Telex IP-223 - Manual (Page 21)

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CHAPTER 2
Communications System Design
Designing an IP-223 system requires an understanding of the radio network and how the various radios and communication
equipment are connected.
The first step in designing an IP-223 system is to create a roadmap of the radio, console, and any other communication
equipment locations. This roadmap must include the following:
• Multicast addresses for each channel of TX (transmit) and RX (receive) communication.
• Port numbers for each channel of TX and RX communication.
• Base IP Addresses assigned to each console and IP-223 on the network.
Network Requirements
Bandwidth
Each VoIP channel requires 50kBit of bandwidth while active. Full-duplex conversation (audio in each direction) requires
100kBit of bandwidth.
NOTE: Most radio voice communications are half-duplex (only in one direction at any one time), thus requiring 50kbits.
Some radio systems transmit go-ahead beeps when it is clear to talk. In order for the console operator to hear the beeps, the
system must support full-duplex communication. Full-duplex bandwidth may only be required for the first few seconds of a
conversation, due to the brief nature of the go-ahead beeps at the beginning of the transmission.
When using a PIB, TDI, C-6200, or the NI-223 for a telephone connection, 100kBit is required since it is a constant, full-
duplex conversation.
Multicast
In general, Telex systems require multicast to function. The network must be able to support the multicast traffic generated by
the system.
It is very common for networks to enable multicast after an IGMP (Internet Group Management Protocol) join message is sent
out, and then prune off branches after a period of time. Due to the intermittent usage patterns of two-way radios, such a system
can appear to work flawlessly for a period of time, then no longer work.