... CoopNet) where end-hosts cooperate to improve network performance perceived by all. In CoopNet, cooperation among peers complements traditional client-server communication rather than replacing it. We focus on the Web flash crowd problem and argue that CoopNet offers an effective solution. We present an evaluation of the CoopNet approach using simulations driven by traffic traces gathered at the MSNBC website during the flash crowd that occurred on September 11, 2001.

Abstract — The impact of routing policy on Internet paths is poorly understood. In theory, policy can inflate shortest-router-hop paths. To our knowledge, the extent of this inflation has not been previously examined. Using a simplified model of routing policy in the Internet, we obtain approximate indications of the impact of policy routing on Internet paths. Our findings suggest that routing policy does impact the length of Internet paths significantly. For instance, in our model of routing policy, some 20 % of Internet paths are inflated by more than five router-level hops. Keywords—Routing, Routing Policy, Policy Routing, Internet Paths I.

This paper addresses the antagonistic relationship between overlay/p2p networks and IPS providers: they both try to manage and control traffic at different level and with different goals, but in a way that inevitably leads to overlapping, duplicated, and conflicting behavior. The creation of a p2p network and the routing at the p2p layer are ultimately treading on the routing functions of ISPs. The paper proposes a solution to develop a synergistic relationship between p2p and ISPs: ISPs maintain an “oracle ” to help p2p networks in making better choices in picking neighboring nodes. The solution provides benefits to both parties. ISPs become able to influence the p2p decisions, and ultimately the amount of traffic that flows in and out of their network, while p2p networks get performance information for “free. ” The reviewers find that the problem is important and the solution is interesting and shows promise. An advantage of the method is that ISPs do not run into legal issues, since they do not engage in caching of potentially illegal content, they just provide performance information. a c m s i g c o m m Public review written by

Remos provides resource information to distributed applications. Its design goals of scalability, flexibility, and portability are achieved through an architecture that allows components to be positioned across the network, each collecting information about its local network. To collect information from differenttypes of networks, Remos provides several Collectors that use differenttechnologies, including SNMP and benchmarking. By matching the Collector to the particular network environmentandbyproviding an architecture for distributing the output of these collectors across all querying environments, Remos collects appropriately detailed information at each site and distributes this information where needed in a scalable manner. Remos has been implemented and tested in a variety of networks and is in use in a number of differentenvironments.

Tools such as pathchar, clink,andpchar attempt to measure the capacity of every Layer-3 (L3) hop in a network path. These tools use the same underlying measurement probing. The key assumption in VPS is that each L3 hop along a path increases the delay of a packet by a "serialization latency", which is the ratio of the packet size over that hop's capacity. Unfortunately, the capacity estimates of VPS tools are sometimes wrong. In this paper, we investigate the source of these errors, and show that the presence of Layer-2 (L2) store-and-forward devices, such as Ethernet switches, have a detrimental effect on the accuracy of VPS tools. Specifically, each L2 store-andforward device introduces an additional serialization latency in a packet's delay, which results in consistent underestimation of that L3 hop's capacity. We analyze this negative effect, deriving the measured capacity of an L3 hop as a function of the L2 link capacities at that hop. Experimental results in local, campus, and ISP networks verify the model, illustrating that L2 devices should be expected in networks of diverse type and size. Finally, we characterize some other sources of error in VPS tools, such as queueing delays, limited clock resolution, variation in ICMP generation delays, and error propagation along the measured path.

Routing asymmetry in the Internet can significantly affect the manner in which we model and simulate its behavior. In this paper, we study routing asymmetry in the Internet and present quantitative evaluations on the extent of such asymmetry today. Our quantitative evaluations provide a measure of the difference between the forward and reverse paths between two end points. Routing asymmetry has not been studied extensively before; this is primarily due to the lack of a systematic approach for quantifying asymmetry except for simply computing the difference between the forward and reverse path lengths. By applying our framework for representing asymmetry, we quantify routing asymmetry for both US higher education academic networks and general commercial networks at two different levels: the Autonomous System (AS) level and the router (or link) level. We take into consideration, not only the difference in the forward and reverse path lengths, but also the AS and link identities and the sequence in which these entities appear on the paths. We measure the AS level routing asymmetry, and provide upper lower bounds on link level routing asymmetry. Our studies show that academic networks appear to be more symmetric than general commercially deployed networks. Furthermore, our studies demonstrate that routing asymmetry exhibits a skewed distribution i.e., a few end-points seem to display a higher extent of participation on asymmetric routes.

