Browse Prior Art Database

Economical Use of Multicast Facility for Resource Queries in a Utility Transport Network

IP.com Disclosure Number: IPCOM000108822D
Original Publication Date: 1992-Jun-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 3 page(s) / 156K

Publishing Venue

IBM

Related People

Auerbach, J: AUTHOR [+9]

Abstract

Disclosed is an efficient use of both point-to-point and multicast routing modes, in a communications network based on fast packet switching facilities such as (*), to support a client-server distributed computing model. While our immediate objective is to provide an infrastructure to support a flexible, high-performance integrated directory service for a wide area network (WAN) that interconnects many types of local networks and devices, the disclosed concept also applies to other types of distributed computing applications in which a client queries a set of servers by sending a multicast, and individual servers may reply directly to the client.

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Economical Use of Multicast Facility for Resource Queries in a Utility Transport Network

       Disclosed is an efficient use of both point-to-point and
multicast routing modes, in a communications network based on fast
packet switching facilities such as (*), to support a client-server
distributed computing model.  While our immediate objective is to
provide an infrastructure to support a flexible, high-performance
integrated directory service for a wide area network (WAN) that
interconnects many types of local networks and devices, the disclosed
concept also applies to other types of distributed computing
applications in which a client queries a set of servers by sending a
multicast, and individual servers may reply directly to the client.

      The following assumptions and terms apply throughout this
article: When a point-to-point routing mode is used over high-speed
links with low bit error rates, any needed reliability and error
recovery can be provided effectively by end-to-end (as opposed to
hop- by-hop) protocols.  A multicast routing mode (i.e., transmission
from a single sender to multiple receivers) is feasible and
cost-effective in such a network.  "Resources" are data sources and
sinks (e.g., including but not limited to LAN stations) that use the
transport services of the WAN.  "Directory service" refers to a
common set of WAN query protocols that map resource (type, name)
tuples to WAN transport addresses, together with the distributed
database that supports them. "Client" and "server" refer to the
sender and receiver of such queries, respectively.  If the client's
query is a "multicast" (i.e., a transmission by one sender to
multiple receivers), then more than one server can receive the query
and, possibly, respond.  The network is engineered such that the
packet loss probability remains acceptable, i.e., does not exceed
some defined threshold, across the average diameter of the network.
Thus even without any mechanism to guarantee perfectly reliable
delivery of every multicast packet to its destination, the
probability that the packets reach all servers that are connected at
the time of the client's transmission is adequately high.  "Access
agents" provide standard interfaces or points of attachment where
protocol-specific LAN traffic is concentrated and switched upon
entering a shared WAN backbone.  Access agents contain one or more
protocol agents responsible for a particular LAN protocol, e.g.,
802.2, TCP.  The access agent handles WAN directory queries for
resources of the type supported by its associated protocol agents.
Access agents can send or receive queries about LAN-resident
resources using the common set of directory protocols defined by the
wide area network.  These queries are sent to access agents of the
same type.

      Before sending a multicast query, the client enables reverse
path accumulation, a feature of the fast packet switching facility.
Reverse path accumulation builds a po...