[Winpcap-users] use of winpcap with PLC net

Jean-Luc Pamart jlpamart at yahoo.fr
Sat Jan 26 20:52:43 GMT 2008


Guy Harris a écrit :
> Jean-Luc Pamart wrote:
>
>> So I have for each PC a INT51X device (ETH <->PLC)
>> My PLC modem (a french brand OLITEC CPL400) is plugged into my home 
>> wires and noting else (the eth connections are useless)
>> It's pretty simple and it works fine !!!
>
> OK, so the modem plugs into your phone line on its Internet side and 
> directly into your home power wires on its LAN side (as well as having 
> a WLAN antenna as well), and the PC's have Ethernet adapters plugged 
> into Ethernet <-> HomePlug bridges, along the lines of the picture at
>
> http://www.olitec.com/tf_powerlan_cpl400.html
>
Yes, the part on the upper left.
>> Before that, I ask to my brand if my CPL/ETH can be put into 
>> promiscuous mode. They don't give me a direct answer, they say that the
>> devices are absolutely "transparent" ... that means I suppose : all 
>> the traffic in the power lines are pushed to the ETH part.
>> On one hand I a not sure of their answer
>
> I wouldn't be sure of it either. Perhaps the person you asked isn't 
> technically knowledgable enough to understand what you were talking 
> about?
>
Yes
>> and on the other hand : when you install the device, you don't have 
>> to configure something :
>> you put the device into the socket and it's ok. And you can change 
>> the devices between PC... So, if the PLC devices must filter the 
>> ethernet
>> packets how they can do ?
>
> Pass all broadcast and multicast traffic from the HomePlug network to 
> the Ethernet, and:
>
> when they start up, pass all unicast traffic from the HomePlug network 
> to the Ethernet;
>
Very important : at the very beginning (when the PLC/ETH bridges are 
powered) they are obliged to pass all the traffic on the PLC "bus ".
So if winpcap is here => we can see this beginning traffic. Am I right ?

> when they see a packet on the Ethernet, remember the source address, 
> and pass to the Ethernet only unicast traffic that's sent to that 
> address.
>
> (That's called "MAC address learning". I think most if not all 
> Ethernet switches work that way.)
>
Ok very classical, I missed that. :-)

>> So, if I can resume the directions :
>>
>> - my devices CPL (with INT51X) must to put in promiscuous mode and I 
>> haven't made this operation
>
> That might be the problem.
>
>> - it's a problem of my 2 ethernets devices (one Linux, one Windows) 
>> they says they go to the promiscuous mode and it's false
>
> It's *possible* that might be the problem, but I think it's unlikely.
>
>> => i will try with USB/CPL in windows
>
> That might be worth trying. With a USB adapter, there might be 
> commands for the "Communications and CDC control" USB device class to 
> put the adapter into promiscuous mode, and that might cause the 
> adapter to capture all traffic on your power wires.

Ok, I'll try that. But I have a doubt : perhaps PLC bridge hasn't the 
capability to pass in promiscuous mode (desperate)
I hace found this document : 
http://www.cnel.ufl.edu/~kkale/5718files/projReport.doc 
<http://www.cnel.ufl.edu/%7Ekkale/5718files/projReport.doc>

    an extract :

    MAC Level Bridging
    In the HomePlug Network System bridging is
    accomplished by source-aware bridging. There are
    two types of bridging prevalent in networks. One is
    transparent bridging while the other is source – aware
    bridging.
    While both use MAC level addressing, in transparent
    bridging the bridge gradually learns the addresses of
    the various stations and stores them in a forwarding
    table. It usually makes use of a spanning tree
    algorithm to avoid loops. Transparent bridging
    requires “promiscuous” reception of frames by the
    bridge. Powerline, because of its unstable nature
    requires the use of acknowledgements, which
    becomes an issue when combined with “promiscuous
    reception”. As acknowledgements occur while the
    station is considered active on the channel, they are
    required to be given special consideration.
    In source-aware bridging the bridge is addressed as an
    individual address in itself. Its address is mentioned
    directly in the frame header. The bridge proxy is
    obtained at the same time as when the station
    performs the initial channel estimation and obtains
    tone mapping.

So, can we say that PLC doesn't use promiscuous mode ? or ?

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