Provide Full deep technical document of Fragment and Padding and MUX

[Morrigan-Ship]

Provide Full deep technical document of Fragment and padding and mux
I know what these are.
but i cannot find official document about them.
everyone cannot read the source code
please provide document

[Morrigan-Ship]

this can help:
https://upb-syssec.github.io/blog/2023/record-fragmentation/
but not enough