[ih] Origin of the loopback interface

[Joe Touch]

> On Oct 23, 2017, at 10:30 AM, Toerless Eckert <tte at cs.fau.de> wrote:
> 
> n Mon, Oct 23, 2017 at 07:26:28AM -0700, Joe Touch wrote:
>> Loopback should not be a substitute for IPC. At least one additional reason is that packets sent there might not end up where you think (they could be tunneled elsewhere, e.g..).
>> Joe
> 
> Architecturally, there should be no reason for another addressing domain ("IPC")
> if IP had a working definition of "node-local addressing". AFAIK, the loopback
> addresses are meant to do this, but the RFCs IMHO do not call this out very
> clearly. In multicast at least there is a node-local scope (FF01). Can't quite
> remember (and to lazy to test now), if in TTL=0 worked to delivery traffic
> only node-local at some point.

You’ve hit the mail on the head. Only routers decrement TTLs. Multihoming works properly only with an internal virtual router inside each host:

J. Touch, T. Faber, “Dynamic Host Routing for Production Use of Developmental Networks,” in Proc. ICNP ’97, Atlanta, Oct. 1997, pp. 285-292.

But that still doesn’t warrant a strict need for self addressing beyond the addresses already available on other interfaces. 

> 
> [ Btw: I could also tunnel any non-IP form of IPC if i have access to the OS.
> ]

You can but why would you? Ipc should be more efficient and necessary anyway  

Joe

> 
> Cheers
>    Teorless
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