Re: DLT_request

[Weber René <rweber () baumer com>]

yes, used endianness is always big endian.
before version 1.2 of gencp standard, exist the possibility to define a protocol endianness - but this is removed with 
version 1.2!
so all endianness of protocol data of cameralink interface should also be big endian.

the protocol transports read and write memory request between host (pc with frame grabber) and a camera.
the data in this requests can be little and big endian in mixed manner ! but this is defined in the next layer the SFNC 
standards of the xml description files of the camera.

what do you mean - makes it sense to define a DLT_request for the CameraLink Protocol ?

Best Regards
Rene Weber



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-----Ursprüngliche Nachricht-----
Von: Guy Harris [mailto:guy () alum mit edu]
Gesendet: Freitag, 13. Januar 2017 21:21
An: Weber René
Cc: tcpdump-workers () lists tcpdump org
Betreff: Re: [tcpdump-workers] DLT_request

On Jan 13, 2017, at 6:49 AM, Weber René <rweber () baumer com> wrote:

> On Jan 11, 2017, at 11:42 PM, Weber René <rweber () baumer com> wrote:
>
> > > We working at software for industrial cameras which are supported by the cameralink standard. We use Wireshark to 
> > > monitor the control interface. We have implemented a solution similar like the u3v dissector and uses link type 
> > > DLT_USER0.  The cameralink interface is basically a serial interface like rs232 uart.
>
> > So this is for GenCP over a serial port, rather than GenCP-over-UDP?
>
> I don't know a GenCP-over-UDP - where can I find some information about this?

OK, they mentioned UDP here:

        http://www.emva.org/wp-content/uploads/GenICam_GenCP_1.2.pdf

but they didn't really mention it as a transport.

> > So do the packets in such a pcap or pcapng file start with the serial prefix described in section 1.5 "Serial 
> > Prefix", followed by the common command data described in section 4.3 "Common Command Data", followed by the 
> > specific command data for the command in question (section 1.6 "Serial Postfix" says there's no postfix for serial 
> > ports)?
>
> correct. U3V in opposite to cameralink has a different prefix and a different endian order.

So the GenCP-over-serial endianness is big-endian, as per

        Appendix

        1. Serial Port Implementations

        This section specializes the generic protocol for the use over a serial link.

        1.1. Byteorder

        For devices communicating over a serial link the byte order of bootstrap registers and protocol fields is 
big-endian.
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