munwar: Dvb Card

Saturday, 22 September 2012

Dvb Card

The DVB driver has been developed for FreeBSD Release 2.2.x. The card is supported as a communication interface and is configurable at IP level with the ifconfig command. Unlike most communication card, it can only receive IP packets. For the packets which are delivered from the IP layer to the the dvb driver, since they cannot be sent by the hardware, they are passed to the link layer tunneling mechanism pseudo-device (lltm).

The lltm pseudo-device handles packets delivered by the dvb driver. Basically, it copies all the packets that could not be sent by the reception harware onto the /dev/ul0 device.

The dvtunneld daemon performes blocking read on /dev/ul0. Every packet which are read, are encapsuled behind an IP header whose destination address is the feed bidirectional IP address. The new packet is then sent over the Internet, as the feed receives it, it decapsulates the datagram, passes it to the link layer of the unidirectional interface which delivers it to higher layers. dvtunneld implements the link layer tunneling mechanism as discussed in the UniDirectional Link Routing working group (IETF), it emulates a broadcast connectivity over a unidirectional link