Sunday, September 6, 2009


3LS (3-Level-Simulator) is a Java based simulator for overlay
networks that uses a central step clock. The system is separated
into three models:
1. Networked

2. Protocol

3. User

The network model is described in terms of distance between nodes in
a 2D space. The protocol model is simply the P2P protocol being used.
The user model generates input from users using a GUI or file.
Communication can only be achieved between directly connected layers.

When running the simulator it is possible to either create the models
for each of the three described levels or to select existing models
from a library. As the simulation runs, each event is displayed on
the screen. Once completed, the simulation data is stored to a file
and this data is accessed by a visualisation tool named AiSee [15].
Currently, an implementation of Gnutella 0.4 exists and has been
tested on a small network of fewer than 20 nodes.

Download Simulator: Please e-mail the creators Nyik San Ting and
Ralph Deters at the University of Saskatchewan for a copy.


NS2 developed at UC Berkeley, is a discrete event simulator
targeted at networking research and provides substantial support for
simulation of many Internet, routing, and multicast protocols. It can
be installed on both Windows (using Cygwin) and Linux but evidently
is more suited to Linux. NS2 is comprised of many various packages to
provide its features (e.g. compatibility with numerous protocols and
providing graphical representation of simulations etc) thus is
notoriously difficult to use.

NS2 implements a vast array of protocols including TCP and UDP,
traffic source behavior such as FTP, Telnet, VBR and CBR.
Additionally, there is router queue management mechanisms such as
Drop Tail, RED and CBQ implemented. NS2 also implements multicasting
and some of the MAC layer protocols for LAN simulations. Currently,
there is only one P2P simulation available for NS2 (Gnutella).
Simulations in NS2 are constructed using a mixture of C++ and OTcl
(Object Orientated version of Tcl created by MIT).

Simulating in NS2 is a four step model.

1. Firstly, add a combination of C++ and OTcl code to the NS2 standard
set of libraries to implement your protocol.

2. Create the simulated network using an OTcl script (define the
nodes, links etc).

3. Run the generated scripts.

4. Analyze the trace files generated by NS2. A graphical model (NAM)
can use the trace files to show a graphical representation of the
simulation. Other tools available include graph plotting.

Due to the realistic nature of the packet level NS2 simulator,
scalability is a major issue. However, like most packet level
simulators NS2 can run in parallel with a number of other machines.
This can increase the maximum number of nodes for a given simulation
but can become difficult to manage. Subsequently, NS2 is commonly
used for simulating small networks and is generally unsuitable for
modelling overlay networks.


The 1,000sqkm Nallamala area is probably the largest stretch of undisturbed forests in south India other than the Western Ghats.

It is considered one of toughest and the most treacherous terrains. Even those well-aware of the tracks can get lost.

Little wonder, the Maoists have made Nallamala — spread across five districts of Kurnool, Mahbubnagar, Prakasam, Guntur and Nalgonda — their haven. The Maoists ruled this region for over a decade by camping in the deep forests and troubled successive governments by unleashing a wave of terror. They ran a parallel government in these five districts taking full advantage of the terrain.

The fissured rocks prevent any water from percolating, resulting in most of the discharge running off as mountain streams to join the Gundlakamma river in the hills.

The Krishna river, which flows majestically through the forests, separates Kurnool and Mahbubnagar districts, while the Srisailam reservoir backwaters are spread across a length of 70 km making it easy for the Maoists to escape.


Nallamala is a range of parallel hills and valleys of the Eastern Ghats in eastern Andhra Pradesh state, southern India. Located south of the Krishna River, the hills run north to south, parallel to the Coromandel Coast on the Bay of Bengal. Their total length is about 265 miles (430 km); the northern boundary is in the Palnad Basin, and the southern boundary is in the Tirupati Hills. Approximately 19 miles (31 km) wide, the Nallamala Range rises to an average elevation of 2,900 to 3,600 feet (900 to 1,100 metres). The rugged, sparsely populated hills are composed for the most part of jumbled quartzites and slates and exemplify the mountain scenery of the Eastern Ghats.