by Keren Bergman and Gil Zussman

The Internet is a crucial worldwide infrastructure that connects over two billion people, offering more than seven billion web pages, transporting roughly 30 exabytes of data a month, and connecting over a billion mobile broadband users. Emerging network services will enable various transformative applications such as 3-D holographic video for telepresence in education and telemedicine. However, the realization of the future Internet requires overcoming significant technological obstacles, which include significant growth in Internet traffic and energy consumption as well as the need to support diverse applications and traffic requirements.

Internet traffic continues to grow at an exponential rate, doubling roughly every one and a half years, driven by an increasing number of users, bandwidth-intensive applications such as video-on-demand, and numerous mobile and wireless platforms. Moreover, the Internet and the cellular networks already account for about 1 percent of the global carbon emissions, and their portion is steadily increasing.

Columbia University was one of the main contributors to the development of the Internet, and since the 1980s, Columbia has retained a leading position in the area of networking. Currently, several faculty members in the Engineering School’s Departments of Electrical Engineering and of Computer Science continue this tradition by dealing with the challenges imposed by issues such as traffic growth, heterogeneous networks, mobility, quality of service requirements, and energy consumption constraints.

Specific areas of research include data center networking (Professors Keren Bergman, Vishal Misra, and Dan Rubenstein), wireless networking (Professors Augustin Chaintreau, Nicholas Maxemchuk, Vishal Misra, Dan Rubenstein, Henning Schulzrinne, Xiaodong Wang, and Gil Zussman), optical networking (Bergman), social networking (Chaintreau), the Internet of Things and cyber-physical systems (Maxemchuk, Schulzrinne, and Zussman), smart grid (Professors Javad Lavaei, Maxemchuk, and Zussman), and future Internet protocols (Misra and Schulzrinne).

The work we do in this field is highly interdisciplinary; for instance, our joint work on access and aggregation networks, both optical and wireless. While the Internet core supports very high data rates by using high-capacity links, routers, and switches, there are major bottlenecks between the core and the access/aggregation networks (i.e., the networks covering metropolitan areas). We are both members of the NSF-funded Center for Integrated Access Networks (CIAN), a 10-university consortium led by the University of Arizona. The Center’s vision is to create transformative technologies for optical aggregation networks, where any application requiring any resource can be seamlessly and efficiently aggregated and interfaced with existing and future core networks at low cost and with high energy efficiency.

Recent advances in the field of optical communications provide new capabilities to optical elements. Instead of functioning as a simple bit pipe, modern devices can continuously make optical measurements on the quality of the data flowing through the links (e.g., measure the bit error rate or optical signal-to-noise ratio). Such measurements can be made directly in the optical domain, without having to convert the signal to the electrical domain. In addition to measurement capabilities, new devices can be dynamically programmed by a network management layer and dynamically configured based on the needs of the network. Our work focuses on leveraging these novel capabilities and the new devices that are being developed by the Center’s researchers in order to develop the CIANbox. The CIAN-box is an information aggregation node that uses real-time optical performance measurements and energy consumption monitoring, to enable application and impairment-aware switching, regeneration, and adaptive coding. Our groups are developing the CIAN-box hardware as well as the software and algorithms that will leverage its capabilities.

Columbia University was one of the main contributors to the development of the Internet, and since the 1980s, we have retained a leading position in the area of networking.

Traditional networking algorithms operate disjointedly in different layers of the networking protocol stack (for example, network applications are designed separately from the routing algorithms, and the routing algorithms do not consider the type of physical medium they are using). However, due to the capability of the CIAN-box to react to measurements of the optical link and to adapt to traffic characteristics, there is a need for network management algorithms that span the various layers of the protocol stack.

In recent years, cross layering has gained popularity in the wireless domain (for example, a cell phone that routes the packet through a Wi-Fi network rather than a cellular network based on the channel quality in both). Hence, bringing these ideas from the wireless to the optical domain and leveraging the CIAN-box hardware components has the potential to significantly improve the performance and to turn optical networks from “dumb pipes” to intelligent networks.

A few industrial collaborations build on the emerging CIAN-box capabilities. For example, Columbia is a member of the Greentouch industry-academia consortium, whose objective is to reduce the energy consumption of telecommunications networks and to build a sustainable Internet. Within this consortium, we are collaborating with the group of Dr. Dan Kilper at Alcatel- Lucent on a project considering the new capability to dynamically add and remove wavelengths. While this capability has the potential for significant energy savings (via turning off electrical and optical equipment when it is not needed), modifying the network on the fly can result in interference to other wavelengths sharing the same fiber. Hence, our groups are developing algorithms and techniques for dynamically modifying transmission and amplification power such that interference will be automatically mitigated and the network could rapidly adapt to required changes.

About the authors
Gil Zussman received his PhD in electrical engineering from the Technion in 2004. Before joining Columbia Engineering, he was a postdoctoral associate at MIT. He is currently an assistant professor of electrical engineering at Columbia, and his research focuses on wireless networks. Zussman has served on the editorial boards of IEEE Transactions on Wireless Communications and of Ad Hoc Networks, and as the Technical Program Committee chair of IFIP Performance 2011. He is a corecipient of four Best Paper Awards and was a member of a team that won the first place in the 2009 Vodafone Americas Foundation Wireless Innovation competition. He is a recipient of the Fulbright Fellowship, the Marie Curie Outgoing International Fellowship, the Defense Threat Reduction Agency (DTRA) Young Investigator Award, and the National Science Foundation CAREER Award.
Keren Bergman is Charles Batchelor Professor of Electrical Engineering and chair of Columbia Engineering’s Department of Electrical Engineering. She directs the Lightwave Research Laboratory and leads multiple research programs on optical interconnection networks for advanced computing systems, data centers, optical packet switched routers, and nanophotonic networkson- chip. She is a fellow of the Institute of Electrical and Electronics Engineers (IEEE) and of the Optical Society of America (OSA), and she currently serves as the coeditor in chief of the IEEE/OSA Journal of Optical Communications and Networking.

Another collaboration takes place with the group of Dr. Peter Magill in AT&T Research and focuses on the placement of nodes (e.g., future CIAN-boxes) that can provide services such as optical signal regeneration and dynamic network reconfiguration. Within this project several routing-constrained location problems are being considered, and algorithms that have the potential to reduce the operator’s operational and deployment cost are being developed.

Finally, optical networks are being increasingly used to support cellular communications. Since smartphone usage is growing rapidly, the increase in bandwidth demands at the edge of the network is putting a strain on the optical backhaul networks, resulting among other things in high-energy usage by cellular providers. In collaboration with Schulzrinne, who is Julian Clarence Levi Professor of Mathematical Methods and Computer Science and professor of electrical engineering, a prototype of the CIAN-box has been integrated with a WiMAX (4G) base station deployed in Columbia as part of the NSF Global Environment for Network Innovations (GENI) project. This optical-wireless integration aims to demonstrate dynamic switching in the optical domain based on information about the quality of the wireless channel.

Indeed, the Internet is fast moving and constantly evolving, but so are the ways in which we are tackling the challenges stemming from its ever-increasing reach and from the numerous new applications it supports. By driving the design of new optical devices, by jointly developing the hardware and networking algorithms, and by using cross-layering, it is possible to intelligently optimize the performance of optical aggregation networks that will carry most of the wireline- and wireless-originated traffic in the Internet.