5ESS Switch
Encyclopedia
The 5ESS Switch is a Class 5 telephone electronic switching system
sold by Alcatel-Lucent
. This digital
central office telephone circuit switching
system is used by many telecommunication
s service provider
s.
(815 Area Code) in 1982, and slowly replaced the 1ESS switch
and other electromechanical and analog systems in the 1980s and 1990s. The 5ESS was also used as a Class 4 telephone switch
or as a mixed Class 4/5 in markets too small for a 4ESS switch
. Approximately half of all U.S. telephone exchange
s are serviced by 5ESS switches. The 5ESS is also exported internationally, and manufactured outside of the U.S. under license.
The development effort for 5ESS reached 5000 employees, producing 100 million lines of code, with 100 million lines of header and makefiles. Evolution of the system took place over 20 years, while three releases were often being developed simultaneously (each taking about 3 years to develop).
A 5ESS-2000 version, introduced in the 1990s, increased the capacity of the SM, with more peripheral modules and more optical links per SM to the CM (see below).
Lucent Technologies (now part of Alcatel-Lucent
) was formerly the AT&T Network Systems division of AT&T, which in turn was formerly known as Western Electric
. The 5ESS came to market as the Western Electric No. 5 ESS, later 5ESS, 5ESS-2000, 5E-XC and is currently marketed as the Alcatel-Lucent 5ESS.
Power for all circuitry is distributed as −48VDC (nominal) and converted to logic or telephone voltages as needed by DC to DC converter
s on each shelf of circuit packs.
s or several hundred trunks or mixture thereof. Each has its own processors, also called Module Controllers, which perform most call handling processes
, using their own memory
boards. Originally the peripheral processors were to be Intel 8086
, but those proved inadequate and the system was introduced with Motorola 68000
series processors. The name of the cabinet that houses this equipment was changed at the same time from Interface Module to Switching Module.
Peripheral units are on shelves in the SM. In most exchanges the majority are Line Units (LU) and Digital Line Trunk Units (DLTU). Each SM has Local Digital Service Units (LDSU) to provide various services to lines and trunks in the SM, including tone generation and detection. Global Digital Service Units (GDSU) provide less-frequently used services to the entire exchange. The Time Slot Interchanger (TSI) in the SM uses random-access memory to delay each speech sample to fit into a time slot which will carry its call through the exchange to another or, in some cases, the same SM.
T-carrier
spans are terminated, originally one per card but in later models usually two, in Digital Line Trunk Units (DLTU) which concentrate their DS0 channels into the TSI. These may serve either interoffice trunks or, using Integrated Subscriber Loop Carrier, subscriber lines. Larger DS3 signals can also have their DS0 signals switched in Digital Network Unit SONET
(DNUS) units, without demultiplexing them into DS1
.
SMs have Dual Link Interface (DLI) cards to connect them by multi-mode optical fiber
s to the Communications Modules for time-divided switching to other SMs. These links may be short, for example within the same building, or may connect to SMs in remote locations. Calls among the lines and trunks of a particular SM needn't go through CM, and an SM located remotely can act as distributed switching
, administered from the central AM. Each SM has two Module Controller/Time Slot Interchange (MCTSI) circuits for redundancy.
In contrast to Nortel
's DMS-100
which uses individual line card
s with a codec
, most lines are on two-stage analog space-division concentrators or Line Units, which connect as many as 512 lines, as needed, to the 8 Channel cards that each contain 8 codecs, and to high-level service circuits for ringing and testing. Both stages of concentration are included on the same GDX (Gated Diode Access) board. Each GDX board serves 32 lines, 16 A links and 32 B links. Limited availability
saves money with incompletely filled matrixes. The Line Unit can have up to 16 GDX boards connecting to the channel boards by shared B links, but in offices with heavier traffic for lines a lesser number of GDX boards are equipped.
ISDN lines are served by individual line cards in an ISLU (Integrated Services Line Unit).
