The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 24, 2004
Filed:
Dec. 17, 1999
Paul J. Frantz, Palo Alto, CA (US);
Cisco Technology, Inc., San Jose, CA (US);
Abstract
A method of modifying the error detection code (EDC) generation and verification logic at both ends of a communications link in a data communications device or system so that user packets and control packets use different EDC algorithms to protect the communications device from control packet spoofing and interference by randomly-generated test data. Data packets are transmitted internally with a standard cyclic redundancy check (CRC) or other error detection coding scheme while control packets are given a different “control” EDC. At the receiving end of the link, the received packet is tested to determine whether the EDC matches the standard or control forms. If the EDC complies with neither of these two requirements, then the packet is discarded. If, however, the packet matches the control EDC but not the standard EDC, it is checked to see if the header is in the expected control format. If the control EDC is present but the header is incorrect, the packet is discarded. Otherwise, the packet is a proper control packet having a control header and is processed according to the usual means employed in such communications device. If the EDC matches the standard data EDC form, the packet is again checked for a control header. If a control header is present, a spoof control packet has been received. The system then sets the appropriate alerts and discards the packet. Otherwise, the packet is a standard data packet having a standard header and is ready for further processing.