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.

Inferring AS-level Internet topology from router-level path traces

Abstract: A number of recent studies characterize AS-level topology of the Internet by exploiting connectivity information contained in BGP routing tables. In this paper, we present an alternative method for discovering AS connectivity by inferring individual AS connections from the Internet's router-level topology. This methodology has several advantages over using BGP routing tables. First, it allows us to obtain AS-level connectivity information at a finer granularity (e.g., multiple connections between a pair of ASs); second, we can discover ASs aggregated in BGP routing tables; and third, we can identify AS border routers, which may allow us to further characterize inter-AS connections. Since border routers have, by definition, multiple interfaces, each with an address in a potentially different AS, a major challenge of our approach is to properly map border routers to their corresponding ASs. To this end, we present in this paper several mapping rules and heuristics for inferring the ASs of border routers and report on results showing the effectiveness and validity of these rules and heuristics.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Delving into internet streaming media delivery: a quality and resource utilization perspective

Abstract: Modern Internet streaming services have utilized various techniques to improve the quality of streaming media delivery. Despite the characterization of media access patterns and user behaviors in many measurement studies, few studies have focused on the streaming techniques themselves, particularly on the quality of streaming experiences they offer end users and on the resources of the media systems that they consume. In order to gain insights into current streaming services techniques and thus provide guidance on designing resource-efficient and high quality streaming media systems, we have collected a large streaming media workload from thousands of broadband home users and business users hosted by a major ISP, and analyzed the most commonly used streaming techniques such as automatic protocol switch, Fast Streaming, MBR encoding and rate adaptation. Our measurement and analysis results show that with these techniques, current streaming systems these techniques tend to over-utilize CPU and bandwidth resources to provide better services to end users, which may not be a desirable and effective is not necessary the best way to improve the quality of streaming media delivery. Motivated by these results, we propose and evaluate a coordination mechanism that effectively takes advantage of both Fast Streaming and rate adaptation to better utilize the server and Internet resources for streaming quality improvement.

Metric Functional Dependencies

Abstract: When merging data from various sources, it is often the case that small variations in data format and interpretation cause traditional functional dependencies (FDs) to be violated, without there being an intrinsic violation of semantics. Examples include differing address formats, or different reported latitude/longitudes for a given address. In this paper, we define metric functional dependencies, which strictly generalize traditional FDs by allowing small differences (controlled by a metric) in values of the consequent attribute of an FD. We present efficient algorithms for the verification problem: determining whether a given metric FD holds for a given relation. We experimentally demonstrate the validity and efficiency of our approach on various data sets that lie in multidimensional spaces.

Towards a UML based approach to role engineering

Abstract: Role based access control (RBAC) is a promising technology for scalable access control. For RBAC to rise to its full potential, the roles must be properly constructed to reflect organizational access control policy and needs. This requires a discipline of Role Engineering to develop various components of RBAC such as role hierarchy, permissions (and permissionrole assignment), and constraints. The importance of Role Engineering has been recognized but very little work has been done to date. In this paper we explore the possibility of using the Unified Modeling Language (UML) to support Role Engineering. We chose UML because it is a de facto standard and refIects a consensus in the modeling community. To investigate the capability of UML for Role Engineering, we represent an existing Role framework recently published by Thomsen, O’Brien, and Bogle. This framework can be modeled in UML, with the assistance of adding a new user defined UML vocabulary.