Tieline Bridge-IT, User Manual

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© Tieline Research Pty. Ltd. 2019
Bridge-IT Manual v4.0
allow it to connect to a LAN. Often a security
measure to only allow access to devices
approved by a network administrator.
Obtaining Public IP Addresses
To send audio streams over the public internet you need to use a public IP address assigned to
you by your ISP (Internet Service Provider).
A public IP address is like your public telephone number and allows you to be contacted over the
internet in much the same way people dial your public telephone number. They come in two forms;
dynamic (DHCP) and static. Most ISPs assign a dynamic public IP address by default, which can
often change without you knowing. This is suitable for a quick demo of your Tieline codec, but for
a permanent installation you will need to request a permanent static public IP address.
Once the Static Public IP address is assigned to your internet connection (router) at the studio you
need to create a link between the public IP address and your codec’s private IP address on the
LAN. This is called Network Address Translation.
Depending upon how your network is configured, it may also be possible to simply connect your
Tieline codec directly into your ADSL modem/router and receive a public address from the router.
Private LAN IP Addresses
By default your Tieline codec will normally be automatically assigned a private IP address when
you connect it to a typical router over a LAN.
Private IP Addresses are associated with LANs and normally reside behind a firewall and are not
visible to the internet. They are generally in the ranges: 10.0.0.1 – 10.255.255.255, 169.254.0.0 –
169.254.255.255, 172.16.0.0 – 172.31.255.255 and 192.168.0.0 – 192.168.255.255 and are
assigned by network DHCP servers and routers.
These IP Addresses are generally assigned for a predefined period (known as a lease) by your
network's DHCP server or router. This IP address will generally expire after the lease period.
DHCP assigned IP Addresses may also change if the device is disconnected for lengthy periods
or if power to the device is turned off and back on. As a result, it is advised that you make this IP
address permanent by assigning it as a Static DHCP IP Address. This will ensure you are able to
always forward incoming audio packets to your codec using the same private IP address at the
studio using port forwarding (see the section on port forwarding for more details). Consult your
Network Administrator if you are unsure how to do this.
Network Address Translation (NAT)
Network Address Translation (NAT) is a method of connecting multiple devices to the internet
using one public IP address.
The best way to explain NAT is to use the example of a phone system at an office that has one
public telephone number and multiple extensions. This type of telephone system allows people to
call you on a single public telephone number and performs the translation and routing of the public
number to a particular private extension. Similarly, in order to receive an IP call from a remote
codec over the public internet, the same network address translation principle applies. NAT and
port forwarding allows a single device, such as a broadband router, to act as an agent between
the public internet and a local private LAN.
The relationship between public and private IP addresses and NAT is displayed in the following
diagram and the following section explains port forwarding configuration in more detail.