Synchronous Optical Networking (SONET) defines optical signals and a synchronous frame structure for multiplexed digital traffic that speeds usually range from 51 Mbps to 40 Gbps. It is a standard for synchronous data transmission on optical media firstly implemented by American National Standards Institute (ANSI). The equivalent of SONET is synchronous digital hierarchy (SDH) that is generally accepted everywhere else in the world. That is why the term “SONET/SDH” is widely used when referring to SONET. SONET is an intelligent system that provides advanced network management and a standard optical interface. Specified in the Broadband ISDN (B-ISDN) standard, SONET backbones are widely used to aggregate T1 and T3 lines.
The line rates for different levels of SONET/SDH signals are shown as following:
SONET was originally designed for the public telephone network. But today, the increased configuration flexibility and bandwidth availability of SONET possesses provide significant advantages over the older telecommunication systems and make it appealing on the Internet.
Reducing the equipment requirements and increasing the network reliability
Provision of overhead and payload bytes – the overhead bytes permit management of the payload bytes on an individual basis and facilitate centralized fault sectionalization
Definition of a synchronous multiplexing format for carrying lower level digital signals and a synchronous structure that greatly simplifies the interface to digital switches, digital cross-connect switches, and add-drop multiplexers
SONET defines clear interoperability standards between different vendors’ products
Definition of a flexible architecture capable of accommodating future applications, with a variety of transmission rates
SONET includes built-in support for ease of management and maintenance