(i) A network simulator is a software program that replicates the functioning of a computer network.
(ii) In simulators, the computer network is typically demonstrated with devices, traffic, etc. and the performance are evaluated.

Trace files can document every incident that happened in the simulation and are used for examination.

Open NMS (Network Management System) is a free and open-source initiative grade network monitoring and management platform. It is established and maintained by a community of users developers and by the open NMS group, it offering services, training and support.

A significant output of simulation is the trace files. Trace files can document every incident that happened in the simulation and are used for examination.

Richard Stallman the free software movement, the beginnings of open source. Collaboration was king in the software world when Richard Stallman joined MIT's Artificial Intelligence Lab in 1971 as a freshman at Harvard University.

OSS projects are collaboration opportunities that improve skills and build connections in the field.
Domains that developers can contribute to the open source community include:
(i) Communication tools.
(ii) Distributed revision control systems.
(iii) Bug trackers and task lists.
(iv) Testing and debugging tools.

(i) Remix
(ii) Remake
(iii) Remanufacture
(iv) Redistribute
(v) Resell
(vi) Study and Learn

Organization related to open source:
(i)  Apache Software Foundation
(ii)  Free Software Foundation
(iii) Linux Foundation
(iv) Open Source Initiative.

(i) In this period of increased competition and cyber crimes, the computers used by indivudals or business organisations may have spy hardwares of rivals.
(ii) Open source hardware technology helps in such threats.
(iii) In this technique we get the components of the hardware and its circuit diagram, so that we can remove suspicious spyware if found.

(i) Software can be used without any cost and restrictions
(ii) Sharing of ideas with the team.
(ii) User friendly.
(iv) We can add the most required features in the software.
(v) We can learn many ideas.
(vi) We can make our program writing skills more efficient

(i) OSS is slightly different from free software.
(ii) Both deal with the ability to download and modify software without restriction or charge.
(iii) In contrast, the OSS criteria, which the Open Source Initiative developed a decade later, place more emphasis on the modification of software, and the consequences of altering source code, licensing, and distribution.
(iii) Obviously, the two overlap; some would say the differences between OSS and free software are more philosophical than practical.
(iv) However, neither should be confused with freeware.
(v) Freeware usually refers to proprietary software that users can download at no cost, but the whose source code cannot be changed.

Network simulation
In a computer network, network simulation is a method whereby a software program models the activities of a network by calculating the communication between the different network objects such as(routers, nodes, switches, access points, links, etc.).
Network simulator
(i)  A network simulator is a software program that replicates the functioning of a computer network.
(ii) In simulators, the computer network is typically demonstrated with devices, traffic, etc. and the performance is evaluated.
Normally, users can then adapt the simulator to accomplish their precise analysis needs.
Network Parameters:
The network parameters define the state of the network (node placement, existing links) and the events (data transmissions, link failures, etc.).
Trace files:
A significant output of the simulation is the trace files. Trace files can document every incident that happened in the simulation and are used for examination.
NS2: NETWORK SIMULATOR version 2.
(i) It was considered explicitly for exploration in network communication and event-driven opensource simulator in computer.
(ii) OTCL and C++ used to create and run NS2.
(iii) NS2 works on Windows and Linux platforms that support wired or wireless network and also use the command line interface as a user interface.
API:
(i) API a pure event base software tool with super simulation design, it has more models which help the user to get desired output easily.

Types of open source licenses are:
(i) Apache License 2.0
(ii) BSD 3-Clause 'New' or 'Revised' license
(iii) BSD 2-Clause "simplified" or "Free BSD" license
(iv) GNU General Public License (GPL)
(v) GNU Library or "Lesser" General Public License (LGPL)
(vi) MIT license
(vii) Mozilla Public License 2.0
(viii) Common Development and Distribution License
(ix) Eclipse Public License
(i) Apache License:
Apache License version 2.0 rights can be applied to both copyrights and patents. Some of the license can be applied only to copyrights and not patents some details of Apache License and Rights are never ending, Worldwide Authority of Rights, Rights for No few or Royalty, Rights are Irrevocable.
(ii) BSD License:
BSD license is a part of a family of the free software license that have much fewer restrictions in distribution as compared to other free software license. Two important version are:
(1) The New BSD License/The NEW Modified BSD License (3 clause "new" or "Revised" license)
(2) The simplified BSD License/Free BSD License (2-clause "simplified" or "free BSD" license)
Both have been accepted as open source license by the open source initiative.
The primary difference between the New and the simplified BSD License is that simplified BSD license emits this clause.
(iii) GNU General Public License:
The General Public License are copy the software, Distribution, charge a fee, change the code base.
(iv) GNU Lesser General Public License:
It grants fewer right to work than GNU GPL. It's generally appropriate for libraries and projects that want to allow linking from non-GPL and non-open-source software. GPL. requires any other project or source that is using the project under GPL also be licensed as GPL: GPL licensed code can't be used for paid and proprietary software.
(v) MIT License:
It's the shortest and most used popular open source license. The main giving of this licnese are copy, modify, merge, publish, distribute, sublicense, etc.

Open Source Software	Proprietary Software
It refers to the software that is developed and tested through open collaboration.	It refers to the software that is solely owned by the individual or the organization that developed it.
Anyone with the academic knowledge can access, inspect modify and redistribute the source code.	Only the owner or publisher who holds the legal property rights of the source code can access it.
The project is managed by an open  source community of developers and programmers.	The project is managed by a closed group of individuals or team that developed it.
They are not aimed at unskilled users outside of the programming community.	They are focused on a limited market of both skilled and unskilled and users.
It provides better flexibility which means more freedom which encourages innovation.	There is a very limited scope of innovation with the restrictions and all.
Examples: Android, Firefox, Libreoffice, Ubuntu, Gname etc..	Examples: Windows, mac Os, iTunes, Google earth. Adobe flash etc.