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X.21 Short Hold Mode Implementation

IP.com Disclosure Number: IPCOM000047928D
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Andersson, KI: AUTHOR [+2]

Abstract

In a data network for circuit switching employing user-transparent short disconnect/reconnect, i.e., Short Hold Mode (SHM) type of operation, the reconnect operation is improved by using a Calling/-Called Line Identification (ID) feature instead of a conventional Exchange Station Identification (XID) request/response unit. SHM operation of X.21 switched feature on a data network, such as the Nordic Public Data Network (NPDN), allows switched circuit connection to be maintained only for as long as it is actually required for the transmission of data. The link between two stations in session is disconnected when there is no data to be sent. This approach is made possible when the following characteristics are present in the network: 1. The connect/disconnect times are extremely short. 2.

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X.21 Short Hold Mode Implementation

In a data network for circuit switching employing user-transparent short disconnect/reconnect, i.e., Short Hold Mode (SHM) type of operation, the reconnect operation is improved by using a Calling/-Called Line Identification (ID) feature instead of a conventional Exchange Station Identification (XID) request/response unit. SHM operation of X.21 switched feature on a data network, such as the Nordic Public Data Network (NPDN), allows switched circuit connection to be maintained only for as long as it is actually required for the transmission of data. The link between two stations in session is disconnected when there is no data to be sent. This approach is made possible when the following characteristics are present in the network: 1. The connect/disconnect times are extremely short. 2. The tariff structure specifies a fairly small fee for the call set-up compared to the charge for connect time.

With SHM a connection between two units is maintained only while there is data available for traffic between the units. If there is no data for transfer, the connection is cleared from the primary side after a short timeout, to be reestablished again from either side when there is new data for transfer. The end user is unaware of the disconnect/reconnect activity. At reconnection, the primary and the secondary session partners must have a way to identify each other. The currently proposed solution for implementation of SHM requires that...