Path: utzoo!censor!geac!torsqnt!news-server.csri.toronto.edu!cs.utexas.edu!usc!samsung!think.com!barmar From: barmar@think.com (Barry Margolin) Newsgroups: comp.protocols.tcp-ip Subject: Re: ? : TCP Data Integrity Message-ID: <1991Feb28.063456.4039@Think.COM> Date: 28 Feb 91 06:34:56 GMT References: Sender: news@Think.COM Distribution: comp Organization: Thinking Machines Corporation, Cambridge MA, USA Lines: 19 In article mock@watt.support.Corp.Sun.COM (Joseph Mocker) writes: >I've been reading up on the TCP/IP protocol suite and I got a question about >TCP. I can't seem to find out how TCP insures data integrity? in the >TCP Segment header, there is a checksum field, but that seems to be only >for the Header information. So by that, we know that the data got to the >right place, but there is nothing that checksums the data sent. Is this up >to the user program? How is data integrity kept in a TCP transaction? You apparently misread. TCP checksums the entire segment. UDP's optional checksum is also of the entire datagram. IP, however, has a header-only checksum, but IP doesn't claim to ensure data integrity. It was designed so that it could be used by applications that care more about speed than accuracy (e.g. digitized voice). -- Barry Margolin, Thinking Machines Corp. barmar@think.com {uunet,harvard}!think!barmar