TELE-audiovision - The World’s Largest Digital TV Trade Magazine - page 154

TELE-audiovision International — The World‘s Largest Digital TV Trade Magazine
— 09-10/2013
should make sure there is
a reliable network connec-
tion between the transmitter
and receiver, otherwise the
broadcast won‘t be reliable.
RTP on the other hand is
not a fundamental protocol
like TCP or UDP. On the con-
trary, RTP is a protocol layer
based on UDP. This means
that as a basis UDP is always
used for RTP. RTP offers a
number of functions that
greatly improve live audio
and video transmissions:
• Data identification
• Time stamps for audio/
video synchronization
• Maintaining the order of
MPEG frames
• Special handling of MPEG
key frames
This just goes to show that
RTP should be used when-
ever all the devices involved
support this protocol.
With Multicasting an au-
dio/video stream is simply
transmitted without any par-
ticular receiver in mind. This
transmission is routed to all
users by the network and
it‘s up to the users to de-
cide if they want to receive
it or not. Obviously this is
extremely practical if more
than one user wants to re-
ceive the same stream. As
many users as desired can
tune in without the need for
additional network band-
width between the transmit-
ter and the switch.
Since the switch has to
process numerous data
packets, it could very quickly
become overloaded when
dealing with a cheap SOHO
product (Small Office, Home
Office) while at the same
time additional data is ex-
changed between users. If,
for example, User 2 doesn‘t
want to take part in Multi-
casting and would rather
send a large file to User 3, it
could happen that the flow of
this data transmission is re-
duced to a snail‘s pace or it
might not function at all.
To utilize Multicasting, with
regard to the IP destination
address it would be good
enough to configure using any
IP address from to This ad-
dress range would be used
by all of the Multicast de-
1. Wireshark capturing the network traffic. Beware that
lots of data is captured during a IPTV broadcast. You
should only capture data for some seconds, otherwise
it will take ages to process all captured packets.
2. After capturing the network traffic for a short
period, there are many analysis tools available within
Wireshark. This picture shows where the traffic
originated. It can be clearly seen that the devices with
IP-address and generated a
huge amount of traffic. Notice the destination IP: they
are multicasting IPs
3. All captured packets can be analyzed individually and
the contents can be viewed, while the header is shown
in a more detailed way.
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