Apparently, once instance of this data corruption problem is caused by an unnamed bandwidth management system. It runs as a bridge, and does not show up in traceroute etc. output. We were able to estimate its location (at 5 ms round-trip time from one endpoint) by analyzing packet arrival times. Until now, this TCP data corruption problem has been observed only when one of the connection endpoints runs a recent LINUX version. Sightings have been reported by sites in Germany and in France. Only recent LINUX versions request the use of timestamp options that cause the tell-tale patterns of "01 01 08 0a" in TCP packets, and that end up being regurgitated as ^A^A^H^J data. I have updated the analysis at ftp://ftp.porcupine.org/pub/debugging/ Wietse Wietse Venema: > This note is about a subtle data corruption problem with TCP data > streams that may bite people as more and more (LINUX) systems are > sending network traffic with TCP-level options turned on. > > Last week, several Postfix users reported mail delivery failures > because sequences of control characters (for example, ^A^A^H) were > being inserted into their SMTP connections, resulting in SMTP > protocol errors and non-delivery of email. > > These data corruption problems are not host specific: they are > observed with both Linux and BSD/OS systems, and with mail sent to > and/or received from systems running Postfix, Sendmail and qmail. > > Over the weekend of March 18, 2000, a few people left tcpdump > running on their machines, in order to record some of these corrupted > SMTP sessions. This note is based on an analysis of that data.
