Browse Prior Art Database

Early Termination of Multicast Queries

IP.com Disclosure Number: IPCOM000122683D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Auerbach, J: AUTHOR [+5]

Abstract

Disclosed is a performance improvement in client-server distributed computing that enables a client to terminate queries early, without requiring all servers to reply. In this model, a single client transmits a query to a group of servers and awaits their replies. Many applications fit this model: only such example is the search of a distributed directory; another example is parallel processing where a client directs a single job stream (such as a series of remote procedure calls) to multiple processors for parallel execution. Performance is a key requirement of such applications. The problem is termination: that is, without requiring all servers to reply, how does the client know when to abandon a query? This disclosure improves performance by enabling a client to terminate queries early.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Early Termination of Multicast Queries

      Disclosed is a performance improvement in client-server
distributed computing that enables a client to terminate queries
early, without requiring all servers to reply.  In this model, a
single client transmits a query to a group of servers and awaits
their replies.  Many applications fit this model: only such example
is the search of a distributed directory; another example is parallel
processing where a client directs a single job stream (such as a
series of remote procedure calls) to multiple processors for parallel
execution.  Performance is a key requirement of such applications.
The problem is termination: that is, without requiring all servers to
reply, how does the client know when to abandon a query?  This
disclosure improves performance by enabling a client to terminate
queries early.

      Throughout, it is assumed that the client needs to receive
replies only from servers that have pertinent information in response
to a query ("positive replies"); there are no "negative replies."  It
is also assumed that each query is labeled with a unique query
identifier (QID), enabling the correlation of queries and replies.

      When a client uses a timer as a means to determine when to
abandon a query, setting the timer appropriately can be difficult,
due to constantly changing network characteristics and conditions.
Conservatively, the timer must be set somewhat longer than necessary
so as not to abandon the query prematurely and lose valuable replies.
In a situation where the client multicasts a query for ALL instances
of a target to a group of servers and the servers are only obliged to
reply if they have the queries information, disclosed are two
alternate ways to terminate a query before the client's timer
expires.
      1. Before performing the multicast query to the server group,
the client determines in advance the number of servers n currently in
the multicast group.  The client obtains this in...