Subject: Re: Another problem with abandon

From: "Jim Sermersheim" <[email-masked]>
Date: Wed, 20 Nov 2002 09:15:53 -0700

So, I feel compelled to add language that highlights this fact.

!!!!!!
This has the effect of limiting LDAP to only be transmitted over transfer protocols that guarantee order. Is this something everyone can live with forever?
!!!!!!

I will consider your silence as a yes.

Jim

>>> "Jim Sermersheim" <[email-masked]> 11/06/02 09:09PM >>>
Your suggestion Kurt, is what the current draft states. I guess if servers want to avoid the problem, they need to keep track of the order in which requests are received.

Jim

>>> "Kurt D. Zeilenga" <[email-masked]> 11/06/02 05:46PM >>>
At 11:54 AM 2002-11-06, John McMeeking wrote:
>First,  I better say that I agree that it would simplify things if abandon
>had a response.  But I don't think we're broke without a response, and some
>could argue we're broke if it is added.

We should avoid that argument. 

I, personally, think we just need a simple clarification here.
In particular, I think we just need to say that the client should
not reuse any message id unless it is safe to do so, otherwise
behavior is undefined.  We can define safe as "obtained a final
response for the operation or completed a subsequently issued
bind operation."  This implies that clients should avoid reuse of
abandon and abandoned message ids, which most do by use of a
message id counter.  That's plenty good enough for most clients.
Those few where it isn't can use other mechanisms (such as never
reusing an abandon/abandoned message id... and doing a rebind if
one runs out of message ids.

>> Also, we need to allow for LDAP to be transferred over other transports
>(like UDP)
>> which don't guarantie delivery.
>
>Talking UDP,

I don't need to consider UDP.

Kurt

---

From: Hallvard B Furuseth <[email-masked]>
Date: Wed, 20 Nov 2002 18:01:00 +0100

Jim Sermersheim writes:

> This has the effect of limiting LDAP to only be transmitted over
> transfer protocols that guarantee order.

I don't think so.  It has the effect that any definition of LDAP for a
protocol which doesn't guarantee order, must reserve message IDs of
abandoned operations until the next bind.

-- 
Hallvard

---

From: Hallvard B Furuseth <[email-masked]>
Date: Wed, 20 Nov 2002 19:35:36 +0100

> abandoned operations until the next bind.

Oops.  It must reserve the message IDs of abandoned operations, period.
The server might receive the abandon after the bind.

-- 
Hallvard

---

From: Simon Spero <[email-masked]>
Date: Wed, 27 Nov 2002 10:31:17 -0500

>>The server might receive the abandon after the bind.
[The message IDs only need to be reserved for 2MSL (for the same reason 
that TCP is supposed to wait that long for TIME_WAIT blocks to expire)]

CLDAP has never been widely used, and has always had a lot of problems 
dealing with  dropped packets and the mapping to a best effort delivery 
service.  For example, if a search request generates a number of search 
responses, there's no way to detect if any of the matches are lost, 
unless all replies are required to fit in a single datagram.  This makes 
CLDAP pretty useless, since it uses the  same high overhead encodings as 
regular LDAP.  

Whoops - I just rediscovered that I was supposed to write something up 
on this eight years ago (mar 94).  

Simon

---

From: Hallvard B Furuseth <[email-masked]>
Date: Thu, 28 Nov 2002 14:38:58 +0100

> that TCP is supposed to wait that long for TIME_WAIT blocks to expire)]

What if the operation being abandoned takes 4MSL (how much is that?) to
execute, and the abandon request is not honored?

> service.

Well, it's not as if I really care about it myself.

-- 
Hallvard