Network Technologies ASI-IP-GTW User Manual

ASI-IP-GTW User's Manual 

 

 Page 

67 

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.