Overcast is an application-level multicasting system that can be incrementally deployed using today's Internet infrastructure. These properties stem from Overcast's implementation as an overlay network. An overlay network consists of a collection of nodes placed at strategic locations in an existing network fabric. These nodes implement a network abstraction on top of the network provided by the underlying substrate network.

While the advantages of multicast delivery over multiple unicast deliveries is undeniable, the deployment of the IP multicast protocol has been limited to "islands" of network domains under single administrative control. Deployment of inter-domain multicast delivery has been slow due to both technical and administrative reasons. In this paper we propose a Host Multicast Tree Protocol (HMTP) that (1) automates the interconnection of IP-multicast enabled islands and (2) provides multicast delivery to end hosts where IP multicast is not available. With HMTP, end-hosts and proxy gateways of IP multicast-enabled islands can dynamically create shared multicast trees across different islands. Members of an HMTP multicast group self-organize into an efficient, scalable and robust multicast tree. The tree structure is adjusted periodically to accommodate changes in group membership and network topology. Simulation results show that the multicast tree has low cost, and data delivered over it experiences moderately low latency. I.

We propose an application level multicast approach, Topology Aware Grouping (TAG), which exploits underlying network topology information to build efficient overlay networks among multicast group members. TAG uses information about path overlap among members to construct a tree that reduces the overlay relative delay penalty, and reduces the number of duplicate copies of a packet on the same link. We study the properties of TAG, and model and experiment with its economies of scale factor to quantify its benefits compared to unicast and IP multicast. We also compare the TAG approach with the ESM approach in a variety of simulation configurations including a number of real Internet topologies and generated topologies. Our results indicate the effectiveness of our heuristic algorithm in reducing delays and duplicate packets, with reasonable time and space complexities.

In this paper, we propose the dissemination tree, a dynamic content distribution system built on top of a peer-to-peer location service. We present a replica placement protocol that builds the tree while meeting QoS and server capacity constraints. The number of replicas as well as the delay and bandwidth consumption for update propagation are significantly reduced. Simulation results show that the dissemination tree has close to the optimal number of replicas, good load distribution, small delay and bandwidth penalties for update multicast compared with the ideal case: static replica placement on IP multicast.

Providing video on demand (VoD) service over the Internet in a scalable way is a challenging problem. In this paper, we propose P2Cast- an architecture that uses a peer-to-peer approach to cooperatively stream video using patching techniques, while only relying on unicast connections among peers. We address the following two key technical issues in P2Cast: (1) constructing an application overlay appropriate for streaming; and (2) providing continuous stream playback (without glitches) in the face of disruption from an early departing client. Our simulation experiments show that P2Cast can serve many more clients than traditional client-server unicast service, and that it generally out-performs multicast-based patching if clients can cache more than ¡£¢¥¤ of a stream’s initial portion. We handle disruptions by delaying the start of playback and applying the shifted forwarding technique. A threshold on the length of time during which arriving clients are served in a single session in P2Cast serves as a knob to adjust the balance between the scalability and the clients ’ viewing quality in P2Cast.

This thesis will describe an approach to supporting overlay networks in the Internet 's network layer. Two primitives, Packet Reflection and Path Painting, will be described and evaluated.

Abstract—Rapid and widespread dissemination of security updates throughout the Internet will be invaluable for many purposes, including sending early-warning signals, updating certificate revocation lists, distributing new virus signatures, etc. Notifying a large number of machines securely, quickly, and reliably is challenging. Such a system must outpace the propagation of threats, handle complexities in a large-scale environment, deal with interruption attacks on dissemination, and also secure itself. Revere addresses these problems by building a large-scale, self-organizing, and resilient overlay network on top of the Internet. We discuss how to secure the dissemination procedure and the overlay network, considering possible attacks and countermeasures. We present experimental measurements of a prototype implementation of Revere gathered using a large-scale-oriented approach. These measurements suggest that Revere can deliver security updates at the required scale, speed and resiliency for a reasonable cost. Index Terms—Network security, overlay network, overloadingbased measurement, resiliency, security update. I.

Many applications can benefit from ubiquitous availability of multicast delivery. Unfortunately IP multicast coverage on the Internet is spotty at best, limited to individual campuses and a handful of service providers. In response to the slow deployment of IP multicast, a number of end-host multicast mechanisms have been developed. End-host multicast lowers the deployment barrier of multicast technology by moving multicast functionality from routers to hosts. Their performance, however, cannot be as good as that of native IP multicast.

We investigate a heuristic application-level (overlay) multicast approach, which we refer to as Topology Aware Group-ing (TAG). TAG exploits underlying network topology data to construct overlay multicast networks. Specifically, TAG uses the overlap among routes from the source to group members to construct an efficient overlay network in a distributed, low-overhead manner. We can easily integrate TAG with delay and bandwidth bounds to construct overlays that satisfy application require-ments. We study the properties of TAG, and quantify its economies of scale factor, compared to unicast and IP multicast. In addition, we compare TAG with delay-first and bandwidth-first Narada/End System Multicast (ESM) in a variety of simulation configurations. We also implement and experiment with TAG on the PlanetLab wide-area platform. Our results demonstrate the effectiveness of our heuristic in reducing delays and duplicate packets, especially when underlying routes are of high quality. 1

Abstract — Continuous media, such as digital movies, video clips, and music, are becoming an increasingly common way to convey information, entertain and educate people. However, limited system and network resources have delayed the widespread usage of continuous media. Most existing on-demand video services, such as VoD, batching and patching, are not scalable. Although the Near VoD service is scalable, it can provide only dozens of videos. In this paper, we propose a scalable and inexpensive video delivery paradigm, named Scheduled Video Delivery (SVD). In the SVD paradigm, users submit requests with specified start time. The SVD system combines requests to form multicasting groups and schedules these groups to meet the deadline. SVD scheduling has a different objective from many existing scheduling schemes. It does not aim at minimizing the waiting time. Instead, it focuses on meeting deadlines and at the same time combining requests to form multicasting groups. SVD provides scalable on-demand video service with much less channels. 1