ency, and performance. GFP is an optical switch interface that lets companies use their SONET facilities more effectively. GFP can be deployed at the edge of a leased SONET network and can then be used to allocate portions of the circuit using virtual concatenation (VCAT). VCAT extends the utility of SONET transport by letting bandwidth be allocated in multiples of 50 Mbps, thus allocating only the bandwidth required by a particular application. In combination with VCAT, the cost effectiveness of GFP is signifi- cantly improved. Enterprises can transport data using optimal band- width allocations, and service providers can maximize the efficiency of their overall network. Furthermore, enterprises can deploy private stor- age over SONET solutions by purchasing storage-specific equipment for SONET and leasing SONET circuits from a service provider. SONET Summary Clearly, SONET is a complex and highly capable standard designed to pro- vide high-bandwidth transport for legacy and new protocol types alike. The overhead that it provisions has the ability to deliver a remarkable col- lection of network management, monitoring, and transport granularity. The European Synchronous Digital Hierarchy, or SDH, shares many of SONET's characteristics, as we will now see. SONET, you will recall, is a limited North American standard, for the most part. SDH, on the other hand, provides high-bandwidth transport for the rest of the world. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Telephony Telephony Most books on SONET and SDH cite a common list of reasons for their proliferation, including a recognition of the importance of the global marketplace and a desire on the parts of manufacturers, there- fore, to provide devices that will operate in both SONET and SDH envi- ronments; the global expansion of ring architectures; a greater focus on network managemen