Since Line Units handle the high voltages and currents of analog lines, their cards fail at higher rates than ones that handle only computer voltages.
drives that each reside on a card. Tape drives
were originally half inch open reel at 6250 bit
s per inch, which were replaced in the early 1990s with 4 mm Digital Audio Tape
cassettes.
The Administrative Module is built on the 3B21D platform and is used to load software to the many microprocessors throughout the switch and to provide high speed control functions. It provides messaging and interface to control terminals. The AM of a 5ESS consists of the 3B20x or 3B21D processor unit, including I/O, disks, and tape drive units. Once the 3B21D has loaded the software into the 5ESS and the switch is activated, packet switching takes place without further action by the 3B21D. Because the processor mirrors its functions, a failure of one side of the processor will not result in a loss of switching.
CMs perform time-divided switching and are provided in pairs; each module (cabinet) belonging to Office Network and Timing Complex (ONTC) 0 or 1, roughly corresponding to the switch planes of other designs. Each SM has four optical fiber links, two connecting to a CM belonging to ONTC 0 and two to ONTC 1. Each optical link consists of two multimode optical fibers with ST connectors to plug into transceivers plugged into backplane wiring at each end. CMs receive time-multiplexed signals on the receive fiber and send them to the appropriate destination SM on the send fiber.
workstation as its Administrative Module.
) such as the TEST channel and Maintenance channel. Typically provisioning
is done either through a command line interface (CLI) called RCV:APPTEXT, or through the menu-driven RCV:MENU,APPRC program. RCV stands for Recent Change/Verification, and can be accessed through Switching Control Center System
. Most service orders, however, are administered through Recent Change Memory Administration Center (RCMAC).
Electronic switching system
In telecommunications, an electronic switching system is:* A telephone exchange based on the principles of time-division multiplexing of digitized analog signals. An electronic switching system digitizes analog signals from subscriber loops, and interconnects them by assigning the digitized...
sold by Alcatel-Lucent
Alcatel-Lucent
Alcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...
. This digital
Digital
A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...
central office telephone circuit switching
Circuit switching
Circuit switching is a methodology of implementing a telecommunications network in which two network nodes establish a dedicated communications channel through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the...
system is used by many telecommunication
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
s service provider
Service provider
A service provider is an entity that provides services to other entities. Usually, this refers to a business that provides subscription or web service to other businesses or individuals. Examples of these services include Internet access, Mobile phone operators, and web application hosting...
s.
History
The 5ESS Class 5 Switch first appeared in Seneca, IllinoisSeneca, Illinois
Seneca is a village in LaSalle and Grundy counties in the U.S. state of Illinois. The population was 2,371 at the 2010 census.The LaSalle County portion of Seneca is part of the Ottawa–Streator Micropolitan Statistical Area, while the small portion that lies in Grundy County is part of the...
(815 Area Code) in 1982, and slowly replaced the 1ESS switch
1ESS switch
The Number One Electronic Switching System, the first large-scale Stored Program Control telephone exchange or Electronic Switching System in the Bell System, was introduced in Succasunna, New Jersey, in May 1965. The switching fabric was composed of reed matrixes controlled by wire spring relays...
and other electromechanical and analog systems in the 1980s and 1990s. The 5ESS was also used as a Class 4 telephone switch
Class 4 telephone switch
A Class 4, or Tandem, telephone switch is a U.S. telephone company central office telephone exchange used to interconnect local exchange carrier offices for long distance communications in the Public Switched Telephone Network....
or as a mixed Class 4/5 in markets too small for a 4ESS switch
4ESS switch
The 4ESS switch is a Class 4 telephone Electronic Switching System that was the first digital electronic toll switch introduced by Western Electric for long distance switching. It was introduced in 1976 in Chicago, Illinois to replace the 4a crossbar switch. The last of 145 in the AT&T network was...
