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SONET is a Synchronous Optical Network, which is standard for connecting fiber-optic transmission systems. This is proposed by Bellcore in the middle of 1980s and is now an ANSI standard.

Sonet defines interface standards at every physical layer of the OSI seven-layer model. The standard defines a hierarchy of interface rates which allows data stream at different rates to be multiplexed. SONET establishes Optical Carrier levels from 51.8 Mbps to 9.95 GBPS. Prior rate standard used by different countries specified which are not compatible for multiplexing. With the help of SONET communication carriers throughout the world can interconnect their existing digital carrier and fiber optic systems.

SONET was originally designed for the public telephone network. Fiber optic cabling already prevailed for long distance voice traffic transmissions, but the existing networks proved unnecessarily expensive to build and difficult to extend for long haul data and video traffic.

SONET is the technology which transmits data at the speed between 155 megabits per seconds and 2.5 gigabits per seconds. To build these high-bandwidth data stream, it multiplexes the channel together having the bandwidth as low as 64 kilobits per seconds into data frames send at fixed intervals. While comparing the Ethernet cabling which spans distance up to 100 meters i.e. 328 feet, SONET fiber technology can run much further. The most interesting characteristics of the SONET is that it supports the ring topology. The figure below is the example of the ring topology the SONET supports.

From the above figure we can find out that the one piece of fiber the working ring handles all the data traffic while the other piece of fiber the protection ring remains standby. If the working ring fails, SONET includes the capability to automatically detect the failure and transfer control to the protection ring in a very short time period some time even in fraction of a second. Due to this reason SONET can be described as a self-healing network technology. As SONET can carry very karge amount of traffic, it would seem on the surface to be an ideal technology for future voice and data broadband networks. SONET competes with several other viable technologies including ATM and Gigabit Ethernet for this role. Due to all these features SONET can be used to extend to reach of fiber channel data center protocol for international data traffic.