[ih] History question -- multi-homing

[Joe Touch]

Hi John (et al.),

> On Sep 10, 2026, at 5:12 PM, John Shoch via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> In a recent post John Day raised an interesting question on
> multi-homing.  There were a couple of quick historical replies and I
> was also going to offer a bit of aditional history, but then realized
> the original question raises a bunch of complicated issues.
> 
> A.  Some thoughts:
> 
> 1.  In the simple case, multi-homing means a device with multiple
> network connections.  We usually think of this as connections to
> different networks, but it could also be multiple connections within
> one network (a device in a cell phone network is multi-homed to
> different cell sites, switching dynamically).
> Yet the broader question is, what do you try to do with it?

Any device with more than one network connection ends up internally needing the equivalent of a router. Every problem I’ve seen stems from either not recognizing this reality or trying to actively avoid it.

> 2.  At the edge, or for a client, multi-homing usually provides some
> redundancy or failover.

Or multiple concurrent paths. Yes, just like any router with multiple links does.

> 3.  At a server multi-homing can also provide improved service or performance.

Servers are not different from clients. In both cases they provide the same capabilities - that of a router and multiple paths.

> So, to discuss "multi-homing" we may need a bit more context -- what
> problem are we trying to solve?

IMO, the lack of the equivalent of a router in most host systems.

Although I’m sure it was discussed before, my first experience with it  in 1997 is documented here:
https://www.ieee-icnp.org/1997/papers/1997-30.pdf

We have similar problems with how middleboxes (NATs and tunnel devices) behave; few systems recognize that a tunnel device must follow host rules on the tunneled side and router rules on the other, as described in detail here:
https://www.strayalpha.com/pubs/isi-tr-711.pdf

Joe