Active Networks

Abstract

Active Networks INTRODUCTIONThe basic goals of active networking (AN) are to create networking technologies that, in contrast to current networks, are easy to evolve and which allow application specific customization. To achieve these goals, AN uses a simple idea, that the network would be easier to change and customize if it were programmable [1][2][3][4][5][6]. While AN has the high-level goals of improving evolvability and customizabilty, there are a number of low-level concerns that must be balanced to achieve these goals. The first of these concerns is flexibility. AN systems aim to significantly improve the flexibility with which we can build networks. The second concern is safety and security. It is crucial that, while adding flexibility, we do not compromise the safety or security of the resulting system. The third concern is performance. If adding flexibility results in a system that cannot achieve its performance goals, it will be pointless. The final concern is usability. It is important that the resulting system not be so complex as to be unusable.One of the basic techniques of AN is that code (program) is moved to the node at which it should execute. One place this idea first arose was in distributed systems supporting process migration. Another significant early influence was in generalization of remote procedure call (RPC) to support remote evaluation (RE). Both of these techniques will be discussed in detail in applications for network management in Chapter 18. The next important step in this direction was a DARPA proposal on the topic of 'Protocol boosters for distributed computing systems'. The idea was to dynamically construct protocols using protocol element insertion and deletion on an as-needed basis, to respond to network dynamics. Protocols were constructed optimistically; that is, ideal operating conditions (no errors, low delays, adequate throughput, etc.) were assumed, and protocol elements (such as error detection and correction mechanisms) were inserted into protocols on-demand, as conditions were encountered that deviated from the best case where the protocol element would not be needed.On the network level the previous concepts resulted in middleboxes [7]. Domain-specific 'middleboxes ' [7] are appearing such as firewalls, network address translators (NATs) and intrusion detection systems (IDSs). Examples of such middleboxes include NATs [8-10], NAT with protocol translator (NAT-PT) [11]