Browse Prior Art Database

Enhancement of Token Passing Protocols on Shared Resource

IP.com Disclosure Number: IPCOM000104832D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Cheng, T: AUTHOR [+3]

Abstract

Disclosed is a method to enhance the Medium Access Control (MAC) function in shared-resource networks, such as buses or rings. The disclosed method can be applied to shared-resource networks irrespective of their topology.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Enhancement of Token Passing Protocols on Shared Resource

      Disclosed is a method to enhance the Medium Access Control
(MAC) function in shared-resource networks, such as buses or rings.
The disclosed method can be applied to shared-resource networks
irrespective of their topology.

      Bus networks are characterized by any-to-any connectivity and
by the fact that transmitted messages can be received by all nodes
attached to the network, simultaneously.  Since the communication
medium in bus networks is shared, a mechanism must be provided to
avoid collisions.  The concept of token passing can be used for this
purpose.  An example of a token-passing mechanism can be found in the
IEEE 802.4 token-passing bus protocol.  The use of a token as a means
to resolve collisions has also been adopted by the IEEE 802.5 token
ring protocol.  In both these bus and token ring protocols, a station
can access the shared medium only after the arrival of the token.

      In this disclosure, a different approach is adopted, in which
all network nodes are informed in advance about the arrival of the
token.  This is done by defining a token rotation sequence, and
having each node maintain enough information to decide when its turn
comes.  This scheme allows multiple visits of the token to one
particular node within a token rotation cycle.  It also enables the
implementation of medium access priorities.

      The token rotation sequence is specified as follows:  ...