Subject: [dhcwg] DHCPv6 client handling of NoBinding in Reply message

From: "Jared P. August" <[email-masked]>
Date: Mon, 12 May 2008 14:21:32 -0400

Hello,

Section 18.1.8. of RFC 3315 states the following:

-----------------
When the client receives a Reply message in response to a Renew or
Rebind message, the client examines each IA independently.  For each
IA in the original Renew or Rebind message, the client:

   -  sends a Request message if the IA contained a Status Code option
      with the NoBinding status (and does not send any additional
      Renew/Rebind messages)
-----------------

I have two questions about what actions the client should take when it
receives a NoBinding as described above:
 
1. If the Reply is in response to a Renew message (meaning that the
original server has disavowed knowledge of the binding), should the
client immediately discontinue using the addresses (and maybe even send
Release messages)? Or should it continue to use the addresses, and then
send a Request for those addresses again?
 
2. If the Reply is in response to a Rebind message, and the server is
not the server that originally granted the addresses, which server
should the client send the Request to: The original server, or the new
one that just sent the NoBinding?

Thank you,

Jared August
Senior Engineer
Treck, Inc.

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---

From: "David W. Hankins" <[email-masked]>
Date: Mon, 12 May 2008 12:40:23 -0700

> send a Request for those addresses again?

This is a frequent question.  The implication of 3315 seems to be
that the client retains the address.  Should the server elect not
to return the address to the client, it will set the lifetimes to
zero, and they can safely be removed at that time.

Chances are good the address(es) will be available, and the client
may retain them without ever losing net.

> one that just sent the NoBinding?

That's a good question.  ISC DHCP performs a request upon the active
lease, which means it would use the original server (any cached
unicast address and server ID).

But it's a fair bet that the reason you are Rebinding is because the
original server is offline or not answering.  If you are Renewing
then it is probably (supposed to be) the original server that is
answering.  It may be better to respond to the NoBinding server in
either case; at least you have reason to think they are online.

I think probably the client should use whatever options the
NoBinding server presented; unicast option (using multicast if
it was not present) and server-ID.

-- 
Ash bugud-gul durbatuluk agh burzum-ishi krimpatul.
Why settle for the lesser evil?	 https://secure.isc.org/store/t-shirt/
-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		     you'll just have to do it again."
Internet Systems Consortium, Inc.		-- Jack T. Hankins
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