Optical Networking Best Practices Handbook

14.1. SUMMARY

Business continuance and disaster recovery applications rely heavily on network survivability and have become even more important after 9/11. Internet protocol (IP), synchronous optical network/synchronous digital hierarchy (SONET/SDH), and various storage-related protocols such as Fibre Channel continue to be the main client layers of the optical layer. The leading survivability mechanisms are still relatively simple and limited in scope: basically, various forms of dedicated 1 + 1 protection (see Table 14.1 for a summary of the different protection schemes [1]).

Within this context, optical layer protection has been deployed primarily in metro WDM networks serving storage applications. In fact, it is hard to sell a metro WDM system today that does not support various forms of simple optical layer protection. In contrast, long-haul WDM networks have relied primarily on SONET/SDH layer protection, with some rare exceptions [1].

14.1.1. Optical Layer Survivability: Why and Why Not

The main reason for having survivability at the optical layer rather than leaving it to the higher layers has not changed: protection at the optical layer is more cost-effective for high-bandwidth services that lack their own robust protection mechanisms. The obvious candidates here are storage networking protocols, which do not have adequate survivability built in. As a result, these applications rely almost entirely on optical layer protection to handle fiber cuts and failure of the networking ...