Alain Jerome Cohen

US Patent:

6820042, Nov 16, 2004

Filed:

Jul 24, 2000

Appl. No.:

09/624092

Inventors:

Alain Cohen - Washington DC
George Cathey - Washington DC
Patrick J. Malloy - Washington DC

Assignee:

Opnet Technologies - Bethesda MD

International Classification:

G06F 1710

US Classification:

703 2, 703 13, 703 17, 703 21, 703 22, 702182, 702186, 702179, 702181

Abstract:

A simulation system and method that combines the advantages of both analytical modeling and discrete-event simulation is disclosed. In a preferred embodiment of this invention, traffic on the network is modeled as a combination of background-traffic and explicit-traffic. The background-traffic is primarily processed in an analytical form, except in the âtime-vicinityâ of an explicit-event. Explicit-events are processed using discrete-event simulation, and the modeled effects are dependent upon the background-traffic. At each occasion that the background-traffic may affect the explicit-traffic, the background-traffic is particularized into events that are modeled at the lower detail level of the explicit-traffic. In this manner, the portions of the network that are unaffected by the explicit-traffic and that have no effect on the explicit-traffic are modeled and processed at an analytical level, consuming minimal processing time and memory resources, while the portion of the network affected by the explicit-traffic and the background-traffic that affects the explicit-traffic are processed at the lower level of detail.

US Patent:

7139692, Nov 21, 2006

Filed:

Dec 20, 2002

Appl. No.:

10/325148

Inventors:

Alain Cohen - Washington DC, US
Pradeep K. Singh - Arlington VA, US
Arun Pasupathy - McLean VA, US
Stefan Znam - Rockville MD, US
Marius Popa - Chevy Chase MD, US

Assignee:

Opnet Technologies, Inc. - Bethesda MD

International Classification:

G06F 9/44

US Classification:

703 21, 703 13, 709235, 37039521

Abstract:

A method and system for flow propagation analysis uses ‘tracers’ that are iteratively propagated through a simulated network between source and destination elements. These tracers are structured to contain traffic flow information from source to destination, and to reflect changes as the flow is affected by each element along the path from source to destination. The resultant flow information at the destination corresponds to the effective throughput from the source to the destination, and the flow information at the output of each intermediate element in the network corresponds to the potentially achievable throughput through that element for the given source-to-destination flow.

US Patent:

7219047, May 15, 2007

Filed:

Mar 28, 2002

Appl. No.:

10/112179

Inventors:

Alain Cohen - Washington DC, US
Pradeep K. Singh - Arlington VA, US
Arun Pasupathy - McLean VA, US
Stefan Znam - Rockville MD, US

Assignee:

OPNET Technologies, Inc. - Bethesda MD

International Classification:

G06F 17/50

US Classification:

703 17, 702179, 702181, 703 21

Abstract:

A sub-system is provided to a discrete event simulator (DES) to expedite simulation execution by first detecting a non-quiescent steady-state condition in the simulated system, and when the steady-state condition is detected, the simulator determines a state, and subsequently simulates the system at a skip-ahead time using this determined state, or a predicted state based on the determined state. Convergence analysis is used to determine whether the system is at, or approaching, a steady-state condition. This convergence skip-ahead process achieves faster analysis by avoiding the computation that would conventionally be required to simulate the system behavior during the time interval that is skipped.

US Patent:

7254389, Aug 7, 2007

Filed:

Apr 9, 2004

Appl. No.:

10/821558

Inventors:

Alain J. Cohen - Washington DC, US
Jerome Plun - Alexandria VA, US
Yevgeny Gurevich - Washington DC, US

International Classification:

H04Q 7/20

US Classification:

455423, 455 6711, 4552261

Abstract:

A simulation system includes a cache structure that stores determined characteristics related to the propagation of an event. If a similar event occurs, and the factors affecting the determination of these characteristics have not changed, the characteristics associated with the new event are retrieved from the cache, rather than being re-determined from the underlying factors. In the example of mobile transceivers, if multiple transceivers share a common set of underlying factors, the determined characteristics of one transceiver can be shared among all of the other transceivers. If the underlying factors are dependent upon geographic area, mobile transceivers that enter a geographic area having associated cached characteristics can use the cached characteristics of other transceivers that are, or had been, in the area. Because the cache process is structured to intercept a call to the routine that determines the characteristics, the modifications to a simulation system to incorporate this caching feature should be minimal.

