Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Work on the standard began in 1980 at Bell Labs and was formally standardized in 1988 in the CCITT "Red Book". By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use. ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance.
Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diodes (LEDs). At low transmission rates data can also be transferred via an electrical interface. The method was developed to replace the plesiochronous digital hierarchy (PDH) system for transporting large amounts of telephone calls and data traffic over the same fiber without the problems of synchronization.
The Primary Rate Interface (PRI) is a telecommunications interface standard used on an Integrated Services Digital Network (ISDN) for carrying multiple DS0 voice and data transmissions between the network and a user.
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. It can be used when the bit rate of the transmission medium exceeds that of the signal to be transmitted. This form of signal multiplexing was developed in telecommunications for telegraphy systems in the late 19th century, but found its most common application in digital telephony in the second half of the 20th century.
In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths of laser light. This technique enables bidirectional communications over a single strand of fiber as well as multiplication of capacity.
Signalling System No. 7 (SS7) is a set of telephony signaling protocols developed in the 1970s, which is used to set up and tear down telephone calls in most parts of the world-wide public switched telephone network (PSTN). The protocol also performs number translation, local number portability, prepaid billing, Short Message Service (SMS), and other services.
The public switched telephone network (PSTN) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony. The PSTN consists of telephone lines, fiber-optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables interconnected by switching centers, such as central offices, network tandems, and international gateways, which allow telephone users to communicate with each other.
The Communications Assistance for Law Enforcement Act (CALEA), also known as the "Digital Telephony Act," is a United States wiretapping law passed in 1994, during the presidency of Bill Clinton.
Lawful interception (LI) refers to the facilities in telecommunications and telephone networks that allow law enforcement agencies with court orders or other legal authorization to selectively wiretap individual subscribers. Most countries require licensed telecommunications operators to provide their networks with Legal Interception gateways and nodes for the interception of communications. The interfaces of these gateways have been standardized by telecommunication standardization organizations. As with many law enforcement tools, LI systems may be subverted for illicit purposes.
Many services running on modern digital telecommunications networks require accurate synchronization for correct operation. For example, if telephone exchanges are not synchronized, then bit slips will occur and degrade performance. Telecommunication networks rely on the use of highly accurate primary reference clocks which are distributed network-wide using synchronization links and synchronization supply units.
Virtual concatenation (VCAT) is an inverse multiplexing technique creating a large capacity payload container distributed over multiple smaller capacity TDM signals. These signals may be transported or routed independently. Virtual concatenation has been defined for SONET/SDH, OTN and PDH path signals.
A digital cross-connect system is a piece of circuit-switched network equipment, used in telecommunications networks, that allows lower-level TDM bit streams, such as DS0 bit streams, to be rearranged and interconnected among higher-level TDM signals, such as DS1 bit streams. DCS units are available that operate on both older T-carrier/E-carrier bit streams, as well as newer SONET/SDH bit streams.
A network monitoring interface card or NMIC is similar to a network card (NIC). However, unlike a standard network card, an NMIC is designed to passively listen on a network. At a functional level, an NMIC may differ from a NIC, in that the NMIC may not have a MAC address, may lack the ability to transmit and may not announce its presence on a network. Advanced NMICs have features that include an ability to offload CPU intensive processing from a system's CPU, accurate time measurement, traffic filtering, and an ability to perform other application specific processing.
Ethernet over PDH or EoPDH is one of many techniques that provided Ethernet connectivity over non-Ethernet networks. Specifically, EoPDH is a standardized methodology for transporting native Ethernet frames over the existing telecommunications copper infrastructure by leveraging the established PDH transport technology. EoPDH is one of several Ethernet transport technologies that enables Telecommunication Service Providers to offer "Carrier Ethernet" services. Also commonly used as a means of connecting businesses to a Metro Ethernet network.
Ethernet over PDH over SONET/SDH (EoPoS) is one of many techniques that provided Ethernet connectivity over non-Ethernet networks. EoPoS is a standardized method for transporting native Ethernet frames over the existing telecommunications optical infrastructure use both the established Plesiochronous Digital Hierarchy (PDH) and Synchronous Digital Hierarchy (SONET/SDH) transport technologies.
Telesoft Technologies is a privately held UK based technology company which develops cyber security, telecoms mobile products and services and government infrastructure. Telesoft has operations in USA, UK and India.
In telecommunications, subnetwork connection protection (SNCP), is a type of protection mechanism associated with synchronous optical networks such as synchronous digital hierarchy (SDH).
Synchronous Ethernet (SyncE) is an ITU-T standard for computer networking that facilitates the transference of clock signals over the Ethernet physical layer. This signal can then be made traceable to an external clock.
Aculab is a privately held, UK-based limited company that was founded in 1978. It is a designer, developer and manufacturer that specialises in providing API-driven, enabling technology sub-systems for telecommunications related OEM products such as are used in fixed line PSTN, wireless and VoIP networks. Aculab's products are sold worldwide, primarily through direct sales and also via the reseller channel. Aculab's headquarters and R&D facilities are located in Milton Keynes, UK. It has a branch office in Norwood, Massachusetts, USA.
IP over DWDM (IPoDWDM) is a technology used in telecommunications networks to integrate IP routers and network switches in the OTN . A true IPoDWDM solution is implemented only when the IP Routers and Switches support ITU-T G.709. In this way IP devices can monitor the optical path and implement the transport functionality as FEC specified by ITU-T G.709/Y.1331 or Super FEC functionality defined in ITU-T G.975.1.