Re: Powerline Ethernet

[Barry Myles <automatedhome@xxxxxxxxxxxxxxx>]

Matthew Walker wrote:

> In particular, how many devices can be used on the same mains circuit?
> The Netgear XE104 'ethernet switch' says 'up to four' can be used, but
> the diagrams show 4 devices sharing one 'switch'.

> Anyone know if this means potentially 4x4 devices can share one mains
> network 'segment' ?

Depends on what you mean by 'device'. Many HomePlug devices like the
XE104 can share a mains segment. By default, they will all talk to each
other. Some HomePlug devices have a single ethernet port and will plug
into a single PC or a router. You could, of course, also plug this
ethernet port into a hub or switch and have multiple ethernet devices
hanging off each one. This is essentially what a XE104 is: a HomePlug
1.0 bridge and a standard 5 port switch [one internally to the homeplug
and 4 available externally].

There are three speeds available: 14, 85 and 200MBit/sec. The 14 and 85
devices ["HomePlug 1.0"] will talk to each other but won't talk
to
200Mbit devices ["HomePlug AV"]. However, multiple 1.0 and
multiple AV
devices will happily co-exist on the same mains segment.

I've had a single mains segment with 4 HomePlug AV devices devices all
happily talking to each other and a couple of switches hanging off two
of them.

> I presume this is a single broadcast domain (maybe switched from the
> wall units?).

At the electrical layer it's a single broadcast domain. At the network
layer different broadcast domains can be separated by setting different
encryption keys on different devices. Only those with the same
encryption key will talk to each other. When you buy a HomePlug device
you get software with it to configure the encryption key. The Devolo
ones come with MAC and linux config software as well as Windows.

--
Barry Myles