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Representing Shared Access Facilities in a Computer Network

IP.com Disclosure Number: IPCOM000109199D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Baratz, AE: AUTHOR [+4]

Abstract

In order to compute routes through a computer network, it is necessary to have a representation of that network's topology. This representation is termed a topology database and consists of the identity and characteristics of the nodes in the network and the connections between them. In a topology database, it is difficult to develop a satisfactory representation of connections that use shared access transport facilities (e.g., X.25 or LAN). This is because such facilities provide an 'any to any' connection capability between nodes. A simple representation would be to include every possible connection between node pairs. However, this representation has the problem of excessive storage; N nodes require O(NY) links.

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Representing Shared Access Facilities in a Computer Network

       In order to compute routes through a computer network, it
is necessary to have a representation of that network's topology.
This representation is termed a topology database and consists of the
identity and characteristics of the nodes in the network and the
connections between them.  In a topology database, it is difficult to
develop a satisfactory representation of connections that use shared
access transport facilities (e.g., X.25 or LAN).  This is because
such facilities provide an 'any to any' connection capability between
nodes.  A simple representation would be to include every possible
connection between node pairs.  However, this representation has the
problem of excessive storage; N nodes require O(NY) links.

      In addition, it may not be possible for a node to maintain
concurrent connections with more than a small percentage of the other
nodes using the shared access transport facility (due to hardware
adapter or system storage limitations).  Whenever such a node cannot
establish any additional connections, it must make this  fact known
to any nodes in the network that are computing routes.  With the
simple representation mentioned above, this requires O(N) update
messages, which can cause excessive message traffic in the network.

      This article addresses these two problems by proposing an
alternative representation of shared access transport facilities.

      A connection network (or virtual node) is used to represent
shared access transport facilities (e.g, X.25 or LAN) in the topology
database.  If there were N nodes with access to such a transport
facility, there would be, without the virtual node representation,
Nx(N-1)  links in the topology database ...