On 1-feb-04, at 17:52, James Craig Burley wrote:
But that is exactly how the Internet does *not* work. It's much more
like starting in NYC, driving to every house in the neighborhood
asking "am I at 100 Maple Lane in LA?" until someone says "I know how
you can get there, just drive east on this road right here for a few
miles".
[...]
(An IP address is *not* a destination; it's merely an
address that could denote a network interface in the same neighborhood
or on the other side of the world. There's basically nothing about it
that inherently says "this is on the other side of the world" to a
packet.)
I don't know where you learned TCP/IP, but the parts about the above
that I can even understand are mostly nonsense. A host creates IP
packets, puts in a destination address and then transmits them. In most
cases the packet will be delivered to the host indicated by the
destination address. There is a fair amout of routing involved here,
but that's not every interesting from an email perspective.
After all, the *packets* will bounce from server to server to get to
the destination.
Since when is a router a server?
It's therefore a case of wishing away reality to insist that, somehow
email messages *themselves* won't do that.
If we mandate that all hosts involved with mailng must be prepared to
receive messages directly from other mailng hosts, there is no reason
why something like that can't be built. This has the advantage that
it's more efficient and "bad" messages can no longer be injected in
places where there badness can't be known or simply isn't known. (This
is the reason I no longer have any MX fallbacks: my server gets to talk
to everyone who wants to email me directly so I get to decide whether I
want to talk to them.)
However the trend is in the opposite direction as more and more hosts
are no longer able to receive incoming sessions and the use of mobile =
intermittently connected devices such as laptops is increasing and
there are still many people using dial up.
Compare email to file transfer, web hosting, instant messagings,
anything else built on TCP/IP. Don't they *all* include mechanisms
for having requests "hop" from server to server?
No.