Subject: [dhcwg] Fwd: Questions about RA flags (M, O) processing

From: 차현욱 <[email-masked]>
Date: Tue, 09 Oct 2007 05:30:48 +0000 (GMT)

Dear, all.

For the previous questions, I checked the behavior of a Windows Vista DHCPv6 client.
Maybe many folks already know this, but I want to share the results and get helpful ideas and advices from the DHC WG.

If the dhcpv6 client received a RA message with M flag set to 1 at first, it begined to solicit by SOLICIT messages. Then, immediately after it received following RA message with M flag set to 0, it released leases addresses by RELEASE messages.
If the dhcpv6 client received a RA message with M flag set to 0 and O flag set to 1 at first, it started as the stateless mode by INFO-REQUEST messages. Then, when it received following RA message with M flag set to 0 and O flag set to 0, it removed all other config informations including DNS server addresses.
When the client received multiple RA messages with flags set to different combinations from different Routers or different links in one router, it performed infinitely iterative operations between stateful (SOLICIT-REQUEST) and stateless (INFO_REQUEST). 

I did not find any RFCs and drafts addressing these issues. Is there anybody who knows helpful informations and experiences of implementations which tackled these?

Many thanks, 

Joseph Cha

------- Original Message -------
Sender : 차현욱<[email-masked]>  E4(선임)/선임/개발1그룹(I/Infra)/삼성전자
Date   : 2007-10-04 17:07
Title  : Questions about RA flags (M, O) processing

Dear, all.

I have questions about RA flags (M, O) processing. 
From the TAHI conformance spec document, I know that if the client already has an active binding, changes of M flag (1->0->1) does not affect behavior of the client. Also, as long as stateless dhcp client initiated does not receive Reply message, changes of O flag (1->0) does not affect behavior of the client.
If so, I want to know cases where changes of flags affect behavior of a client after it was triggered(or enabled) in the manner of stateful or stateless mode. 
Please give me detailed scenarios and explanations. 
Thank you in advance.

Regards, 

Joseph HyunWook Cha

The truth will set you free !!!

Software Engineer 
Development Part 1. I/Infra  
Network System Division 
Tel 031-279-3804  Mobile 010-3024-3804

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From: Alexandru Petrescu <[email-masked]>
Date: Tue, 09 Oct 2007 14:45:43 +0200

차현욱 wrote:
> Dear, all.
> 
> For the previous questions, I checked the behavior of a Windows Vista
>  DHCPv6 client. Maybe many folks already know this, but I want to 
> share the results and get helpful ideas and advices from the DHC WG.
> 
> If the dhcpv6 client received a RA message with M flag set to 1 at 
> first, it begined to solicit by SOLICIT messages. Then, immediately 
> after it received following RA message with M flag set to 0, it 
> released leases addresses by RELEASE messages. If the dhcpv6 client 
> received a RA message with M flag set to 0 and O flag set to 1 at 
> first, it started as the stateless mode by INFO-REQUEST messages. 
> Then, when it received following RA message with M flag set to 0 and 
> O flag set to 0, it removed all other config informations including 
> DNS server addresses. When the client received multiple RA messages 
> with flags set to different combinations from different Routers or 
> different links in one router, it performed infinitely iterative 
> operations between stateful (SOLICIT-REQUEST) and stateless 
> (INFO_REQUEST).

GReat to know thanks.

For information, linux recent kernels seem to ignore the M==1 flag in RA
and do auto-configure addresses statelessly, without invoking DHCPv6
transactions.  Which is not very good, it should do DHCPv6 SOLICIT, IMHO.

> I did not find any RFCs and drafts addressing these issues. Is there 
> anybody who knows helpful informations and experiences of 
> implementations which tackled these?

Err... rfc4862 (recently upgrading rfc2462 says):
> o  Removed the text regarding the M and O flags, considering the 
> maturity of implementations and operational experiences. ManagedFlag
> and OtherConfigFlag were removed accordingly.  (Note that this change
> does not mean the use of these flags is deprecated.)

Reading this text one would think that M flag is no longer used in RA.
Then reading rfc4861 (recently obsoletes rfc2461) one sees:
> M              1-bit "Managed address configuration" flag.  When set,
> it indicates that addresses are available via Dynamic Host
> Configuration Protocol [DHCPv6].

So, yes, I think rfcs and their implementations should be updated
accordingly.

Alex

> 
> Many thanks,
> 
> Joseph Cha
> 
> ------- Original Message ------- Sender : 차현욱 
> <[email-masked]>  E4(선임)/선임/개발1그룹(I/Infra)/삼성전자 Date   : 
> 2007-10-04 17:07 Title  : Questions about RA flags (M, O) processing
> 
> 
> Dear, all.
> 
> I have questions about RA flags (M, O) processing. From the TAHI 
> conformance spec document, I know that if the client already has an 
> active binding, changes of M flag (1->0->1) does not affect behavior 
> of the client. Also, as long as stateless dhcp client initiated does 
> not receive Reply message, changes of O flag (1->0) does not affect 
> behavior of the client. If so, I want to know cases where changes of 
> flags affect behavior of a client after it was triggered(or enabled) 
> in the manner of stateful or stateless mode. Please give me detailed 
> scenarios and explanations. Thank you in advance.
> 
> Regards,
> 
> Joseph HyunWook Cha
> 
> Software Engineer Development Part 1. I/Infra Network System Division
> ------------------------------------------------------------------------
> 
> 
> 
> _______________________________________________ dhcwg mailing list 
> [email-masked] https://www1.ietf.org/mailman/listinfo/dhcwg

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