[ih] Origin of the loopback interface

[Toerless Eckert]

On Sun, Oct 22, 2017 at 03:19:50AM -0700, Paul Vixie wrote:
> multihoming is one of the great unsolved problems in internetworking. we 
> do it properly on routers -- there, the loopback has the router's "real" 
> ip address -- but only because the router is on-path and can inject its 
> loopback address (which usually is not subnetted) into the topology.

I am not sure if multihoming is a great unsolved problem in internetworking.
It just seems to be a problem with IPs ideology. As opposed to let's say
CLNS ideology of node addresses.

In the early 90th i had on pretty much every vendors unix system available nodes
with 10 Mbps ethernet and FDDI, and of course the FDDI on each node worked
randomnly 90% of the time (especially in a ring with 10++ vendor NICs). In
the face of NFS, the only way to keep the network running was to let those
MHH participate in the IGP and inject their addresses as host routes.
And when IPv6 came out i was so disappointed that it still did not
acknowledge / describe the notion of node addresses.

Now with IETF ANIMA WG and ACP, we're automation the creation and routing for
node addresses and try to figure out how to use the correct terminology.
"loopback" seems to be the common term used for "internal" interfaces. Not
that there is a real definition of "internal" interfaces either. And of
course there is also no IPv6 architecture description that "loopback" addresses
could have global scope addresses. Thats just a decade old deployment reality
not described by the architecture.

And thats just the tip of the iceberg.

Cheers
    Toerless