. Approximately half of all U.S. telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
s are serviced by 5ESS switches. The 5ESS is also exported internationally, and manufactured outside of the U.S. under license.
The development effort for 5ESS reached 5000 employees, producing 100 million lines of code, with 100 million lines of header and makefiles. Evolution of the system took place over 20 years, while three releases were often being developed simultaneously (each taking about 3 years to develop).
A 5ESS-2000 version, introduced in the 1990s, increased the capacity of the SM, with more peripheral modules and more optical links per SM to the CM (see below).
Lucent Technologies (now part of Alcatel-Lucent
Alcatel-Lucent
Alcatel-Lucent is a global telecommunications corporation, headquartered in the 7th arrondissement of Paris, France. It provides telecommunications solutions to service providers, enterprises, and governments around the world, enabling these customers to deliver voice, data, and video services...
) was formerly the AT&T Network Systems division of AT&T, which in turn was formerly known as Western Electric
Western Electric
Western Electric Company was an American electrical engineering company, the manufacturing arm of AT&T from 1881 to 1995. It was the scene of a number of technological innovations and also some seminal developments in industrial management...
. The 5ESS came to market as the Western Electric No. 5 ESS, later 5ESS, 5ESS-2000, 5E-XC and is currently marketed as the Alcatel-Lucent 5ESS.
Architecture
5ESS has three main kinds of Module: AM is Administrative Module, which contains the central computers. CM is Communications Module, which is the central time-divided switch of the system. SM is Switching Module which in most exchanges is the majority of equipment. SM performs multiplexing, analog/digital coding, and other work to interface with the outside world. Each has a controller, a small computer whose CPUs and memories, like most common equipment of the exchange, are duplicated for redundancy. Distributed system lessens the load on the Central Administrative Module (AM) or main computer.Power for all circuitry is distributed as −48VDC (nominal) and converted to logic or telephone voltages as needed by DC to DC converter
DC to DC converter
A DC-to-DC converter is an electronic circuit which converts a source of direct current from one voltage level to another. It is a class of power converter.- Usage :...
s on each shelf of circuit packs.
Switching Module (SM)
Each SM handles several hundred to few thousand telephone lineTelephone line
A telephone line or telephone circuit is a single-user circuit on a telephone communication system...
s or several hundred trunks or mixture thereof. Each has its own processors, also called Module Controllers, which perform most call handling processes
Signalling (telecommunications)
In telecommunication, signaling has the following meanings:*the use of signals for controlling communications...
, using their own memory
Computer memory
In computing, memory refers to the physical devices used to store programs or data on a temporary or permanent basis for use in a computer or other digital electronic device. The term primary memory is used for the information in physical systems which are fast In computing, memory refers to the...
boards. Originally the peripheral processors were to be Intel 8086
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...
, but those proved inadequate and the system was introduced with Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
series processors. The name of the cabinet that houses this equipment was changed at the same time from Interface Module to Switching Module.
Peripheral units are on shelves in the SM. In most exchanges the majority are Line Units (LU) and Digital Line Trunk Units (DLTU). Each SM has Local Digital Service Units (LDSU) to provide various services to lines and trunks in the SM, including tone generation and detection. Global Digital Service Units (GDSU) provide less-frequently used services to the entire exchange. The Time Slot Interchanger (TSI) in the SM uses random-access memory to delay each speech sample to fit into a time slot which will carry its call through the exchange to another or, in some cases, the same SM.
T-carrier
T-carrier
In telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and South Korea....
spans are terminated, originally one per card but in later models usually two, in Digital Line Trunk Units (DLTU) which concentrate their DS0 channels into the TSI. These may serve either interoffice trunks or, using Integrated Subscriber Loop Carrier, subscriber lines. Larger DS3 signals can also have their DS0 signals switched in Digital Network Unit SONET
Sonet
Sonet may refer to:* Sonet Records, European record label* Synchronous optical networking * Saab Sonett...
