Physical Layer
| This section requires expansion. |
The physical layer refers to the first layer in the OSI networking model. The ATM and SDH layers are the regenerator section level, digital line level, transmission path level, virtual path level, and virtual channel level. The physical layer is modeled on three major entities: transmission path, digital line and the regenerator section. The regenerator section refers to the section and photonic layers. The photonic layer is the lowest SONET layer and it is responsible for transmitting the bits to the physical medium. The section layer is responsible for generating the proper STS-N frames which are to be transmitted across the physical medium. It deals with issues such as proper framing, error monitoring, section maintenance, and orderwire. The line layer ensures reliable transport of the payload and overhead generated by the path layer. It provides synchronization and multiplexing for multiple paths. It modifies overhead bits relating to quality control. The path layer is SONET's highest level layer. It takes data to be transmitted and transforms them into signals required by the line layer, and adds or modifies the path overhead bits for performance monitoring and protection switching.
Read more about this topic: Synchronous Optical Networking
Famous quotes containing the words physical and/or layer:
“... life is moral responsibility. Life is several other things, we do not deny. It is beauty, it is joy, it is tragedy, it is comedy, it is psychical and physical pleasure, it is the interplay of a thousand rude or delicate motions and emotions, it is the grimmest and the merriest motley of phantasmagoria that could appeal to the gravest or the maddest brush ever put to palette; but it is steadily and sturdily and always moral responsibility.”
—Elizabeth Stuart Phelps (1844–1911)
“The writer in me can look as far as an African-American woman and stop. Often that writer looks through the African-American woman. Race is a layer of being, but not a culmination.”
—Thylias Moss, African American poet. As quoted in the Wall Street Journal (May 12, 1994)