Streams; Stream Types - Harris CM-30 Installation & Operation Manual

2 –Functional Design
queries from the router. It supports the proprietary IGMP statistics MIB to account for all incoming and
outgoing messages.

2.2 Streams

Within the NetXpress LX multiplexer or an original Intraplex multiplexer, the CM-30 IP interface
module uses packet streaming to transport audio signals.
2.2.1

Stream Types

2.2.1.1 Unidirectional
Packet streams can be unidirectional or bidirectional. In other words, streams can travel in one
direction (transmitted or received) or two directions (transmitted and received). The CM-30 module
supports both unidirectional and bidirectional packet streaming.
Most circuit types (such as voice and two-way data circuits) are bidirectional, or full-duplex. Full-
duplex circuits require identical full-duplex (transmit or receive) channel modules at both ends of the
channel they occupy within a system. Other circuit types (such as program audio channels) are
unidirectional (simplex). They always have a transmitter module at one end and a receiver module at
the other. Most bidirectional (full-duplex) channel modules can also be set up to operate in a
unidirectional (simplex) mode.
2.2.1.2 Unicast versus Multicast
Packet streams can also be classified as unicast or multicast. Unicast describes transmitting a piece of
information (a packet stream in this case) from one point to another point. Unicast transfer mode is
still the predominant form of transmission on LANs and within the Internet. Standard unicast
applications include HTTP, SMTP, FTP, and Telnet.
Multicast describes communication where a piece of information is sent from one or more points to a
set of other points (a multicast group address). There may be one or more senders and the
information is sent to a set of receivers (there may be no receiver or any number of receivers). With
multicasting, the same packet is delivered simultaneously to a group of clients. Multicast applications
must use the UDP (User Datagram Protocol) transport protocol, since TCP (Transmission Control
Protocol) only supports the unicast mode.
Most circuits provided by Intraplex multiplexer systems are unicast, including those provided with the
NetXpress LX system. However, several types of channel modules can be configured for point-to-
multipoint operation (multicast). For example, you can set up a single program audio transmitter
module and several program audio receiver modules in a point-to-multipoint or "broadcast" circuit
configuration, allowing multiple locations to receive the same program audio signal.
If your network does not support multicasting, you can configure the NetXpress LX system to multi-
unicast up to four destinations. The programming source must be in contiguous time slots on TDM Bus
A. The receivers can be on the internal TDM bus. Section 4.3.3.4 – TDM Bus Mapping Configuration
gives additional multi-unicast information.
2.2.1.3 Voice Streams versus Data Streams
Streams which are intended to carry information for voice grade audio modules often require
additional signaling information to support pulse dialing, off-hook condition call progress or ringing
states. Special signaling support is required to transport this added information. Voice audio streams
carrying telephone calls are also prone to audio echo back from the receiver. You can use echo
canceling circuits to eliminate this problem. Streams used for transporting linear or compressed
wideband audio modules or other forms of raw information present their data directly into each
channel and do not require signaling support.
Harris Corporation
Intraplex Products
NetXpress LX & CM-30 Installation & Operation Manual
versus Bidirectional
Version 1, September 2010
2-3