In this paper, a novel cost model for active networks is proposed. Active networks allow band,width-processing trade-off by introducing processing at intermediate nodes inside the network. The flows travelling through active nodes use the processing resources at the node to adapt to the current conditions of network. For example, a flow may compress to avoid traffic congestion in a heavily loaded region of the network, or to minimize the cost of transmission. We first argue that the current network cost models are not sufficient for analyzing the bandwidth-processing tl-ade-off because: 1) they do not associate any cost with the processing performed at the node, and 2) flows in active networks are no longer of constant rate throughout the route from origin to destination. We then introduce a novel cost model suitable for active network cost analysis that takes into account the additional expense of processing at active nodes. We demonstrate the advantages of this cost model over traditional models by implementing schemes that perform connection admission, reservation and routing in an active network using the new model. We show that the traditional models and I-outing schemes, when used for active networks, yield non-optimal results. The new cost model allows for quantitative trade-off between bandwidth and processing leading to optimal I-outing and reservation decisions.
