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10/5/2009
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Open source in general means that the underlying principles are open for all to see, to discuss and to improve - and that any resulting improvements are in turn open to all. It can be a powerful alternative to the usual closed and proprietary development methods, especially in the development of standards when the aim is to spread a technology rather than to protect or licence the intellectual property. Open source software is essentially a development methodology using the open source approach.
Open source software assumes that allowing more people to look at, and contribute to, the source code helps to improve it and makes for faster and better development as well as improving stability, efficiency (more compact code) and security. It is also much more likely to be compliant to international standards in contrast to proprietary software. Its close cousin – free software – is a more radical social concept as well as being ambiguous as to whether it is about freedom or price.
The development methodology for open source software includes the right to inspect, modify and redistribute the underlying programming code. One definition of it is detailed on the web-site of the Open Source Initiative (http://www.opensource.org/ ). The open source movement originated in 1984 with Richard Stallman devising a variant of the Unix operating system and was taken forward by Linus Torvalds in 1991 to produce the Linux operating system. In between, and since, thousands of programmers have contributed code to these and other activities and transformed what was perceived to be creaky software for nerds and techies into reliable mainstream products.
The commonly associated realisation of open source software to most people is the Linux operating system. Linux is now finding its way into business applications and is the basis for many bespoke operating systems for mobile phones, personal digital assistants, set-top boxes, cash registers and many other devices. Many proprietary applications vendors have ported their software to run on Linux, e.g. SAP, the biggest ERM (enterprise resource management) vendor.
Other operating systems, such as TinyOS for networked sensors (motes), are also built on open source lines. However, open source software goes well beyond operating systems. In practice it also embraces thousands of utilities and applications. For example it includes ERM and CRM (customer relationship management) systems, e.g. Compiere, and databases, e.g. MySQL.
Open source software is generally free in the sense of being open for all to see (and modify) rather than being free in the sense of given away, but irrespective of its acquisition cost it is clearly not without cost in terms of support. Many mainstream vendors (e.g. IBM, HP) are now supporting open source products, giving business users confidence to deploy them. Open source can thus transform how software is developed, sold and supported.
Open systems interconnection (OSI) model
As networks developed and complexity was added to complexity there were numerous attempts at describing networks by layers.
The development of data networks made this particularly important to help people design constituent parts of an overall end-to-end service capability, including understanding how all the messages between layers were defined by various protocols. A vast amount of international effort went into defining, by 1995, a seven layer reference model known as the open system interconnection model. At the time a large proportion of the effort went into defining the protocols. These are rarely used and were largely superseded even by the time agreement was reached, leading to disillusionment at the time. However, in practice the abstraction of the issues and the underlying principles have been found to be enduringly useful.
It is probably true that many realisations do not exactly conform to the 7 layer model (or pre-date it, such as the Signalling System No 7 or TCP/IP) but it is equally probably true that most realisations can be easily related to the principles. The structure of the seven layers and the underlying principles are therefore a key part of understanding telecommunications and computer networks.
A software programme that runs on a computer and makes the hardware available to other programmes, called application programmes, through an applications programmer interface (API). An operating system handles all the internal functions and housekeeping aspects, including directories and files on internal storage media and the running of more than one application at the same time. It also handles the input and output devices and any other peripheral devices.
Operating systems can range from very small programmes, such as the Tiny-OS for motes, through the well known operating systems on personal computers to very large programmes on main-frame computers and embedded within telephone exchanges. Many operating systems are proprietary but many others (including Linux and Tiny-OS) are open-source. Some of the best known OS are Microsoft DOS (disk operating system) and its various successor Windows versions, and Unix. The latter comes in many proprietary forms - including Sun Solaris, IBM AIX and Apple OS X as well as the Linux open-source variant.
Telecommunications still aspires to a clear separation between the hardware (the telecommunications network) and the applications. Many of the principles of Intelligent Networks (IN) were aimed at an intelligence layer replicating computer OS functions to work with the underlying network resource, but only achieved partial success. The introduction of internationally standardised APIs, such as Parlay, take the realisation of the concept of a network operating system one stage further.
