EP0366589A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Method of maintaining integrity of data during message transmission in a data communication system
Assignee: International Business Machines Corp
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Filing: 1989-10-10
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Granted: —
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Expires: 2009-10-10
Abstract
Abstract In complex networks, data frames may be routed through different systems having different frame or addressing requirements. When the frames are transferred or bridged between such systems, known changes may have to be made in the frame contents to accommodate these requirements. To maintain the integrity of error checking provided by Cyclical Redundancy Checking (CRC) techniques, a system receiving frame modifies a Frame Check Sequence (FCS) field value only as a function of the known or planned changes to be made in the frame. If unplanned changes, that is errors, are introduced at the receiving system, application of standard CRC error checking techniques at the next system to receive the frame will indicate those errors.
Inventors
- 👤 David Ran Irvin
- 👤 Kian-Bon Sy
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 21:04
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/004; H04L1/0056; H04L1/0057; H03; H03M; H03M13/00; H03M13/03; H03M13/05; H03M13/09; H03M13/093; H04L1/0078; H04L1/0083
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
157 words
A method of maintaining integrity of data contained in data frames being routed along a path through a data communications system, in which data frames are transferred from a source station to a destination station through one or more intermediate stations and, predetermined changes are made in each data frame at an intermediate station; said method comprising the steps of: applying a predetermined algorithm to each frame at the originating station to calculate a frame check sequence value (FCS), and modifying the frame check sequence value at each intermediate station on the path by applying the same algorithm to planned changes in the selected fields at the intermediate station to derive a frame check sequence modifier (FCS (m)), and modifying the frame check sequence value contained in the frame received at the intermediate station as a function of the value of said modifier, thereby permitting the next station to detect data errors introduced at the intermediate station.
Claim 2
Independent Claim
157 words
A method of maintaining integrity of data contained in data frames being routed along a path through a data communications system, in which data frames are transferred from a source station to a destination station through one or more intermediate stations and, predetermined changes are made in each data frame at an intermediate station; said method comprising the steps of: applying a predetermined algorithm to each frame at the originating station to calculate a frame check sequence value (FCS), and modifying the frame check sequence value at each intermediate station on the path by applying the same algorithm to planned changes in the selected fields at the intermediate station to derive a frame check sequence modifier (FCS (m)), and modifying the frame check sequence value contained in the frame received at the intermediate station as a function of the value of said modifier, thereby permitting the next station to detect data errors introduced at the intermediate station.
Claim 3
Dependent Claim
153 words
The method as defined in Claim 1 wherein the step of deriving the frame check sequence modifier further comprises the steps of: determining the number of bits k in the selected fields, calculating a first variable equal to the product of xk and (xm-1 xm-2 + xm-3 + ... x + 1) where m is the number of bits in the frame check sequence value, calculating a second variable equal to the remainder resulting from division of the first variable by a predetermined polynomial, setting a third variable equal to the product of xm and the value of the selected fields expressed as a polynomial, calculating a fourth variable equal to the remainder resulting from division of the third variable by the predetermined polynomial, summing the second and fourth variables, taking the 1's complement of results of said summing step, and taking the 1's complement o the results of the immediately preceding step.
References Cited (Backward Citations)
No citation records indexed.
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