(DNUS) units, without demultiplexing them into DS1
Digital Signal 1
Digital signal 1 is a T-carrier signaling scheme devised by Bell Labs. DS1 is a widely used standard in telecommunications in North America and Japan to transmit voice and data between devices. E1 is used in place of T1 outside North America, Japan, and South Korea...
.
SMs have Dual Link Interface (DLI) cards to connect them by multi-mode optical fiber
Multi-mode optical fiber
Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus...
s to the Communications Modules for time-divided switching to other SMs. These links may be short, for example within the same building, or may connect to SMs in remote locations. Calls among the lines and trunks of a particular SM needn't go through CM, and an SM located remotely can act as distributed switching
Distributed switching
Distributed switching is an architecture in which multiple processor-controlled switching units are distributed. There is often a hierarchy of switching elements, with a centralized host switch and with remote switches located close to concentrations of users....
, administered from the central AM. Each SM has two Module Controller/Time Slot Interchange (MCTSI) circuits for redundancy.
In contrast to Nortel
Nortel
Nortel Networks Corporation, formerly known as Northern Telecom Limited and sometimes known simply as Nortel, was a multinational telecommunications equipment manufacturer headquartered in Mississauga, Ontario, Canada...
's DMS-100
DMS-100
The DMS-100 Switch is a line of Digital Multiplex System telephone exchange switches manufactured by Nortel Networks.The purpose of the DMS-100 Switch is to provide local service and connections to the PSTN public telephone network. It is designed to deliver services over subscribers' telephone...
which uses individual line card
Line card
A line card or Digital Line Card is a modular electronic circuit on a printed circuit board, the electronic circuits on the card interfacing the telecommunication lines coming from the subscribers to the rest of the telecommunications access network.A line card commonly interfaces the twisted pair...
s with a codec
Codec
A codec is a device or computer program capable of encoding or decoding a digital data stream or signal. The word codec is a portmanteau of "compressor-decompressor" or, more commonly, "coder-decoder"...
, most lines are on two-stage analog space-division concentrators or Line Units, which connect as many as 512 lines, as needed, to the 8 Channel cards that each contain 8 codecs, and to high-level service circuits for ringing and testing. Both stages of concentration are included on the same GDX (Gated Diode Access) board. Each GDX board serves 32 lines, 16 A links and 32 B links. Limited availability
Limited availability
When customers of the public switched telephone network make telephone calls, they commonly make use of a telecommunications network called a switched-circuit network. In a switched-circuit network, devices known as switches are used to connect the caller to the callee...
saves money with incompletely filled matrixes. The Line Unit can have up to 16 GDX boards connecting to the channel boards by shared B links, but in offices with heavier traffic for lines a lesser number of GDX boards are equipped.
ISDN lines are served by individual line cards in an ISLU (Integrated Services Line Unit).
Since Line Units handle the high voltages and currents of analog lines, their cards fail at higher rates than ones that handle only computer voltages.
Administrative Module (AM)
AM is a dual processor mini main frame computer of the AT&T 3B series, running UNIX-RTR. AM contains the hard drives and tape drives used to load and backup the central and peripheral processor software and translations. Disk drives were originally several 300 megabyte SMD multiplatter units in a separate frame. Now they consist of several redundant multi-gigabyte SCSISCSI
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
drives that each reside on a card. Tape drives
Magnetic tape data storage
Magnetic tape data storage uses digital recording on to magnetic tape to store digital information. Modern magnetic tape is most commonly packaged in cartridges and cassettes. The device that performs actual writing or reading of data is a tape drive...
were originally half inch open reel at 6250 bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s per inch, which were replaced in the early 1990s with 4 mm Digital Audio Tape
Digital Audio Tape
Digital Audio Tape is a signal recording and playback medium developed by Sony and introduced in 1987. In appearance it is similar to a compact audio cassette, using 4 mm magnetic tape enclosed in a protective shell, but is roughly half the size at 73 mm × 54 mm × 10.5 mm. As...
cassettes.
