Subject: Re: [MOBILE-IP] Mobile IP Challenge/Response Extensions

From: "Karim El-Malki (ERA)" <[email-masked]>
Date: Wed, 8 Dec 1999 15:15:31 +0100

Hi Charlie

>  Actually, there are two things wrong with that sentence.  A good
>  replacement sentence might be:
>
>     Just as with Mobile IP, this default algorithm MUST be able to be
>     configured for selection at any arbitrary 32-bit SPI outside of
>     the SPIs in the reserved range 0-255.

I have some comments on this sentence.
Should "MUST be able to be configured" be "MAY be configured"?
For the case in which only a shared secret is available and no SA
has been established, it should be possible to use a reserved
SPI value (e.g. SPI=3) to specify the use of the default algorithm.
I think that this case should be considered.

Also, "Just as with Mobile IP" sounds as if this is not Mobile IP.

Regards
Karim

---

From: "Charles E. Perkins" <[email-masked]>
Date: Wed, 8 Dec 1999 08:11:22 -0800

Hello Karim,

> Should "MUST be able to be configured" be "MAY be configured"?

The intention is to require for any compliant implementation that
the algorithm be configurable at any SPI.  Then, since the
implementation
is guaranteed to support such configurability, the algorithm MAY
subsequently be configured at any SPI.

> I think that this case should be considered.

It might be a good idea to request establishment of SPI==3 (or some
other value) for the default algorithm.  But, can you describe the
way that a shared secret can be established without at the same
tiem establishing a security association?

> Also, "Just as with Mobile IP" sounds as if this is not Mobile IP.

How about "Just as with RFC 2002"?

Regards,
Charlie P.