Subject: Node Req: Issue31: DHCPv6 text (ignore previous mails)

From: [email-masked]
Date: Thu, 20 Nov 2003 11:12:52 +0200

Hi all,

Please ignore previous mails on this topic,  here is the proposed text:

thanks,
John

> >  In addition, in the absence of a router,
> >    IPv6 Nodes that implement DHCP MUST attempt to use DHCP.
> > 
> > ==> what does "in the absence of a router" mean?  maybe this needs to be
> > made slightly more explicit to be unambiguous..
> 
> Suggested text?

reword:

   For those IPv6 nodes that implement DHCP, those nodes MUST use DHCP
   upon the receipt of a Router Advertisement with the 'M' flag set (see
   section 5.5.3 of RFC2462).  In addition, in the absence of a router,
   IPv6 Nodes that implement DHCP MUST attempt to use DHCP.

to:

   Nodes that implement DHCP MUST use DHCP upon the receipt of a 
   Router Advertisement with the 'M' flag set (see section 5.5.3 of 
   RFC2462).  In addition, in the absence of a router,
   IPv6 Nodes that implement DHCP MUST attempt to use DHCP.  In this 
   context, 'use DHCP' means trying to obtain both address(es) and 
   other configuration information through DHCP.

> >    For those IPv6 Nodes (acting as hosts) that implement DHCP, those
> >    nodes MUST use DHCP upon the receipt of a Router Advertisement with
> >    the 'O' flag set (see section 5.5.3 of RFC2462).  In addition, in the
> >    absence of a router, hosts that implement DHCP MUST attempt to use
> >    DHCP.
> > 
> > ==> attempt to use DHCP _for what_ ?  Getting stateful information, of
> > course, not the addresses?
> 
> Suggested text?

reword:

   For those IPv6 Nodes (acting as hosts) that implement DHCP, those
   nodes MUST use DHCP upon the receipt of a Router Advertisement with
   the 'O' flag set (see section 5.5.3 of RFC2462).  In addition, in the
   absence of a router, hosts that implement DHCP MUST attempt to use
   DHCP. For IPv6 Nodes that do not implement DHCP, the 'O' flag of a
   Router Advertisement can be ignored.  Furthermore, in the absence of
   a router, these types of node are not required to initiate DHCP.

to:

   IPv6 Nodes (acting as hosts) that implement DHCP, MUST use DHCP upon 
   the receipt of a Router Advertisement with the 'O' flag set (see 
   section 5.5.3 of RFC2462).  In addition, in the
   absence of a router, hosts that implement DHCP MUST attempt to use
   DHCP. In this context, 'use DHCP' means trying to obtain only other 
   configuration information through DHCP, not address(es).

   IPv6 Nodes that do not implement DHCP can ignore the 'O' flag 
   of a Router Advertisement.  Furthermore, in the absence of
   a router, these types of node are not required to initiate DHCP.

(these are not only editorial issues IMHO, especially the latter one, 
if someone is envisioning that in absence of a router, DHCP should try 
to get an address as well, from the context of other config 
information)

--------------------------------------------------------------------
IETF IPv6 working group mailing list
[email-masked]
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------

---

From: [email-masked] (Jun-ichiro itojun Hagino)
Date: Thu, 20 Nov 2003 22:40:55 +0900 (JST)

> Please ignore previous mails on this topic,  here is the proposed text:

	the change has to be synchronized with 2462bis effort, am i right?

itojun

---

From: Bob Hinden <[email-masked]>
Date: Thu, 20 Nov 2003 11:50:29 -0800

John,

>    other configuration information through DHCP.

Please remind me why the "in the absence of a router" text is there.  I am 
having a hard time thinking about a scenario where there would be a DHCP 
server, but no router.  The presences of a DHCP relay agent would also need 
a router to be useful.

Thanks,
Bob

---

From: Tim Chown <[email-masked]>
Date: Thu, 20 Nov 2003 21:26:10 +0000

> server, but no router.  The presences of a DHCP relay agent would also need 

One assumes that the router would invariably be the relay agent...
 
Tim

---

From: Thomas Narten <[email-masked]>
Date: Fri, 21 Nov 2003 13:27:36 -0500

> >    other configuration information through DHCP.

For my tastes, there is too much protocol specification above (use of
MUST language). Better to just cite the existing standards.

> server, but no router.  The presences of a DHCP relay agent would also need 

Perhaps because folk have forgotten about existing text in 2461 &
2462? :-)

From section RFC 2461 6.3.7:

>    If a host sends MAX_RTR_SOLICITATIONS solicitations, and receives no
>    Router Advertisements after having waited MAX_RTR_SOLICITATION_DELAY
>    seconds after sending the last solicitation, the host concludes that
>    there are no routers on the link for the purpose of [ADDRCONF].
>    However, the host continues to receive and process Router
>    Advertisements messages in the event that routers appear on the link.

RFC 2462, Section 5.5.2 says:

> 5.5.2.  Absence of Router Advertisements
> 
>    If a link has no routers, a host MUST attempt to use stateful
>    autoconfiguration to obtain addresses and other configuration
>    information. An implementation MAY provide a way to disable the
>    invocation of stateful autoconfiguration in this case, but the
>    default SHOULD be enabled.  From the perspective of
>    autoconfiguration, a link has no routers if no Router Advertisements
>    are received after having sent a small number of Router Solicitations
>    as described in [DISCOVERY].

We can debate whether the current text makes sense, but it reflects
the thinking at the time...

Thomas

---

From: Bob Hinden <[email-masked]>
Date: Fri, 21 Nov 2003 11:19:30 -0800

Thomas,

>MUST language). Better to just cite the existing standards.

Yes, I agree.

>Perhaps because folk have forgotten about existing text in 2461 &

I figured there must be some reason why this text was there.  That's why I 
asked :-)

>the thinking at the time...

Agreed.  Since I don't think DHCPv6 wasn't very far along at the time this 
was written, I wonder if we were thinking about other kinds of stateful 
autoconfiguration that might be useful when there was no router.  Must be 
in the mail archives.

However, this doesn't seem like a useful behavior now.  I think it would be 
best to not restate it in node requirements.

Also, I think we should revisit this text in the RFC2462bis 
effort.  Changing the MUST to MAY in the 5.5.2 paragraph looks like the 
right change to me, but that's a different email thread.

Bob