[linux-dvb] Re: DVB-CA slot types

[Andrew de Quincey <adq_dvb@lidskialf.net>]

Hi, thanks for all the info, that really helped!

> > CA_CI_LINK
> > This sounds like it would correspond to the EN50221 link layer... i.e.
> > the data would consist of multiple interleaved fragmented packets.
>
> I thought "link layer" and "transport layer" were synonymous...

From my reading of EN50221, the link layer multiplexes packets from multiple 
connections over the one physical CAM interface. The packets are fragmented 
into multiples of the physical CAM interface buffer size, and have a 2 byte 
header giving the connection ID and a More/Last flag.

The transport layer is then layered on top of that, and consists of a 
command/response protocol. They're kind of linked in that that the transport 
layer protocol is used to setup the connection IDs in the link layer, but the 
document does define them as seperate concepts.

As we're writing complete packets for connections to/from the userspace API, 
and not a stream of multiplexed fragments, or commands to control the 
physical hardware, it seems to me this is transport layer.


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