Graphs are commonly used to model the structure of internetworks, for the study of problems ranging from routing to resource reservation. A variety of graph models are found in the literature, including regular topologies such as rings or stars, "well-known" topologies such as the original ARPAnet, and randomly generated topologies. Less common is any discussion of how closely these models correlate with real network topologies. We consider the problem of efficiently generating graph models that accurately reflect the topological properties of real internetworks. We compare properties of graphs generated using various methods with those of real internets. We also propose efficient methods for generating topologies with particular properties, including a Transit-Stub model that correlates well with Internet structure. Improved models for internetwork structure have the potential to impact the significance of simulation studies of internetworking solutions, providing basis for the validi...

Graphs are commonly used to model the topological structure of internetworks, to study problems ranging from routing to resource reservation. A variety of graphs are found in the literature, including fixed topologies such as rings or stars, "well-known" topologies such as the ARPAnet, and randomly generated topologies. While many researchers rely upon graphs for analytic and simulation studies, there has been little analysis of the implications of using a particular model, or how the graph generation method may a ect the results of such studies. Further, the selection of one generation method over another is often arbitrary, since the differences and similarities between methods are not well understood. This paper considers the problem of generating and selecting graph models that reflect the properties of real internetworks. We review generation methods in common use, and also propose several new methods. We consider a set of metrics that characterize the graphs produced by a method, and we quantify similarities and differences amongst several generation methods with respect to these metrics. We also consider the effect of the graph model in the context of a speciffic problem, namely multicast routing.

this paper a dynamic routing method is introduced that is applicable to any given parameter set. It cooperates with the resource management of network nodes and considers the QoS requirements of multimedia streams for routing decisions. Section 2 introduces the architecture of our solution called QoSFinder. In Section 3 we deal with details of the routing protocol. Section 4 reports on experience with our implementation of QoSFinder and presents simulation and test results. Finally, Section 5 provides an outlook on future research in this area. 2 QoSFinder: A Routing Method for Continuous-Media Streams

Many new applications in networks require support for multicast communication. In addition, continuous data streams such as audio and video require real-time performance guarantees to ensure quality of service. We introduce a model for real-time multicast channels and present a set of scalable algorithms for the dynamic joining and leaving of destination nodes in this environment. In particular we present an algorithm for finding a good attachment point to the multicast tree. We also describe detailed admission tests that preserve the guarantees given to existing channels. Our algorithm for a leaving node specifies in particular the resources to be released in the network. We also discuss tree reorganization issues. 1 Introduction Modern networks have much higher data rates than traditional networks. These high data rates enable new kinds of applications, in particular multimedia applications. However, the inclusion of multimedia data streams into data networks poses new problems: t...

We consider the problem of optimal multicast routing with Quality of Service con-straints motivated by the requirements of interactive continuous media communica-tion, e.g., real-time teleconferencing. We concentrate on distributed algorithms for determining a tree over the network topology, rooted at the source and spanning the

Graph models are commonly used in studying solutions to internetworking problems. This paper considers several random graph models that have been used to model internetworks, and considers ways to characterize the properties of these graphs. By matching the characteristics of the random graphs to the characteristics of real internetworks, more accurate modeling can be achieved. College of Computing Georgia Institute of Technology Atlanta, Georgia 30332--0280 1 Introduction Accompanying the rapidly increasing use of large networks and internetworks has been a corresponding growth in research on internetworking. Researchers working in internetwork communication generally adopt one of three methods to evaluate their ideas: ffl They implement their ideas on a real internetwork. This approach has obvious difficulties, including the problem of getting access to an internetwork of reasonable size that can tolerate experimentation. ffl They implement their ideas on a smaller network and e...

In this paper, we introduce and solve the multicast routing problem for virtual circuit environment without making any assumptions about the communication patterns, or about the network topology. By multicast we refer to the case were one source transmits to several destination the same information. Also, we allow arbitrary interleaving of subscription patterns for different multicast groups, i.e. the destinations for each group arrive at an arbitrary order and may interleaved with destinations of other groups. Our goal is to make route selection so as to minimize congestion of the bottleneck link. This is the first analytical treatment for this problem in its full generality. The main contribution of this paper is an online competitive routing strategy that has an O(log n log d) competitive factor where n is the size of the network and d( n) is the maximum size of a multicast group. Lab. for Computer Science, MIT. Supported by Air Force Contract TNDGAFOSR-86-0078, ARO cont...

Emerging high speed Broadband Integrated Services Digital Networks (B-ISDN) will carry traffic for services such as video-on-demand and video teleconferencing, which require resource reservation along the path on which the traffic is sent. As a result, such networks will need effective admission control algorithms. The simplest approach is to use greedy admission control; in other words, accept every resource request that can be physically accommodated. However, non-greedy admission control can lead to better network performance in many situations. This thesis develops several non-greedy algorithms that out-perform greedy admission control algorithms. Some of the algorithms are evaluated using simulations while others are evaluated using the theory of competitive analysis. The thesis considers both unicast communication (connections with two end-points) and multicast communication (connection with more than two end-points). The results of the thesis have already had a direct influence on the algorithms used in several commercial networks.

) Baruch Awerbuch 1;2 Yossi Azar 3 Rainer Gawlick 2 1 Johns Hopkins University 2 Laboratory for Computer Science, MIT 3 Tel-Aviv University May 3, 1994 Abstract This paper introduces the problem of selective online multicast and presents an log O(1) n thruput competitive solution, which handles issues of route selection and admission control, in general networks with n nodes. For each node and each multi-cast (broadcast) group, we assume that the node has an arbitrary probability with which it wishes to join the group. 1 Introduction Motivation. The introduction of fiber technology gives rise to new applications, such as interactive TV and video-conferencing, that feature multi-point communication. Applications with multi-point communication can be modeled as sources that broadcast information to subscribing nodes along a spanning (Steiner) tree. In modern networks, (e.g., ATM networks [deP91, Bou92], high-speed networks [ACG + 90, CG88, ACG91, CGG91], or private vi...

This paper addresses the problem of multicast (i.e., point to multipoint) routing in ATM networks. In particular, formal experimental methods are used to evaluate the relative performance of three simple multicast routing algorithms on simple mesh-based networks, using call-level simulation. The performance