SCOUG-Help: The debacle of email (hi Steven)

Next Meeting: Sat, TBD
Meeting Directions

Be a Member
Join SCOUG

Navigation:

20 Most Recent Documents
Search Archives
Index by date, title, author, category.

Features:

Mr. Know-It-All
Ink
Download!

Supporting Warpstock Phoenix 2023

Supporting Warpstock Orlando 2022

SCOUG:

Home

Email Lists

SIGs (Internet, General Interest, Programming, Network, more..)

Online Chats

Pictures from Sept. 1999

The views expressed in articles on this site are those of their authors.

warptech
SCOUG was there!

SCOUG, Warp Expo West, and Warpfest are trademarks of the Southern California OS/2 User Group. OS/2, Workplace Shell, and IBM are registered trademarks of International Business Machines Corporation. All other trademarks remain the property of their respective owners.

The Southern California OS/2 User Group
USA

SCOUG-HELP Mailing List Archives

Return to [ 14 | March | 2003 ]

>> Next Message >>

Date: Fri, 14 Mar 2003 03:04:52 PST8

From: Peter Skye <pskye@peterskye.com >

Reply-To: scoug-help@scoug.com

To: scoug-help@scoug.com

Subject: SCOUG-Help: The debacle of email (hi Steven)

Content Type: text/plain

=====================================================
If you are responding to someone asking for help who
may not be a member of this list, be sure to use the
REPLY TO ALL feature of your email program.
=====================================================

> Peter Skye said:
>
> >The Domain Name Server returns a round-robin value

Steven Levine wrote:
>
> That's not the way I understand it. If you look at the
> raw response to an:
>
> nslookup -q=MX earthlink.net
>
> which should be equivalent to the request the mail server
> makes. Everything comes back in a single IP packet. This
> implies up to the mail server to do the round robin.

I just ran NSLOOKUP a few times and got different responses.
Yes, all of the Earthlink mail servers are listed -- but not
in the same order. Yet they are in modulo numerical
sequence so it's not just a case of randomly grabbing data
from a database or a sort which doesn't maintain existing
sequence.

Following are the results I got for 9 successive NSLOOKUPs.
The cross-reference table of server url to IP address never
changes so I haven't shown it, but the sequence of the urls
does change in round-robin fashion:

earthlink.net preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net preference = 5, mail exchanger = mx06.earthlink.net
earthlink.net preference = 5, mail exchanger = mx00.earthlink.net
earthlink.net preference = 5, mail exchanger = mx01.earthlink.net
earthlink.net preference = 5, mail exchanger = mx02.earthlink.net
earthlink.net preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net preference = 5, mail exchanger = mx04.earthlink.net

earthlink.net preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net preference = 5, mail exchanger = mx04.earthlink.net
earthlink.net preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net preference = 5, mail exchanger = mx06.earthlink.net
earthlink.net preference = 5, mail exchanger = mx00.earthlink.net
earthlink.net preference = 5, mail exchanger = mx01.earthlink.net
earthlink.net preference = 5, mail exchanger = mx02.earthlink.net

earthlink.net preference = 5, mail exchanger = mx02.earthlink.net
earthlink.net preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net preference = 5, mail exchanger = mx04.earthlink.net
earthlink.net preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net preference = 5, mail exchanger = mx06.earthlink.net
earthlink.net preference = 5, mail exchanger = mx00.earthlink.net
earthlink.net preference = 5, mail exchanger = mx01.earthlink.net

earthlink.net preference = 5, mail exchanger = mx00.earthlink.net
earthlink.net preference = 5, mail exchanger = mx01.earthlink.net
earthlink.net preference = 5, mail exchanger = mx02.earthlink.net
earthlink.net preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net preference = 5, mail exchanger = mx04.earthlink.net
earthlink.net preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net preference = 5, mail exchanger = mx06.earthlink.net

earthlink.net preference = 5, mail exchanger = mx01.earthlink.net
earthlink.net preference = 5, mail exchanger = mx02.earthlink.net
earthlink.net preference = 5, mail exchanger = mx03.earthlink.net
earthlink.net preference = 5, mail exchanger = mx04.earthlink.net
earthlink.net preference = 5, mail exchanger = mx05.earthlink.net
earthlink.net preference = 5, mail exchanger = mx06.earthlink.net
earthlink.net preference = 5, mail exchanger = mx00.earthlink.net

> Next time you are near your sendmail box, get iptrace a
> try. It's possible the mail server is making a different
> kind of request, but if so, I've never found the
> definition. Got a pointer to where this might be defined?

IPTRACE would be a good way to see if the DNS is actually
supplying them in round-robin fashion.

I did a search on some of the DNS RFCs for "robin" and found
that RFC 1034 (1987) discusses a resolver which sits between
the DNS and the requesting program and does some round-robin
selection. I only searched the older RFCs because I haven't
downloaded them in a while, thus I don't have the newer
ones. And if the writer of an RFC calls it something other
than round "robin" then my search wouldn't catch it.

O'Reilly has a new version of their DNS book (for BIND
probably). I almost bought it a couple of months ago but
then said to myself, "Who is ever going to ask me a question
about DNS?"

The documentation for the OS/2 port of BIND has a brief
mention of "ROUND_ROBIN" (apparently a switch, you can turn
it on or off) but the O'Reilly book would be a better source.

A Google search (!) on "dns robin" returned a *lot* of hits;
this one was first:

http://www.webopedia.com/TERM/R/Round_Robin_DNS.html

- Peter

=====================================================

To unsubscribe from this list, send an email message
to "steward@scoug.com". In the body of the message,
put the command "unsubscribe scoug-help".

For problems, contact the list owner at
"rollin@scoug.com".

=====================================================

>> Next Message >>

Return to [ 14 | March | 2003 ]

The Southern California OS/2 User Group
P.O. Box 26904
Santa Ana, CA 92799-6904, USA