Subject: Re: RE: Re: [dhcwg] Operational problem caused by inconsistent RA M andOflags

From: HYUN WOOK CHA <[email-masked]>
Date: Mon, 07 Jan 2008 23:59:01 +0000 (GMT)

Hemant,

Please see my inline comments.

> Personally, as a router person, any network I see with more than one
> router serving the same link seems brain-damaged to me - at least in
> corporate wired LANs or access concentrator networks like cable modem
> deployments there should be only one router serving one link.

> To begin with, you should not have hosts behind modems see two different
> router RA's. Unless there is a very common deployment with over several
> tens of millions of hosts getting affected, any problem is not serious
> enough to consider for the deployment.

I am also a router person developing routers targetting medium and small sized enterprises markets.
Because IPv6 has been not widely deployed in Korea, one of main purposes of my initial posting is to confirm that we should consider this scenario as normal cases even if it is not common and you are the first answerer. I expect that more comments and clear reasons will be given by you and other experts.

> Lastly, even though you did reply to John's question to clarify your
> deployment, I still don't understand your deployment. In replying to
> John's questions on deployment scenario, you mention a modem, but the
> modem is not shown anywhere in your picture. I have snipped your
> original picture below.

I clarified my previous picture as below.

                                     ------------------
                                     | ISP2                  |
    -----------------        | Access_Router2 |
    | ISP1                |       ------------------
    | Acess_Router1 |                   |
    -----------------            CPE_Router
             |                                   |
       CPE_Modem                        |
             |RA(P1, M=1)                 |RA(P2, M=0)
    -------------------------------------------- link0
                 |        |       |       |
                pc1    pc2    pc3   pc4

Thank you.

Jospeph Hyunwook Cha

-----Original Message-----
From: HYUN WOOK CHA [mailto:[email-masked]] 
Sent: Friday, January 04, 2008 11:26 PM
To: Thomas Narten
Cc: ???; dhc WG; ???; ???; ???
Subject: Re: Re: [dhcwg] Operational problem caused by inconsistent RA M
andOflags

Dear Thomas, 

Thank you for your answer. I want to clarify this issue more. 
As for finite bindings obtained via DHCPv6,  you are right. However,
after all addresses with finite lifetimes expire, DHCPv6 clients will
continue to search servers to obtain stateful addresses again. IMO, this
result is to be avoid from the view of the purpose of triggering DHCPv6
client using RA flags. 
In addition, if clients obtained addresses with inifinite lifetimes,
there may be inefficient or bad cases where hosts will be affected by
those addresses. I have no idea what is the cases, but we should
consider this condition.

Joseph HyunWook Cha

------- Original Message -------
Sender : Thomas Narten<[email-masked]> 
Date   : 2008-01-04 10:41 (GMT+09:00)
Title  : Re: [dhcwg] Operational problem caused by inconsistent RA M and
Oflags

HYUN WOOK CHA <[email-masked]> writes:

> Could you tell me why the M flag's change from TRUE to FALSE should 
> not stop DHCPv6 clients?

Because the wording in 2462 says not to do this. Specifically, it
says:

> If the value of the ManagedFlag changes from TRUE to FALSE, the host 
> should continue running the stateful address autoconfiguration, i.e., 
> the change in the value of the ManagedFlag has no effect.

If DHCP is really no longer to be used (and no longer works), the
addresses obtained via DHCP will expire after their lifetime expires. 

Thomas

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