[Winpcap-users] sending over slip

Gianluca Varenni gianluca.varenni at cacetech.com
Tue Jun 10 18:48:54 GMT 2008

----- Original Message ----- 
From: "Guy Harris" <guy at alum.mit.edu>
To: <winpcap-users at winpcap.org>
Sent: Monday, June 09, 2008 6:16 PM
Subject: Re: [Winpcap-users] sending over slip

> On Jun 9, 2008, at 1:14 PM, AmenophisIII wrote:
>> since im not using "normal" ppp, but slip
> SLIP?  Wow.  Now *that's* a blast from the past....
>> i was wondering if thats
>> exactly the same cause.
> Probably.  I suspect SLIP plugs into the Windows networking stack the 
> same way that PPP does, i.e. through NDISWAN:
> http://msdn.microsoft.com/en-us/library/ms798376.aspx
> or something like it.  That's the part of the OS that translates  incoming 
> PPP - and probably SLIP - frames into fake Ethernet frames  before handing 
> them to the Windows networking stack, and transforms  outgoing Ethernet 
> frames being sent over a PPP - or probably SLIP -  connection into PPP or 
> SLIP frames before handing them to the WAN  miniport driver.


> I'm not certain why it's not possible to transmit on a PPP/WAN 
> connection, but I suspect that whatever the reason is also applies to 
> SLIP/WAN connections.

The reason is because in order to capture from PPP/WAN connections, we use 
the Microsoft NetMon component, which does not support transmission.

>> i do see ethernet frames when capturing with wireshark too, although
>> slip doesnt use ethernet, so im quite sure...
>> if its the same...  i guess it wont change (ever), correct?
> Probably not, unless there's some way in which a driver can put itself  on 
> the "other side" of NDISWAN.  I'm not sure there is any way for a 
> non-Microsoft driver (such as the WinPcap driver) to do that.

No idea either. NDISWAN is a sort of "black hole". The documentation is at 
most sparse, inaccurate and not complete. In practice, it's completely 
undocumented. :-(

Have a nice day

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