Visual Networks, Inc.

Visual Networks Technologies, Inc.

John E Hasselkus

James D Ennis, Jr

Thomas R Nisbet

Robert Troutman

James D Ennis

Robert J Norberg

Kenneth J Rehbehn

Matthew A Tucker

David E Wheeler, Jr

Robert C Troutman

R Scott Drysdale

David Wheeler

A data transmission system includes probes connected between end user sites and a data switching network. Each probe is connected to the switching network via an access channel wherein transmission circuits establish paths between the sites through the access channel and switching network. The probes capture and retransmit data traveling between the sites over respective transmission circuits, and can thereby insert service level analysis (SLA) messages into the data traffic in order to actively communicate network performance information to other probes. For each transmission circuit, the probes periodically collect measurements related to one or more network performance metrics, including: round-trip delay (RTD), data delivery ratio (DDR) and network availability. During each SLA measurement cycle, a sequence of SLA messages is exchanged over each transmission circuit, which messages contain data used to determine RTD and DDR. Optionally, the SLA message contents and protocol are designed to allow the SLA messages to be encapsulated in a single, standard data unit of any conventional data transmission protocol, such as an ATM cell. Consequently, the messaging system can be used with any data transmission protocol and in interworked networks without modification of the message data payload. The SLA measurements collected by the probes can be transmitted to a console in communication with the probes for processing, display, and archiving.

Method and apparatus for performing service level analysis of

A system for measuring peak throughput in packetized data networks includes a remote monitoring probe and console. The probe is connected to a packetized data network to monitor network activity, while the console is in communication with the probe via a communications medium. The probe maintains a plurality of counters associated with different ranges of utilization percentage for access channel and individual circuit bandwidth. For each sampling interval, the probe measures the access channel and individual circuit bandwidth utilization and increments the appropriate counters associated with the percentage ranges encompassing the measured bandwidth utilizations. The console polls the probe for the percentage counter data to selectively display the access channel or individual circuit bandwidth utilization in the form of a bar graph and pie chart. The access channel and/or individual circuit bandwidth may ultimately be adjusted based on the displayed data. Alternatively, the system may analyze the data and determine conservative, moderate and aggressive recommendations for bandwidth adjustment. In addition, the system can generate reports containing the access channel or individual circuit bandwidth utilization for a user-specified time period, and the recommendations for bandwidth adjustment.

Method and apparatus for measurement of peak throughput in packetized

Measurement of round-trip delay or travel time in a communications network during in-service operation is accomplished by use of two probes, situated at respective points of interest along the communication network, and a processor. The probes receive identifiable data patterns normally transmitted over the communications network and generate a time stamp when each pattern arrives at or leaves the respective point. Each probe further generates a pattern identifier based on the data in the pattern and stores the identifier and time stamp as a pair in a buffer internal to each probe. Once the internal buffer contents exceed a predetermined amount of data, the processor receives the data from the buffers and matches pattern identifiers between the buffers to locate the departure and arrival time stamps of each pattern traveling between the probe points. Thereafter, the processor calculates an average of round-trip delay or travel times based on the departure and arrival time stamps of several patterns traveling in both directions between the probe points.

Method and apparatus for non-intrusive measurement of round trip delay

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Germantown, MD, United States of America

John E Hasselkus