Wireshark-bugs: [Wireshark-bugs] [Bug 9427] Dissector for T1-channels-over-raw-Ethernet protocol
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From: bugzilla-daemon@xxxxxxxxxxxxx
Date: Fri, 22 Nov 2013 00:28:14 +0000

Comment # 31 on bug 9427 from 
(In reply to comment #26)
> The Frame-Relay data is one sequential stream of data.  As far as I know, it
> will follow protocols to take the L3 data and add FR encapsulation at L2,
> then pass to the L1 signal to the T1.

What happens here is almost certainly that:

    the L3 frames are encapsulated in Frame Relay frames by adding an address
field and an FCS;

    the resulting L2 frames are handed to a device that bit-stuffs the bit
sequence and puts flag values (01111110) between the frames, and puts the
resulting bit stream onto the T1.

> Not a programmer, but seems to me that knowing the payload start an end,

Again, if by "payload" you mean "a Frame Relay frame", I strongly suspect the
payload start and end is indicated by flag values in the bit stream.

> then the bytes for each slot/channel of the T1, which has no T1 framing (all
> stripped off by Guisys)

That framing is independent of the HDLC-style Frame Relay framing with the flag
values.

> the original L2 data from the PE (and it's L3 and
> higher payload) would be availble for decode in WS.

...once you strip out the inserted 0's.

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