Network Communications News (NCN) June 2016 | Page 18

F E AT U R E

choosing the right LAN

The data rate of the switch is an important consideration.

The number of ports – the
connections available on the switch
– can vary between one switch and
another, but the usual configurations are
12, 24 and 48 ports. Each port allows you
to connect an IP device, but not all ports
are the same. There are several types of
ports with different characteristics.
The RJ-45 format is the most common
and is the one most of us will recognise. It
is the format which enables the connection
for most IP devices. The SFP ports
are typically used to connect switches
together or connect LAN switches to
servers. Some ports are combined, or
‘combo-ports’, and offer the flexibility to
use RJ-45 or SFP connectors.

3. LAN performance
The data rate of the switch is an
important consideration and will have
a significant impact on the price of
the switch. You will need to take into
account the applications and devices
which will be used on the network now,
and over the next five years.
Fast Ethernet switches currently
offer a speed of up to 100Mb/s per port,
whereas Gigabit Ethernet can transmit
data over the network 10 times faster.
If you are looking to future-proof the
business’s IT, sustainability is on the side
of gigabit or gigabit ready Ethernet.

4. Power to the
network means PoE
Each IP device will need to be powered
electrically. Simply accommodating the

amount of power cables required to run
all these devices can quickly become a
problem for a business. A switch which
is Power over Ethernet (PoE) capable is a
solution to this problem.
Developed to provide electric
power to IP devices such as phones,
cameras and access points, a PoE
switch delivers power along the same
Ethernet cable as data is transferred.
This has the benefit of reducing the
amount of electrical cabling, reducing
power consumption, avoiding
inadvertent disconnections and
providing secure power for the devices
by installing an uninterruptible power
supply (UPS).
However, the arrival of power hungry
IP devices requires a more powerful PoE
standard – this is called PoE+. These
ports can deliver twice the power of
standard PoE and are therefore the best
way of ensuring that the network can
support all the IP devices necessary to
run and grow a business. Whichever
switch you choose, be sure to check that
it provides enough electrical power to
run all IP devices, and take into account
that 15 per cent of LAN switch electrical
power will be lost in a network through
transmission along the Ethernet cables.

5. The numbers game How many ports?
How many switches?
When considering how many ports
you will need, it is not as simple as
counting the amount of RJ-45 wall
sockets in an office - not all devices will

use these sockets. Cameras, servers
and access points will not use the
standard wall sockets, and not even
IP phones will necessarily need one. If
the business is looking to upgrade to
IP phones, it is possible for them share
the same wall socket as a PC, meaning
you will not need to need to worry
about installing more wall sockets or
purchasing more switches.
When considering whether the
business needs a 12, 24 or 48 port
switch, several factors will come
into play depending on the LAN
infrastructure criteria. The economic
criteria is fairly straight forward - with
the same functionality, it is cheaper
to buy one 48 port switch than two
24 port switches. Take into account
the layout of the premises or security
considerations as you may be advised
to choose two 24 port switches. If you
are using one 48 port switch for two
floors of a building, chances are that
the cable conduit may simply be too
small to house 24 cables and you also
need to consider that Ethernet cable
is expensive and is limited to a length
of 100m.
In the event of a switch failure,
the whole network will be down if the
business is running the entire LAN
infrastructure off of a single switch. Split
this over two switches and it will still have
operational capability even in the event
of a switch failure.

6. Connecting
multiple switches
If you do choose to run a LAN using
two or more switches you will need
to interconnect them. The most
conventional method of doing this is
called ‘the stack’. This is where you
pile the switches up and connect them
via the stack port – simple! This stack
of switches can now be managed as
a single switch, and the configuration
and maintenance of the system will be
greatly simplified. Be careful to avoid
using access ports to connect switches
together as the data capacity required
may exceed the capacity of that port.
If your need for additional ports
forces you to look at adding more
switches, it is possible to connect
multiple stacks via an aggregation
switch. In this instance, you will need
to connect via the uplink port as it
allows high throughput between
switches. For added security,
it is usually advised to use two
aggregation switches, the second
acting as a backup to the first.

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