Network Simulators

Network Simulators

When talking about networking or data communication we define network as a group of connected communicating devices such as Computers and Printers. Communication occur according to certain principles or rules that are followed by the vendors which develop or build these devices to which these devices follow. As these devices such as routers, switches, hubs, load balancers, modems etc are costly that no body can easily afford them. For example you are student of IT and you want to research about network devices and their behavior then you cannot afford the devices ( as normally students or researchers don't afford ) . So what we should do? Do we have any other option ? any alternative ? Yes off course we have solution. That is simulation. Simulators are the software that are designed to help to understand the behavior of devices, the behavior of network, limitations of certain protocols and related issues.
Generally speaking, network simulators try to model the real world networks. The principal idea is that if a system can be modeled, then features of the model can be changed and the corresponding results can be analyzed. As the process of model modification is relatively cheap than the complete real implementation, a wide variety of scenarios can be analyzed at low cost (relative to making changes to a real network). Network simulator always contain the
However, network simulators are not perfect. They can not perfectly model all the details of the networks. However, if well modeled, they will be close enough so as to give the researcher a meaningful insight into the network under test, and how changes will affect its operation.
Here i am listing some Network simulators that are useful for the researchers, students which are preparing for exams such as CCNA  Routing and Switching, 100-101 ICND1, 200-101 ICND2 and IT professionals.
Basically Network simulators fall under two categories
1. Commercial simulators
Some of the network simulators are commercial which means that they would not provide the source code of its software or the affiliated packages to the general users for free. All the user s have to pay to get the license to use their software or pay to order specific packages for their own specific usage requirements.
2. Open source simulators
The open source network simulator has the advantage that everything is very open and everyone or organization can contribute to it and find bugs in it. The interface is also open for future improvement. It can also be very flexible and reflect the most new recent developments of new technologies in a faster way than commercial network simulators.

Network simulators name
Commercial	OPNET, QualNet
Open source	NS2, NS3, OMNeT++, SSFNet, J-Sim

Commercial Simulators

1) OPNET

Opnet is now part of riverbed.
The Riverbed SteelCentral Network Planning and Configuration Management (NPCM) family of products, formerly known as OPNET Network Engineering and Operations Planning (NEOP), includes SteelCentral NetAuditor for intelligent network configuration management, SteelCentral NetPlanner for predictive, multi-layer network planning, and SteelCentral NetCollector for real-time network data management

It is extensive and powerful simulation software with wide variety of possibilities to simulate entire heterogeneous networks with various protocols.

The mechanism followed by OPNET is known as discrete event system which means that the system behavior can simulate be modeling the events in the system in such a same order of scenarios as the user has setup.

Generally the OPNET can be able to perform three main functions such as modeling, simulating and analysis. It provide very simple but comprehensive graphical environment for modeling, modeling means to create all kind of models of protocols.

OPNET has different type of modules and tools that increase its development capabilities, including OPNET modeler,model library, planner and different analysis tools. The network industries widely used this simulation tool for observing performance, on the basis of evaluation of local and wide area networks and performance modeling. OPNET is very expensive package, because it has very powerful capabilities for developing different scenarios.

The main feature of this simulator is 

1. Wireless modeling also customizable
2. Scalable wireless simulation support
3. GUI-based debugging

Now OPNET is under Riverbed and now Network Planning and Configuration Management 
(NPCM)

The Riverbed SteelCentral Network Planning and Configuration Management (NPCM) family of products, formerly known as OPNET Network Engineering and Operations Planning (NEOP), includes SteelCentral NetAuditor for intelligent network configuration management, SteelCentral NetPlanner for predictive, multi-layer network planning, and SteelCentral NetCollector for real-time network data management.

The Network Planning and Configuration Management suite includes:

SteelCentral NetCollector: Industry-leading deep network data management tool to acquire comprehensive from the network.

SteelCentral NetAuditor: Ensures network integrity, security, and policy compliance by performing automated network-wide audits and analyzing your network.

SteelCentral NetPlanner: Automates network analysis and network planning of multi-technology, multi-vendor networks.

2) QUALNET
QUALNET is based on the GloMoSim used by Scalable Network Technologies (SNT) and has a full graphical user interface to accomplish almost all the job.

QualNet® software (QualNet) is a tool for scientists, engineers and network planners to create virtual models of all types of data, voice and video networks.

The models are comprised ofnodes representing the network elements and endpoints (routers, switches, access points, ground stations, satellites, mobile phones, radios, sensors, PCs, servers, firewalls and other security equipment) and the links that interconnect the nodes (LAN segments, internet circuits, radio transmissions, Wi-Fi signals, LTE connections, etc.).

The following QualNet features provide a unique capability for accurate, efficient simulation of large-scale, heterogeneous networks:

• Robust set of wired and wireless network protocol and device models, useful for simulating diverse types of networks.
• Optimized for speed and scalability on one processor, QualNet executes equivalent scenarios 5-10x times faster than commercial alternatives
• Designed from the ground-up as a parallel simulator, QualNet executes your simulation multiples faster as you add processors.
• A robust graphical user interface covers all aspects of the simulation, from scenario creation and topology setup, integration of custom protocols, through real-time execution of network models from within the GUI, animation, to post-simulation statistical analysis.
• QualNet has been used to simulate high-fidelity models of wireless networks with as many as 50,000 mobile nodes.

