Li C Zhang

US Patent:

6957357, Oct 18, 2005

Filed:

Jul 31, 2001

Appl. No.:

09/920138

Inventors:

Zhen Liu - Tarrytown NY, US
Cathy Honghui Xia - White Plains NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F001/04

US Classification:

713503, 713400

Abstract:

A method, computer program product, and data processing system for estimating and correcting the amount of clock skew in end-to-end network timing measurements is disclosed. Measured delays are combined with their time of measurement to create ordered pairs. These ordered pairs represent points within a Cartesian plane. The convex hull of these points is determined, and an optimal line segment from the resulting polygon is selected and extrapolated to create an affine function estimating clock skew over time. The optimal line segment of the polygon is one that optimizes a selected objective function. The objective function is selected so as to be an appropriate measurement of the accuracy of the resulting linear function as an estimate of the actual clock skew.

US Patent:

7194649, Mar 20, 2007

Filed:

May 29, 2002

Appl. No.:

10/157610

Inventors:

Zhen Liu - Tarrytown NY, US
Cathy Honghui Xia - White Plains NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1/12

US Classification:

713400, 713375, 713503

Abstract:

Several algorithms are provided to estimate and remove relative clock skews from delay measurements based on the computation of convex hulls. The algorithms are linear in the number of measurement points for the case with no clock resets. For the more challenging case with clock resets, i. e. , the clocks are reset to some reference times during the measurement period, linear algorithms are provided to identify the clock resets and derive the best clock skew lines. The algorithms are also extended to environments in which at least one of the clocks is controlled by Network Time Protocol. These algorithms can also be extended for active clock synchronization to replace or further improve Network Time Protocol.

US Patent:

7272707, Sep 18, 2007

Filed:

May 19, 2004

Appl. No.:

10/849357

Inventors:

Zhen Liu - Tarrytown NY, US
Mukund Raghavachari - Baldwin Place NY, US
Bowei Xi - Beijing, CN
Cathy Honghui Xia - Croton-on-Hudson NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 15/177

US Classification:

713 1, 707 3, 706 19, 718102, 709223

Abstract:

In one embodiment, the present invention is a method and apparatus for automatic system parameter configuration for performance improvement. One embodiment of the inventive method involves formulating a black box optimization problem, and solving the optimization problem using an enhanced smart hill climbing method. The smart hill climbing method includes both a global and a more precise local search to identify an optimal solution. In one embodiment, one or both of the global and local searches employs a weighted Latin Hypercube Sampling method in combination with importance sampling techniques to yield improved search results.

US Patent:

7296256, Nov 13, 2007

Filed:

Oct 20, 2003

Appl. No.:

10/689807

Inventors:

Zhen Liu - Tarrytown NY, US
Petar Momcilovic - New York NY, US
Honghui Xia - Croton-on-Hudson NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 9/44
G06F 9/45

US Classification:

717104, 717149, 717154

Abstract:

Method for modeling the performance of an Information Technology system are disclosed. The method includes the steps of receiving performance data of the system; receiving data of transaction flows and system topology; and inferring service demand parameters based on the received data. If closed form expressions are available to characterize the system, an optimization algorithm based on minimum distance between predicted and measured response times and may be used to obtain the performance parameters. Alternatively, a discrete event simulator together with a set of meta-heuristic search methods may be applied to obtain the optimized performance parameters.

US Patent:

7386611, Jun 10, 2008

Filed:

Dec 10, 2002

Appl. No.:

10/315335

Inventors:

Daniel Manuel Dias - Mohegan Lake NY, US
Richard Pervin King - Scarsdale NY, US
Zhen Liu - Tarrytown NY, US
Mark Steven Squillante - Pound Ridge NY, US
Honghui Xia - Croton on Hudson NY, US
Shun-Zheng Yu - Guangdong, CN
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 15/173

US Classification:

709224

Abstract:

Apparatus and methods for identifying traffic patterns to web sites based on templates that characterize the arrival of traffic to the web sites are provided. Based on these templates, determinations are made as to which web sites should be co-located so as to optimize resource allocation. Specifically, web sites whose templates are complimentary, i. e. a first web site having a peak in arrival traffic at time t and a second web site that has a trough in arrival traffic at time t, are designated as being candidates for co-location. In addition, the present invention uses the templates identified for the traffic patterns of web sites to determine thresholds for offloading traffic to other servers. These thresholds include a first threshold at which offloading should be performed, a second threshold that takes into consideration the lead time needed to begin offloading, and a third threshold that takes into consideration a lag time needed to stop all offloading of traffic to the other servers.

US Patent:

7490234, Feb 10, 2009

Filed:

Aug 3, 2007

Appl. No.:

11/833345

Inventors:

Zhen Liu - Tarrytown NY, US
Mukund Raghavachari - Baldwin Place NY, US
Bowei Xi - Beijing, CN
Cathy Honghui Xia - Croton-on-Hudson NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 15/177
G06F 7/08

US Classification:

713 1, 713100, 707 3, 706 19

Abstract:

In one embodiment, the present invention is a method and apparatus for automatic system parameter configuration for performance improvement. One embodiment of the inventive method involves formulating a black box optimization problem, and solving the optimization problem using an enhanced smart hill climbing method. The smart hill climbing method includes both a global and a more precise local search to identify an optimal solution. In one embodiment, one or both of the global and local searches employs a weighted Latin Hypercube Sampling method in combination with importance sampling techniques to yield improved search results.

US Patent:

7593353, Sep 22, 2009

Filed:

Mar 13, 2004

Appl. No.:

10/800305

Inventors:

Zhen Liu - Tarrytown NY, US
Anton Riabov - New York NY, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H04L 12/28

US Classification:

370256, 370390, 370432

Abstract:

A method for constructing an overlay multicast tree to deliver data from a source to an identified group of nodes is provided in which a plurality of nodes are identified and mapped into multidimensional Euclidean space. A geometric region is constructing having a size that is the minimum size necessary to contain the source and all the nodes. Once constructed, a tree is created beginning at the source and including all of the nodes within the geometric region.

US Patent:

7739099, Jun 15, 2010

Filed:

Dec 22, 2005

Appl. No.:

11/315692

Inventors:

Zhen Liu - Tarrytown NY, US
Honghui (Cathy) Xia - Briarcliff Manor NY, US
Fan Zhang - North Bergen NJ, US
Li Zhang - Yorktown Heights NY, US

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 7/60
G06F 9/45
G06F 11/30
G06F 15/173
G06F 9/44

US Classification:

703 22, 703 2, 702182, 709223, 717104

Abstract:

A system and method for performance modeling for an information technology (IT) system having a server(s) for performing a number of types of transactions includes receiving data for system topology and transaction flows and receiving performance measurement data for the IT system. The measurement data is clustered into multiple regimes based on similarities. Service demand and network delay parameters may be inferred based on clustered data.