Technical data

126 Theoretical and general applications www.westermo.com
Switch
A switch is similar to a hub in that it is the central connection point for the network.
The difference is that the switch keeps track of which devices are connected to its
respective ports. When data is sent to a device in the network, the recipient address is
checked by the switch and data is only sent to the port where the device is connected
(switched network). In this way the network is not overloaded with unnecessary traf-
fic. Another advantage is an increase in security, as it is more difficult to access informa-
tion that is not intended for the computer in question.
A layer 2 switch is a type of bridge.
A layer 3 switch is a type of router.
Consequently, in some contexts the terms switch, bridge and router are used synony-
mously.
Managed and unmanaged switches are other terms that are used regularly. The dif-
ference is that you can communicate with a managed ( monitorable) switch, which
normally takes place through SNMP, also refer to pages 138 to 143.
Gateway
A gateway connects together networks, but its main task is to convert data between
different protocols, for example, between AppleTalk and TCP/IP. Apart from convert-
ing protocols, a gateway also supports different formats, character codes, addresses,
etc.
Firewall
A firewall is special equipment or software that only forwards traffic when specific
requirements have been met, other traffic is refused. This means that users in a net-
work can be protected from prohibited traffic. Usually there is a firewall between a
local network and the Internet. You can also have firewalls on internal networks or
together with equipment that makes it possible to call into a network. Rules varying in
degree of complexity are used to determine what the firewall allows to pass. When,
where and how a firewall is used is controlled by the security requirements placed on
the network. There are a large number of products on the market to choose
between, from a combination of hardware and software solutions to firewalls that can
be downloaded as “freeware” and used on your own computer.
Switch
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