Georg Hampel

Applying Software-Defined Networking to the telecom domain

The concept of Software-Defined Networking (SDN) has been successfully applied to data centers and campus networks but it has had little impact in the fixed wireline and mobile telecom domain. Although telecom networks demand fine-granular flow definition, which is one of SDNs principal strengths, the scale of these networks and their legacy infrastructure constraints considerably limit the applicability of SDN principles. Instead, telecom networks resort to tunneling solutions using a plethora of specialized gateway nodes, which create high operation cost and single points of failure. We propose extending the concept of SDN so that it can tackle the challenges of the telecom domain. We see vertical forwarding, i.e. programmable en- and decapsulation operations on top of IP, as one of the fundamental features to be integrated into SDN. We discuss how vertical forwarding enables flow-based policy enforcement, mobility and security by replacing specialized gateways with virtualized controllers and commoditized forwarding elements, which reduces cost while adding robustness and flexibility.

The tradeoff between coverage and capacity in dynamic optimization of 3G cellular networks

For 3G cellular networks, capacity is an important objective, along with coverage, when characterizing the performance of high-data-rate services. In live networks, the effective network capacity heavily depends on the degree that the traffic load is balanced over all cells, so changing traffic patterns demand dynamic network reconfiguration to maintain good performance. Using a four-cell sample network, and antenna tilt, cell power level and pilot fraction as adjustment variables, we study the competitive character of network coverage and capacity in such a network optimization process, and how it compares to the CDMA-intrinsic coverage-capacity tradeoff driven by interference. We find that each set of variables provides its distinct coverage-capacity tradeoff behavior with widely varying and application-dependent performance gains. The study shows that the impact of dynamic load balancing highly depends on the choice of the tuning variable as well as the particular tradeoff range of operation.

Dynamic optimization in future cellular networks

With multiple air-interface support capabilities and higher cell densities, future cellular networks will offer a diverse spectrum of user services. The resulting dynamics in traffic load and resource demand will challenge present control loop algorithms. In addition, frequent upgrades in the network infrastructure will substantially increase the network operation costs if done using current optimization methodology. This motivates the development of dynamic control algorithms that can automatically adjust the network to changes in both traffic and network conditions and autonomously adapt when new cells are added to the system. Bell Labs is pursuing efforts to realize such algorithms with research on near-term approaches that benefit present third-generation (3G) systems and the development of control features for future networks that perform dynamic parameter adjustment across protocol layers. In this paper, we describe the development of conceptual approaches, algorithms, modeling, simulation, and real-time measurements that provide the foundation for future dynamic network optimization techniques.

An economically viable solution to geofencing for mass-market applications

Geofencing services deliver location-relevant information to mobile subscribers, who enter a geographic “fence” or boundary around the informations demarcation area. With Geographic Positioning System (GPS) capabilities on many phones, such services facilitate a variety of mass-market applications ranging from mobile proximity marketing to proximity-based dating. Applications delivering such services operate on top of a geofencing engine that manages location tracking of subscribers and returns triggers when fence-crossing events occur. We discuss the critical aspects of geofencing and the challenges faced when deploying such services to the mass market. We present an economically viable geofencing solution that scales to large populations and supports a high number of fences per subscriber. Through distributed processing supported by an appropriate client-server protocol, this solution optimizes the air interface usage and mobile battery power. The technical viability of our solution is supported by actual traffic data from mobile proximity marketing and a social networking service.

The new paradigm for wireless network optimization: a synergy of automated processes and human intervention

With the evolution of wireless technologies, the optimization process for the radio access network has undergone a dramatic increase in complexity. This trend is driven by the introduction of multiple objectives for packet data services, the increasing network heterogeneity resulting from technology overlays, and the growing demand for nondisruptive optimization of operating networks. In a multidisciplinary effort, Bell Laboratories has developed a new optimization methodology that tackles these challenges using automated processes. We show that the paradigm shift toward automation requires the development of several interdependent algorithms each designed to cope with a particular optimization task. In the application described, human intervention proves indispensable; it demands a new kind of expertise that combines understanding of the automated processes with knowledge of network operation. Through examples we illustrate the variety of tasks that have to be automated and where guidance is needed through human control. The development of these automated processes is an important step toward dynamic optimization routines that are integrated into the network and adjust the network in a real-time manner.

Lightweight security solution for Host-based mobility & multi-homing protocols

Host-based mobility and multi-homing protocols allow hosts to change their location or network interface during ongoing sessions in a cost-efficient, technology-agnostic manner. Since these solutions enjoy resurgence with the rise in mobile internet traffic, they are faced with the problem of providing sufficient security without impairing the economical benefits. We present a lightweight security solution to protect such protocols against redirection- and DoS attacks. Our solution combines methods of weak authentication with proof of session ownership. We discuss how this solution creates a level of protection that requires more (sometimes significantly more) effort to break than conducting corresponding attacks using the existing Internet signaling protocols.

Capacity estimation for growth planning of cellular networks in the presence of temporal and spatial traffic fluctuations

Mobile traffic patterns are subject to rapid fluctuations over time, hence making network growth planning a cumbersome task for cellular-network providers. We introduce a network capacity metric that captures both temporal and spatial traffic fluctuations, and that can be derived from hourly service measurements as used for network growth planning. In a simulation trial, we compare this new metric to traditional methods that derive network capacity from performance evaluations of daily busy-hour traffic or time-averaged cell-load levels. We show that in the presence of temporal and spatial traffic fluctuations, the traditional methods overestimate network capacity and incorrectly project the relative gains achieved through capacity enhancement measures such as cell-hardware upgrade or dynamic load-balancing features.

Securing Host-Based Mobility and Multi-Homing Protocols against On-Path Attackers

Host-based mobility and multi-homing protocols allow hosts to migrate ongoing transport sessions between networks or network interfaces. While such protocols can facilitate vertical mobility in a cost-efficient and access-agnostic manner, they are hard to secure when strong authentication between end points is not available. We present a balanced security solution which protects these protocols against redirection- and DoS attacks performed by on-path adversaries, while demanding only insignificant processing overhead on the end nodes. The solution is based on proof of session ownership using secret/answer chains as well as temporal separation and routability tests. It creates a level of protection that requires more (in some cases, significantly more) effort to break than conducting corresponding attacks through existing Internet signaling protocols. We discuss how this solution can strengthen the security of Multi-path TCP. We further show how it improves the security of route-optimized Mobile IPv6 while permitting operation without home agent.

MOSAIC: Stateless mobility for HTTP-based applications

We present a mobility solution for stateless applications, where the mobile host can change its IP address as well as the content servers used by ongoing client sessions. This allows content retrieval to always use the locally optimal source when the host moves between networks. We refer to this approach as “stateless mobility” since neither the network nor the content servers hold mobility-related state information. Our mobility solution, referred to as MOSAIC, is applied to HTTP sessions using GET method invocation, which represent a large fraction of mobile Internet traffic. By moving MOSAIC underneath the socket interface, we create a generic application-independent feature. We realized a lightweight implementation using an L3 packet filter, which promises easy portability to other platforms. MOSAICs overall concept is evaluated via measurements using public Internet services.