Wireshark-bugs: [Wireshark-bugs] [Bug 9427] Dissector for T1-data-over-TCP protocol from Guisys
Comment # 9
on bug 9427
from brett.meyer@bt.com
(In reply to comment #8)
> (In reply to comment #7)
> > Ethernet Frame Structure [Brett: not the payload of Test3 trace frames]
>
> Presumably you mean that the frames in the test3.pcapng file *are* in a
> format that has:
>
> > • The structure is as follows; 6+6+2+2+960+4+4 = 984
> > 1. Destination MAC address (6-bytes) - in this example; ff ff ff ff ff ff
> > 2. Source MAC address (6-bytes) - in this example; 00 00 25 af 00 00 Ramtec
> > mfg
> > 3. Packet Length (2-bytes) - for T1-payload this will always be; 03 c6
> > 4. A Packet Sequence Number (2-bytes) - in this case; 00 00 (but will
> > increment each Frame)
>
> followed by "the T1 content".
>
> If so, that means that it's running atop raw Ethernet/802.3, with no 802.2
> header, and thus is not a valid Ethernet frame according to IEEE Std 802.3,
> meaning that Wireshark will need a special hack in order to tell it to
> dissect the frames as T1-over-Ethernet frames rather than as normal Ethernet
> frames. (I.e., it's not a matter of "configuring" Wireshark; there will
> need to be code changes or, at least, a plugin dissector.)
>
> So that part isn't hard to dissect once we somehow hook a dissector in to
> catch those non-standard Ethernet frames.
>
> Moving on:
>
> > The T1 content
> > 1. Only T1 payload or content is transferred to the Ethernet Frame (no T1
> > Framing
> > or Overhead)
> > 2. The Packets always start with DS0 Channel-1 (unless the T1 slips due to
> > incorrect clocking)
> > 3. and continues through to DS0 channel-24
>
> So does that mean that every 3 bytes of the T1 content have 24 bits, the
> first of which is the bit in channel 1, the second of which is the bit in
> channel 2, and so on, with the last bit being the bit in channel 24?
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I've asked Guisys to comment by the following comment to Mike:
Guy is now stuck in a good place, same place I am, I think. See the attached
comment from the bug please, I believe questioning the map of router layer 2
frame with payload is delivered to the T1, and of course how to extract it.
Thanks - Brett
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