Subject: Re: [MOBILE-IP] [Fwd: Home Agents list: understanding of the list of global addresses]

From: Dave Johnson <[email-masked]>
Date: Tue, 22 Feb 2000 15:28:01 -0500

>Hi!
>
>I sent this to the mailing list last week, but it didn't come back (does
>the mailing list confirm messages?) and nobody answered so far,
>therefore I am let to believe this didn't reach its target.
>Maybe I will be more lucky with direct emailing...
>
>> I would like to ask for your understanding of the following, found in
>> draft-ietf-mobileip-ipv6-10.txt, page 17, about the Home Agents list:
>>
>>           -  One or more global IP addresses for this home agent,
>>              learned through Prefix Information options with the
>>              Router Address (R) bit is set, received in Router
>>              Advertisements from this link-local address.  Global
>>              addresses for the router in a Home Agents List entry MUST
>>              be deleted once the prefix associated with that address is
>>              no longer valid [17].
>>
>> Does this mean that a node might keep, for each home agent (on each
>> interface), at least one global address? Hence, it could only keep the
>> *one* with longest lifetime (and no list of several global addresses is
>> required)?
>> I don't see any drawback here, unless a prefix expires before its
>> advertised lifetime.
>
>Obviously, storing only one global address for each HA is simpler than
>dealing with a whole list and various expiration times. Therefore, I
>would appreciate to understand the reasons behind this requirement of
>storing many global addresses as provided by the router advertisements
>of a single HA.
>
>Guilhem Tardy.

I think it would be fine to keep only the global address with the
longest lifetime for each home agent.  I put the language in there as
it is, due to the simularity with various pieces of Neighbor
Discovery.  In particular, the reason for suggesting that you should
keep multiple addresses is to handle the case of a node's (a home
agent's, in this case) prefix changing.  However, since you never use
these home agent addresses to open a TCP connection to it (for
example), I think there is no need to keep the older addresses (with
the older prefix and shorter remaining lifetime).  I need to think
about this more carefully, but I think what you are suggesting is
fine.

                                        Dave

---

From: Meeta Sharma <[email-masked]>
Date: Tue, 22 Feb 2000 22:02:53 -0800

Hi,

I have one doubt, in RFC2002 , there is nothng mentioned about the
scenario when the home agent crashes!
What if the home agent crashes and the mobile node is in the foreign
network, and there is no home agent on the LAN, to capture the packets
destined for Mobile node, so the packets would be lost and the mobile node
would not know this till it's registration does not expire! Then wouldn't
this lead to an erroneous situation and further degradation???

Looking forward to your response,
Thanks,
Meeta