Subject: [dhcwg] additional questions on dhcpv6-28

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Thu, 23 Jan 2003 17:18:30 +0900

Hello,

I still have a couple of questions (and one tiny comment) of
draft-ietf-dhc-dhcpv6-28.txt.

This is the comment:

In the following line of Section 18.1.6.

      MRC   REL_MAX_MRC

should be

      MRC   REL_MAX_RC

And the followings are questions:

1. What should the client do if the preferred lifetime is larger than
   the valid lifetime for an IA address option in a reply message (to
   request/renew, etc)?

   I think the address should be ignored, as an analogy to the rule
   (c) of RFC 2462 Section 5.5.3, but the dhcpv6 draft is silent on
   this.

2. Does DHCPv6 have a notion of "infinite" lifetimes (and T1/T2
   values)?  If we apply an analogy to RFC 2461, 0xffffffff should be
   "infinity."  Does this make sense for DHCPv6 as well?  I don't have
   a particular opinion, but the DHCPv6 spec should be clear on this,
   because an implementation may or may not apply the analogy to RFC
   2461, which may cause interoperability issues.
   BTW: our current implementation applies the analogy, i.e., we treat
   0xffffffff as infinity.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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From: Ralph Droms <[email-masked]>
Date: Thu, 23 Jan 2003 16:26:19 -0500

Comments in line...

- Ralph

At 05:18 PM 1/23/2003 +0900, JINMEI Tatuya / 
>In the following line of Section 18.1.6.

Yes, thanks for catching that problem.

>    (c) of RFC 2462 Section 5.5.3, but the dhcpv6 draft is silent on

I suggest adding this text to follow the first paragraph of section
18.1.8., Receipt of Reply Messages, in draft-ietf-dhc-dhcpv6-28.txt.

    The client discards any addresses found in any IAs it receives for
    which the preferred lifetime is greater than the valid lifetime.

Are there other cases of invalid parameters or configuration that
should be mentioned here?

>    BTW: our current implementation applies the analogy, i.e., we treat

I think DHCPv6 should treat 0xffffffff as "infinity" in the case of
time values like lifetimes, T1 and T2.  As you implemented
draft-ietf-dhc-dhcpv6-28.txt, did you find any places where the
inclusion of a time value for "infinity" caused a problem with
interpretation of the spec?  Can we simply add a statement early
in the specification, perhaps somewhere in Section 5, "DHCP Constants",
defining 0xffffffff as infinity?

---

From: Jun Xie <[email-masked]>
Date: Thu, 23 Jan 2003 20:05:50 -0800

At 04:26 PM 1/23/03 -0500, Ralph Droms wrote:
[...]
>should be mentioned here?

How about T1/T2 greater than the shortest valid lifetime in an IA?
Is it valid or not? Should it explicitly mention that the combination
of preferred lifetime = 0 and valid lifetime > 0 is valid?

-Jun

---

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Sun, 26 Jan 2003 14:19:01 +0900

>>>>> On Thu, 23 Jan 2003 16:26:19 -0500, 
>>>>> Ralph Droms <[email-masked]> said:

> should be mentioned here?

Regarding the valid and preferred lifetimes, we may have to consider
some or all of the following cases:

- advertise message (from the server to the client)
- solicit, renew, and rebind messages (from the client to the server)

If we take the option "all", the simplest clarification (if any) would
be to update Section 22.6. (IA Address Option), like

     The client and the server ignore any IA Address Options found in
     any IAs they receive for which the preferred lifetime is greater
     than the valid lifetime.

BTW: we may also have to consider the same question you raised for the
case of T1 > T2 > 0: which part of the message should the receiving
node ignore (discard)?
  - the invalid IA Address Option only
  - the entire IA_NA or IA_TA option that contains an invalid IA
    Address Option
  - the entire message

> defining 0xffffffff as infinity?

You may also want to update the following part of Section 22.4:

   Recommended values for T1 and T2 are .5 and .8 times the
   shortest preferred lifetime of the addresses in the IA, respectively.

so that the meaning of ".5 and .8 times" is clear when the "shortest"
lifetime is infinity.  Our implementation sets T1 and T2 to infinity
(0xffffffff) in this case.

					JINMEI, Tatuya