Philippe Houdoin wrote:
> Okay, here is what I've understand on STUSB Linux official driver internals:
>
> - the box only transmit on ADSL line what he receive from a out USB bulk
> endpoint, and transfer what he receive from same ADSL line to the host, via
> a in USB bulk endpoint.
yes
> Does it support only ATM network?
yes
> So ,what is the purpose of the MAC address
> he *publish* in its serial number USB string descriptor?
Every ATM card has a MAC address too.
> - the main job of the driver is the assembly of PPP frames in AAL5 packets,
> following PPPoA RFC specifications. Same in other way, he extract PPP frames
> from AAL5 packets received. Is it right?
Yes and no.
The driver does not do ppp. It only takes a arbitrary packet and puts it in AAL5. It
does not know
what kind of packet it is.
For PPPoE for example it is a LLC of VCMUX encapsulated Ethernet frame. (see rfc2684)
> - the SARLib is used to truncate a PPP frame in any AAL5 packet needed, and
> reassemble AAL5 packets in single PPP frame. So, who do the PPPoA
> encapsulation? The driver code, using SARLib functions for
> (un)packetization, or something hidden in Linux kernel, say Linux ATM
> module?
The PPPoA and PPPoE is done above the Linux ATm layer.
PPPoA or PPPoE
|
Linux ATM
|
speedtouch.c and SARLib
|
Linux USB
|
USB
|
SpeedTouch USB modem
> - In PPPoA specifications, the PPP frames are AAL5 *packetized* directly,
> without any modification to PPP frame content? Contrary to PPPoE who need to
> modify PPP frame so that PPP compression escape sequences don't break PPPoE
> headers recognition. Am I right here?
No.
PPPoA does not have any escape sequences in it's PPP packets.
A PPPoA packet is 0x00 0x21 followed by the IP packet. (For data packets anyway)
For PPPoE you get PPP in PPPoE in Ethernet in ATM.
If you can get a linux system and a Speedtouch modem, you can see all traffic passing
by if you turn
on DEBUG and DEBUG_PACKET.
If you want more info about the protocols, there are links to the RFC's on this page:
http://linux-usb.sourceforge.net/SpeedTouch/
or
http://sarlib.sourceforge.net/
> Thanks for any reply, even an strong "NO!"
> Sorry for poor english.
I wil hold an eternal grudge against you for that ;)
J.
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