## 3 Purpose  
The detailed analysis of the state of the art leaves one feeling that the issue of network processing has been addressed so far in only a very timid and tangential manner, which suggests that there is a need for a more direct and comprehensive coverage of the subject (Table 1). Active networks perform processing with the primary aim of modifying the operation of the network at any given time. While also allowing the inclusion of user code in the network nodes, this scenario is accomplished only as a possibility that the user opens and is not offered in any way as an additional functionality provided by the network. Overlay networks could be used to optimise the flow of information in the underlying network. Most of the existing approaches belong to the first group (route optimisation), which refers mostly to routing issues, while the existing approaches that are dedicated to the second method (information optimisation) are limited to a simple process of simplification of the information in the terminal nodes. The i-NP technology is a step closer to the concept of processing in the network that is presented here, but its purpose and approach are again \begin{table}
\begin{tabular}{l l} \hline
**Approach** & **Main objective** \\ \hline Active networks & Modify the operation of the network at any given time \\ Overlay & May be used (a) to optimise the flow of information in the underlying network, or (b) to \\ networks & perform a simple process of simplification of the information in the terminal nodes \\ In-Network & Minimising the energy consumption by reducing the amount of information that must \\ Processing & be sent \\ PIN & Take advantage of the waiting times in the queues of routers, the idle processing \\  & capacity in the intermediate nodes, and the information that passes through the network \\ \hline \end{tabular}
\end{table} 
Table 1: Main network processing approaches to date and PIN. limited. It is focused mainly on minimising energy consumption, for which it relies mainly on a reduction in the amount of information that must be sent. Its current applicability is limited mainly to the field of wireless sensor networks. This approach rarely considers the possibility of enriching the information as it passes through the network, and it is not common to account for issues concerning the network, such as instantaneous load conditions on the network or QoS. A detailed review of the history shows that existing approaches are isolated and limited, which opens the possibility of developing the subject in a comprehensive and direct way (Table 2). The terms \"limited\" and \"rarely\" mean that existing solutions of this alternative offer very little support for this specific functionality. Some features could be implemented with existing approaches, but PIN has a larger vision and may be more suitable for complex applications. We are convinced that network processing can provide significant value in certain environments. The development using existing techniques is possible, but it would involve a major change in their original design, especially for complex applications. We think that a new model with a broader approach could be used in a more natural way and may be more suitable. PIN was conceived as a more comprehensive solution than the existing solutions so far. The main objective of PIN is much wider than the purpose of existing approaches, to include important features such as heterogeneity, QoS profiles, and the benefits of an object-oriented approach. IDM/PIN could deal with very heterogeneous networks and devices, including data link and network technologies. It is also a transport-independent solution. It also allows the definition of QoS profiles that affect the behavior of the virtual network, based on details of the application or user preferences. For example, to prioritize which flow is processed in the routers depending on the identity of the user that sends or receives the data. IDM/PIN routers are objects, and the processing components in the routers are also objects.