US Patent:

7469203, Dec 23, 2008

Filed:

Aug 20, 2004

Appl. No.:

10/923214

Inventors:

Alain J. Cohen - Washington DC, US
Pradeep Singh - Arlington VA, US

Assignee:

OPNET Technologies, Inc. - Bethesda MD

International Classification:

G06F 17/50
G06F 9/45
G06F 14/173
G06F 11/30

US Classification:

703 17, 703 13, 703 22, 709224, 709225, 709226, 702182

Abstract:

A simulation method and system partitions network traffic into background traffic and explicit traffic, wherein explicit traffic is processed in detail, and background traffic is processed at a more abstract level. The packets of explicit traffic are modeled in complete detail, so that precise timing and behavior characteristics can be determined, whereas large volumes of traffic are modeled more abstractly as background flows, and only certain aspects, such as routing through the network, are simulated. Tracer packets are used to model the background traffic and carry a number of characteristics of interest for generating simulation results. In this manner, the effect of the background traffic on the explicit traffic can be modeled at each network element. The abstract processing of background traffic is facilitated by techniques that include multi-variate table look-up, neural networks, and the like.

US Patent:

7688743, Mar 30, 2010

Filed:

Jul 27, 2006

Appl. No.:

11/494692

Inventors:

Alain J. Cohen - Washington DC, US
Pradeep K. Singh - Arlington VA, US
Vinod Jeyachandran - Rockville MD, US
Nitin Gupta - Chevy Chase MD, US

Assignee:

OPNET Technologies, Inc. - Bethesda MD

International Classification:

H04L 12/26
H04L 12/28

US Classification:

370245, 370252, 370389

Abstract:

A routing validation method and system identifies routers that are likely to be the cause of differences in forwarding tables associated with two versions of a network. Each destination sub-network prefix is processed to identify all the routers that exhibit differences in their forwarding table for this prefix. Each router exhibiting a difference is assessed to determine whether the difference may have been propagated to this router from another router. If the difference could not have been propagated from another router, this router is identified as a potential source of the observed difference. By eliminating routers that could have received the effects of the differences from another router, the task of identifying the root cause of the observed differences is substantially reduced in complexity.

US Patent:

7693699, Apr 6, 2010

Filed:

Aug 11, 2006

Appl. No.:

11/503553

Inventors:

Pradeep K. Singh - Arlington VA, US
Raymond Onley - Hagerstown MD, US
Nishant Gupta - Rockville MD, US
Alain J. Cohen - Washington DC, US

Assignee:

OPNET Technologies, Inc. - Bethesda MD

International Classification:

G06F 17/50

US Classification:

703 13, 709223, 707203

Abstract:

In a network simulation system, a compiler is provided to support incremental updates to the configuration data associated with the modeled network. Each incremental change is identified and logged, to facilitate configuration management and select roll-backs to prior configurations. Because each update is processed and managed individually, and integrated automatically into the overall system configuration, the overhead associated with keeping a configuration database up-to-date is substantially reduced, thereby increasing the likelihood that all configuration changes will be reflected in the modeled network. In a preferred embodiment, the same data is used to incrementally update the configuration model and to execute the change in the actual system, thereby further reducing the overhead and assuring a correspondence between the modeled network and the actual network.

US Patent:

7729256, Jun 1, 2010

Filed:

Jul 13, 2005

Appl. No.:

11/180879

Inventors:

Patrick J. Malloy - Washington DC, US
Michael Cohen - Chicago IL, US
Alain J. Cohen - Washington DC, US

Assignee:

OPNET Technologies, Inc. - Bethesda MD

International Classification:

G01R 31/08
G06F 15/173

US Classification:

370235, 709224

Abstract:

A system/method searches a traffic stream for a sequence of “matching” packets that exhibit a high degree of correlation or similarity to a sequence of “reference” packets. The correlation between matching and reference packets is based on a degree of correspondence between individual packets, as well as the sequence-order of the corresponding packets. A variation of the Needleman-Wunsch algorithm is preferably used to select corresponding packets in the traffic stream that provide a sequence-order that best matches the sequence-order of the reference packets, based on a measure of the correspondence for each match, and a penalty associated with each non-match. The algorithm is further modified to reduce the required search-space for finding corresponding packets in the traffic stream.