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Date:      Thu, 13 Feb 2003 23:09:06 -0800
From:      Terry Lambert <tlambert2@mindspring.com>
To:        Brad Knowles <brad.knowles@skynet.be>
Cc:        Rahul Siddharthan <rsidd@online.fr>, freebsd-chat@freebsd.org
Subject:   Re: Email push and pull (was Re: matthew dillon)
Message-ID:  <3E4C9612.2777D62E@mindspring.com>
References:  <20030211032932.GA1253@papagena.rockefeller.edu>				 <a05200f2bba6e8fc03a0f@[10.0.1.2]>				 <3E498175.295FC389@mindspring.com>			 <a05200f38ba6f51f20eff@[10.0.1.2]>			 <3E49C434.D8D497EE@mindspring.com>		 <a05200f44ba6fe5dff1a0@[10.0.1.2]>		 <3E4A83BC.8A15E7C3@mindspring.com>	 <a05200f4fba70847460b3@[10.0.1.2]>	 <3E4B12F5.2608BBB@mindspring.com> <a05200f5cba7146e25655@[10.0.1.2]> <3E4BB64E.A9AEED28@mindspring.com> <a05200f06ba71eac7fe1c@[10.0.1.2]>

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Brad Knowles wrote:
> At 7:14 AM -0800 2003/02/13, Terry Lambert wrote:
> >>          Okay, what parts of the problem doesn't Perdition solve?
> >
> >  Replication and failover.
> 
>         True.  But is the POP3/IMAP4 proxy really the best place to try
> to solve this problem?

No... but does  proxy really solve anything, then, more than
a DNS rotor solves?  All it really does is add a single point
of failure.  Unless you can target a subset of back end content
servers, you might as well use DNS round-robin.  Using a proxy
implies the back end replica problem is *already* solved.


> >  The result is that you provide a unified view onto a backend farm,
> >  but you lack replication and failover in the back-end, and it does
> >  not magically appear, merely because you are running Perdition.
> 
>         Fair enough.  But how does this relate to the domain problem?
> That's all you had mentioned previously.

A proxy server doesn't solve the domain problem; Perdition was
*your* answer to the domain problem.  8-).


> >  There are other POP3 and IMAP4 proxies that can do the same things
> >  Perdition can: it's no big deal.
> 
>         I've done some research in this area.  I'd be interested to know
> which ones you're talking about.

The Cyrus one seems OK.  Personally, I'd never use a proxy for
this, except to front-end the authentication.  Even then, it's
somewhat of a tossup as to whether it really has any utility,
unless it's capable of targetting a subset of the back end (in
other words, it has a priori knowledge of where the replica
lives; maybe it does LDAP lookups to select a backend server to
point the client to).  At that point, you are better taking the
LARD/CARD approach, and adding "referral" to the IMAP4 protocol,
and just handling it at the server level as a peering relationship,
so the reason you'd do it is to avoid modifying client programs.


> >                                    In fact, it doesn't deal with
> >  LDAP, which is probably where the routing to the back end store will
> >  occur.
> 
>         Do I really need to quote the relevant sections of
> perdition/db/ldap/perdition.schema, dated Mar 27, 2002?

Maybe I should say "doesn't deal with LDAP the way it should"
instead?

-- Terry

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