[Freeciv-Dev] Re: (PR#6707) Announce server on LAN

["Todd Goodman" <tsg@xxxxxxxxxxxxx>]

* Raimar Falke <i-freeciv-lists@xxxxxxxxxxxxx> [031105 12:02]:
> On Wed, Nov 05, 2003 at 05:59:14AM -0800, Todd Goodman wrote:
> > * Raimar Falke <i-freeciv-lists@xxxxxxxxxxxxx> [031105 07:23]:
> > > On Tue, Nov 04, 2003 at 02:16:00PM -0800, John Bauman wrote:
> > > > > So if we choose 224.0.0.1 we know that all hosts are on this group AND
> > > > > we know that the TTL is irrelevant since the packets are routed.
> > > > Why do you want to use an address that all hosts are on? Wouldn't it be
> > > > better if only the hosts that cared got messages (as small as they may 
> > > > be)?
> > > 
> > > Do you know how you join with your computer a special multicast group? 
> > > I don't.
> > 
> > Yes, the way he was doing it (SIOCADDMULTI).
> 
> SIOCADDMULTI isn't mentioned in the patch. Do you suggest that we add
> this ioctl call to freeciv? How portable is it?

If you're going to use multicast then it's the right way to do it.

It should be portable between Linux and BSDs (including Solaris.)

> 
> If not what OS command do I have to execute to call this ioctl?

Inside of the Freeciv server and Freeciv client it should make an
SIOCADDMULTI ioctl() call to add itself to whatever multicast group we
want to use.

> 
> > You do it on the server and clients and now only those hosts who
> > care about receiving the packets get them.
> 
> > > It reduced the usefulness of the new feature if you had to adjust your
> > > OS in some way. But there is already a default group and it is limited
> > > so that you don't spam the whole internet.
> > 
> > You don't have to adjust your OS.  The server and clients do it
> > programatically.  You set TTL to 1 so you don't send anything off LAN.
> > 
> > There's nothing the user needs to do (unless their OS doesn't support
> > multicast, in which case it doesn't matter what you do as this feature
> > wouldn't work...)
> 
> > There's a pretty good chance that traffic to 224.0.0.1 will never make
> > it off the local network no matter what you set the TTL to as the router
> > isn't supposed to forward it regardless.
> 
> And this IMHO a feature. And equivalent to setting TTL to 1. So what
> is the advantage of your solution?

It's a feature, but IMNHO it's wrong to try to use multicast to send to
every host on the local network.

You can set the TTL to a configurable value (default 1) and use a
different multicast group.

That's the point of multicast, send it to a group of destinations that
want to receive it, but not to every station on the LAN.

Todd

> 
>       Raimar
> 
> -- 
>  email: rf13@xxxxxxxxxxxxxxxxx
>  "The two rules for success in life are:
>   1) Never tell them everything you know."