Editing Transmission Control Protocol (section)

====Error detection====
Sequence numbers allow receivers to discard duplicate packets and properly sequence out-of-order packets. Acknowledgments allow senders to determine when to retransmit lost packets.

To assure correctness a checksum field is included; see {{slink||Checksum computation}} for details. The TCP checksum is a weak check by modern standards and is normally paired with a [[cyclic redundancy check|CRC]] integrity check at [[layer 2]], below both TCP and IP, such as is used in [[Point-to-Point Protocol|PPP]] or the [[Ethernet]] frame. However, introduction of errors in packets between CRC-protected hops is common and the 16-bit TCP checksum catches most of these.<ref>{{Cite conference|last1=Stone |last2=Partridge |title=Proceedings of the conference on Applications, Technologies, Architectures, and Protocols for Computer Communication |chapter=When the CRC and TCP checksum disagree |journal=ACM SIGCOMM Computer Communication Review |pages=309–319 |year=2000 |chapter-url=http://citeseer.ist.psu.edu/stone00when.html |doi=10.1145/347059.347561 |citeseerx=10.1.1.27.7611 |isbn=978-1581132236 |s2cid=9547018 |access-date=2008-04-28 |archive-date=2008-05-05 |archive-url=https://web.archive.org/web/20080505024952/http://citeseer.ist.psu.edu/stone00when.html |url-status=live }}</ref>