Emulation Experimentation Using the Extendable Mobile Ad-hoc ...

EMANE was developed using cross platform tool
kits to support Linux, OS X and MS Windows experiment
testbed environments 2 .
The remainder of this paper is organized as follows:
Section 2 describes the modular EMANE software
architecture and component types. Section 3
describes the rationale for realistic wireless models
and identifies existing wireless models, as well
as models under development within EMANE. Section
4 lists some of the current programs utilizing
EMANE. Section 5 provides a near term road map
for EMANE and planned future work.
2 Architecture
EMANE implements a highly flexible modular architecture
capable of accommodating a wide range
of experiment testbeds. The flexibility of EMANE
centers around its ability to centralize or distribute
some or all of an experiment’s emulation processing
across any number of testbed nodes. XML inputs
to the emulator control the types of processing
deployments and their respective locations, as
well as the types of emulation modules to instantiate.
The modularity of EMANE comes from a
set of well defined component APIs that allow independent
development of emulation module plugins,
while retaining the ability to deploy and control
these components in a consistent generic manner.
There are three main types of EMANE components:
Network Emulation Modules, Emulation
Boundaries and Emulation Event Components.
All EMANE components are implemented as
Dynamic-Link Libraries and referred to as plugins.
All plugins, regardless of type, implement a set of
common interfaces to allow generic creation, configuration,
and control. In addition, plugins implement
a set of specialized interfaces which vary
based on their respective type. EMANE uses a layered
XML approach to instantiate any number of
plugins and configure each plugin with any number
of input parameters. The XML configuration
is designed to minimize the amount of redundant
information necessary to create an EMANE deployment.
This is done by building a hierarchical series
of emulation element groups. Each level in the hierarchy
encapsulates the previous level(s) while still
allowing tailoring of parameters from the level(s)
below.
2 EMANE is developed using The ADAPTIVE Communication
Environment (ACE TM )[1] and The XML C parser
and toolkit of Gnome (libxml2)[2].
2
2.1 Network Emulation Modules
A Network Emulation Module (NEM) is a logical
component that encapsulates all the functionality
necessary to emulate a particular type of network
technology. Each NEM is composed of two types
of plugins: a Medium Access Control (MAC) Layer
plugin and a Physical (PHY) Layer plugin. Instantiated
NEM component layers are configured and
then connected to the layer immediately above and
below. NEM layers communicate with each other
using a generic message passing interface. Each
layer is capable of communicating cross-layer control
messages and Over-The-Air (OTA) messages
with their neighboring layers (See Figure 1). Examples
of cross-layer messages include: per packet
RSSI, carrier sense, and transmission control messages.
Each layer has the capability to generate
OTA messages for communication with respective
layer counterparts contained in different NEMs.
Layers may also append and strip layer specific
headers to OTA messages.
Figure 1: NEM Stack with Boundary and OTA connections
(Left). NEM Stack showing physical and
logical communication paths (Right).
NEMs are created and managed by a NEM Platform
Server. NEMs managed by the same NEM
Platform Server are referred to as being part of the
same platform (See Figure 2). The determination
as to how many NEM platforms are required to support
a given emulation experiment is a function of
the number of NEMs, the complexity of the emulation
modules, and the processing and memory
resources available. Inter-NEM communication is
manged by the NEM Platform Server. NEMs belonging
to the same platform use in memory message
passing. NEMs belonging to different platforms
communicate using a multicast channel.
The EMANE infrastructure delivers all OTA mes-