[Sis-SCPS-INTEREST] flow !!

[Feighery, Patrick D.]

The flow of packets between user and kernel space under Linux via the
TAP method is quite simple.
 
Linux has something called a TAP interface (see
http://vtun.sourceforge.net/tun/faq.html for more information on this
interface).  This interface is like any other network interface within
the kernel.  However it has the additional capability to allow a
application in user space to open up the tun/tap device and read and
write to it.  When reading from it you are reading ethernet frames
(minus CRC and flags), and when writing to it, you need to write
ethernet frames.  Given this capability you just need to create an
ethernet bridge between one of the tap devices and the LAN side
ethernet interface, and another bridge between tap device and the WAN
side ethernet interface
 
When the linux box receives a frame on the LAN interface it will bridge
it to the tap interface.  The SCPS gateway is hanging a read(), so it
get the frame.  When SCPS writes a frame to the tap interface, it is
bridged to the corresponding real physical interface and it puts the
frame out on the wire.
 
Conceptually it is that simple.
 
As for compiling a kernel, honestly  to configure the kernel I would
google for instructions.  I am not a linux guru by any means and with
the various techniques that can be used...  finding a more
authoritative source would be a better bet. The following site came up,

 
http://www.linuxplanet.com/linuxplanet/tutorials/202/1/
 
Pat
 


________________________________

	From: sis-scps-interest-bounces at mailman.ccsds.org
[mailto:sis-scps-interest-bounces at mailman.ccsds.org] On Behalf Of
trilok kumar saini
	Sent: Wednesday, February 08, 2006 4:21 AM
	To: sis-scps-interest at mailman.ccsds.org
	Subject: [Sis-SCPS-INTEREST] flow !!
	
	

	
	Hi All..
	can anybody tell me in detail when a m/c is configured as a
SCPS gateway, how is the flow of packets through different layers
between entering and exit ethrenet interface of the gateway.. 
	How are original kernel and SCPS layers are linked...
	
	bye 

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