On Friday 27 January, Kristian R. Evensen defended his PhD thesis Aggregating the Bandwidth of Multiple Network Interfaces to Increase the Performance of Networked Applications.

Devices capable of connecting to two or more different networks simultaneously, known as host multihoming, are becoming increasingly common. For example, most laptops are equipped with a least a Local Area Network (LAN) and Wireless LAN (WLAN) interface, and smartphones can connect to both WLANs and HSDPA-networks. Being connected to multiple networks simultaneously allows for desirable features like bandwidth aggregation and redundancy.

Enabling and making efficient use of multiple links requires solving several challenges related to deployment, link heterogeneity and dynamic link behavior. Even though multihoming has existed for a long time, for example routers require being able to connect to different networks, most existing operating systems, network protocols and applications do not take host multihoming into consideration. The default behavior is still to use a single link for all traffic. Using a single link is, for example, often insufficient to meet the requirements of popular, bandwidth intensive services like video streaming.

In this thesis, we have focused on bandwidth aggregation on host multihomed devices. Bandwidth aggregation is to merge physical links into one logical link that offers a higher bandwidth. Even though bandwidth aggregation has been a research field for several years, the related work has failed to consider the challenges present in real world networks properly, or does not apply to scenarios where a device is connected to different networks.

In order to solve the deployment challenges and enable the use of multiple interfaces in a way that works in a real-world network environment, we have created a platform-independent framework, MULTI. MULTI works in the presence of NAT, automatically detects and configures the device based on changes in link state, and notifies the application(s) of any changes.

MULTI was used as the foundation for designing transparent and application-specific bandwidth aggregation techniques. A transparent bandwidth aggregation technique is a technique that requires no modifications to the application, nor the operating system at either the sender or receiver. An application-specific technique, on the other hand, is an extension to an existing application or application type.

The application-specific bandwidth aggregation technique presented in this thesis, improve the performance of quality adaptive video streaming. The technique was evaluated with different types of streaming in both a controlled network environment and real-world networks. Adding a second link gave a significant increase in both video and playback quality. The technique is not limited to video streaming or the system/protocols we have worked with. As long as two common requirements are met, the technique can be applied.

In many cases, it is not possible to extended the application directly with multilink support. Working on the network-layer allows for the creation of transparent bandwidth aggregation solutions. A transparent, network-layer bandwidth aggregation solution must cater to the behavior of the different transport protocol in order to achieve efficient bandwidth aggregation. The transparent bandwidth aggregation techniques introduced in this thesis are targeted at Universal Datagram Protocol (UDP) and Transmission Control Protocol (TCP), the two most popular transport protocols in the internet today.

The December issue of the SIGMM Records is out. They can be found here. We can announce the first call for nominations for ACM SIGMM’s new award, the Nicolas Georganas TOMCCAP Award, which will be awarded for the best paper that was published in ACM TOMCCAP in 2011. You can also find the call for another award, the ACM History Fellowship award.

We are pleased to introduce to you a new columnist for the Records. Pablo Cesar will from this issue on report about an Open Source project in every issue. This issue talks about LIRe, an image retrieval library.

Christian Timmerer reports from the 98th MPEG meeting, which concluded some important work and is preparing for new challenges.

The education column presents a book on image and video processing that you may find interesting in your teaching. You can also find a report from Ed-Media, a conference that discusses the use of multimedia for education.

You can also read the PhD thesis summaries provided by three candidates who have recently passed their doctoral exams, you find pointers to the latest issues of TOMCCAP and MMSJ, and several announcements from ACM and SIGMM.

On Wednesday 11 January, Dominik Kaspar defended his PhD thesis Multipath Aggregation of Heterogeneous Access Networks.

In his thesis, Dominik Kaspar explores different ways to increase the speed and reliability of Internet connections by transmitting data over several networks simultaneously. One of the proposed solutions, which can be used by Web browsers and other HTTP-based applications, resulted in a U.S. patent. This method uses logical file segmentation and request pipelining to split a file over numerous Internet paths and recombine it at the destination. Experiments with live video streaming showed that this approach is highly efficient and can be deployed in a lightweight manner.

Furthermore, the thesis investigates the negative effects of data reordering. When data packets are sent over several Internet connections that differ in speed, the packets are likely to arrive out of order. Especially for the TCP communication protocol, which transports the majority of Internet traffic, packet reordering is known to be very destructive. To reduce packet reordering, a scheduler was designed that keeps track of the connection speeds and smartly sends packets so that they always arrive in order at the destination. In addition, a large set of experiments was carried out in which TCP was exposed to various degrees of packet reordering. Thereby, several parameters were identified, which, when correctly tuned, lead to improved TCP performance over multiple networks.

While related research often introduces complexity to third-party servers or to long-established network protocols, the proposed solutions target an easy deployment. Implemented and tested in real-world networks, the thesis shows the benefit of simultaneously using multiple Internet connections to achieve a higher data throughput.

Two articles that were published on the Norwegian website forskning.no provides some coverage of MPG’s projects Romus and Verdione.

The article “Nettvideo hakket videre” talks a lot about results on P2P streaming with network coding, but a lot of the information contained in the articles is based on Pengpeng’s work on video quality assessment. Including a snapshot of the famous squirrels from Big Buck Bunny in two qualities.

The other article, “Video-overført verdensopera”, is about Verdione. It is based on Norunn Torheim’s telephone interviews with Niels Lund and Carsten, and provides a summary of the challenges that Verdione faced in actually bringing our technology to the artists.