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4. Carrier Networks > Technologies Used in Carrier Networks
Technologies Used in Carrier Networks
Carriers use a mix of Synchronous Optical Network (SONET), Gigabit Ethernet, and older technologies to support legacy networks based on Time-Division Multiplexing (TDM) (T1 and T3) as well as analog circuit-switched voice. Newer networks deploy Optical Transport Network (OTN)–compliant gear athat can efficiently carry both SONET for legacy circuit-switched voice and Gigabit Ethernet for IP data and VoIP traffic.
Note
Legacy is a term used to describe networks and equipment that are based on older technologies such as TDM and analog voice service.
Circuit-Switched Voice and T1/T3 over Fiber
SONET is a North American standard for multiplexing streams of traffic onto fiberoptic cabling and transporting it at Optical Carrier (OC) speeds. SONET was developed to aggregate (multiplex) and carry TDM and circuit-switched voice traffic from multiple sources. The international version of SONET is Synchronous Digital Hierarchy (SDH). SONET SDH carries traffic at Synchronous Transfer Mode (STM) rates. Traffic carried between cities in Europe or in undersea cables is often referred to as being carried at STM-1 (155Mbps) or STM-16 (2.5Gbps) speeds. See Table 4-1 in the “Appendix” section at the end of this chapter for optical carrier and synchronous transfer mode speeds. SONET equipment using STM speeds can communicate with North American–type SONET gear.
