Round Table
Services - Communications
Broadband
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Broadband is always available, always on,
always go. There is
no need to dialup to make a connection to the ISP. Once you have connected
your broadband modem or router to your broadband connection the
internet is constantly at your finger tips. Bandwidth, the rate
at which data is transmitted, is considerably greater than dialup.
Actual transmission rates depend on the type of broadband and the
packages the broadband provider is selling. Broadband
comes in various flavours such as ADSL, SDSL, broadband cable, satellite and
wireless. |
ADSL
Asymmetric Digital
Subscriber Line (ADSL) is probably the most common of broadband
flavours. The technology makes use of unused frequencies that exist in
the telco's telephone cabling. A key word here is
"asymmetric" which in this context means that the bandwidths
allocated to the downstream and upstream directions are unequal.
Typically bandwidth in the downstream direction from the ISP to your
PC is greater than in the upstream direction. Upstream is from your PC
to the ISP.
The reason for this arrangement is that surfing the
internet is the most common use for being online. Data is being sent
in both directions however most of the data is in the form of web
pages heading downstream (approximately 8:1 in favour of downstream).
It therefore makes sense to give more bandwidth to downstream
traffic.
ADSL charges are normally based on a one time set
up fee. An ADSL modem is often an additional cost. A modem is
sometimes included in the set up cost if the broadband supplier is
running a product promotion drive to encourage take up. A monthly
subscription fee is then payable. There is no limit to time spent
online and voice calls can be initiated and received whilst online.
The comparatively low upstream bandwidth may not be
suitable if you are hosting a service. The terms and conditions of the
ADSL agreement may indeed prohibit you from hosting. Check before
signing up.
There are various ADSL standards. The full rate
offering is capable of downstream speeds of 1.5Mbps to 9Mbps and
16kbps to 640 kbps upstream. G.Lite ADSL is a "plug and
play" standard that was developed for the consumer market. It has
a maximum downstream of 1.5Mbps and 160kbps upstream. Both are capable
of simultaneous voice and data connectivity. Actual bandwidth and
pricing will depend on your service provider. The higher the bandwidth
the higher the cost.
SDSL
Symmetric Digital
Subscriber Line (SDSL), note the word "symmetric", has equal
downstream and upstream data rates. SDSL
is not as readily available as ADSL. Data rates range from 128kbps to
2.32Mbps. Once again actual data rates of the SDSL connection depend upon the services that
the provider is offering. SDSL tends to be more of a data only
technology. There are also many flavours of SDSL with varying data
transfer and voice carrying ability characteristics. Options include
SDSL, SHDSL, HDSL and IDSL.
Cable
In areas where cable
television services are available broadband cable may be an option for
data. Downstream rates range from 256kbps to 2Mbps depending upon
the package. Cable broadband, just like the other broadband flavours,
is always on.
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