Hi all:
In Format-02,it is suggested that the hoplimit in ipv6 header should be
treated as non-compressed field. I think this byte,that is to say,the hoplimit
can also be compressed.
The reason is as follows:
In Format-02, adaptation layer is used to find route and send packet.In the
mesh delievery frame, there is a "hops left" field which is decreased by one
when the packet passes one router. Hence,we can use the "hops left" in mesh
delievery frame instead of the hoplimit in the ipv6 header.
And if we compress the hoplimit, how can it be obtained at the destination
node? we can use the idea of tunnel for reference. Before sending a ipv6
compressed packet,we can get the hoplimit out, and put its value to the "hops
left" in mesh delivery field, then,we needn't transfer the hoplimit any longer
when the packet is routed. And at the destination node ,when we want to use the
hoplimit, we can get the "hops left" value in mesh delivery field out,and put
its value to the hoplimit.In this way,we can compress the hoplimit.
Therefore,the ipv6 header can be compressed to only one octet.
It's noted that the length of hoplimit in ipv6 header is 8bits, the length of
hop left in mesh delivery field is 6bits. Here we can assume that 6 bits
hoplimit is enough in 6lowpan.
copy hoplimit to hopsleft copy hopsleft to
hoplimit
origin packet--------------------------->compressed
packet-------------------------->origin packet
Any comments is welcome.
Thanks.
Regards,
Gao Shuai
[EMAIL PROTECTED]
2006-05-22
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