Subject: [mobile-ip] question on MIPv4 long/short extension formats (second attempt)

From: "Niko A. Fikouras" <[email-masked]>
Date: Mon, 26 May 2003 15:26:12 +0200

It seems that I am having a problem sending this mail, please excuse any 
duplicate copies.

Hi all,

in RFC3344 sections 1.10 and 1.11 define respectively the long and short
extension formats. I would be grateful if anyone could answer the
following questions:

Is it possible for a certain Type to define different Sub-Types each
following a different (short/long) extension format, i.e. for Type 1,
Sub-Type 10 follows the short extension format while Sub-Type 11 follows
the long extension format.

Assuming that the previous case is correct, a mip software processing
such extensions would determine their Length with the help of the
Sub-Type. However, in the short extension format the Sub-Type field is
preceded by the Length field. In that case, the mip software would not
know whether to interpret the second byte of the extension as a Length
field or as a Sub-Type field.

Thanks in advance
niko

---

From: Henrik Levkowetz <[email-masked]>
Date: Mon, 26 May 2003 15:46:30 +0200

On Mon, 26 May 2003 15:26:12 +0200
"Niko A. Fikouras" <[email-masked]> wrote:
[...]
> field or as a Sub-Type field.

I guess if you could convince the working group that it would be a good
idea to have different subtypes of an extension follow different
(short/long) extension formats, it might be possible to define it that
way, but because of the reason you give in the second para. above, I'd
say it would be quite improbable that the working group could be
convinced to buy into such a definition... :-)

If you're looking at how to implement extension coding/decoding, I'd
suggest you assume that the extension format is fixed to be short or
long as soon as the extension number is given.

	Henrik

-- 
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