Purpose of this patch

We believe that the introduction of dynamically loadable libraries substantially improves the current way of developing extensions to ns2 and its usability. A list of offered advantages is reported below:

• People can develop add-ons for ns2 (e.g. introducing new agents, packet types, protocols) without having to modify the core simulator.
• New packet headers and types, as well as packet tracers, could be defined to assist debugging, collection of statistics and inter-module communication. These can also be loaded on demand according to user's needs.
• Dynamic libraries can be loaded at simulation time, with no need to recompile the whole ns2 distribution or to keep different ns2 binaries.
• The installation of third-party ns2 extensions is made easier, thereby facilitating their dissemination.
• Dynamic libraries will make life easier for lab technicians and students. In fact, an official ns2 version can be installed by the administrator and students can just build and use their preferred extensions independently.
• Besides, these modifications will make ns2 more modular and scalable. Adding new features to the simulator will be easier and backward compatibility will be preserved.