Said designer will then, grudgingly, write an appendix standard, usually calling it something like "legacy protocol support".
And that is the only part that anyone actually uses.
And then people paying the bill for the network notices all the processing and bits-on-the-wire overhead they are paying for that they never use, and demand that layers of complexity and cost be peeled off and thrown away, so that carrying IP datagrams be cheaper and faster.
This gets iterated down to the underlying real physical wire.
- "IP over PPP over V.44bis over dialup POTS" and "IP over ISDN", to
- "IP over SS7 T1/E1", to
- "IP over ATM", to
- "IP over SONET", and now
- "IP over WDM" and "IP over lightwave"
Quit trying. Just give up, and cut to the chase. Whenever you have an idea for pumping bits over any distance, either as technology startup, an industry consortium, a standards body, or even a maker/hacker playing around with open source hardware and unlicensed spectrum, just set it up to carry IPv4 and IPv6 datagrams as close as possible to the real underlying carrier (using PPP if really necessary), and then stop.
The only possible sane exception would be adding FEC (forward error correction) and detecting and retransmitting on carrier and bit garbling (like what 802.11 does).
But, don't waste your time and anyone else's money on anything more.