zero valid lifetime

Hi, all.

I was confusing about valid lifetime.

<draft-ietf-ipv6-rfc2462bis-08.txt> says
RA with the value 0 of valid lifetime is invalid, if RA isn't authenticated.

  5.5.3  Router Advertisement Processing
  ------------------------------------------------------------------------
  1044       2.  If RemainingLifetime is less than or equal to 2 hours, ignore
  1045           the Prefix Information option with regards to the valid
  1046           lifetime, unless the Router Advertisement from which this
  1047           option was obtained has been authenticated (e.g., via Secure
  1048           Neighbor Discovery [RFC3971]).  If the Router Advertisement
  1049           was authenticated, the valid lifetime of the corresponding
  1050           address should be set to the Valid Lifetime in the received
  1051           option.
  ------------------------------------------------------------------------

Furthermore chapter 8 also says it is invalid clearly.

  8.  Acknowledgements
  ------------------------------------------------------------------------
  1217    Erik Nordmark.  Thanks also goes to John Gilmore for alerting the WG
  1218    of the "0 Lifetime Prefix Advertisement" denial of service attack
  1219    vulnerability; this document incorporates changes that address this
  1220    vulnerability.
  ------------------------------------------------------------------------

But <draft-ietf-ipv6-2461bis-04.txt> says,
the value 0 is just a special case.

  6.3.4.  Processing Received Router Advertisements
  ------------------------------------------------------------------------
  2945       - If the prefix is already present in the host's Prefix List as

  2954         the result of a previously-received advertisement, reset its
  2955         invalidation timer to the Valid Lifetime value in the Prefix
  2956         Information option.  If the new Lifetime value is zero, time-out
  2957         the prefix immediately (see Section 6.3.5).
  ------------------------------------------------------------------------

Unauthenticated RA with valid Lifetime=0 is invalid packet, right?
I feel putting text to 6.3.4 makes 2461bis more clear.
How do you think?

Thanks,

------------------------------------------------------------------------
Yukiyo Akisada <Yukiyo.Akisada@jp.yokogawa.com>

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