I'm seeing occasional errors in files transmitted using TCP (FTP) and I am
trying to locate the source. Since this has been seen with two different
machines I am trying to rule out my infrastructure (switches/routers) as
having any part in this.
It is my understanding that CRC is used at all OSI layers (including layer
4 (tcp)). When doing a IP routing hop, the packet could theoretically be
altered due to a memory error in a router (it's changed for the TTL
anyway) and the IP CRC recalculated and therefore the IP checksum is
"correct" but the data in the packet is not. Would this be caught by the
TCP checksum (L4) when the packet arrives at the end host? I have always
presumed that this would be the case.
I am using Cisco 12000 and 7200 routers, and Extreme Networks switches
(both for L2 and L3). Could any of these meddle with the TCP checksum?
They are theoretically capable of doing this since they support NAT, but
when not in NAT mode, would they?
-- Mikael Abrahamsson email: swmike@swm.pp.se
This archive was generated by hypermail 2b29 : Sun Aug 04 2002 - 04:11:57 EDT