Browse Prior Art Database

Data Overlap Architecture

IP.com Disclosure Number: IPCOM000121044D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 3 page(s) / 109K

Publishing Venue

IBM

Related People

Craddock, DF: AUTHOR [+3]

Abstract

A significant problem in the development of effective communications systems for teleprocessing is the need to relay information from one data link to another as quickly as possible. This process is even more critical in the case of interactive data transfers (e.g., transfers where each command or data is acknowledged before the next is sent). The data overlap architecture discussed here provides a significant performance enhancement over the traditional store-and-forward approach, by having the communications controller generate responses after correctly receiving the data, rather than waiting for a response from the remote station.

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Data Overlap Architecture

      A significant problem in the development of effective
communications systems for teleprocessing is the need to relay
information from one data link to another as quickly as possible.
This process is even more critical in the case of interactive data
transfers (e.g., transfers where each command or data is acknowledged
before the next is sent). The data overlap architecture discussed
here provides a significant performance enhancement over the
traditional store-and-forward approach, by having the communications
controller generate responses after correctly receiving the data,
rather than waiting for a response from the remote station.

      In a store-and-forward approach, a message transmitted from one
unit (which shall be referred to as the master) is received by the
communications controller and is stored temporarily.  It is then sent
on to the receiving station (referred to as the slave), where it is
acknowledged or acted upon, resulting in a response message in the
return direction.  This return message is then stored by the
communications controller and is forwarded to the master station.
Once this message is received a second command or data message can be
initiated.  The communications controller usually must perform some
speed or protocol conversion, so it cannot be simply eliminated.
(See Fig. 1).

      A variation of this approach begins transmission of the data
being received before the entire message is received. This allows the
near simultaneous relay of the data down the link.  This only works
when going from a fast link to a slow link and still requires the
slave's response to reach the master before the next data message can
be transmitted.

      In the data overlap approach, the first message is transmitted
from the master to the communications controller.  Once it is
received, the communications controller determines the required
response to the message and transmits this response back to the
master station at the same time as it is forwarding the message to
the slave station.  The master is then free to send the next message
before the slave has even responded to the first...