Adaptive applications, such as real-time multimedia streaming applications, are increasingly using TCP as their underlying transport protocol. To adapt the content, an elastic application needs a prediction of the future available bandwidth. Unfortunately, the socket API does not allow an application to get information from the transport layer. Therefore, this paper proposes an approach where a monitor collects packet information from the network interface, creates a time series by sampling the packet information, and uses prediction models to assess the future available bandwidth. We collected more than 55000 raw TCP traces among various hosts in the Internet, sampled them at intervals from 0.01 to 5 seconds, and use standard linear and autoregressive prediction models, including Bestmean, AR, MA and ARMA, to determine the normalized prediction error. We find that the prediction error varies significantly as a function of the above parameters. We therefore derive a simple criterion that allows an adaptive application to dynamically adjust the prediction parameters to reduce the prediction error. We evaluate the benefit of this criterion on the number of correctly received frames at the client, which corresponds to the perceived video quality by the user.

The ability to limit unsolicited traffic in the Internet is important to defy DDoS attacks and to contain the spread of worms and viruses. The concept of capabilities, which requires that sources must acquire tokens prior to sending data, has been successfully applied on an end-to-end base to protect end systems. In this paper, we propose edge-based capabilities (EC), an architecture that prevents DDoS attacks and malware spread at the edge. EC introduces a novel network element termed gate. The gate controls IP packets that have previously been authenticated by an end-to-end mechanism. Authenticated traffic carries a session-specific tag in the IP header. Packets with valid tags are forwarded by the gate whereas traffic without or with wrong tags is treated with low priority or even dropped. EC achieves efficiency and scalability by defining a single lock against which tags are compared, removing the need to store per-flow information in the gate. Compared to related proposals, EC is easy to deploy as the gate can be added incrementally and EC requires only a single network element to be added at the edge

Traditional approaches to mirroring, caching, and content distribution have an underlying assumption that minimizing network hop count minimizes client latency. However, with uncongested backbones and potentially high-latency service times for dynamic content, such techniques are of limited effectiveness. We present an architecture in which dispatchers at an overloaded Internet data center (IDC) redirect requests for dynamic content to a geographically remote but less loaded IDC. We show with both analytical modeling as well as testbed experiments that the delay savings of redirecting requests to a lightly loaded IDC can far outweigh the overhead in interIDC network latency. Consequently, client end-to-end delays are significantly reduced without requiring modifications to clients, servers, or DNS.

Multipath streaming is used by resource intensive applications to stream their data over multiple, disjoint paths, thereby cumulating the resources of the different subpaths. The trend towards application-layer implementations of communication protocols allows the deployment of a multipath streaming protocol in the current Internet. However, because resource availability fluctuates in the Internet, a multipath streaming protocol must be combined with other mechanisms to address these fluctuations, e.g., adaptation. This paper describes two approaches to combine adaptation and multipath streaming. The first approach separates the two mechanisms and thereby allows a multipath streaming that is transparent to the application, whereas the other combines the two mechanisms in the application context. This paper compares the two approaches along various parameters. It shows that the first approach is easier to deploy from an engineering point of view, but the separation of multipath streaming and adaptation yields significant drawbacks. Especially, synchronization problems due to different latencies along the paths that form the multipath setup may lead to a significant drop in the quality of data.

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 different types of networks and from hosts on those networks, Remos provides several collectors that use different technologies, such as SNMP or benchmarking. By matching the appropriate collector to each particular network environment and by providing 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. Prediction services are integrated at the user-level, allowing history-based data collected across the network to be used to generate the predictions needed by a particular user. Remos has been implemented and tested in a variety of networks and is in use in a number of different environments.

Active services are application-specified programs that are executed inside the network. The location where the active service is executed plays an important role. The dynamic behavior of networks requires that the selection of the most suitable location to instantiate a service is done at run time. To dynamically place an active service, information about the network (topology, bandwidth) and application (type of the service) is necessary. This paper describes a method to dynamically search for available active service locations in the Internet. To be deployed in the current Internet, a solution is required to (i) scale well to large networks, (ii) to demand as little changes to the Internet as possible, especially not at lower network layers. Finally, the solution must be flexible and customizable to take application requirements into account. The proposed solution makes use of the routing path between two end systems. Active service locations that are located close to the routing path are then found via DNS queries. The evaluation shows that the application pays an overhead at startup time. For applications that can tolerate a startup delay, we show with two experiments using a video application that the quality of the application can be increased by dynamic placement of active services.

Sometimes a client that receives a multimedia stream from a server can change the connection used to transfer the data. There may be multiple paths or multiple servers, but a switch from one connection to another requires a handoff. During such a handoff, the player (of the video and/or audio stream) should be fed with a constant data stream so that they player does not have to stop. Handoffs can be used in addition to adaptive (frame-dropping) filters to improve the quality of multimedia streams as received by the client.This paper investigates the influence of several factors on the quality of the multimedia stream during the handoff: the time needed to establish the connection to the new server, the size and the fill degree of the client buffer, the length of the synchronization phase (where both the old and the new connection are sending) and the most appropriate start packet for the new connection. The evaluation showsm that a handoff can be a viable solution if an appropriate strategy is chosen to phase over from the old connection to the new one.