Since posting a summary of replies to my query about the meaning of the
"le0: trailer error" on July 20, three additional responses were
Dan Penrod (firstname.lastname@example.org)
Zenon Dewicki (email@example.com)
Matthew R. Hofener (firstname.lastname@example.org)
While in agreement with the responses quoted in the summary, they provided
additional information that might be of interest.
David Penrod quotes from "TCP Illustrated Volume 1 - The Protocols" by
W. Richard Stevens:
2.3 Trailer Encapsulation
RFC 893 [Leffler and Karels 1984] describes another form of
encapsulation used on Ethernets, called trailer encapsulation.
It was an experiment with early BSD systems on DEC VAXes that
improved performance by rearranging the order of the fields in
the IP datagram. The variable-length fields at the beginning
of the data protion of the Ethernet frame (the IP header and the
TCP header) were moved to the end (right before the CRC). This
allows the data portion of the frame to be mapped to a hardware
page, saving a memory-to-memory copy when the data is copied in
the kernel. TCP data that is a multiple of 512 bytes in size
can be moved by just manipulating the kernel's page tables.
Two hosts negotiated the use of trailer encapsulation using an
extension of ARP. Different Ethernet frame type values are
defined for these frames.
Nowadays trailer encapsulation is deprecated, so we
won't show any examples of it. Interested readers are referred
to RFC 893 and Section 11.8 of [Leffler et al. 1989] for
and goes on to add:
So that's what it is... an old kludge to speed up TCP/IP performance on
ethernets. Generally it's not used anymore. It is a flag that can be
set with the 'ifconfig' command.
Matthew Hofener quotes the Sun "System and Network Administration" manual,
Appendix B, "Error Messages from the Monitor and Boot Program", pg. 812.
le%d: trailer error
An incoming packet claimed to have a trailing header but did not.
Again, many thanks to all who responded.
This archive was generated by hypermail 2.1.2 : Fri Sep 28 2001 - 23:09:06 CDT