[ih] History question -- multi-homing

[John Day]

It doesn’t need a router (no relay) if the device is the destination. It does need to participate in the routing algorithm to advertise what it is connected to.

> On Sep 11, 2026, at 10:57, Joe Touch via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> 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
> 
> 
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