Subject: RE: New LDUP requirements draft

From: [email-masked] (Richard V Huber)
Date: Wed, 28 Mar 2001 19:29:25 -0500

This started out as a reply to Steven Legg's message, but I guess it is
now also a reply to Tim Hahn, Ed Reed, and Kurt Zeilenga.

P7 is a protocol requirement.  The change between previous drafts and
draft -07 was to make it clearer what atomicity information has to be
carried by the protocol.  I don't think this clarification makes it
inconsistent with other parts of the document.

Requirements MM5 and MM6 address what happens when conflicts arise in
multi-master replication that cannot be resolved by the normal conflict
resolution mechanism and would thus cause data loss:

  MM5.  Multi-master replication MUST NOT lose information during
  replication.  If conflict resolution would result in the loss of
  directory information, the replication process MUST store that
  information, notify the administrator of the nature of the conflict
  and the information that was lost, and provide a mechanism for
  possible override by the administrator.

  MM6.  Multi-master replication MUST support convergence of the values
  of attributes and entries.  Convergence may result in an event as
  described in MM5.

So P7 talks about what atomicity information the LDUP protocol must
carry; MM5 and MM6 talk about what happens when you get an
"unresolvable" conflict.  I think they are mutually consistent.

Rick Huber

: From: "Steven Legg" <[email-masked]>
: To: "'Richard V Huber'" <[email-masked]>, <[email-masked]>
: Cc: <[email-masked]>, <[email-masked]>, <[email-masked]>
: Subject: RE: New LDUP requirements draft
: 
: Rick, et al,
: 
: > -We feel that discussion of propagating end state vs. changes is about
: > implementation.  Rather, P6 (now P7 due to other changes) has been
: > rewritten to explicitly require propagation of atomicity of LDAP
: > operations as defined in RFC 2251. We feel it is now self justifying.
: 
: I don't know how I should interpret the new P7 requirement, reproduced
: immediately below.
: 
: > P7.  The protocol MUST preserve atomicity of LDAP operations as defined
: > in RFC2251 [RFC2251].
: 
: The wording is the same in draft-ietf-ldup-replica-req-07.txt and
: draft-ietf-ldup-replica-req-08.txt.
: 
: At face value P7 could be interpreted as requiring a previously accepted
: update to be rejected during replication processing if any part of the
: update, e.g. a single modification in a modify request, is not performed
: because it is redundant, e.g. it attempts to insert a value that already
: exists, or has been superseded, e.g. a more recent update deleted the
: value.
: 
: This interpretation is at odds with other sections of the requirements
: document, contrary to the author's position as I understood it, and
: contrary to the working group consensus, so P7 must mean something else.
: 
: What exactly is P7 requiring of the LDUP protocol ?
: 
: Regards,
: Steven

---

From: "Steven Legg" <[email-masked]>
Date: Fri, 30 Mar 2001 16:37:42 +1000

Rick,

Richard V Huber wrote:
> carried by the protocol.

In my opinion, the requirement is now less clear. The requirement might
now clarify what atomicity information has to be carried by the protocol
but we've lost the immediate context that we are talking about "atomicity
information that must be carried in the protocol". It don't think it is
enough to expect readers will fill in the missing context by noting it
is a *protocol* requirement.

Incidentally, the current draft defines the term "Atomicity Information"
but doesn't use it anywhere.

> I don't think this clarification makes it

Given the understanding that P7 is still about what atomicity information is
required to be carried in the protocol then I agree that it is consistent
with other parts of the document, but my problem is that I believe the
current wording suggests other (possibly inconsistent) interpretations.
A casual reader might not notice that their interpretation doesn't
fit with the rest of the document. Each requirement should be clear
and able to stand on its own without having to analyse the other
requirements to weed out the correct interpretation.

Regards
Steven

---

From: "Ryan Moats" <[email-masked]>
Date: Fri, 30 Mar 2001 08:45:59 -0600

See <rm>...</rm> inline below...  Ryan

Rick,

<rm>Steve, you've totally lost me here.  I don't see where the context
has been lost.  The section talks about protocol and it say specifically
what the protocol must carry.  I disagree that it is less clear.</rm>

<rm>That's true, but I think we should wait until consensus on P7
before removing that definition. We may find we need it again.</rm>

<rm>I saw a similar problem with the previous version and
so we added the reference to RFC 2251 specifically to provide some
clarity.  Are you asking for "LDAP operations" to be replaced by
"LDAP modify operations"?</rm>

Regards
Steven