This paper introduces AntNet, a novel approach to the adaptive learning of routing tables in communications networks. AntNet is a distributed, mobile agents based Monte Carlo system that was inspired by recent work on the ant colony metaphor for solving optimization problems. AntNet's agents concurrently explore the network and exchange collected information. The communication among the agents is indirect and asynchronous, mediated by the network itself. This form of communication is typical of social insects and is called stigmergy. We compare our algorithm with six state-of-the-art routing algorithms coming from the telecommunications and machine learning elds. The algorithms' performance is evaluated over a set of realistic testbeds. We run many experiments over real and arti cial IP datagram networks with increasing number of nodes and under several paradigmatic spatial and temporal tra c distributions. Results are very encouraging. AntNet showed superior performance under all the experimental conditions with respect to its competitors. We analyze the main characteristics of the algorithm and try to explain the reasons for its superiority. 1.

Recent studies provide evidence that Quality of Service (QoS) routing can provide increased network utilization compared to routing that is not sensitive to QoS requirements of traffic. However, there are still strong concerns about the increased cost of &OS routing, both in terms of more complex and frequent computations and increased routing protocol over-head. The main goals of this paper are to study these two cost components, and propose solutions that achieve good routing performance with reduced processing cost. First, we identify the parameters that determine the protocol traffic overhead, namely (a) policy for triggering updates, (b) sen-sitivity of this policy, and (c) clamp down timers that limit the rate of updates. Using simulation, we study the relative significance of these factors and investigate the relationship between routing performance and the amount of update traf-fic. In addition, we explore a range of design options to reduce the processing cost of QoS routing algorithms, and study their effect on routing performance. Based on the con-clusions of these studies, we develop extensions to the basic QoS routing, that can achieve good routing performance with limited update generation rates. The paper also ad-dresses the impact on the results of a number of secondary factors such as topology, high level admission control, and characteristics of network traffic.

We evaluate several routing protocols for mobile, wireless, ad hoc networks via packet level simulations. The protocol suite includes routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, end-to-end delay and routing load for a given traffic and mobility model. It is observed that the new generation of on-demand routing protocols use much lower routing load. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and delay performance. 1. Introduction A mobile, ad hoc network [4] is an autonomous system of mobile hosts connected by wireless links. There is no static infrastructure such as base stations. If two hosts are not within radio range, all message communication between them must pass through one or more intermediate hosts that double as router...

Abstract. Mobile ad hoc networks are characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Design of efficient routing protocols in such networks is a challenging issue. A class of routing protocols called on-demand protocols has recently found attention because of their low routing overhead. We propose a technique that can reduce the routing overhead even further. The on-demand protocols depend on query floods to discover routes whenever a new route is needed. Our technique utilizes prior routing histories to localize the query flood to a limited region of the network. Simulation results demonstrate excellent reduction of routing overheads with this mechanism. This also contributes to a reduced level of network congestion and better end-to-end delay performance of data packets.

Abstract—We discuss an implementation of QoS routing extensions to the OSPF routing protocol and evaluate its performance over a wide range of operating conditions. Our evaluations are aimed at assessing the cost and feasibility of QoS routing in IP networks. The results provide insight into the respective weights of the two major components of QoS routing costs, processing cost and protocol overhead and establish strong empirical evidence that the cost of QoS routing is well within the limits of modern technology and can be justified by the performance improvements. I.

ns c ○ is LBNL’s Network Simulator [24]. The simulator is written in C++; it uses OTcl as a command and configuration interface. ns v2 has three substantial changes from ns v1: (1) the more complex objects in ns v1 have been decomposed into simpler components for greater flexibility and composability; (2) the configuration interface is now OTcl, an object oriented version of Tcl; and (3) the interface code to the OTcl interpreter is separate from the main simulator. Ns documentation is available in html, Postscript, and PDF formats. See

this paper, we concentrate on improving this trade-off by devising methods that increase the performance of QoS routing, when cost constraints, i.e., limitations on link state update traffic, affect the accuracy of the information on which it operates. In particular, we study the performance of "safety-based" routing, which incorporates knowledge of the underlying inaccuracy in computing a "safety" measure for links, and uses it when computing paths. Using detailed simulations, we evaluate the effectiveness of safetybased routing and investigate the dependence of its performance on the assumptions made when computing link safety. Our findings show that for many operating conditions, safety-based routing is successful in improving routing performance while maintaining low update traffic volumes.

In this paper we evaluate several routing protocols for mobile, wireless, ad hoc networks via packet level simulations. The ad hoc networks are multi-hop wireless networks with dynamically changing network connectivity owing to mobility. In the protocol suite includes several routing protocols specifically designed for ad hoc routing, as well as more traditional protocols, such as link state and distance vector, used for dynamic networks. Performance is evaluated with respect to fraction of packets delivered, end-to-end delay and routing load for a given traffic and mobility model. Both small (30 nodes) and medium sized (60 nodes) networks are used. It is observed that the new generation of on-demand routing protocols use much lower routing load, especially with small number of peer-to-peer conversations. However, the traditional link state and distance vector protocols provide, in general, better packet delivery and end-to-end delay performance. 1 Introduction A mobile, ad hoc networ...

Simulation is an important tool in network protocol development, providing an effective way to perform controlled experiments, consider alternative designs, understand protocol interactions, and examine scales and topologies that are difficult to create in the laboratory. However, the scale and heterogeneity of today's networks create challenges for network simulation. In particular, configuring simulation inputs, properly modeling the myriad of interacting protocols, and processing and visualizing simulation output is becoming increasing difficult. The VINT project is developing a set of tools centered around ns simulator and nam network animator to meet these challenges. This paper describes the current status and future directions of this ongoing work. 1 Introduction The rapid diffusion of internetworking technology brings two major sources of stress to the underlying protocol mechanisms and associated design methods: scale and heterogeneity. Scale must be consid- This research ...

Quality of Service (QoS) routing algorithms have become the focus of recent research due to their potential for increasing the utilization of an Integrated Services Packet Network (ISPN) that handles requests with QoS requirements. While heuristics for determining paths for such requests have been formulated for a variety of QoS models, little attention has been given to the overall processing complexity of the QoS routing architecture. Although ondemand path computation is very attractive due to its simplicity, many believe that its processing cost will be prohibitive in environments with high request rates. In this work, we first characterize the processing cost of QoS routing algorithms that use the constrained widest-shortest path heuristic to compute QoS paths in a link state based routing environment. By simulating a variety of realistic traffic conditions we investigate the effectiveness of path precomputation in reducing the amount of routing protocol computation. We mainly wan...