Packet-switched telephony:
From POTS to packets
Unlike circuit-switched POTS, which always require use of the
Public Switched Telephone Network (PSTN), VoIP technology
has enabled telephony and other new and novel features and
services to run over dedicated and wireless networks including
even your computer network. These newer network types
use packet-switched protocols.
Packet-switched VoIP puts voice signals into packets. Along
with the voice signals, VoIP packets include both the sender’s
and receiver’s network addresses. VoIP packets can traverse
any VoIP-compatible network. Along the way, they can choose
alternate paths because the destination address is included in
the packet. The routing of the packets is not dependent on
any particular network route.
In a circuit-switched network, the destination address is not
included in the signal; routing directions are determined physically
by the actual POTS line. So the routing must follow a
specific network line similarly to how a train follows a designated
set of railroad tracks. If the line is down, the call cannot
go through.
In a packet-switched network, if one of the network lines is
down, the packet can switch while in route between locations
to another working route to keep the call up. Using VoIP, voice
signals can be packetized like computer data packets. This
enables companies to consider using the same network
infrastructure to support both data and voice applications.
Companies can consolidate their physical networks (while
maintaining redundancy in their routing patterns) and build
an enterprise-class communications network with the latest
advanced IP-based features.
VoIP makes possible other services that older telephony systems
cannot do. The VoIP protocols, or simply IP, as many
have begun to call it for short, are interoperable. This term
means that the IP protocols will work well with all kinds of
networks. VoIP is valuable because it fundamentally operates
the same way in all network types. IP protocols are also highly
portable. This means they will work with any IP-enabled enduser
device such as an IP telephone, computer, or even a
Personal Digital Assistant (PDA). VoIP works everywhere!