Practical Math and Algorithms for TCP/IP checksum

Document Type Expired Internet-Draft (individual)
Author Heikki Heikkila
Last updated 2013-05-08 (latest revision 2012-11-04)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document reformulates the definition of TCP/IP checksum. The new formulation is equivalent to the traditional one, but it uses much simpler mathematics, avoiding concepts like "one's complement sum". This document attempts to be helpful for both newbies and seasoned engineers when considering checksum problems. Practical calculation and software examples are included.


Heikki Heikkila (

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