The Administrative Module is built on the 3B21D platform and is used to load software to the many microprocessors throughout the switch and to provide high speed control functions. It provides messaging and interface to control terminals. The AM of a 5ESS consists of the 3B20x or 3B21D processor unit, including I/O, disks, and tape drive units. Once the 3B21D has loaded the software into the 5ESS and the switch is activated, packet switching takes place without further action by the 3B21D. Because the processor mirrors its functions, a failure of one side of the processor will not result in a loss of switching.
Communication Module (CM)
The oddly named Communications Modules form the central time switch of the exchange. 5ESS runs on a Time-Space-Time (TST) topology in which the Time-Slot-Interchangers (TSI) in the Switching Modules (SM) assign each phone call to a time slot for routing through the CM.CMs perform time-divided switching and are provided in pairs; each module (cabinet) belonging to Office Network and Timing Complex (ONTC) 0 or 1, roughly corresponding to the switch planes of other designs. Each SM has four optical fiber links, two connecting to a CM belonging to ONTC 0 and two to ONTC 1. Each optical link consists of two multimode optical fibers with ST connectors to plug into transceivers plugged into backplane wiring at each end. CMs receive time-multiplexed signals on the receive fiber and send them to the appropriate destination SM on the send fiber.
Very Compact Digital Exchange
The VCDX (Very Compact Digital eXchange) was marketed to small telephone companies and was used in some instances as a large PBX. It consisted of a single Switching Module, had no Communications Module, and used a Sun MicrosystemsSun Microsystems
Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...
workstation as its Administrative Module.
Signaling
The 5ESS has two different signaling architectures Common Network Interface (CNI) Ring and Packet Switch Unit (PSU).Operations, Administration, Maintenance, and Provisioning
The system is administered through an assortment of teletypewriter "Channels" (also called the system consoleSystem console
The system console, root console or simply console is the text entry and display device for system administration messages, particularly those from the BIOS or boot loader, the kernel, from the init system and from the system logger...
) such as the TEST channel and Maintenance channel. Typically provisioning
Provisioning
In telecommunication, provisioning is the process of preparing and equipping a network to allow it to provide services to its users. In NS/EP telecommunications services, "provisioning" equates to "initiation" and includes altering the state of an existing priority service or capability.In a...
is done either through a command line interface (CLI) called RCV:APPTEXT, or through the menu-driven RCV:MENU,APPRC program. RCV stands for Recent Change/Verification, and can be accessed through Switching Control Center System
Switching Control Center System
The Switching Control Center System was an Operations Support System developed by Bell Laboratories and deployed during the early 1970s. This computer system was first based on the PDP-11 product line from Digital Equipment Corporation and used the CB Unix operating system and custom application...
. Most service orders, however, are administered through Recent Change Memory Administration Center (RCMAC).
See also
- 1ESS switch1ESS switchThe Number One Electronic Switching System, the first large-scale Stored Program Control telephone exchange or Electronic Switching System in the Bell System, was introduced in Succasunna, New Jersey, in May 1965. The switching fabric was composed of reed matrixes controlled by wire spring relays...
- 3B21D
- 4ESS switch4ESS switchThe 4ESS switch is a Class 4 telephone Electronic Switching System that was the first digital electronic toll switch introduced by Western Electric for long distance switching. It was introduced in 1976 in Chicago, Illinois to replace the 4a crossbar switch. The last of 145 in the AT&T network was...
- Telephone exchangeTelephone exchangeIn the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
- Office classification
- Class 5 telephone switch
- PRX (telephony)PRX (telephony)The PRX205 is a processor controlled reed relay telephone exchange developed by Philips Telecommunicatie Industrie BV in Hilversum during the late 1960s and early 1970s. The first public switch was installed in Overvecht in Utrecht in 1972. About half of all sales were in the Netherlands...
External links
- Massachusetts Institute of Technology 5ESS diagram