| |
VOIP Advantages & Disadvantages
Cost
In general, phone service via VoIP costs less than equivalent
service from traditional sources but similar to alternative
PSTN service providers. Some cost savings are due to using a
single network to carry voice and data, especially where users
have existing under-utilized network capacity they can use for
VoIP at no additional cost. One must note that the maximum upstream
in your Internet connection is the final throttle and service
is not as good as standard telco services.
VoIP to VoIP phone calls on any provider are typically free,
whilst VoIP to PSTN calls generally costs the VoIP user. Free
VoIP to PSTN services are rare. A notable provider is VoIP User.
There are two types of PSTN to VoIP services: DID and access
numbers. DID will connect the caller directly to the VoIP user
while access numbers requires the caller to input the extension
number of the VoIP user. Access numbers are usually charged
as a local call to the caller and free to the VoIP user while
DID usually has a monthly fee. There are also DID that are free
to the VoIP user but is chargeable to the caller.
Functionality
VoIP can facilitate tasks that may be more difficult to achieve
using traditional phone networks:
Incoming phone calls can be automatically routed to your VoIP
phone, irrespective of where you are connected to the network.
Take your VoIP phone with you on a trip, and anywhere you connect
it to the Internet, you can receive your incoming calls. Call
center agents using VoIP phones can work from anywhere with
a sufficiently fast Internet connection. VoIP phones can integrate
with other services available over the Internet, including video
conversation, message or data file exchange in parallel with
the conversation, audio conferencing, managing address books
and passing information about whether others (e.g. friends or
colleagues) are available online to interested parties.
Drawbacks
VoIP technology still has a few shortcomings that have led some
to believe that it is not ready for widespread deployment. However,
many industry analysts predicted that 2005 was the "Year of
Inflection," where more IP PBX ports shipped than legacy digital
PBX ports.
Implementation challenges
Because IP does not provide any mechanism to ensure that data
packets are delivered in sequential order, or provide any Quality
of Service guarantees, VoIP implementations may face problems
dealing with latency (especially if satellite circuits are involved),
and jitter. They are faced with the problem of restructuring
streams of received IP packets, which can come in any order
and have packets delayed or missing, to ensure that the ensuing
audio stream maintains a proper time consistency. This problem
has been addressed by Ubicom with their StreamEngine Technology.
Another main challenge is routing VoIP traffic to traverse certain
firewalls and NAT. Intermediary devices called Session Border
Controllers (SBC) are often used to achieve this, though some
proprietary systems such as Skype traverse firewall and NAT
without a SBC by using users' computers as super node servers
to route other people's calls.
Keeping packet latency acceptable can also be a problem, due
to network routing time (buffering, switching) and transmission
distances (more relevant under satellite links).
Reliability
Conventional telephones are connected directly to telephone
company phone lines, which in the event of a power failure are
kept functioning by back-up generators or batteries located
at the telephone exchange. However, household VoIP hardware
uses broadband modems and other equipment powered by household
electricity, which may be subject to outages. In order to use
VoIP during a power outage, an uninterruptible power supply
or a generator must be installed on the premises. It should
be noted that many early adopters of VoIP are also users of
other phone equipment such as PBX and cordless phone bases that
also rely on power not provided by the telephone company.
Some broadband connections may have less than desirable reliability.
Where IP packets are lost or delayed at any point in the network
between VoIP users, there will be a momentary drop-out of voice.
This is more noticeable in highly congested networks and/or
where there is long distances and/or interworking between end
points.
| |
