Browse Prior Art Database

Selective Repeat Protocol for Communication Systems

IP.com Disclosure Number: IPCOM000039971D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bux, W: AUTHOR [+3]

Abstract

This article discloses an improvement for a protocol in a communication system in which messages or packets are transferred in frames between partner stations over a network, and in which, in case of an error, the transmission of frames is selectively repeated. In particular, the article proposes an improvement of the Checkpoint Mode protocol (CPM), which is a special type of Selective Repeat protocol. CPM employs two types of frames: information frames and checkpoint frames. Each of the information frames which are sent from sender to receiver has a field Ns for the current number of the respective frame.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 1 of 1

Selective Repeat Protocol for Communication Systems

This article discloses an improvement for a protocol in a communication system in which messages or packets are transferred in frames between partner stations over a network, and in which, in case of an error, the transmission of frames is selectively repeated. In particular, the article proposes an improvement of the Checkpoint Mode protocol (CPM), which is a special type of Selective Repeat protocol. CPM employs two types of frames: information frames and checkpoint frames. Each of the information frames which are sent from sender to receiver has a field Ns for the current number of the respective frame. The checkpoint frames, which are sent from receiver to sender, have a field Nr for positively acknowledging the latest correctly received information frame, and a field for values Nx which are a negative indication of information frames which were not yet correctly received. The CPM protocol is covered in detail in U.S. Patent 4,439,859. It is suggested that two additional fields are introduced in the checkpoint frames, as shown in the table below, for counting and acknowledging also the checkpoint frames and not only the information frames. The two fields are destined for a value Cs which is the current number of the respective checkpoint frame, and for a value Cr which is the number of the last correctly received checkpoint frame. The improved checkpoint frame has the following fields: Cs is used to sequentially number the checkpoint fr...