George C. Polyzos

Multicast routing for multimedia communication

The authors present heuristics for multicast tree construction for communication that depends on: bounded end-to-end delay along the paths from source to each destination and minimum cost of the multicast tree, where edge cost and edge delay can be independent metrics. The problem of computing such a constrained multicast tree is NP-complete. It is shown that the heuristics demonstrate good average case behavior in terms of cost, as determined by simulations on a large number of graphs. >

A Survey of Information-Centric Networking Research

The current Internet architecture was founded upon a host-centric communication model, which was appropriate for coping with the needs of the early Internet users. Internet usage has evolved however, with most users mainly interested in accessing (vast amounts of) information, irrespective of its physical location. This paradigm shift in the usage model of the Internet, along with the pressing needs for, among others, better security and mobility support, has led researchers into considering a radical change to the Internet architecture. In this direction, we have witnessed many research efforts investigating Information-Centric Networking (ICN) as a foundation upon which the Future Internet can be built. Our main aims in this survey are: (a) to identify the core functionalities of ICN architectures, (b) to describe the key ICN proposals in a tutorial manner, highlighting the similarities and differences among them with respect to those core functionalities, and (c) to identify the key weaknesses of ICN proposals and to outline the main unresolved research challenges in this area of networking research.

A parameterizable methodology for Internet traffic flow profiling

We present a parameterizable methodology for profiling Internet traffic flows at a variety of granularities. Our methodology differs from many previous studies that have concentrated on end-point definitions of flows in terms of state derived from observing the explicit opening and closing of TCP connections. Instead, our model defines flows based on traffic satisfying various temporal and spatial locality conditions, as observed at internal points of the network. This approach to flow characterization helps address some central problems in networking based on the Internet model. Among them are route caching, resource reservation at multiple service levels, usage based accounting, and the integration of IP traffic over an ATM fabric. We first define the parameter space and then concentrate on metrics characterizing both individual flows as well as the aggregate flow profile. We consider various granularities of the definition of a flow, such as by destination network, host-pair, or host and port quadruple. We include some measurements based on case studies we undertook, which yield significant insights into some aspects of Internet traffic, including demonstrating (i) the brevity of a significant fraction of IP flows at a variety of traffic aggregation granularities, (ii) that the number of host-pair IP flows is not significantly larger than the number of destination network flows, and (iii) that schemes for caching traffic information could significantly benefit from using application information. >

TCP performance issues over wireless links

This article discusses the problems arising when the TCP/IP protocol suite is used to provide Internet connectivity over existing and emerging wireless links. Due to the strong drive toward wireless Internet access through mobile terminals, these problems must be carefully studied in order to build improved systems. We review wireless link characteristics using wireless LANs and cellular communications systems as examples. We then outline the performance problems of the TCP/IP protocol suite when employed over those links, such as degraded TCP performance due to mistaking wireless errors for congestion. We present various proposals for solving these problems and examine their benefits and limitations. Finally, we consider the future evolution of wireless systems and the challenges that emerging systems will impose on the Internet protocol suite.

Application of sampling methodologies to network traffic characterization

The relative performance of different data collection methods in the assessment of various traffic parameters is significant when the amount of data generated by a complete trace of a traffic interval is computationally overwhelming, and even capturing summary statistics for all traffic is impractical. This paper presents a study of the performance of various methods of sampling in answering questions related to wide area network traffic characterization. Using a packet trace from a network environment that aggregates traffic from a large number of sources, we simulate various sampling approaches, including time-driven and event-driven methods, with both random and deterministic selection patterns, at a variety of granularities. Using several metrics which indicate the similarity between two distributions, we then compare the sampled traces to the parent population. Our results revealed that the time-triggered techniques did not perform as well as the packet-triggered ones. Furthermore, the performance differences within each class (packet-based or time-based techniques) are small.

Service discovery for mobile Ad Hoc networks: a survey of issues and techniques

This article surveys research in service advertising, discovery, and selection for mobile ad hoc networks and related issues. We include a categorization of service discovery architectures for MANETs and their modes of operation, presenting their merits and drawbacks. We pay particular attention to cross-layer service discovery - a special class of efficient service discovery approaches for MANETs. We also present security issues and discuss service description options, service selection mechanisms, and service-state maintenance techniques. We conclude with a summary, an outlook, and directions for future research in this area.

TCP and UDP performance over a wireless LAN

We present a comprehensive set of measurements of a 2.4 GHz DSSS wireless LAN and analyze its behavior. We examine issues such as host and interface heterogeneity, bidirectional (TCP) traffic and error modeling, that have not been previously analyzed. We uncover multiple problems with TCP and UDP performance in this system. We investigate the causes of these problems (radio hardware, device drivers, network protocols) and discuss the effectiveness of proposed improvements.

Multicasting for multimedia applications

The authors investigate multicast routing for high-bandwidth delay-sensitive applications in a point-to-point network as an optimization problem. They associate an edge cost and an edge delay with each edge in the network. The problem is to construct a tree spanning the destination nodes, such that it has the least cost, and so that the delay on the path from the source to each destination is bounded. Since the problem is computationally intractable, the authors present an efficient approximation algorithm. Experimental results through simulations show that the performance of the heuristic is near optimal.<<ETX>>

IP multicast for mobile hosts

We present alternative designs for efficiently supporting multicast for mobile hosts on the Internet. Methods for separately supporting multicasting and mobility along with their possible interactions are briefly described, and then various solutions to the combined problem are explored. We examine three different multicast delivery mechanisms and compare them based on their efficiency and impact on host protocol software. We describe proposals for integrating multicasting and mobility in the Internet architecture. We first present IP extensions for host mobility and other extensions for multicasting. We then examine local multicasting mechanisms, focusing on a group membership protocol that is optimized for wireless point-to-point links. Next, we examine the problems of sending and receiving multicast datagrams in a wide area network. For multicast reception, we describe three alternative proposals and compare them by examining both their applicability and their performance, as well as possible tradeoffs among the two.

Developing Information Networking Further: From PSIRP to PURSUIT

PSIRP (Publish-Subscribe Internet Routing Paradigm) is an EU FP7 funded project that has developed a clean-slate architecture for the future Internet, based on the publish-subscribe primitives (rather than the send-receive ones), all the way down to the core networking functions. The PSIRP vision is a pure information-centric Internet architecture, possibly providing remedies to many of the current Internet problems. In PSIRP, all is information and everything is about information. Content-based identities, recursive application of ideas, cryptographic techniques, and the Trust-to-Trust principle are all extensively used to achieve the design goals. Furthermore, incentive compatibility and socio-economic considerations are guiding the design from the outset, to ground the project in reality and to provide credible and viable potential deployment paths. The project has developed, implemented, and preliminarily evaluated solutions for rendezvous, topology formation and routing, and information forwarding, with ongoing work currently focusing in experimenting.