Re: Message Routing Philosophy

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.