1. Introduction

The past ten years has witnessed the rapid development of computer networks, accompanied by an increased demand for new value-added services to meet the highly varying requirements of end-users. For example, new alternative levels of service are currently needed at various points of the Internet to provide a better than traditional "best-effort" service, such as admission control, DiffServ and IntServ/RSVP mechanisms, MPLS technology, QoS Routing, as shown in Figure 1 [1].

Figure 1: Example of new services in today's Internet

The need for these services has resulted in more and more functionality having to be deployed inside the network, which lead to engineer programmable networking infrastructures that offered open and extensible programming interfaces providing abstraction between hardware and software. The IN concept [2] was a solution that emerged from the telecommunications sector and defined open interfaces to the switching control plane, thus easing the deployment of third party novel control software and services. The Opensig [3] community is also based on open-interfaces and virtual node abstractions, and regroup projects such as the IEEE Project 1520 [4] and Columbia University xbind [5] project allows the programmability of management and control planes in diverse networks.

In IP networks, the DARPA community introduced Active Networks in which service construction is based on code mobility through "active" packets that contain not only data, but also code, and "active" nodes that perform customized computations...