Hi Jonathan, all,
 
a few comments/questions about multicast address compression in hc-01:
- is there a need to respect the 16 bit address formats defined in
RFC4944 when compressing addresses. I though these formats were defined
for layer 2 16 bits addresses, while the compressed addresses in the ip
header are rather independant.
- with 9 bits group-id, we do not support sollicited node and a few
"well known" addresses (though most significant are supoprted), should
we work on a format with different length possible?
Also the current group-id mapping is stateful. A stateless model would
avoid the need to store many mappings, and seems feasible as most
group-ids start with a large number of 0 bytes.
 
we could use one more bit for destination address mode: something like
000 128
001 unicast 64
010 unicast 16
011 unicast 0
100 multicast 32 (for e.g. sollicited node), one byte flags + scope,
3bytes = last 3 bytes
101 multicast 24 flags + scope + last 2 bytes
110 multicast 16 bits : flags + scope + last byte
...
 
this way we also incorporate flags.
 
the issue is that we need one more bit for this...
 
does it make sense?
Best,
Julien
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