As we increase our dependency upon networked communication, the incentive to compromise and degrade network perlbrmance increases lbr those who wish to disrupt the flow of information. Attacks that lead to such compromise and degradation can come in a variety of forms, including distributed denial of service (DDoS) attacks, cutting wires, jamming transmissions, and monitoring/eavesdropping. Users can protect themselves from monitoring by applying cryptographic techniques, and the recent work has explored developing networks that react to DDoS attacks by locating the source(s) of the attack. However, there has been little work that addresses preventing the other kinds of attacks as opposed to reacting to them. Here, we discuss how network overlays can be used to complicate the job of an attacker that wishes to prevent communication. To amplify our point, we focus briefly on a study of preventing DDoS attacks by using overlays.

Abstract — Application-layer multicast (ALM), as alternative to IP multicast, provides group communication without the need for network infrastructure support. To improve the reliability of ALM service, path diversity has been studied and two schemes to construct diverse paths for hosts are proposed. One is the random multicast forest (RMF) and the other is topology-aware hierarchical arrangement graph (THAG). RMF makes the paths from the media source to a participating host diverse by selecting parents for each host randomly, while THAG makes the paths node-disjoint by constructing multiple independent multicast trees, where any interior node in a multicast tree will be leaf node in all the other multicast trees. Topology-awareness is implemented in both schemes to make them efficient for media delivery. We compare the reliability and efficiency of THAG and RMF through extensive simulation. The results show that the reliability of THAG has been improved up to 20 % compared with RMF. The efficiency metrics, such as RDP, link stress, and delay variation among different trees in THAG, are also smaller than or almost the same as that in RMF. The results indicate that THAG is a reliable and efficient ALM scheme for streaming media service. 1 Keywords—Streaming media, application-layer multicast, faulttolerant, topology-awawe I.

In this paper, our objective is to quantify the extent of the routing asymmetry in the Internet: the measure of the difference between the forward and backward paths between two end points. Routing asymmetry has not been studied extensively. Most of the previous studies only consider asymmetry in terms of length and there is a lack of a systematic approach for quantifying asymmetry. One of the challenges in quantifying asymmetry is the formulation of an appropriate set of metrics that can effectively capture various notions of asymmetry. We point out that asymmetry could be of various types. We propose a framework to quantify the routing asymmetry between end hosts and propose two new metrics: Absolute Asymmetry and length-based Normalized Asymmetry. Our metrics capture the differences in (a) the identities of the entities along the forward and reverse paths, (b) the sequence in which the entities appear on the paths and (c) the path length in a seamless way. We apply our framework to real Internet measurement data and examine routing asymmetry at the Autonomous System (AS) level. We deduce the routing asymmetry distribution based on our framework, and we find that about 14 % of pairs of routes considered display AS level routing asymmetry. Furthermore, our studies demonstrate that the routing asymmetry exhibits a skewed distribution, since a few end-points are consistently members of asymmetric pairs.

Abstract. Current methods of routing are based on network information in the form of routing tables, in which routing protocols determine how to update the tables according to the network changes. Despite the variability of data in routing tables, node addresses are constant. In this paper, we first introduce the new concept of variable addresses, which results in a novel framework to cope with routing problems using heuristic solutions. Then we propose a heuristic routing mechanism based on the application of genes for determination of network addresses in a variable address network and describe how this method flexibly solves different problems and induces new ideas in providing integral solutions for variety of problems. The case of ad-hoc networks is where simulation results are more supportive and original solutions have been proposed for issues like mobility.