Randall Alan Cieslak

US Patent:

54024161, Mar 28, 1995

Filed:

Jan 5, 1994

Appl. No.:

8/177873

Inventors:

Randall A. Cieslak - Scarsdale NY
Christos J. Georgiou - White Plains NY
Chung-Sheng Li - Ossining NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H04L 1256

US Classification:

370 60

Abstract:

A packet switch system having a buffer occupancy reduction mechanism for controlling data flow through switched nodes of the system to avoid congestion and reduce required buffer storage at the nodes. For an isochronous connection, buffers are initially allocated at each switching node connection to ensure listless transmission of packets. A buffer occupancy trace for the connection is recorded and the delay time of an isochronous packet at a particular switch port is returned to a preceding switch port. The preceding switch port employs the feedback message to delay subsequent packets through the connection to reduce the queuing time at the particular switch port. Once the isochronous connection has stabilized, buffer reallocation is performed wherein a scheduler at each switch node along the connection attempts to combine buffer allocations for different isochronous connections. This occurs provided the corresponding buffer occupancy traces of the isochronous connections do not overlap. Buffer occupancy reduction is therefore accomplished through the delaying of isochronous packets propagated through the connections of the packet switch system and the reallocating of buffers initially assigned to two or more isochronous connections.

US Patent:

54758130, Dec 12, 1995

Filed:

Jul 18, 1994

Appl. No.:

8/277377

Inventors:

Randall A. Cieslak - Scarsdale NY
Donald F. Ferguson - Yorktown Heights NY
Jakka Sairamesh - New York NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G06F 1134

US Classification:

39518202

Abstract:

Failures are detected in servers of a transaction processing system, and transactions are routed to less failure prone servers in the system. Servers in the transaction processing system which are faulty for some transaction classes but good for others are detected, and such servers are used in a judicious manner to maximize the throughput and minimize the response time of the system. Error prone servers are occasionally probed to determine if they have improved in terms of their error characteristics. The mechanism implemented consists of three elements. The first is the selection of a routing algorithm based on the state of the transaction processing system. Second, transactions are used to probe systems considered too faulty for use in order to determine if they have improved in terms of their failure characteristics. Finally, soft ABENDs are detected. The algorithm for transaction routing to detect and control the problem of failing servers in a transaction processing system consists of two parts: The first part routes transactions to servers based on the length of the server queues, the response time of the transactions (i. e.