QUALNET supports a wider range of network and analysis like

• MANET
• QoS
• Wired Network
• Satellite
• Cellular

Advantages of QUALNET

• Very good debugging support as it is integrated with Microsoft Visual Studio, so you can debug line by line (through breakpoints)
• Good GUI support and you can even modify GUI as well by yourself and can add your own menus/protocols using XML.

3) NETSIM

The Cisco Network Simulator, Router Simulator & Switch Simulator

NetSim utilizes Boson's proprietary Network Simulator, Router Simulator® and EROUTER® software technologies, along with the Boson Virtual Packet Technology® engine, to create individual packets. These packets are routed and switched through the simulated network, allowing NetSim to build an appropriate virtual routing table and simulate true networking.

The Boson NetSim Network Simulator is an application that simulates Cisco Systems' networking hardware and software and is designed to aid the user in learning the Cisco IOS command structure.

For many individuals, the availability of Cisco routers and switches is often limited. The cost and fragility of equipment makes rack rentals impractical at this level. Boson NetSim makes it possible to design and configure a network with 42 different router models and 5 different switch models* to choose from without having to pay a lot of money, or worrying about transporting and damaging valuable equipment.

VERSIONS

There are two versions of NetSim. There is a current version called Cisco CCNA Network Simulator v5.00, which is also packaged and sold by Cisco Systems as part of its CCNA training material. This CCNA version is $150 and offers a credit to the full version if you decide to upgrade at a later date. In late July 2004, there will be a new CCNP version released called Boson NetSim for CCNP v6.00. This version will have the full feature set that allows coverage of the CCNP track and will support, to a degree, the CCIE track. The big difference between the two versions is the advanced commands (such as routing protocol BGP) will be supported and enabled in the CCNP version. Boson is also offering upgrades to anyone with V5.x of its NetSim product to the new version 6.

Advantages of NETSIM

1. Supports 42 routers, 7 switches* and 3 other devices
2. Simulates network traffic with virtual packet technology
3. Provides two different viewing styles: Telnet mode or Console mode
4. Supports up to 200 devices on one Network Topology

Open Source Simulators

CLOONIX

Cloonix is a tool to help in the automatic building and configuration of simulated networks composed of virtual qemu-kvm guest machines and emulated lan wires between them.

The Cloonix network simulator provides a relatively easy-to-use graphical user interface. Cloonix recommends KVM to create virtual machines but it also supports other virtualization technologies such as LXC. Cloonix provides a wide variety of pre-built filesystems that can be used as virtual machines and provides simple instructions for creating other virtual machine root filesystems

Cloonix is a Linux router and host simulation platform. It fully encapsulates application, host, and network l2 and l3 into a relatively easy-to-use simulation GUI. Network delay and loss characteristics can be configured per link.

The current uses for cloonix are:

• demontration of network-related softwares,
• anti-regression tests of network-related softwares,
• trials of software in alien environments,
• experiments of softwares without impact on host setup.
• production in a reproductible controled environnement.

The Cloonix development team released an update to Cloonix version 26 in May 2015.

GNS3 ( Graphical Network Simulator )

GNS3 is a graphical network simulator focused mostly on supporting Cisco and Juniper software. GNS3 has a large user base, made up mostly of people studying for Cisco exams, and there is a lot of information freely available on the web about using GNS3 to simulate Cisco equipment.

GNS3 can also be used to simulate a network composed exclusively of VirtualBox and/or Qemu virtual machines running open-source software. GNS3 provides a variety of prepared open-source virtual appliances, and users can create their own.

GNS3 is a free, open source network simulation tool you can load on your PC to run Cisco router simulations. With GNS3 you can create network lab topologies for use when studying for your Cisco certification exams (CCNA, CCNP, CCIE, etc) or to test out a configuration before deploying it.

This program is a frontend for some emulators and virtual machine managers, forming a complete framework. The most important pieces are:

1. Dynamips: an emulator for Cisco IOS devices.
2. QEMU: a virtual machine manager (VMM) that allows the use of PCs with a lot of different operating systems currently running, or even Cisco ASAs and Juniper JunOS routers.
3. VirtualBox: another multiplatform VMM.
4. Integrated Ethernet, ATM and Frame Relay switches.
5. A Cloud object that allows the interconnection of the simulated network with the outside world.

GNS3 website lists the following as some of the features provided by the simulator:

1. Design of high quality and complex network topologies
2. Emulation of many Cisco router platforms and PIX firewalls
3. Simulation of simple Ethernet, ATM and Frame Relay switches
4. Connection of the simulated network to the real world
5. Packet capture using Wireshark

OMNeT++

OMNeT++ is also a discrete event simulator. It is a component-based architecture. Componentsare also called modules and are programmed in C++. The components are then assembled into larger components and models by using a high-level language. Its function is similar to that of OTcl in NS2 and Python in NS3. OMNeT++ also provides GUI support, and due to its modular architecture, the simulation kernel can be embedded into all kinds of different user s' applications.

OMNeT++ is not a simulator in itself but rather a simulation framework. Instead of containing explicit and hardwired support for computer networks or other areas, it provides the infrastructure for writing such simulations. Specific application areas are catered by various simulation models and frameworks, most of them are open source. These models are developed completely independently of OMNeT++

It has a generic architecture, so it can be (and has been) used in various problem domains:

• modeling of wired and wireless communication networks
• protocol modeling
• modeling of queueing networks
• modeling of multiprocessors and other distributed hardware systems
• validating of hardware architectures
• evaluating performance aspects of complex software systems
• in general, modeling and simulation of any system where the discrete event approach is suitable, and can be conveniently mapped into entities communicating by exchanging messages.