Sun Microsystems SunLink SNA 9.1 PU2.1, Руководство по настройке

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D-1
IBM Token Ring Concepts
D
This appendix contains the following sections:
•
Overview - provides an overview of the IBM Token Ring network.
•
Frame Formats - describes the frame formats used to transmit information on
a IBM Token Ring network.
•
Source Routing and Multiple-Ring Operation - describes how to
interconnect multiple rings using Token Ring bridges.
D.1 Overview
The IBM Token Ring is a Local Area Network (LAN) based on a token passing
access method. This token passing access method consists of a special frame,
called a token, that continuously circles the network medium, known as the
ring. A station that needs to communicate with another station must obtain the
token, change it from free to busy, append any applicable data, and transmit
the information. The receiving station recognizes that the frame is being
directed toward it by addressing information embedded in the data, and the
receiving station copies the data into its internal buffers and then releases the
frame back to the ring. When the station that initially sent the data receives the
frame that it transmitted, it examines any frame status information that was set
by the second station, removes the data from the ring, and releases a free
token. The next station on the ring then has the opportunity to transmit data, if
necessary, or pass the free token to the next station. This procedure continues
indefinitely.