1 7 6 T A L K S W I T C H US E R G U I D E • N O R T H A M E R I C A
The IETF’s philosophy is simplicity: specify only what you need to specify. IP
just initiates, terminates and modifies sessions. In this guide, the term IP is
often used in place of VoIP.
TalkSwitch phone systems use the Appello® SIP Stack for VoIP
communications. The Appello® SIP Stack was developed by TalkSwitch,
a division of Centrepoint Technologies Inc.
What is a VPN?
VPN stands for Virtual Private Network. It is a means of having the
advantages of a private network on a shared public infrastructure like the
Internet.
Can a VPN help to carry data securely over the Internet?
A VPN provides security by using encryption/decryption. Using a process
called tunneling, private data is encrypted and encapsulated before being
sent across the network. The packets of information are sent to their
destination. Only the ones with the correct protocol information can enter a
company’s network.
A VPN is most useful for providing employees with remote access to the
company network without compromising security. Encryption can have a
negative impact on the call quality because of the increased overhead on the
network connection. IPSec adds approximately 10% overhead to VPN traffic.
What’s the difference between a public IP address and a private
IP address?
A public IP address is a globally unique number that identifies a device on
the Internet. If you want someone on the Internet to connect to you, they
must know your public address. Also known as your real or external address.
Private IP addresses are typically assigned to devices on a Local Area
Network (LAN) and are not routable outside the LAN. Private IP addresses
are usually in the range 192.168.x.x, 172.16.x.x or 10.x.x.x. These IP
addresses are used where you have multiple computers all sharing the same
Internet connection.
To access the Internet, a computer or VoIP device must have an IP address.
So what do you do if your ISP (Internet Service Provider) has provided you
with only one IP address but you have more than one device that requires
Internet access? The solution is to give each of the devices on the LAN a
private IP address. A router makes them work by performing Network
Address Translation (NAT — See the next topic for details).
Addresses of the form 192.168.x.x, 172.16.x.x or 10.x.x.x are not recognized
on the Internet and can only be used for private networks. For example, if
you tell someone on the Internet to connect to you using a 192.168.x.x
