On Jul 03 2008, at 12:01, Geoff Mulligan wrote:
Carsten,
I think that this is a neat idea. As you state there may be many
layer 2 mesh implementations that need some sort of intermediate
header
and for them all to use NALP seems like a bad idea.
When we talked about this I thought we considered using the reserved
bits of NALP to carry the length value so that 0010xxxx would be the
extension header identifier and length. I'm not opposed to use
1101xxxx, I was just wondering about the change.
Well, I thought NALP was "Not a Lowpan", so given that this packet
*is* a Lowpan packet, the number space sounded inappropriate.
I'm not sure I like the idea of splitting headers greater than 16
bytes
into two pieces with two extension headers. What about again using an
escape value of 1111 to indicate the length is 15 plus the next byte.
This has the advantage that the headers don't have to be broken into
artificial pieces.
The pieces may not at all be artificial, though.
Having an escape value to use more than 16 bytes out of ~80 does sound
like unneeded complexity to me.
If we don't use the NALP reserved space, has anyone considered
allowing
addresses in this space to be registered for specific layer 2 mesh
protocols and to extend it to another byte if the 6 lower bits are
all 1
- 00111111
Let's do that when that other mesh protocol rings at the front door...
Unfortunately, it seems though that at the last meeting in Nice ISA100
decided NOT to utilize this idea that we had worked out and plan to
continue to just use NALP. Oh well, I think that this is still an
excellent extension to 4944 and may be used by others.
ISA100 might still be able to use new input like this, if we agree
that this is the way forward.
Gruesse, Carsten
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