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Prontonet IP Decoder User Manual v5.4.1.1.doc
66
Multicast considerations:
Internet Protocol (IP) multicast is a bandwidth-conserving
technology that reduces traffic by simultaneously delivering a single
stream of information to thousands of corporate recipients and
homes.
Multicast is based on the concept of a group. An arbitrary group of
receivers expresses an interest in receiving a particular data
stream. This group does not have any physical or geographical
boundaries—the hosts can be located anywhere on the Internet.
Hosts that are interested in receiving data flowing to a particular
group must join the group using IGMP. All this is done
automatically by ProntoNet IP Decoder when establising a
connection.
Multicast traffic is rejected when going through the Internet, since
most IP servers on the Internet do not currently support the
multicasting part of the protocol, except when using VPNs, because
VPN’s encapsulates IP packets as unicast frames, so routers simply
see an ordinary packet.
All IP multicast group addresses will fall in the range of 224.0.0.0
to 239.255.255.255, but some of them are reserved, that’s why the
range of addresses from 224.0.1.0 through 238.255.255.255 are
called globally scoped addresses.
There should only ever be one transmitter connected to a
MULTICAST group or else audio reception errors will occur.
For transmitting MULTICAST audio the Prodys proprietary protocol
“Prodys eXtended Real Time Protocol (PX-RTP) will be used.
The ProntoNet transmitter cannot be in automatic encoding mode.
To guarantee a constant delay all the units must synchronise their clocks.
Each receiver will activate a clock-sync algorithm that adjusts its PLL
(Phase-Lock Loop).
V.4
Prodys Proprietary set of protocols
Prodys has developed this proprietary set of protocols to carry out IP streaming
connections, due to the lack of a standard in this regard:
•
Prodys Real Time Control Protocol (P-RTCP): This is a protocol based
on TCP that allows for the establishment and termination of a
connection as well as for the negotiation of the codec mode (automatic
audio synchronisation in all modes).
•
Prodys Real Time Protocol (P-RTP): This is a protocol based on UDP
used for the transmission of audio.