JPS Communications NXU-2, Installation And Operation Manual

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NXU-2 Operations Manual
JPS Communications, Inc.
6-1
6 NXU-2 FAQ (Frequently Asked Questions)
6.1 General
This section provides answers to some frequently asked questions about the installation and
operation of the NXU-2.
How much network bandwidth does the NXU-2 consume?
The NXU-2 bandwidth usage varies depending on the application. When COR is inactive and
no audio is being transmitted across the link the bandwidth usage is essentially zero, since a
small “keep-alive” packet is only sent every 4 seconds. When COR is activated and the default
voice compression method is used, audio will be sent across the link at approximately 15Kbps.
If a full-duplex connection is active (COR is active on each end) then the total bandwidth usage
for audio will be approximately 30Kbps. Selecting a different voice compression method will
increase the bandwidth accordingly. Voice compression method 2 will require approximately
18Kbps (half-duplex), method 3 will require 27Kbps, method 4 will require 36Kbps, and
method 5 will require approximately 70Kbps. If RS-232 data is being sent simultaneously then
the bandwidth will be increased by the RS-232 data rate, plus the TCP overhead.
Can I use the NXU-2 on a dialup connection?
No. The NXU-2’s network connection is via Ethernet. Most dialup (telephone line) modems
only provide RS-232 connections, but even if an Ethernet connection to a dialup is available,
the NXU-2 may not operate properly since the connection speed is not guaranteed on a dialup
connection. Poor telephone lines or varying line conditions may cause a dialup modem to
reduce its connection speed without the user being aware of this condition. For this and other
reasons, dialup connections are not supported by the NXU-2.
My network is behind a firewall. How can I make the NXU-2 work?
Firewalls provide network security by limiting access into the network from the outside.
Sometimes this causes difficulty when installing network equipment such as the NXU-2. There
are two solutions to this problem. You can install the NXU-2 on the outside of the firewall, or
you can open a hole in the firewall so that the port specifically used by the NXU-2 is
accessible. The NXU-2 does not pose a security risk to other computers or devices on the
network, since it cannot be made to access files or forward information to other systems. If you
choose to open a hole in your firewall, you will need to allow access to port 1221 (or to the port
you have selected if you have used the PORT command, see section 3.3.6 Setting VoIP Port
(Optional)) for TCP and UDP services. Contact your network administrator for approval and
assistance with firewall settings.