FAMILY-HISTORIAN-USERS-L Archives

Archiver > FAMILY-HISTORIAN-USERS > 2003-06 > 1054632547


From: "Roger" <>
Subject: RE: [FHU] Messages out or order.
Date: Tue, 3 Jun 2003 10:29:07 +0100
In-Reply-To: <002d01c322b6$70a723e0$034528d5@oemcomputer>


>On: Sunday, May 25, 2003 1:08 PM
>Margaret North asked:
>
>I appear to be receiving messages out of order. Messages are arriving with
>a response to an earlier email, but the earlier email with the question is
>not arriving until a couple of days later!
>
>Has anyone else experienced this? Does anyone know if it is likely to be a
>problem at my end or what?

Margaret,

I doubt that the problem is anything to do with the FH list - so this reply
is somewhat off topic.

It is not unusual for e-mail messages from a list server to arrive out of
order. This is because, on the Internet, E-mail can take many different
routes between computers; these multiple paths enable higher volumes of
traffic to be handled and provide a degree of resilience. (Indeed, the
original Internet was designed for resilience so that in the event of a war
electronic communications might continue even though various network
components were destroyed.)

For our list, the server hosting the list may have several routes to the
Internet. In addition, your ISP may have several POP3 e-mail servers and
network paths for collecting e-mail from around the world and delivering it
to customers such as yourself. So, someone sends a "query" message to the
list and the server copies the message to everyone on the list. Your copy is
sent to you by, say, path "A". Then a "reply" comes from someone via the
list server and your copy of this "reply" is sent to you from the list
server via a different route to the original query, say by path "B". If
there is a problem on path "A", such as a server or network fault, the
e-mail on path "A" will be held up for a time (or, in the worst, case may
never be delivered to). Meanwhile, the copy of the e-mail "reply to the
query" being sent to you via path "B" is delivered to you. At a later time,
when the problem on path "A" is fixed, the original "query" message to the
list may be delivered to you. Voila, although the two original messages (the
query and first reply) were sent in order, the copies to you arrive in the
reverse order.

There is no guarantee of delivery of e-mail on the Internet and certainly no
mechanism to ensure that individual e-mails will arrive in the same order
(i.e. in time) as they were sent. This is one reason why, from time to
time, you will get messages delivered "out of order", missing messages and
duplicate messages. However, in the main the Internet does a pretty good
job. :-)


I trust that answers your question. :-)

Roger Horton



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