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166 MESSAGING SYSTEMS
The inherent effi ciencies of fax transmission over the Internet or other packet -
based IP networks can lead to lower network costs as the incremental cost of one
more packet transmission generally is negligible, if not zero, and generally is not
distance sensitive. This cost structure compares favorably with a relatively expensive
fax call over the PSTN. IP - enabled fax devices essentially incur no usage - sensitive
transmission costs other than those possibly imposed by an IP fax service provider;
the costs of so enabling a device vary widely but generally can be justifi ed for fax -
intensive environments. Devices not so enabled must make use of an IP gateway
from a service provider, with the costs to the end user of transmission in this environment
varying widely and not necessarily comparing favorably with the traditional
approach.
In either case, access to the packet network is on the basis of a local call, which
does not carry a per - minute charge in many countries. A number of telcos in the
United States and abroad support IP fax, as do some Internet Service Providers
(ISPs) and most fax service bureaus. IP fax – capable routers have the ability to
transmit a fax over an IP network assuming that the level of delay is acceptable and
to default to the more conventional means of transmission over the PSTN when
delays are deemed unacceptable [11 – 14] . Such routers also have the ability to secure
the fax document during transmission via the IPsec ( IP security ) encryption mechanism,
thereby providing a substantial level of security over the inherently insecure
public Internet. In the absence of a defi ned relationship between fax routers running
matching encryption software, the IP fax user is at risk in transmitting over the
Internet. As testimony to issues of IP fax security, I just received an e - mail response
from a hotel chain asking me to fax some information. The following cautionary
statement appeared at the end of the message: “ Please be advised that our fax
machines transmit through the internet. [sic] For your protection, please block out
any non - essential information such as the last twelve numbers of your credit card
account. ”
4.1.7 Fax Features
Fax capability comes in a variety of forms from simple and inexpensive stand - alone
Group III fax machines to integrated devices that combine the capabilities of a fax
machine, printer, copier and scanner and culminating in Group IV fax servers with
IP networking capabilities. Available features include the following:
• Blocking: If caller ID is available on the fax line, the user can build a list of
junk fax numbers to be blocked.
• Broadcasting: Also known as group fax , broadcasting allows the user to
program a distribution list of fax telephone numbers intended to receive a
given fax. The machine will transmit the document to the target numbers, in
sequence.
• Color: Color fax was specifi ed in T.30E. While color lengthens transmissions
times considerably and reduces the number of pages that can be stored in
memory, it certainly is an aesthetic improvement over black and white. Some
fax machines using bubble jet, inkjet, or laser print technology offer color, as
well as black - and - white, fax capabilities.