Wolfgang Braun

Learn More
We explain the notion of software-defined networking (SDN), whose southbound interface may be implemented by the OpenFlow protocol. We describe the operation of OpenFlow and summarize the features of specification versions 1.0–1.4. We give an overview of existing SDN-based applications grouped by topic areas. Finally, we point out architectural design(More)
In this paper we consider carrier networks using only OpenFlow switches instead of IP routers. Accommodating the full forwarding information base (FIB) of IP routers in the switches is difficult because the BGP routing tables in the default-free zone currently contain about 500,000 entries and switches have only little capacity in their fast and expensive(More)
Loop-Free Alternates (LFAs) are a local fast-reroute mechanism defined for IP networks. They are simple but suffer from two drawbacks. Firstly, some flows cannot be protected due to missing LFAs, i.e., this concept does not provide full protection coverage, which depends on network topology. Secondly, some LFAs cause loops in case of node or multiple(More)
BACKGROUND Metastases of renal cell carcinoma (RCC) to the thyroid gland are uncommon. There is no clear consensus regarding the role of surgery in metastatic disease to the thyroid since most clinical studies include small numbers of patients. Also, risk factors associated with disease progression following thyroidectomy are not yet defined. We examined(More)
Glyoxylate metabolism was studied inBacillus fastidiosus, which is known to degrade uric acid and allantoin via glyoxylic acid. Enzymes of the glycine-serine pathway, of the oxalate pathway and of the β-hydroxyaspartate pathway were not detected in cell-free extracts. Glycoxylate carboligase, which catalyzes the formation of tartronic semialdehyde (TSA)(More)
A system was constructed to allow direct visualization of the coronary microcirculation of a beating rat heart under a microscope. An electrocardiogram (EKG) triggered strobe is used on the video recording and display system to "stop" the action of the beating heart so the surface microvessels can be directly observed. Experimental results are recorded on(More)
Maximally redundant trees (MRTs) have been suggested in IETF as a new promising method for fast rerouting in IP networks. Unlike loop-free alternates (LFAs), they can protect against all link and node failures if topology allows. In this work, we compare MRTs and not-via addresses, which also guarantee full-failure coverage. We evaluate path lengths and(More)
In this paper we propose a novel resilience scheme for OpenFlow-based Software-Defined Networking (SDN). To forward packets in line speed, OpenFlow switches store their flow tables in expensive, limited TCAM due to which the stored tables cannot be large. Most resilience mechanisms require additional entries thus the implementation in OpenFlow may quickly(More)
We find that the molecular beam epitaxy of Fe3Si on GaAs(001) observed by real-time x-ray diffraction begins by the abrupt formation of 3 monolayer (ML) high islands and approaches two-dimensional layer-by-layer growth at a thickness of 7 ML. A surface energy increase is confirmed by ab initio calculations and allows us to identify the growth as a(More)