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The Direction of the Optical-Networking Market
PDF of this tutorial7. The Competitive Landscape
Carriers have invested heavily in SONET/SDH– and ATM–based transport platforms to enable service delivery to enterprise customers, but these legacy systems are not ideal for the new age of gigabit-speed services. How do these two and other techniques, in comparison to WDM, stack up as the foundation of the emerging services infrastructure?
- SONET/SDH—SONET/SDH is an effective technology for aggregating multiple low-speed (<optical carrier–level 3 [OC–3]) data applications and multiple sites onto a common infrastructure linked out to the wide area. But the cost and reduced performance of protocol-conversion equipment required to convert ESCON applications, for example, to OC–3 or T3 links is prohibitive, and there is no viable SONET service available today for even higher-speed protocols such as 1.062–Gbps fibre channel and FICON.
- ATM—Like SONET/SDH, ATM is suitable for aggregating sub–OC–3 data applications. But ATM solutions offer no interfaces for speeds faster than 622 Mbps, and they are cost prohibitive for a variety of reasons, not least among which is the overhead cell tax (5 bytes per 48-byte payload) that proves costly for file transfer of large data volumes.
- Internet protocol (IP)—Although IP is widely promoted as the single and only protocol for data transfer, the inherent limitations of maximum packet length presently do not enable IP to provide an adequate substitute for ESCON and fibre channel protocols.
WDM, which is high-performance, protocol-transparent, reliable, scalable, and simply installed and managed, is carriers’ most affordable approach for aggregating traffic and penetrating markets immediately with first-class services.
