Comtech EF Data DTMX5000 SpectraCast - Manual (Page 20)

Introduction DTMX5000 IP Gateway
1–6 Rev. 1
1.3.1 IP Multicast
The DTMX5000 receives TCP/IP datagram addressed to subscribers and maps them onto
a DVB compatible MPEG2 transport stream. The DTMX5000 is capable of mapping two
types of datagrams.
Unicast Packets Each unicast packet is addresses to one individual user.
Multicasts Packets Multicast packet are addressed are addressed to a group of users, and are
simultaneously sent to all members of the group. These packets are usually for
the distribution of files, or for streaming audio or video. It is possible to disable
Multicast broadcasting if, example: this type of transmission is being handled by
a separate DTMX5000. It is also possible to enable multicasting for predefined
channels only.
1.3.2 IGMP Client
The DTMX5000 acts as an IGMP client (RFP 1122). For each registered multicast
channel that it forwards, the unit generates an IGMP request and replies to IGMP queries.
The IGMP protocol is managed on the Transportation NIC only.
1.3.3 Data Mapping and DVB Mapping
Data mapping specifies how IP datagrams are mapped onto the output transport stream.
There are three mapping modes.
•
Piping
•
Streaming
•
Multiprotocol Encapsulation
Data piping and data streaming are proprietary mapping, data piping without encryption
and data streaming with encryption. Multiprotocol encapsulation is used for compatibility
with other DVB based systems.
1.3.4 Quality of Service
Quality of Service (QoS) Management is a feature that determines the amount of
bandwidth each subscriber is allocated. This feature can either be enabled or disabled.
•
When QoS is enabled, subscribers receive their bandwidth share according to the
level of service specified in their individual subscription fees.
•
When QoS is disabled, the DTMX5000 will provide best effort service, resulting
in the available bandwidth being equally divided among the various subscribers.