Dear authors,
I would speak about 6lowPAN hc-15 draft document.
Section 4 describes the ipv6 next header compression and in 4.2 ipv6
extension header encoding is shown.
So incidentally in a 802.15.4 127 byte long packet I could have a mesh
header and a fragmentation header like RFC4944 describes; after those
a lowpan_IPCH dispatch with in-line ipv6 fields, like it is shown in
figure 1 on page 5. All those headers (RFC4944 and figure 1 ones) in a
single 802.15.4 packet.
But figure 11 on page 14 shows that we could have other headers like
in IPv6 (so-called extension-header), and they could be heavy like
router header or they grows on-the-fly like hop-by-hop header.
So my questions are: do those extension headers have to be present in
every fragment of an IPv6 packet? And if it is so, doesn't it seem
like wasting a lot of space? Let's say that I want to send a message
and I have to write entirely the IPv6 source and destination addresses
and I want a routing header too, even with 4 addresses, I fill 80 out
of 127 bytes only for addresses. Is this example right or I understand
wrongly the document? And after these considerations, is it necessary
to change the rule to calculate the datagram size field in RFC4944
fragmentation header?
Best regards
Giulio Ministeri
from University of Padova, Italy
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