Introduction to MPLS Network Reliance and Recovery

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Around the country, you will find highways under repair. A good many of these highways have bypass roads or detours to allow traffic to keep moving around the construction or problem areas. Traffic rerouting is a real challenge for highway departments, but they have learned that establishing detour paths before construction begins is the only way to keep traffic moving (see Figure 4.1).

Figure 4.1: Traffic Detour

The commitment to keep traffic moving has been a staple of philosophy in voice and telephone communications since their inception. In a telephony network, not only are detour paths assigned before a circuit is disconnected (make before break), but the backup or detour paths must be of at least the same quality as the links that are to be taken down for repair. These paths are said to be prequalified (tested) and preprovisioned (already in place).

Historically in IP networking, packets found their own detours around problem areas; there were no preprovisioned bypass roads. The packets were in no particular hurry to get to their destinations. However, with the convergence of voice communications onto data networks, the packets need these bypass roads to be preprovisioned so that they do not have to slow down for the equivalents of construction or road failures.

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