Browse Prior Art Database

Topological Addressing on Loops

IP.com Disclosure Number: IPCOM000045648D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Croisier, A: AUTHOR

Abstract

In communications systems having multiple terminals in a loop or similar configuration, a specific address is assigned to each terminal so that messages may be routed from the control communication host system to the terminals and back. An individual address is generally incorporated in each terminal as part of the hardware or programming during installation. This article describes a system In which the terminals are all identical and yet can be individually addressed by the host system and will recognize their own addresses as such.

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Topological Addressing on Loops

In communications systems having multiple terminals in a loop or similar configuration, a specific address is assigned to each terminal so that messages may be routed from the control communication host system to the terminals and back. An individual address is generally incorporated in each terminal as part of the hardware or programming during installation. This article describes a system In which the terminals are all identical and yet can be individually addressed by the host system and will recognize their own addresses as such.

The proposed system assumes that the terminals are connected in a loop configuration. It also assumes that the information bits are arranged in time as a periodic sequence of time slots, frames and superframes (by increasing order of size).

It is further assumed that the terminals are able to acquire bit, slot and frame synchronization through some means not described here.

Two-bit positions in each frame need to be reserved for superframe synchronization and station topological address recognition. They are used as follows.

The host system generates a unique periodic sequence of bits whose length is equal to the number of frames in a superframe. The unique sequence is such that its origin is easily identified in each period.

The unique sequence is inserted by the host in both the first and second reserved bit positions of each frame. The bits contained in these two positions are thus identical for any given frame as they leave the host system. The two-bit positions are referred to as SF (superframe) and DSF (delayed superframe).

Each terminal passes the SF bit unchanged to the next terminal on the loop, and it also passes the DSF bit but with one frame delay. In other words, each DSF bit received is stored for one full frame before being passed to the next terminal.

When a terminal recognizes the origin of the SF sequence, it knows that it is receiving the first frame in the superframe. The terminal now counts the number of frames which elapse until it sees th...