Hi Jonathan,
thanks for the reference.
Shall we then consider that the format in RFC4944 is kind of deprecated,
or "not recommended"
or just not optimally compressed.
Anthony
Le 03/11/2010 00:44, Jonathan Hui a écrit :
Hi Anthony,
The difference you noted is intentional. See this prior message for
background:
http://www.ietf.org/mail-archive/web/6lowpan/current/msg02379.html
--
Jonathan Hui
On Nov 2, 2010, at 9:35 AM, Anthony Baire wrote:
Hi all,
the 6lowpan-hc draft (Section 3.3.2) describes how to derive an
interface ID from a 802.15.4 short address:
A short IEEE 802.15.4 address is 16 bits in length. Short addresses
are mapped into the restricted space of IEEE EUI-64 addresses by
setting the middle 16 bits to 0xfffe, the bottom 16 bits to the short
address, and all other bits to zero. As a result, an IID generated
from a short address has the form:
0000:00ff:fe00:XXXX
where XXXX carries the short address. The universal/local bit is
zero to indicate local scope.
But this is not identical to the method described in RFC 4944 (Section 6)
All 802.15.4 devices have an IEEE EUI-64 address, but 16-bit short
addresses (Section 3 <http://tools.ietf.org/html/rfc4944#section-3> andSection
12 <http://tools.ietf.org/html/rfc4944#section-12>) are also possible. In these
cases, a "pseudo 48-bit address" is formed as follows. First, the
left-most 32 bits are formed by concatenating 16 zero bits to the 16-
bit PAN ID (alternatively, if no PAN ID is known, 16 zero bits may be
used). This produces a 32-bit field as follows:
16_bit_PAN:16_zero_bits
Then, these 32 bits are concatenated with the 16-bit short address.
This produces a 48-bit address as follows:
32_bits_as_specified_previously:16_bit_short_address
The interface identifier is formed from this 48-bit address as per
the "IPv6 over Ethernet" specification [RFC2464
<http://tools.ietf.org/html/rfc2464>]. However, in the
resultant interface identifier, the "Universal/Local" (U/L) bit SHALL
be set to zero in keeping with the fact that this is not a globally
unique value.
According to RFC 4944, the resulting interface id should look like:
YYYY:00ff:fe00:XXXX (where YYYY is derived from the PAN ID)
The PAN ID is not included in 6lowpan-hc. Is this an omission ?
Best Regards
Anthony Baire
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