[ih] principles of the internet

[John Day]

Not the same thing.  One must ensure that all copies of a message are 
out of the network.  Dick Watson proved that reliable transfer 
requires bounding 3 timers.  Actually, it is stronger than that, 
bounding them is both necessary and sufficient. Applies to all 
protocols that do synchronization.

At 18:43 +0100 2010/06/04, Tony Finch wrote:
>On Thu, 3 Jun 2010, John Day wrote:
>>
>>  There is no MPL for mail.
>
>If you mean "maximum packet lifetime" then how about RFC 5321 section 6.3:
>
>    Simple counting of the number of "Received:" header fields in a
>    message has proven to be an effective, although rarely optimal,
>    method of detecting loops in mail systems.  SMTP servers using this
>    technique SHOULD use a large rejection threshold, normally at least
>    100 Received entries.  Whatever mechanisms are used, servers MUST
>    contain provisions for detecting and stopping trivial loops.
>
>Tony.
>--
>f.anthony.n.finch  <dot at dotat.at>  http://dotat.at/
>CROMARTY FORTH TYNE DOGGER: SOUTHEAST 4 OR 5, BECOMING VARIABLE 3 OR 4. SMOOTH
>OR SLIGHT, OCCASIONALLY MODERATE AT FIRST IN CROMARTY. FOG PATCHES FOR A TIME,
>SHOWERS LATER IN TYNE AND DOGGER. MODERATE OR GOOD, OCCASIONALLY VERY POOR.