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Browse Prior Art Database

Two Phase Resource Queries with a Suppressible Second Phase

IP.com Disclosure Number: IPCOM000122660D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 3 page(s) / 163K

Publishing Venue

IBM

Related People

Derby, JH: AUTHOR [+5]

Abstract

Disclosed is a method to perform distributed queries for local area network (LAN) resources using a two-phase query procedure having a low-cost phase I and a suppressible high-cost phase 2, that applies to a networking environment where LANs are interconnected by a wide area network (WAN). Under conditions to be defined below, one or more servers sends a PENDING reply during phase 1 that signals the client to suppress phase 2. It minimizes the number of LAN broadcasts affecting all LAN segments of a bridged LAN, and takes advantage of fast switching capabilities such as those disclosed in (*).

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 38% of the total text.

Two Phase Resource Queries with a Suppressible Second Phase

      Disclosed is a method to perform distributed queries for
local area network (LAN) resources using a two-phase query procedure
having a low-cost phase I and a suppressible high-cost phase 2, that
applies to a networking environment where LANs are interconnected by
a wide area network (WAN). Under conditions to be defined below, one
or more servers sends a PENDING reply during phase 1 that signals the
client to suppress phase 2.  It minimizes the number of LAN
broadcasts affecting all LAN segments of a bridged LAN, and takes
advantage of fast switching capabilities such as those disclosed in
(*).

      The following terminology applies throughout this article.
Resources are sources and sinks of data that use the WAN's transport
services.  Directory Service is a collection of functions that uses a
distributed database to support the mapping of resource (type, name)
tuples to WAN transport addresses.  Queries to the directory database
use a client-server distributed computing paradigm such as that of
Advanced Peer-to-Peer Networking.  Client refers to the sender of a
query.  Server refers to the receiver of a query.  Depending on the
protocol, the server may send a reply to the client.  If the client's
query is a multicast (i.e., a one-to-many transmission), then more
than one server can receive the query and, possibly, respond.  Access
agents provide standard interfaces or points of attachment where
protocol-specific LAN traffic enters the WAN.  Access agents contain
one or more protocol agents.  A protocol agent knows a particular LAN
protocol, for example, IEEE standard 802.2 or 802.5.  Access agents
assume the role of client or server to initiate or respond to
directory queries.  Access agents associated with a LAN handle
queries for resources of the particular type supported by the
protocol agent(s).

      When an access agent detects a message on the local LAN
addressed to an unknown destination LAN station, rather than
broadcasting the message to all interconnected LANs as a bridge
would, it sends a query to like access agents.  This invention
applies to queries of the type that cause an access agent
conditionally to perform some type of signaling on the attached LAN,
the results of which are returned to the client that initiated the
query.  It is assumed that:

      A function exists to populate an access agent directory with
data about local resources; and

      LAN protocols that cause a client directory agent to initiate a
query use timers to terminate an unsuccessful query.

      The client access agent sends this initial query, called a
"phase 1 query", as an unreliable multicast.  The client labels the
query with a unique query identifier (QID) in order to correlate
query replies, and so that the network can unambiguously distinguish
one query from another.  (Each reply will carry the same QID as the
related query.)  The...