5ESS Switching System Overview and Analysis

The 5ESS Switching System is a highly advanced telecommunications system developed by Bell Labs in the 1980s. It was designed to provide high-capacity switching and routing capabilities for large-scale telephone networks.

The 5ESS system was built using a modular architecture, consisting of a central control unit and multiple line and trunk cards. This design allowed for easy upgrades and expansion of the system.

One of the key features of the 5ESS system is its ability to handle large volumes of traffic, with some systems able to support over 100,000 telephone lines. This made it an ideal solution for large telephone networks and regional Bell operating companies.

The 5ESS Switching System has a rich history that spans over four decades.

It was first introduced in 1982 as the Western Electric No. 5 ESS and commenced service in Seneca, Illinois on March 25, 1982.

The 5ESS was designed to replace the Number One Electronic Switching System (1ESS and 1AESS) and other electromechanical systems in the 1980s and 1990s.

Approximately half of all US central offices are served by 5ESS switches.

The 5ESS technology was transferred to the AT&T Network Systems division upon the 1984 breakup of the Bell System.

Here's a brief overview of the ownership and marketing history of the 5ESS:

The 5ESS switch is still in widespread use in the public switched telephone network (PSTN) in the United States and elsewhere, but they are being replaced with more modern packet switching systems.

The 5ESS Switching System has a modular, distributed architecture that's made up of three main components: the Administrative Module, Communications Module, and Switching Module. Each of these modules plays a crucial role in the system's overall functionality.

The Administrative Module contains the central computers, which are duplicated for redundancy. This ensures that the system remains operational even in the event of a failure. The Communications Module is the central time-divided switch of the system.

The Switching Module makes up the majority of the equipment in most exchanges and performs tasks such as multiplexing and analog and digital coding to interface with external equipment. It also has a controller, a small computer with duplicated CPUs and memories, for added redundancy.

Power for all circuitry is distributed as –48 VDC (nominal), and converted locally to logic levels or telephone signals. This allows the system to operate efficiently and reliably.

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The 5ESS software development was a massive undertaking, requiring five thousand employees to produce 100 million lines of system source code, mostly in the C language.

The sheer scale of the project was staggering, with 100 million lines of header files and makefiles also being produced.

The development effort took place over 20 years, with three releases often being developed simultaneously, each taking about three years to complete.

These simultaneous releases meant that the development team had to be incredibly organized, with a complete development system and team being set up for international sales in parallel to the U.S. version.

The development systems used were Unix-based mainframe systems, with around 15 of these systems active at the peak.

These systems included development machines, simulator machines, and build machines, among others.

Developers' desktops were initially multi-window terminals, versions of the Blit developed by Bell Labs, but were later replaced by Sun workstations in the mid 1990s.

The source code management system used SCCS, which utilized "#feature" lines to separate source code between releases, between features specific to US or Intl, and the like.

Developers could customize their text editors, such as vi and Emacs, to work with the appropriate view of a file, hiding parts that were not applicable to their current project.

The change request system used the SCCS MR to create named change sets, tied into the IMR system which had purely numeric identifiers.

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The 5ESS Switching System has a modular, distributed architecture that's made up of three main components. These components work together to provide a robust and efficient system.

The Administrative Module (AM) contains the central computers, which are responsible for controlling the system. Each AM has a controller, a small computer with duplicated CPUs and memories, for redundancy.

The Communications Module (CM) is the central time-divided switch of the system. It's responsible for multiplexing, analog and digital coding, and other work to interface with external equipment.

The Switching Module (SM) makes up the majority of the equipment in most exchanges. It performs multiplexing, analog and digital coding, and other work to interface with external equipment, just like the CM.

Here are the three main components of the 5ESS Switching System:

Power for all circuitry is distributed as –48 VDC (nominal), and converted locally to logic levels or telephone signals. This ensures that the system can operate efficiently and effectively.

The Very Compact Digital Exchange (VCDX) was developed to provide an inexpensive and effective way to offer ISDN and other digital services in an analog switching center.

It was marketed to mostly non-Bell telephone companies, and was capable of serving as a switch for small wire centers of fewer than ~400 lines.

The VCDX was also used as a large private branch exchange (PBX), and was a standalone unit with a single Switching Module and no Communications Module.

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Its Sun Microsystems SPARC workstation ran the UNIX-based Solaris operating system, executing a 3B20/21D processor MERTOS emulation system, acting as the VCDX's Administrative Module.

