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VoIP / IP Telephony
Consult Teleco's list of internet VOIP provider
VoIP
VoIP is a set of technologies
that uses the Internet or private IP networks
for Voice communication, substituting or complementing
the conventional telephony systems.
Communication |
Characteristics |
| Computer
to Computer |
- Peer-to-peer;
- Uses free services such as Skype,
MSN Messenger, Yahoo Messenger, among
others;
- The computers are responsible for
call signaling and control.
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| Computer to telephone |
- PSTN Gateway needed;
- Peer-to-peer up to the gateway;
- uses pre or post paid services such
as the SkypeOut, Net2Phone, V59, among
others;
- The gateway is responsible for call
signaling and control.
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Regulations
Anatel regulates telecommunications
services and do not regultates the technologies used to implement
them. VoIP technologies are used only for implementing
the telephony services, but they are not the
service itself. A specific regulation for VoIP
in Brazil does not exist yet.
IP Telephony
IP Telephony is a VoIP based
service which presents quality and functionalities
that are, at least, equivalent to the conventional
telephony services. The subscriber needs an IP
telephone or an IP adapter for a conventional
telephone and an IP broad band service to connect
to the IP telephony network. In addition, the
service can be accessed from a computer running
a soft-phone software.
Service |
Characteristics |
Consumer |
- Provided by Operators with IP Telephony
Networks that are interconnected to the
conventional telephony networks (public
and cellular services) ;
- The Operator provides the IP telephone
or IP adapter and the broad band connection;
- The subscriber receives a phone number
from the operators assigned numbering
range;
- Originates and receives calls either
for/from IP telephones and conventional
telephones (public and cellular services);
- In addition, the subscriber can be
connected to the Operator network through
any IP broad band connection, either
in the subscriber address or any other
addresses, using the same phone number
and even keeping the contracted service
rates;
- Call control and signaling (as well
as the aditional services and gateways)
are managed by equipments especially
designed for this purpose(Soft-switches);
- Examples of IP Telephony Operators: Vonage, AT&T
- CallVantage e GVT.
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Enterprise |
- Uses IP PBX's and corporative data
networks;
- The user uses a computer or an IP
telephone or an IP adapter and a data
connection from the corporative network;
- The user receives a number from the
corporative extensions numbering range;
- Originates and receives calls either
for/from IP telephones, computers and
conventional telephones (public and cellular
services);
- The user can be connected to the corporative
network eihter in the regular office
or any another address of the company
keeping the assigned extension number
and configured services;
- Call control and signaling (as well
as the aditional services and gateways)
are managed by equipments especially
designed for this purpose (Call Manager).
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Protocols for VoIP / IP Telephony
Signaling IP Protocols
(Call control)
- H.323 - Packet
Based Multimedia Communications Systems (ITU-T). Used
by IP telephones, computers, IP adapters,
signaling controllers (soft-switches and
call managers) and gateways for call control
(establishment and hang-up). It is an older
and complex protocol and it has been used
with less frequency in IP telephony systems.
- SIP - Session Initiation
Protocol (IETF). It has the same
purpose of H.323, however it is a modern
and less complex protocol, and it has been
used more frequently in VoIP systems.
Gateway Control Protocols
(Signaling)
- MGCP - Media Gateway
Control Protocol (IETF). Used by
gateways controllers and gateways for call
control (establishment and hang--up).
- MEGACO - Gateway
Measured Protocol Control (IETF/ITU-T). It
has the same purpose of MCGP, however it
was developed to be an alternative protocol,
which can be used by gateways distributed
controllers, multicast controllers (Conference)
and interactive audible reply units.
Media Protocols
(Voice Transport)
-
RTP - Real-Time Transport Protocol
(IETF). Responsible for Real -time
Voice transport between computers and gateways.
It is currently the preferred standard
for this purpose.
RTCP - Real-Time Transport Control
Protocol (IETF). Responsible for
controlling the Voice transport performed
by RTP in VoIP systems.
Additional Information
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