And, if you are using a 1988 TCP stack on a 4.3 system, you are not
likely to ever efficiently utilize a higher speed link
What higher speed link? I'm very happy with 384 kbps symmetric, using
SDSL as ARPANET replacement. I have designed and built my own SDSL to
EIA-530 CSU/DSU so I can use a Cisco 2500 router instead of that nasty
new-fangled Netopia which has (oh horror!) RJ45 Ethernet instead of
proper AUI. Oh, did I forget to mention that my Ethernet is coaxial?
To me all that UTP stuff isn't true Ethernet.
and will not
behave well on any link. TCP has come a long way in the past 12
years. (Of course, I can't guess what "mostly unchanged" means.)
Backward compatibility rules!