this information, a routing protocol must be used. For GMPLS, both the OSPF and the IS-IS protocols are being modified to support this function (see Figure 6.9).

Figure 6.9: Link Status Distribution

Typology State Management

Link-state routing protocols, such as OSPF and IS-IS, can be used to control and manage the link state typology (see Figure 6.10).

Figure 6.10: Topology Information

Path Management

In previous chapters, we determined that MPLS can use RSVP to establish a link from end to end. However, if MPLS data traverses telecom networks, other protocols such as UNI, PNNI, or SS7 must be implemented. Path management can be a real challenge because several standards organizations are involved in the process. Currently, the IETF is working on modifications to RSVP and Label Distribution Protocol (LDP) to extend those protocols to allow for GMPLS path management and control (see Figure 6.11).

Figure 6.11: Path and Link Management Control

Link Management

In MPLS, the LSP is used to establish and tear down links and aggregate links. In GMPLS, the ability to establish and aggregate optical channels is required. LMP extends the MPLS functions into an optical plane where link building improves scalability (see Figure 6.12).

Figure 6.12: Link Management

Protection and Recovery

Intelligent optical networking allows inflexible optical networks to interact with each other. With GMPLS, instead of having one ring with a backup ring for protection, the network creates a true mesh that allows for several different paths (see Figure 6.13). Optical networking can go from a one-to-one protection method to a one-to-many protection method.

Figure 6.13: SONET Matrix

Checkpoint 

Answer the following true/false questions.

1. Link Management Protocol (LMP) extends MPLS functions into an optical plane.

2. GMPLS could use OSPF and IS-IS for link-state typology purposes.

3. RSVP and LDP are being modified by the IETF for GMPLS path management.

4. GMPLS was developed independently of all other MPLS protocols.

Answers: 1. True; 2. true; 3. true; 4. false.

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