AT&T Labs

About: AT&T Labs is a based out in . It is known for research contribution in the topics: Network packet & The Internet. The organization has 1879 authors who have published 5595 publications receiving 483151 citations.

Measurement and analysis of IP network usage and behavior

Abstract: Traffic, usage, and performance measurements are crucial to the design, operation and control of Internet protocol networks. This article describes a prototype infrastructure for the measurement, storage, and correlation of network data of different types and origins from AT&T's commercial IP network. We focus first on some novel aspects of the measurement infrastructure, then describe analyses that illustrate the power of joining different measured data sets for network planning and design.

On external memory graph traversal

Abstract: We describe a new external memory data structure, the buffered repository tree, and use it to provide the first non-trivial external memory algorithm for directed breadth-first search (BFS) and an improved external algorithm for directed depth-first search. We also demonstrate the equivalence of various formulations of external undirected BFS, and we use these to give the first I/O-optimal BFS algorithm for undirected trees.

Hole-Assisted Few-Mode Multicore Fiber for High-Density Space-Division Multiplexing

Abstract: A seven-core few-mode multicore fiber in which each core supports both the LP01 mode and the two degenerate LP11 modes has been designed and fabricated for the first time, to the best of our knowledge. The hole-assisted structure enables low inter-core crosstalk and high mode density at the same time. LP01 inter-core crosstalk has been measured to be lower than -60 dB/km. LP11 inter-core crosstalk has been measured to be around -40 dB/km using a different setup. The LP11 free-space excitation-induced crosstalk is simulated and analyzed. This fiber allows multiplexed transmission of 21 spatial modes per polarization per wavelength. Data transmission in LP01/LP11 mode over 1 km of this fiber has been demonstrated with negligible penalty.

Improved circular layouts

Abstract: Circular graph layout is a drawing scheme where all nodes are placed on the perimeter of a circle. An inherent issue with circular layouts is that the rigid restriction on node placement often gives rise to long edges and an overall dense drawing. We suggest here three independent, complementary techniques for lowering the density and improving the readability of circular layouts. First, a new algorithm is given for placing the nodes on the circle such that edge lengths are reduced. Second, we enhance the circular drawing style by allowing some of the edges to be routed around the exterior of the circle. This is accomplished with an algorithm for optimally selecting such a set of externally routed edges. The third technique reduces density by coupling groups of edges as bundled splines that share part of their route. Together, these techniques are able to reduce clutter, density and crossings compared with existing methods.

A Functional Approach to External Graph Algorithms

Abstract: We present a new approach for designing external graph algorithms and use it to design simple external algorithms for computing connected components, minimum spanning trees, bottleneck minimum spanning trees, and maximal matchings in undirected graphs and multi-graphs. Our I/O bounds compete with those of previous approaches. Unlike previous approaches, ours is purely functional--without side effects--and is thus amenable to standard checkpointing and programming language optimization techniques. This is an important practical consideration for applications that may take hours to run.