Re: [6lowpan] tentative rev 12 format draft: draft-ietf-6lowpan-format-12.txt

> From: Carsten Bormann <cabo@tzi.org>

>  >   Typically, this field needs to encode a maximum length of 1280
>  >   (IEEE 802.15.4 link MTU as defined in this document), and as much
>  >   as 1500 (the default maximum IPv6 packet size if IPv6
>  >   fragmentation is in use).  Therefore, this field is 11 bits long,
>  >   which works in either case.

Uhh.. the max IPv6 packet size is over 65Kbytes! It's just that
depending on MTU, it gets fragmented to smaller pieces on a specific
interface/link. Thus, this MTU (and resulting IPv6 packet size) is
whatever the 6lowpan decides to specify.

And, of course, the TCP protocol stack tries to avoid fragmenting, and
uses whatever size fits the MTU. But for UDP, the packet size is
totally under application control (like Blackberry sometimes uses(?)
4-8Kb UDP packets).

> (If we had wanted to explain anything about this field, it should  
> have been that this is *NOT* the datagram size, but the IPv6 packet  
> size, i.e. the result of any IPv6 fragmentation that may already have  
> happened.)

_______________________________________________
6lowpan mailing list
6lowpan@ietf.org
https://www1.ietf.org/mailman/listinfo/6lowpan