A fluid-based model of time-limited TCP flows

Design methodologies for TCP/IP based networks is one of the most challenging topic in research on telecommunications networks. The main difficulty consists in modeling congestion control mechanisms because it involves feedback from the network. In this perspective, in this paper we develop an accurate analytical framework for networked TCP applications supporting both Slow Start and Congestion Avoidance algorithms. To this end we enhance the TCP fluid model introduced in the previous literature considering also TCP sources aimed at transmitting a prefixed quantity of data such as file transfer or network browsing. The proposed model addresses a network of routers supporting any Active Queue Management (AQM) techniques, provided that the equations describing the AQM rules implemented in the routers are introduced in the fluid framework. The proposed framework allows designers to study not only the steady-state behavior of the network, but also the transient behavior when a set of TCP sources start to transmit or finish transmitting. Moreover the model results provide the average values of the queue length in each router even when some of them are not bottleneck ones. (C) 2003 Elsevier B.V. All rights reserved.