Re: Re: xPL bridging loop prevention

[Mal Lansell <mal@xxxxxxxxxxx>]

Actually, no :-)  The hop count should be left as it is.  I asked this
very same question a few weeks ago, and the answer was that the hop is
incremented only when the underlying network changes - such as when a
message moves from an RS232 to an IP network.

The hop isn't really that useful, IMHO, because it doesn't identify
where the increments occur.

Example:

An xPL message is sent from a serial device.  The xPL app that
interfaces the serial port to the PC increments the hop count and
broadcasts the message.  The bridge will  receive a message (via the
hub) with a hop=2.

Another message is sent over the internet using your bridge
applications.  When it arrives, suppose the hop is incremented to 2.
When that message is broadcast and then received back from the hub, it
will still have a hop=2.

The first message should be sent over the bridge, the second should be
blocked.  However, the hop count is the same in both cases.

Your best bet is to leave the hop alone, and just compare messages as I
described.

Mal


Mark Hindess wrote:

>
> On 17 November 2005 at 10:47, "Mal Lansell"
<mal@xxxxxxx> wrote:
> >
> > I'm actually quite a way through writing a non-.NET replacement. 
No
> > use to you of course because you're running in Linux, but I do
have
> > a solution for the problem you mention.
>
> Indeed, but I'm sure it will be appreciated by others on this list.
>
> Thanks for your description of the bridge algorithm.  I'll see if that
> gets me over the problems I was having when I get a bit more time over
> the weekend.
>
> I assume that the bridge is incrementing the hop count, dropping
message
> with excessive hop counts, and that the hop count is being ignored for
> the purposes of hashing?
>
> Regards,
> Mark.
>
>
>
>
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