Operational Support Systems (OSS)
Operational Support Systems are the components that a company – normally a Telco or other communications service provider - uses to run its network and business. Typical types of activities that would be met using OSS are taking a customer’s order, configuring network components, creating a bill and managing faults. See also billing.
A wide ranging generic term in telecommunications referring to the many functions and people who keep the network and services running to provide customer service.
See Operations for the IP environment, BTTJ, Vol 18, No 3.
A widely used term in telecommunications and will usually nowadays refer to a network operator but it can refer to a telephone operator or switchboard operator. A network operator usually means a company with a licence to operate a telecommunications network.
The terms telephone operator or switchboard operator originated in the days before automated switching where a central exchange was staffed by telephone operators who answered incoming calls from a customer (then called a subscriber) and put the call through to its destination. Telephone operators subsequently operated private branch exchanges. In both cases automation replaced the use of a human in telephone call routing but even to this day incoming calls to a company can be answered and put through by a human operator (who usually has some additional office related function). In both private and public networks the use of a human operator is referred to as operator assistance.
A contraction of operational expenditure, i.e. expenditure on operating the business. Usually the same as currex (current account expenditure) which is used to distinguish it from capital expenditure (capex). Opex can be used in the context of operational support systems (OSS) expenditure where it may not equate to total currex.
Optical fibre systems are the mainstay of terrestrial telecommunications transmission systems, including undersea and transatlantic links. The principal of guided light waves in glass was first proposed by Kao and Hockham in 1966 building on other work such as the invention of the laser in 1960. They became established in the late 1970s and rapidly made co-axial cables obsolete for long distance transmission and severely curtailed the growth of terrestrial microwave links. They also stopped dead the emerging development of waveguides for long distance links.
Optical fibres for long-distance telecommunications are hair thin (the glass part is about 125mm in diameter) but their success also depends upon a range of opto-electronics and mechanical connectors and splicing (jointing) arrangements, as well as the terminal high-speed digital electronic systems. Not all optical fibres are for long-distance telecommunications: some are of larger diameter and are made of plastic and used for very short distance links.
Ref: Kao, K. C. and Hockham, G. A. Dielectric fibre surface waveguide for optical frequencies, Proc IEE, 113, 7, pp1151 - 1158, July 1966.
This is a generic term for telecommunications core transmission networks. A similar term, optical transport networks (OTNs) is used for networks capable of transporting a variety of different types of customer data protocols directly across multiple wavelengths on optical backbones.
Evolution of optical core networks, BTTJ, Vol 20, No 4.
See also Ultra-long-haul WDM transmission systems, BTTJ, Vol 20, No 4.
A collective term referring to all the electronic devices used in conjunction with optical fibre transmission systems and mainly comprising light emitting diodes (LED)and laser light sources and P-type intrinsic N-type (PIN) diode and avalanche photo diode (APD) detectors. Very accurately specified opto-electronic devices can allow multiple wavelengths to be used over a single fibre - see WDM.
A contraction of opto-electronics.
Orthogonal frequency division multiplexing (OFDM)
This is a modulation technique for wireless systems that first splits the signal and then modulates multiple sub-carriers across the available spectrum. It was rejected as a standard for 3G cellular systems which used CDMA in preference. However, it is being adopted for non-cellular wireless systems such as 802.11(a and g), 802.16a (WiMAX) and for digital video broadcasting (DVB-T). There are proprietary versions as well.
Outside plant - see external plant
In telephone networks overloads can be caused by the following (either singly or in combination):
- media-stimulated mass-calling events
- emergencies
- network equipment failures
- auto-scheduled calling
In the absence of effective overload controls such overloads would threaten the stability of the telephone system and cause a severe reduction in successful call completions. Although the principles were developed in a circuit-switched voice environment, the same principles extend to newer network technologies. See Adaptive network overload controls, BTTJ, Vol 20, No 3.
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