[Openais] Re: [Linux-cluster] new userland cman

[Steven Dake]

On Mon, 2005-10-03 at 13:20 -0400, Lon Hohberger wrote:
> On Mon, 2005-10-03 at 08:10 +0100, Patrick Caulfield wrote:
> 
> > >>neutral
> > >>-------
> > >>- Always uses multicast (no broadcast). A default multicast address is supplied
> > >>if none is given
> > > 
> > > 
> > > If broadcast is important, which I guess it may be, we can pretty easily
> > > add this support...
> > > 
> > 
> > I was going to look into this but I doubt its really worth it. It's just any
> > extra complication and will only apply to IPv4 anyway.
> 
> I think broadcast is quite important, actually - although I also think
> that it should *not* be the default.
> 
> Multicast doesn't always work very well (in practice) on existing
> networks, and works poorly (if at all) over things like crossover
> ethernet cables and hub-based private networks.  You know, the cheap
> stuff hackers use in their houses to play with cluster software ;)
> 

I have tested the multicast with both crossover point to point as well
as hub networks.  Actually the way the protocol works, switches are not
even necessary.  There are very few (less then 1%) link collisions with
a hub network even at 90% network load.

> Broadcast is far more likely to work out of the box in the above cases,
> and isn't hard to implement (... actually, it's easier than multicast).
> 

Adding this should just be a few lines of code.  I'll see if I can work
out a patch today.

Regards
-steve

> Also, IPv6 isn't what I'd call "mainstream" just yet, so supporting all
> the hacks we can with IPv4 isn't necessarily a bad thing ;)
> 
> -- Lon
>