Although Fax over IP has the potential to deliver
many benefits it is not always the appropriate solution
for every network and care must be taken in choosing
whether to deploy a traditional PSTN fax platform
or an IP solution.
The starting point for your evaluation must be to
consider the topology of the existing network to
determine those parts, if any, that may already be
equipped to support an IP fax environment. Having
mapped out the existing network we must then decide
what other equipment must be deployed in the enterprise,
in addition to the fax server, to complete the IP
fax implementation.
Until relatively recently it was necessary to install
hardware cards to integrate fax into your communications
infrastructure. With the ever increasing power available
from a single platform it is now possible to move
to a software only solution for the fax interface.
Which option is right for you will depend on a number
of factors which we are happy to discuss with you,
just follow the link to our Free
FoIP Consultation. The key differences between
these technology options are set out below.
Fax cards Verses Software only solutions
Fax Cards
The hardware card provides onboard chips to perform
digital signalling processing (DSP’s); this
does not provide an overhead on the platform CPU
as all processing is carried out by the hardware
card. This does, however, provide an issue in sourcing
hardware as it is becoming more and more difficult
to source hardware with the required number and
size of slots.
If considering purely cost, however, the later Brooktrout
hardware cards support both T.30 (traditional fax)
and T.38 (FoIP) and as such may be redeployed into
a FoIP environment, thus saving the costs of moving
to a software only solution.
Software
In a software based solution, the fax data packets
are processed by the platform’s CPU and require
no additional hardware. In this way the fax software
may be deployed anywhere on the organisation’s
network, including virtual servers. Software solutions
are marginally cheaper than purchasing hardware
cards.
Considerations
It cannot be assumed that moving to a software driven
IP Fax solution will inevitably result in an overall
reduction in the hardware required to process fax
messages as they pass through your enterprise.
You will obviously remove the need for fax cards
but you may have to add additional steps to allow
faxes to reach their final destination as they
pass through IP switches, routers and gateways
on their way to the PSTN.
Faxing speeds
Hardware based fax boards support transmission speeds
of up to 33.6 kilobits per second whereas at this
time most of the industry currently transmits fax
traffic over T.38 at a maximum of 14.4 kbps.
There are exceptions, however, such as Lane’s
Passport fax server which uses the latest Dialogic® products
including the Brooktrout® SR140 and the DMG3000 & DMG4000
Media Gateway Series which enable enterprises to
deploy fax server solutions into existing VoIP installations,
while leveraging their existing IP infrastructure.
The addition of V.34 T.38 allows these products to
transmit fax data at 33.6 kbps.
Voice integrated solutions.
FoIP does not, at this time, support voice integrated
features such as DTMF (dual tone multi frequency).
If you require this feature you should select a
fax card and PSTN solution for your fax server.
Capacity and Bandwidth
A T.38 (IP Fax) session is open for the entire duration
of a fax transmission and therefore requires a
dedicated channel between the IP network and the
fax server for the duration of the call. In this
way the channel capacity for the IP Fax server
is no different were it to be an IP solution or
a PSTN solution. In addition to this, unlike IP
voice, most IP fax needs a consistent signal quality
and cannot operate with latency in the network.
Lane has developed a remote service for processing
the T.38 anywhere on the enterprise, allowing the
T.38 service to be deployed adjacent to any gateway,
thus reducing the network overhead and removing the
problems associated with network latency.
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