Telcordia Technologies

About: Telcordia Technologies is a based out in . It is known for research contribution in the topics: Network packet & Node (networking). The organization has 3097 authors who have published 4737 publications receiving 237882 citations.

Model-based testing of a highly programmable system

Abstract: The paradigm of model based testing shifts the focus of testing from writing individual test cases to developing a model from which a test suite can be generated automatically. We report on our experience with model based testing of a highly programmable system that implements intelligent telephony services in the US telephone network. Our approach used automatic test case generation technology to develop sets of self checking test cases based on a machine readable specification of the messages in the protocol under test. The AETG/sup TM/ software system selected a minimal number of test data tuples that covered pairwise combinations of tuple elements. We found the combinatorial approach of covering pairwise interactions between input fields to be highly effective. Our tests revealed failures that would have been difficult to detect using traditional test designs. However, transferring this technology to the testing organization was difficult. Automatic generation of cases represents a significant departure from conventional testing practice due to the large number of tests and the amount of software development involved.

Congestion control for multimedia services

Abstract: The problem of congestion control in high-speed networks for multimedia traffic, such as voice and video, is considered. It is shown that the performance requirements of high-speed networks involve delay, delay-jitter, and packet loss. A framing congestion control strategy based on a packet admission policy at the edges of the network and on a service discipline called stop-and-go queuing at the switching nodes is described. This strategy provides bounded end-to-end delay and a small and controllable delay-jitter. The strategy is applicable to packet switching networks in general, including fixed cell length asynchronous transfer mode (ATM), as well as networks with variable-size packets. >

Method and apparatus for detecting spoofed network traffic

Abstract: A method and apparatus for detecting spoofed IP network traffic is presented. A mapping table is created to indicate correlations between IP address prefixes and AS numbers, based on routing information collected from a plurality of data sources. At each interface of a target network, IP address prefixes from a training traffic flow are acquired and further converted into AS numbers based on the mapping table. An EAS (Expected Autonomous System) table is populated by the AS numbers collected for each interface. The EAS table is used to determine if an operation traffic flow is allowed to enter the network.

The Estimation of Ultrametric and Path Length Trees from Rectangular Proximity Data

Abstract: A least-squares algorithm for fitting ultrametric and path length or additive trees to two-way, two-mode proximity data is presented. The algorithm utilizes a penalty function to enforce the ultrametric inequality generalized for asymmetric, and generally rectangular (rather than square) proximity matrices in estimating an ultrametric tree. This stage is used in an alternating leastsquares fashion with closed-form formulas for estimating path length constants for deriving path length trees. The algorithm is evaluated via two Monte Carlo studies. Examples of fitting ultrametric and path length trees are presented.

Method and apparatus for program updating

Abstract: A computer system is disclosed in which individual executing process can be replaced with updated or corrected versions of themselves without interrupting or otherwise interfering with the operation of the computer system. In particular, embedded in the process itself is a command or function or subroutine call which operates to overlay the process code in memory with an updated version of itself, without losing or altering the relationships of the process to the other processes in the computer. As an example, in a UNIX system, the execute command can be used to perform the replication function. The replication process can be triggered by an inter-process signal, by the occurrance of an external condition, or by a triggering signal embedded in the normal data input to the process.