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Re: [RRG] arguments for map and encap

It's true that there has been a historical assumption that "an address
is an address is an address" and that this has become the essential
implement in applying the end-to-end principle (which was written
down in 1984 [Saltzer] and resurrected in RFC 1958). Afaics, the
essential requirement to apply the e2e principle is an identifier
that asserts that a given packet belongs to a given packet stream.
Given that, the end system doesn't care about any aspect of the
network at all. But we can't avoid the fact that the identifier used
by the vast majority of software is the bitstring known as an address
in the socket API. You can do what you like below the transport layer
as long as you deliver that bitstring. In the real world, we can't change 
that (which is why NATs are such a mess, of course).


Brian -

I fully agree that both sender and receiver need a stable identifier for
packet exchanges. But stability does not necessitate that the identifier 
be the same for the sender and for the receiver.  NATs demonstrate this.

Of course, I do understand yours and many other people's concerns about
NATs. My stance, however, is that the hard problems with NATs are due to 
their limitations in global host reachability and robustness to path
changes. The mere fact that an address looks different on different sides 
of a NAT is much easier to deal with.

- Christian



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