Synchronous Digital Hierarchy
Synchronous Digital Hierarchy is a standard technology for transmitting data on optical media. This is the equivalent to synchronous Optical Network.
Multi Service Access Node which is also known as multi service access gateway is a device installed in a telephone exchange that connects customers telephone lines to core network. This enables telephone, ISDN and broadband from a single platform.
A digital subscriber line access multiplexer is actually a network device mostly located in the telephone exchange of the telecommunications operators. Using multiplexing technique it connects multiple customer digital subscriber line to high speed digital communications channel.