Re: [dhcwg] How should a DHCPv6 server respond to retransmitted packets

"Raymond J. Jayabal" <raymondjayaraj@yahoo.com.sg> Sat, 26 October 2002 23:08 UTC

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From: "Raymond J. Jayabal" <raymondjayaraj@yahoo.com.sg>
To: <dhcwg@ietf.org>
Cc: <jraymond@icr.a-star.edu.sg>
References: <4.3.2.7.2.20021025083729.00b859d8@funnel.cisco.com>
Subject: Re: [dhcwg] How should a DHCPv6 server respond to retransmitted packets
Date: Sat, 26 Oct 2002 02:28:29 +0800
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Hi,

Stumbled upon what may or may not be a problem, given that (b) is an
acceptable alternative to (c), as follows.

                              *  *  *

Whether (b) or (c), the client will receive 2 or more REPLY packets.

As the client will leave its 'waiting-for-REPLY' state when it receives
REPLY #1, I assume it will drop REPLY #2 and subsequent REPLY packets
and configure itself based on REPLY #1.

Further assume that the server (or the network it serves, or the
information services it rely on to satisfy client requests) is in
State-1 when request #1 arrives, and State-2 when request #2 arrives.

If (b) is allowed, then the REPLY packets will differ in content. Since
REPLY #2 is last to leave the server, it would have committed to memory
that it sent State-2 data to the client, whereas the client would have
configured itself with State-1 data. This doesn't seem to be a good
situation in the general sense, even if it happens for a short while.

In case of (c), both client and server will always be synchronised.
When State-2 happens, server will know exactly which clients need
updating.

Does this disqualify (b) as an alternative? Or is it still an acceptable
implementation?

- Ray


----- Original Message -----
From: "Ralph Droms" <rdroms@cisco.com>
To: "Raymond Jayaraj" <raymondjayaraj@yahoo.com.sg>
Cc: <dhcwg@ietf.org>rg>; <jraymond@icr.a-star.edu.sg>
Sent: Friday, October 25, 2002 8:41 PM
Subject: Re: [dhcwg] How should a DHCPv6 server respond to retransmitted
packets


> In the case of Information-request, the answer is (b) or (c), depending on
> the implementation.  The responses to retransmitted Informat-request
> messages are likely to be identical, so the use of a response cache
> shouldn't affect the results of the message exchange.
>
> - Ralph
>
> At 10:26 AM 10/25/2002 +0800, Raymond Jayaraj wrote:
> >Hi all,
> >
> >How should a server respond to retransmitted packets
> >received after a
> >REPLY packet is sent, e.g.:
> >
> >DHC6CLIENT      DHC6SERVER      INFOSERVER
> >|               |               (e.g. LDAP)
> >|               |               |
> >|1)INFO-REQ     |               |
> >|>>>            |               |
> >|   >>>         |               |
> >|      >>>      |               |
> >|         >>>   |               |
> >|            >>>|2)processing/retrieve info
> >|3)INFO-REQ     |>>>>>>>>>>>>>>>|
> >|>>>            |<<<<<<<<<<<<<<<|
> >|   >>>      <<<|               |
> >|      >>><<<   |               |
> >|      <<<>>>   |               |
> >|   <<<      >>>|               |
> >|<<< 4)REPLY    |5)???          |
> >
> >What should (5) be? Should the server:
> >
> >a) drop (3) and subsequent duplicates (base on
> >transaction id).
> >
> >b) reprocess the request and retransmit the reply,
> >i.e. do (2)&(4)
> >    again.
> >
> >c) retransmit the reply, i.e. do (4) again.
> >
> >d) do any of the above (implementation specific).
> >
> >No indication for the above could be found in the
> >draft. I suspect
> >it should be a) or d), but it'd be nice to know for
> >sure.
> >
> >------------------------------------------------------------------------
> >Raymond J. Jayabal                 | ICR, A-STAR
> >jraymond@icr.a-star.edu.sg         | 20 Science Park
> >Rd #02-34/37
> >Tel: +65 6870 9330                 | Singapore 117674
> >------------------------------------------------------------------------
> >
> >
> >
> >
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