Hi JP,
I don't think your statement is entirely true. L3 forwarding at each
radio hop only requires fragmentation/reassembly at each radio hop. I
guess you could argue this is 1-hop mesh under (subsequent fragments
know the next-hop destination based on forwarding information from the
first fragment), but if you're doing L2 fragmentation, I don't see any
way around it.
Maybe I'm not understanding your model, so let me try to reiterate it
and you can tell me where I'm wrong - you have datagrams fragmented at
L2 and you want to forward those fragments at L2 using L3 information.
That model seems a bit strange to me and I'm not sure how it would
work if you have an IPv6 HBH Options header to process. It would seem
cleaner just to say that we're fragmenting at L3. At that point I'd
rather just stick a fragmentation header after the L3 addressing
information, but then that's starting to look awfully like an IPv6 +
fragment header. I know you're trying to find a middle ground so that
we can forward fragments using L3 information so that we can avoid hop-
by-hop fragmentation/reassembly and not violate the IPv6 min MTU
requirement. I'd like to see that too. Is it okay to say that, yes, we
are doing L3 fragmentation but that those fragments must be
reassembled before exiting the 6lowpan network?
--
Jonathan Hui
On Aug 18, 2008, at 12:10 PM, JP Vasseur wrote:
Hi,
On 8/18/08 7:45 PM, "Jonathan Hui" <[EMAIL PROTECTED]> wrote:
There are multiple implementations (route-over and mesh-under) that
successfully utilize the current format today. If you want
addressing information in each L2 fragment, then forward at L2. If
you want to forward everything at L3, then fragment hop-by-hop. L3
routing is agnostic to the specific layer that forwarding occurs.
JP> this was not Julien’s point: depending on how you fragment you
may or you may not (in this case) be able to route at each hop of
course. Without addressing info in each fragment, this implies L2
forwarding and thus a mesh-under solution.
Thanks.
JP.
--
Jonathan Hui
On Aug 18, 2008, at 10:35 AM, JP Vasseur wrote:
Which requires a mesh under solution and does not work with route
over ....
Thanks.
JP.
On 8/11/08 6:39 PM, "Jonathan Hui" <[EMAIL PROTECTED]> wrote:
On Aug 11, 2008, at 1:40 AM, Julien Abeille (jabeille) wrote:
Does fragment 2 look like:
FRAGN dispatch, datagram size, tag and offset | HC1 dispatch |
HC1 encoding = 0xFB | HC2encoding | IPv6 hop limit | compressed
source and dest UDP port | UDP checksum | rest of UDP payload
or
FRAGN dispatch, datagram size, tag and offset | HC1 dispatch |
HC1 encoding =0x FA | IPv6 hop limit | rest of UDP payload
Neither. Everything after the frag header is considered part of
the fragmented payload.
--
Jonathan Hui
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