The VCDX used the CO's normal telephone power sources, which were very large uninterruptible power supplies, and had connections to the CO Digital cross connect system for T1 access, etc.

For small wire centers, the VCDX function was usually served by Remote Switching Modules (RSM's), which were controlled by T1 lines connected to a DLTU unit, and could have up to 10 T1's.

RSM's could have multiple units in an office, and were often used as a Class-5 wire center for small to medium towns hosted from a 5ESS located in a larger city.

The RSM's were linked with T1 lines, and the size was dictated by the number of time slots needed for each peripheral unit.

There was also an Optical Remote Module (ORM) that could be used, which was connected via coax from a MUX unit and fed to a TRCU, which converted the coax to connection to the DLI.

The 5ESS Switching System is made up of three main components: the Administrative Module (AM), the Communications Module (CM), and the Switching Module (SM). Each of these components plays a crucial role in the functioning of the system.

The AM is a dual-processor mini main frame computer that runs UNIX-RTR and contains the hard drives and tape drives used to load and backup software. The AM is built on the 3B21D platform and provides high-speed control functions, messaging, and interface to control terminals.

The CM forms the central time switch of the exchange and performs time-divided switching. It's provided in pairs and each module belongs to Office Network and Timing Complex (ONTC) 0 or 1. The CM receives time-multiplexed signals and sends them to the appropriate destination SM.

The SM handles several hundred to a few thousand telephone lines or trunks and has its own processors, called Module Controllers, which perform most call handling processes. Each SM has Local Digital Service Units (LDSU) to provide various services to lines and trunks, and Global Digital Service Units (GDSU) provide less-frequently used services to the entire exchange.

Here are the main components of the 5ESS Switching System:

The Switching Module (SM) is the heart of the 5ESS Switching System, handling hundreds to thousands of telephone lines or trunks.

Each SM has its own processors, called Module Controllers, which perform most call handling processes using their own memory boards. These processors were originally supposed to be Intel 8086, but they proved inadequate, so the system was introduced with Motorola 68000 series processors instead.

The SM has several peripheral units, including Line Units (LU) and Digital Line Trunk Units (DLTU), which are usually located on shelves within the SM. These units provide various services to lines and trunks in the SM, such as tone generation and detection.

Local Digital Service Units (LDSU) provide services to lines and trunks within the SM, while 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.

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T-carrier spans are terminated in Digital Line Trunk Units (DLTU), which concentrate their DS0 channels into the TSI. These units can serve either interoffice trunks or subscriber lines using Integrated Subscriber Loop Carrier.

Here's a breakdown of the services provided by the SM's peripheral units:

Each SM has two Module Controller/Time Slot Interchange (MCTSI) circuits for redundancy, ensuring that calls are not affected in case of a failure.

The 5ESS Switching System has a modular architecture consisting of three main components: the Administrative Module (AM), Communications Module (CM), and Switching Module (SM). Each component plays a vital role in the system's operation.

The Communications Module forms the central time switch of the exchange, using a time-space-time (TST) topology to assign phone calls to time slots for routing. CMs are provided in pairs, each belonging to Office Network and Timing Complex (ONTC) 0 or 1.

The Communications Module receives time-multiplexed signals on the receive fiber and sends them to the appropriate destination Switching Module on the send fiber. Each SM has four optical fiber links, two connecting to a CM belonging to ONTC 0 and two to ONTC 1.

The 5ESS Switching System uses two different signaling architectures: Common Network Interface (CNI) Ring and Packet Switching Unit (PSU)-based SS7 Signaling. This allows for efficient and reliable communication between different components of the system.

Here are the main interfaces and protocols used in the 5ESS Switching System:

Our system is designed to support a wide range of services, ensuring seamless communication and integration with various networks.

Basic and enhanced voice services are available, allowing for clear and efficient communication.

ISDN and Centrex services are also supported, providing reliable and high-speed data transmission.

Operator services are available for assistance and guidance, making it easy to navigate through complex communication systems.

Emergency call routing is a critical feature, ensuring that critical calls are prioritized and connected to the right resources.

Intelligent Network (IN) services enable advanced call management and routing capabilities.

Voice and data integration with legacy and modern networks is also supported, allowing for a smooth transition and compatibility with existing infrastructure.

Here are some of the services supported by our system:

The 5ESS Switching System is a complex network that requires regular maintenance and analysis to ensure optimal performance.

Lesson 4, Initialization Analysis, covers procedures for post-recovery analysis of Administrative Module Initializations, Communication Module Initializations, Switching Module Initializations, and Common Network Interface Initializations.

