Open Source Concepts: One Mark Questions, Book Back Answers and Notes

About Open Source Concepts

Medium ~60 min study

When you buy proprietary software, you get a program that runs but you cannot see how it was written. Open source software is the opposite: the source code is published, so any programmer can read it, find bugs, fix them and add features. Linux, Firefox and LibreOffice are familiar examples, and they were built this way by people across the world.

The unit separates two ideas that are often mixed up. Richard Stallman's free software movement is about the user's freedom to run, study, change and share a program. The Open Source Initiative later took a more practical view, stressing that open code simply produces better software. From there the unit moves to licences such as the GNU GPL and Apache, India's NRCFOSS and the BOSS operating system, and two open source tools for networks: NS2 for simulating a network and OpenNMS for monitoring a real one.

Questions here usually test definitions and names. You should be able to tell open source, free software, freeware and proprietary software apart, recall that NS2 is written in C++ and OTcl and produces trace files, state that OpenNMS is written in Java and has Meridian and Horizon releases, and give the full forms of BOSS, NRCFOSS and FCAPS.

What you'll learn

• Distinguish open source software, free software, freeware and proprietary software with an example of each.
• Explain what a licence does and how the GPL differs from the Apache licence.
• State the full forms and purpose of NRCFOSS and BOSS.
• Explain why NS2 uses both C++ and OTcl.
• Describe what a trace file records in an NS2 simulation.
• Compare the Meridian and Horizon releases of OpenNMS, and explain why open source hardware can be trusted more than closed designs.

Before you start

• What an operating system is and how software is installed.
• Basic network terms such as node, link and router.
• The difference between a compiled program and an interpreted script.

Open Source Concepts explained

Open Source Software, Licences and Network Tools

Open Source and Free Software

Software falls broadly into two groups. Proprietary software keeps its source code secret, and the user may only run the program under the seller's terms. Open source and free software make the source code available. Richard Stallman started the free software movement in the 1980s. It is built on four freedoms: to run the program, to study and change it, to share copies, and to share your changed version. The open source movement came about a decade later. It allows much the same things but argues for them on practical grounds: when many developers can see the code, bugs are found faster and the software becomes more stable and efficient.

Licences and Indian Initiatives

Publishing code does not mean giving up all rights. Open source software is released under a licence that sets the rules for using and sharing it. Permissive licences such as the Apache License 2.0 and the BSD licences let others reuse the code with few conditions. Copyleft licences such as the GNU General Public License (GPL) require that any modified version you distribute must also be released under the GPL. In India, NRCFOSS (National Resource Centre for Free and Open Source Software) promotes the use and study of free and open source software. C-DAC developed BOSS (Bharat Operating System Solutions), a Linux distribution that supports Indian languages and is used in government offices.

Network Simulation with NS2

Building a network only to discover it performs badly is expensive, so engineers simulate it first. NS2 (Network Simulator 2) is an open source, discrete event-driven simulator for wired and wireless networks. It uses two languages. C++ handles the detailed work of processing packets and running protocols, because that part must be fast. OTcl (Object-oriented Tool Command Language) is used to write scripts that set up the nodes, links and traffic, because scripts are quick to change. When the simulation runs, NS2 writes a trace file that records each packet event, which can be analysed afterwards.

Network Monitoring with OpenNMS

A simulator predicts behaviour; a management system watches a live network. OpenNMS is an open source network management platform written in Java. It can monitor very large networks and automatically discovers the devices on them. It is based on the FCAPS model (Fault, Configuration, Accounting, Performance, Security), with its main strength in fault and performance management, alerting administrators when something goes wrong. It comes in two releases: Meridian, a stable version with long-term support for businesses, and Horizon, which is updated often and gets new features first.

Open Source Hardware

The same idea applies to hardware. With closed hardware, a buyer cannot check whether something harmful, such as a hidden tracking chip, was added during manufacture. Open source hardware publishes its circuit diagrams, designs and component lists. Anyone can study them, confirm what the device contains, modify the design and build or sell their own version, so the user keeps control over the equipment.

Common mistakes to avoid

• Treating free software and open source software as the same idea. Free software is argued for as a matter of user freedom (the four freedoms); open source is argued for as a better way to develop software.
• Calling freeware open source. Freeware costs nothing, but its source code is closed and you are not allowed to change it.
• Saying NS2 uses a single language. NS2 uses C++ for the simulator core and OTcl for the scripts that describe the network.
• Thinking open source hardware cannot be used commercially. Its published designs can be studied, changed, built and sold.

Test yourself on these with the practice test, then check the worked reasoning in the solved MCQs.

Frequently asked questions

What is the difference between free software and open source software?

Both give you the source code. Free software, as Stallman defined it, is about the user's rights to run, study, change and share a program; free means freedom, not zero price. Open source makes a practical case: open code leads to better software through wide collaboration. Most programs meet both definitions, but the reasoning behind them differs.

What is the BOSS operating system?

BOSS stands for Bharat Operating System Solutions. It is a Linux distribution developed in India by C-DAC. It supports many Indian languages, which makes it suitable for government offices and schools, and it reduces dependence on imported proprietary operating systems.

Why does NS2 use both C++ and OTcl?

Each language does the job it suits. C++ is compiled and fast, so it runs the packet-level work where speed matters. OTcl is an interpreted scripting language, so it is used to describe the topology and simulation settings, which you can change and rerun without recompiling.

What is a trace file in NS2?

A trace file is a text file NS2 writes while a simulation runs. Each line records an event, such as a packet being sent, received or dropped, with the time it happened. After the run, you analyse the trace file to measure things like delay and packet loss.

How is OpenNMS Horizon different from OpenNMS Meridian?

They are the two releases of OpenNMS. Meridian is the stable release with long-term support and security updates, suited to businesses that need reliability. Horizon is released more often and gets new features first, suited to users who want the latest developments.

Why would an organisation choose open source hardware?

Because its full design is published, the organisation can check exactly what is in the device and confirm there is no hidden spyware or tracking component. It can also modify the design to suit its needs or have the hardware made by a supplier it trusts.