off-list discussion

[Alan Cox]

> > You might want to seriously consider using IPX for the heartbeat - that cuts
> > out ARP and most routing.
> 
> By IPX you mean Novell's protocol?  I don't know anything about it.  Can
> you say a little more?

IPX has no ARP and for link local frames no network routing applied. It also
supports a thing called "nebios flood fill" which might be quite interesting
for such applications.

IPX addresses use MAC addresses as node addresses (hence no ARP). IPX frames
are unreliable datagrams from node to node or node->broadcast (node FFFFFF)

It has the minimal interaction with routing layers. 

The flood fill packet is fun as what that does is to propogate through routers
up to 8 networks away so its a "search and find" type frame, but with rather
high network impact.

Alan