Network Technologies DVB-ASI to IP - Manual (Page 67)

ASI-IP-GTW User's Manual
Page 67
5.3 Overview of Video over IP
5.3.1 Protocol mapping
One of the core functions in the ASI-IP-GTW is the IP encapsulation of
the MPEG-2 transport streams. The task is basically to encapsulate
video packets into IP frames, using the right headers.
Figure 34 shows how the transport can be separated into various
layers.
Figure 34. Protocol mapping
The MPEG-2/DVB layer is specified in ISO/IEC 13818-1.
The ASI-IP-GTW is able to handle both Multi-Program Transport
Streams (MPTS) and Single-Program Transport Streams (SPTS). In the
current version, the ASI-IP-GTW operates in a transparent mode. The
unit will encapsulate and de-capsulate complete transport streams
without changing the streams. This means that no insertion or removal
of NULL packets is performed and PCR is sent transparently through
the unit.
Control data are handled differently from transport stream data on the
next layer. RTP as defined in RFC1889 is applied for the MPEG-2
transport stream data. Three types of protocols are used for control
data. HTTP is used when the unit is configured and monitored via the
internal WEB server. SNMP is used for alarm traps and simple status
polling. Telnet is used for development purposes.
The transport stream data are handled according to RFC768 on the
UDP layer. The operator can configure destination port for the MPEG-2
transports stream. The MTU for Ethernet is usually 1500 bytes. This
limits the number of transport stream packets to embed into the
outgoing Ethernet/IP frames to be between 1 and 7.
TCP is used for control data.