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Retransmission for Variable Length Blocks of Data on Delay Lines

IP.com Disclosure Number: IPCOM000076313D
Original Publication Date: 1972-Feb-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Day, RG: AUTHOR [+2]

Abstract

This is an apparatus for the minimization of the retransmission of messages between a high-speed data source (reentrant delay line) and a data sink, over a band-limited channel (noisy telephone line) operating within numerous constraints. Data within the circulating delay line is subdivided into sectors defining the maximum length of messages storable therein. Because of the large magnitude data rate differential between the delay line and telephone channel, messages are copied from the delay line into the transmission logic on a per character basis. Individual tag bits associated with each message character are set in a first state and indicate whether a character is to be copied. As a character is copied, its tag is changed to a second state. Consequently, if a message is to be retransmitted (i.e.

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Retransmission for Variable Length Blocks of Data on Delay Lines

This is an apparatus for the minimization of the retransmission of messages between a high-speed data source (reentrant delay line) and a data sink, over a band-limited channel (noisy telephone line) operating within numerous constraints. Data within the circulating delay line is subdivided into sectors defining the maximum length of messages storable therein. Because of the large magnitude data rate differential between the delay line and telephone channel, messages are copied from the delay line into the transmission logic on a per character basis. Individual tag bits associated with each message character are set in a first state and indicate whether a character is to be copied. As a character is copied, its tag is changed to a second state. Consequently, if a message is to be retransmitted (i.e., recopied from the delay line) its tags must be reset. Such tag resetting appears necessary whether some or all of the characters of a sector are to be recopied. It is within this context that it is desired to restrict the transmission of blanks between the last message character and the end of the sector. The apparatus contemplates stopping the recopying after detecting the first blank character. The first blank character is transmitted and serves as an EOM for the retransmitted message. Because the first blank has been altered (a tag bit is associated therewith), subsequent recopying would include the first blank character. Therefore, the number of blanks sent with the message represents the number of retransmissions.

Consider a delay line 7 used to store data in a terminal and that data is to be transmi...