Joe Touch wrote:
I.e., once you split a 1500 byte packet into 1280 and 220 and
encapsulate each of the results, you get to do it again.
Considering a possibility of recursive tunneling, that is a
poor way of fragmentation. 1500 should be divided into 750 and
750 as is documented in rfc791:
For example, one could implement
a fragmentation procedure that repeatly divided large datagrams in
half until the resulting fragments were less than the maximum
transmission unit size.
Without fragmentation, arbitrary recursive direct (IP-in-IP) tunneling
is impossible.
It does not mean fragmentation must be supported by outer or inner
IP layer as IP over fragmented_IP or fragmented_IP over IP.
Instead, fragmentation information may be placed between outer and
inner IP headers as IP-tunnelling_header_with_fragmentation_info-IP
or IP over fragmentation_layer over IP.
Masataka Ohta