Hi Carsten,
I think part of the confusion comes from some of the text in RFC
4862. In particular, RFC 4862 seems to indicate that a particular
link defines a fixed length for IIDs (RFC 4944 currently defines IIDs
to be 64 bits). Then RFC 4862 has the following text:
"If the sum of the prefix length and interface identifier length does
not equal 128 bits, the Prefix Information option MUST be ignored."
And RFC 4944 has text to remind of the above constraint:
"An IPv6 address prefix used for stateless autoconfiguration [RFC4862]
of an IEEE 802.15.4 interface MUST have a length of 64 bits."
So one question is whether it's possible to utilize a 'variable sized'
IID to generate global addresses. We already have 64-bit IIDs when
generating global addresses from EUI-64s. It may be a bit strange to
have two different IID lengths for a 6lowpan link, so defining a 17-
bit IID already bends rules a bit. Would it be too much of a stretch
to say that using a short address, we can generate an IID of length
between 16 and 64 bits? :)
--
Jonathan Hui
On Mar 29, 2010, at 8:35 AM, Carsten Bormann wrote:
On Mar 29, 2010, at 17:10, 6lowpan issue tracker wrote:
(0000:0000:0001:xxxx), where xxxx is the short address.
I didn't quite understand from the Discussion in Anaheim what is
better about
::1:xxxx
than
::ff:fe00:xxxx
If we can stick to the latter, we don't really have to change 4944.
In favor of preparing a lasting fix for 4944, I would make the
following change to -06:
The reconstituted address is built from the 16-bit address xxxx by
1) computing the address:
::ff:fe00:xxxx
2) replacing the bits in this address by the bits actually given by
the prefix in the context.
In other words, the prefix in the context overrides the address
generated by step 1.
For example, if 64-bit prefix pppp:pppp:pppp:pppp is given, the
result is:
pppp:pppp:pppp:pppp::ff:fe00:xxxx
while if a 112-bit prefix nnnn:nnnn:nnnn:nnnn:nnnn:nnnn:nnnn is
given, the result is:
nnnn:nnnn:nnnn:nnnn:nnnn:nnnn:nnnn:xxxx
Gruesse, Carsten
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