Jesper Dangaard Brouer has written an awesome thesis on something that has plagued those of us stuck using asymmetrical network connections for ages and ages now. What’s more, he has patches which will soon be available for the Linux kernel.
Finally, a functional way of dealing with ATM overhead without wasting precious bandwidth planning for the worst case scenario. (i.e. use ~ 60% of your sync speed to deal with overhead when much of that is not really lost unless you’re sending many small ethernet packets.)