Subject: RE: Applicability of LDAP Content Sync to loosely coupled replica sets

From: "Kurt D. Zeilenga" <[email-masked]>
Date: Sat, 07 Jun 2003 18:56:28 -0700

(Before responding to your latest post on with thread, I'd like
to discuss this point just a bit more because it seems to be
part of reason why we're disagreeing.)

At 06:36 PM 6/5/2003, Jeff Parham wrote:
>The key difference between LCUP and LDAP
>Content Sync is the ability to assert the "member objects" without
>forcing a reload.  The implication is that an incremental sync can force
>the client to drop previous knowledge, which seems to be the heart of
>the problematic example I illustrated.  LCUP doesn't have such a
>mechanism; knowledge is lost only on a full reload. 

And previously you said:
>Objects can be removed from the client only upon an LCUP full reload...

These statement surprises mean because I believe LCUP because
supports such a mechanism to remove objects during incremental
update.  However, I was re-reading the draft-ietf-ldup-lcup's
appendix of features left out of LCUP and came across this statement:

   The leftSet feature is particularly useful because it indicates to   
   the client that an entry is no longer within the client's search    
   specification and the client can remove the associated data from its
   data store.  Ironically, this feature is the hardest to implement on
   the server because the server does not keep track of the client's    
   state and has no easy way of telling which entries moved out of scope
   between synchronization sessions with the client.  A compromise could
   be reached by only providing this feature for the operations that    
   occur while the client is connected to the servers.

That is, this appendix implies that LCUP's entryLeftSet feature is
only available during persist mode.  That seems consistent with your
recent comments in this thread.

However, this seems quite counter to Section 4.2.7 which implies
that entryLeftSet is used during incremental synchronization
and the convergence guarantee implies that the server is to use
this to advise the client to drop knowledge as needed.

Please clarify.

Kurt

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From: [email-masked] (Mark C Smith)
Date: Mon, 09 Jun 2003 10:01:18 -0400

Kurt D. Zeilenga wrote:
> ... However, I was re-reading the draft-ietf-ldup-lcup's

If I remember correctly, the entryLeftSet feature was not in the 
original LCUP proposal but was added later due to popular demand. The 
appendix is just out of date. At least I am pretty sure it is. I have a 
vague memory of asking Rich Megginson to remove some of the material 
from that appendix; maybe I missed this one. Note that the entryLeftSet 
BOOLEAN is not optional, so servers must supply a value regardless of 
what sync mode is in use.

-Mark