To recover from an initialization, it's essential to identify why the initialization occurred so corrective actions can be performed to prevent reoccurrence. This lesson presents a post-initialization analysis that analyzes Initialization Messages, other Printouts associated with the initializations, and Administrative Module Postmortem printouts.

Lesson 5, TMS Post Mortem and Asynchronous Failure Analysis, presents procedures to analyze TMS failure printouts and identify the circuitry involved with the failure. It provides a detailed description of the CM2 Office Network and Timing Complex (ONTC) and TMS terminations.

The lesson also identifies how to determine the direction (CM or SM) the TMS error was received from, and includes register breakdown examples, charts, and references to Alcatel-Lucent's Dyna Text 5ESS Switch support documentation.

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Lesson 13, Peripheral Unit Error Analysis, presents two procedures to identify and correct Peripheral Unit Errors. The lesson starts by defining Peripheral Unit Errors and what they can escalate to, and presents the Peripheral Unit Error Analysis procedure stated in Alcatel-Lucent's 5ESS Switch System Maintenance Requirements and Tools document (235-105-110).

Both procedures can identify failing circuits and components, and this lesson includes references to Alcatel-Lucent's Dyna Text 5ESS Switch support documentation and relates procedures in the lesson to the documentation.

The Alcatel-Lucent 5ESS Switching System is a Class-5 digital telephone switch introduced in 1982 by Western Electric/AT&T.

It's one of the most widely deployed Class-5 telephone exchanges, supporting over 100 million subscriber lines globally.

Engineered for service provider and carrier environments, the 5ESS delivers robust, multiservice switching for voice, data, and signaling traffic.

The 5ESS is built on a fully distributed architecture comprising Administrative, Communication, and Switching Modules.

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This architecture offers reliability, scalability, and high availability across diverse operating conditions.

The 5ESS has a modular design, composed of Administrative Modules (AM), Communications Modules (CM), and Switching Modules (SM), allowing for scalable and flexible deployment.

Here are some key features of the Lucent 5ESS:

The 5ESS Switching System is designed with reliability and maintenance in mind. The system features redundant processors for both access and switching modules, which automatically switch to a backup in case of a failure.

This ensures that the system remains operational even if one of the processors fails, minimizing downtime. The system also supports dual power inputs, allowing it to operate on either DC or AC configurations.

In addition to these features, the 5ESS Switching System includes built-in diagnostics, such as test access, error logs, and status indicators, to help identify and troubleshoot issues. Most of the system's components are also hot-swappable, allowing them to be replaced without interrupting service.

Here are some key reliability and maintenance features of the 5ESS Switching System:

Peripheral Error Analysis is a crucial step in maintaining the reliability of complex systems like the 5ESS Switch System.

Peripheral Unit Errors can escalate to more serious issues if left unchecked, making their identification and correction essential.

The 5ESS Switch System Maintenance Requirements and Tools document outlines a procedure for Peripheral Unit Error Analysis, which involves identifying failing circuits and components.

Analyzing Switching Module Event History (Postmortem) printouts is another procedure that can help identify failing components.

This approach can be related to the Dyna Text 5ESS Switch support documentation for further guidance.

Reliability & Maintenance is a crucial aspect of any system, and the 5ESS Switch is no exception. Dual processors for AM and SMs with automatic failover ensure that the system remains operational even in the event of a processor failure.

The 5ESS Switch is designed to be highly reliable, with features such as dual power inputs that support both DC and AC configurations. This means that the system can continue to function even if one power source is lost.

Built-in test access, error logs, and status indicators provide valuable diagnostic tools for maintenance personnel. These features enable quick and easy identification of issues, reducing downtime and improving overall system reliability.

Most components of the 5ESS Switch are hot-swappable, allowing for field replacement without service interruption. This means that maintenance personnel can replace faulty components without having to take the entire system offline.

Here are some of the key features that contribute to the reliability and maintainability of the 5ESS Switch:

The 5ESS Switching System is a powerful tool for managing network communications. It supports up to 192 Switching Modules (SMs).

One of the key features of the 5ESS Switch is its ability to perform routine maintenance and self-maintenance. This ensures that the system runs smoothly and efficiently.

The 5ESS Switch also includes line and trunk scanning functions, which help to identify and diagnose issues within the network. This can be a huge time-saver for network administrators.

Here are some of the key specifications of the 5ESS Switch: