Author: RRi
Page - 39 -
Version 1.0
Date: 10-2019
BLANKOM-IPQAM-801_User_Manual_ENv1.0.docx
IPQAM-801 DVB-C A/C Modulator IP to QAM User Manual
Multicast (as opposed to unicast) is used to send UDP packets from 1 source to multiple
destination servers. This is useful for example for streaming from a satellite/DVB-T receiver to
multiple receiving PCs for playback. Multicast can also be used on the output of an encoder to
feed multiple streaming servers. Multicast only works with UDP and is not possible with TCP
due to the 2 way nature of TCP, most commonly multicast is used with RTP and MPEG2-TS.
A multicast IP address must be chosen according to IANA information, we recommend using an
address in the range 239.0.0.0 to 239.255.255.255 as this is reserved for private use. Using
multicast addresses in the 224.0.0.0 range may clash with existing services and cause your
stream to fail. For more details see
http://www.iana.org/assignments/multicast-
addresses/multicast-addresses.xml
Choosing a UDP port number for multicast streams is also important. Even if you use a
different multicast IP for each of your streams, we strongly recommend using different UDP
port numbers as well. This is because a server and all software running on the server receives
ALL multicast traffic on an open port and extra processing is required to filter out the required
traffic. If the each stream arrives on a different port, the server can safely ignore any traffic on
ports that are not open. Port numbers MUST be chosen so that don't clash with any existing
services or ephemeral ranges. The ephemeral range for Windows Vista, 7, 2008 is 49152 to
65535, for older Windows it is 1025 to 5000 and for Linux it is 32768 to 61000. For more
information on Windows see
http://support.microsoft.com/kb/929851
taken to avoid system ports 0 to 1024. See
http://www.iana.org/assignments/service-names-
port-numbers/service-names-port-numbers.xml
Generally one of the unassigned User Ports
(1024-49151) should be used, you can run the netstat -abn (as admin under windows)
command to see which ports are currently in use.
Registered port
A registered port is a
(a sub-address defined within the
, in the
range 1024–49151) assigned by the
Internet Assigned Numbers Authority
(IANA) (or by
Corporation for Assigned Names and Numbers
(ICANN) before March 21, 2001,
before 1998) for use with a certain protocol or application.
Ports with numbers 0–1023 are called system or well-known ports; ports with numbers 1024-
49151 are called user or registered ports, and ports with numbers 49152-65535 are called
dynamic and/or private ports.
Both system and user ports are used by transport protocols
(TCP, UDP, DCCP, SCTP) to indicate an application or service.
Ports 0–1023 – system or
Ports 1024–49151 – user or registered ports
Ports >49151 – dynamic / private ports
https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers
