Figure out whether we need a new fragmentation type or not about otrv4

[tcz001]

I don't see any reason for a new fragmentation type, any thoughts?

[tdruiva]

@tcz001 same for me, I don't see reason to change.
Well, if we keep supporting instance tag in the way it is today, probably we don't need to change frag format.

The way how it is defined, doing fragmentation after generating the message and just fragmenting outgoing message when it's configured looks enough.

Also, it is important keep the fragmentation support because of the IM protocols limitations.
Like, here we can see the different message size, for different protocols.

[olabini]

Of course we need to keep fragmentation. But the problem is that the version information is INSIDE the fragmented package - which means if we use the SAME fragment specifier for OTRv4, a processor has no way of knowing whether it's a v3 or v4 package until it has opened up the fragmentation. This could be unimportant or it could be important. I seem to remember we needed that information early in the process for the J extension, but I could be misremembering.

This is why we need to think through the spec from an implementation perspective.