Browse Prior Art Database

Bit Stealing Technique on Multipoint Synchronous Data Link

IP.com Disclosure Number: IPCOM000044679D
Original Publication Date: 1984-Dec-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Callens, P: AUTHOR

Abstract

This device improves the throughput usability of multidrop lines operating with SDLC (synchronous data link control) or HDLC (high level data link control) procedure. It allows non-priority DTEs (N) to transmit on the return channel to the master modem during the idle times of the priority DTEs (P). This idle time may be due, in a number of systems, to terminals systematically sending for a given delay time W a series of flags (01111110) whenever they are idle while being polled rather than losing a polled slot (Fig. 1). The device (D) installed in each modem detects the IDLE framing flags (i.e., sequence of consecutive F = "01111110") which are emitted in front of their answer by the DTEs (P) when they answer to a poll emitted regularly by the master DTE (P1).

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Bit Stealing Technique on Multipoint Synchronous Data Link

This device improves the throughput usability of multidrop lines operating with SDLC (synchronous data link control) or HDLC (high level data link control) procedure. It allows non-priority DTEs (N) to transmit on the return channel to the master modem during the idle times of the priority DTEs (P). This idle time may be due, in a number of systems, to terminals systematically sending for a given delay time W a series of flags (01111110) whenever they are idle while being polled rather than losing a polled slot (Fig. 1). The device (D) installed in each modem detects the IDLE framing flags (i.e., sequence of consecutive F = "01111110") which are emitted in front of their answer by the DTEs (P) when they answer to a poll emitted regularly by the master DTE (P1). If the DTE (N) with address "n" has raised its request to send (RTS), the device replaces a fixed number of IDLE FLAGS by the bits from this DTE (N). Fig. 2 shows that this operation occurs any time the tributary DTE (P) raises its request to send RTS
(P), i.e., any time the master DTE (P) polls this "n" terminal. At the master modem, as soon as the carrier detection (CD) is raised by the demodulator, the received data are switched to the DTE (N). When the "F" is detected, the data is switched to the DTE (P).

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