Re: Request for new DLT value for Wireshark Dissector

[Schemmel, Hans-Christoph <Hans-Christoph.Schemmel () cinterion com>]

Guy Harris <guy <at> alum.mit.edu> writes:

> So are any of those fields optional?  For example, is the fragment ID
optional?  If so, what indicates whether
> it's present?  If nothing is optional, why is the header size not always 7?


The size of the header depends on the number of PPP packets in the payload of
the MUX frame. The Header_Size indicates whether Msg_ID, Freq_ID, Start_Pos,
End_Pos, and Flag are present.
For example:
The header of a frame without PPP packet is
| Header_Size (=0) | Direction | MUX_Frame

The header of a frame with one PPP packet is
| Header_Size | Msg_ID | Freq_ID | Start_Pos | End_Pos |  Flag  | Direction |
MUX_Frame

The header of a frame with two PPP packet is
| Header_Size | Msg_ID | Freq_ID | Start_Pos | End_Pos |  Flag  | Msg_ID |
Freq_ID | Start_Pos | End_Pos |  Flag  | Direction | MUX_Frame


Kind regards,
Christoph Schemmel

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