Subject: [mobile-ip] Prefix lifetime

From: "Peter Grimstrup (TED)" <[email-masked]>
Date: Wed, 19 Dec 2001 12:43:45 +0100

I'm not very familiar with the ND procedures, but anyway here is
my question:

Section 9.1 in ID-15 says:
                                                "The lifetime for
the each Binding Cache entry MUST NOT be greater than the minimum
remaining valid lifetime for all subnet prefixes on the mobile
node's home link."

When a prefix is no longer to be used, the lifetime is decreased
eventually to zero, when the prefix is removed.
While decreasing the lifetime, i.e. when the value has become
"low", it doesn't seem reasonable to use this value as limit
on granted lifetime of a BU.
Could this be avoided by only minimising over prefixes with
nonzero preferred lifetime - or have I misunderstood?

Thanks
	Peter
----------------------------------------------------------------
Peter Grimstrup          Systems Developer
Ericsson Telebit A/S     tel: +45 89 38 52 75
Skanderborgvej 232       fax: +45 89 38 51 01
DK 8260 Viby J, Denmark  e-mail: [email-masked]

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From: Mattias Pettersson <[email-masked]>
Date: Thu, 20 Dec 2001 10:18:16 +0100

Hi Peter,

> nonzero preferred lifetime - or have I misunderstood?

There's something on this as well:

9.8.4. Lifetimes for Changed Prefixes

   As described in Section 9.1, the lifetime returned by the home
   agent in a Binding Acknowledgement MUST be no greater than the
   remaining valid lifetime for the subnet prefix in the mobile node's
   home address.  Furthermore, as described in Section 10.9, Binding
   Updates sent by the mobile node to other nodes MUST use a lifetime no
   greater than the remaining lifetime of its home registration of its
   primary care-of address.  These limits on the binding lifetime serve
   to prohibit use of a mobile node's home address after it becomes
   invalid.  The mobile node SHOULD further limit the lifetimes that it
   sends on any Binding Updates to be within the remaining preferred
   lifetime for the prefix in its home address.

So MN SHOULD limit BU lifetime to preferred lifetime, and HA MUST limit
it to valid lifetime. Sounds fine to me. Deprecated (pref <= 0)
addresses are still valid to use.

/Mattias