Do you also have a problem with 64-bit systems that have provisions for 64 bits of address space? In your book they also seem like a waste, and we should have designed something closer to ~48 bits of address space.
No, I wouldn’t make the same comment if it was just a 64bit address space. Some excess isn’t necessarily bad, but excess on top of excess is. If that makes sense.
My edit I made last night might seem to imply otherwise, but that was due to me being a bit terse with that part and I can’t go back and edit further now.
A 64 bit address space wouldn't be an excess though, it would be outright too small.
The whole point of L3 is to provide a layer of routing and aggregation on top of L2. Routing and aggregation requires sparse allocations, so L3 requires more address space than L2 does. L2 is 64 bits for new protocols today (which are supposed to be using EUI-64), so L3 needs to be more than 64 bits.
People would complain loudly if we didn't use a power of two, so here we are at 128 bits.
