Evaluation and Optimization of Context-Based Stability and Quality-of-Service Measures in Overlay Networks


Funding since April 2015 over 24 months by the DFG.

Contact person:

M. Sc. Martin Backhaus(technical) Prof. Dr.-Ing. Günter Schäfer (administrative)

Brief description

The establishment of logical communication networks based on underlying transport networks is a common concept in many areas of network engineering. It is applied in various domains such as peer-to-peer networks, data center architectures, virtual private network (VPN) configuration, WDM network planning for large ISPs, the Smart Grid, and in numerous designs for the Future Internet. Common to all these applications is a structural tripartition into underlay (the transport network), overlay (the logical network) and an edge mapping that assigns transport paths in the underlay to logical relations in the overlay. Due to their importance for the functionality of today's IT infrastructures, the use of overlay networks that are particularly resistant to failures and sabotage is indispensable.

However, a deliberate structural optimization in overlay networks has so far mainly taken place under efficiency aspects or through local formation of a backup path per overlay connection. Consequently, the removal or utilization of a few underlay connections can decisively degrade the quality of service and availability parameters of the overlay, since a large number of overlay connections can be affected. The determination of such critical structures and the investigation of realistic attack possibilities are prerequisites for a qualitative assessment of the resilience of an overlay. At the same time, they form the basis for optimizations, since identified weak points can be eliminated by adapting the overlay structure or the edge mapping. However, in an overlay scenario, the relevant metrics no longer have their usual properties of classical networks. Due to the dependencies between underlay and overlay connections, the MaxFlow-MinCut theorem loses its validity and correlation measures equivalent on classical networks may differ. Different generalizations with strongly differing computational properties result. Furthermore, the interactions between overlay and underlay may influence load-dependent quality-of-service parameters such as throughput, jitter, and signal delays. Small changes in the bandwidth of underlay connections can already lead to sensitive quality of service degradations in the overlay due to unfavorable edge mappings.

Based on these observations, the project aims to maximize context-based stability and performance measures of overlay networks. In detail, the project comprises four main sub-goals: Investigation and further development of attacker models in overlay scenarios, improvement of analysis methods for context-based stability and performance of overlay networks, application of analysis methods to representative overlay networks, stability optimization of overlay graph and edge mapping.

Publications in the project
[BaSc17c]Backhaus, Martin; Guenter Schaefer: Worst-Case Attacker Models for Two-Layered Networks Based on the Minimum Overlay Cut, IEEE ISCC, 2017.
[BaSc17b]Backhaus, Martin; Guenter Schaefer: Towards Optimally Resilient Topologies against Optimal Attacks, IEEE/IFIP IM - DISSECT, 2017 Winner of the Best Paper Award.
[BaSc17a]Backhaus, Martin; Guenter Schaefer: Towards Construction of Efficient and Optimally Resilient VPN Topologies by Exactly Calculating Maximum Disjoint Paths, IEEE ICC, 2017.
[BaSc16]Backhaus, Martin; Guenter Schaefer: Backup Paths for Multiple Demands in Overlay Networks, IEEE GIIS, 2016.