Getting Connected – Network Devices

A look at different network devices and the functions they perform

There are a variety of different devices that can be used to connect other devices to a network such as; switches, routers and access points.  Other devices, such as Patch Panels, can be used to distribute network access throughout a building.  Due to the way that networking has evolved, older technology components, such as hubs, bridges and repeaters, can often still be found within network systems.
This post looks at some of those devices and how they’re utilised to provide network services.

Legacy Devices

A Network Hub
A hub, also known as a Multiport Repeater, is a networking device that’s used to connect the nodes in a physical star topology into a logical bus topology.  Network Hubs contain multiple ports that can have devices connected to it.

When a device transmits data to a port in the hub, it is copied and then transmitted to all other ports so that every node is able to access the data.  However, only the node specified to receive the data reads it, whilst all others ignore the information.

A five port Ethernet hub (the 6th port provides an external connection, most likely to the Internet)

There are two types of hub, known as passive and active.

  • Passive hubs simply have their ports physically wired together and therefore is able to connect devices connected to it without the aid of power.  This type of hub acts like a patch, merely making the electrical connection between devices without repeating or transmitting any of the data that passes through it.
  • Active hubs are true multiport repeaters.  They receive the incoming data from a device and then boosts the signal to send it out to all other ports within the hub
Network Bridges
A network bridge is simply an older version of a network switch (see below). Bridges have the same basic functionality as that of a switch, but they have fewer ports and are software, rather than hardware-based.
Network Repeaters
Repeaters, also known as signal extenders, are devices that are able to regenerate a network signal to boost it’s strength over longer transmission distances.  Through the use of a repeater, it’s possible to exceed the normal limitations imposed by the various networking technologies on signal lengths.
Network Switches
A network switch is a device that is able to join multiple computing devices together within the same Local Area Network (LAN).  A step on from hubs, switches only forward received data to the intended destination, causing them to be considered slightly ‘smarter’ than hubs and, therefore, more common.
It’s also possible to connect switches to other switches, thereby greatly increasing the capacity for devices within the LAN but without sacrificing performance.
A 50 port Ethernet switch
Troubleshooting a switch is generally easier than on a hub due to each port having it’s own status indicator light.
Power over Ethernet (PoE)
PoE is a system of transferring both electrical power and data to remote devices over an Ethernet network through twisted-pair cables and falls under the IEEE 802.3af standard.  This technology makes it possible to place devices such as network switches, wireless access points, digital or cctv cameras and VoIP telephones where it would be inconvenient or impossible to run electrical power.
PoE proivides up to 15.4 W of power and requires CAT 5 or higher copper cable.
There is an updated standard, IEEE 802.3at which is also known as Power over Ethernet+ (PoE+).  PoE+ can provide up to 25.5 W of power per port and is backwards compatible with IEEE 802.3af devices.
PoE+ makes it possible to connect a broader range of devices to the network, such as;
  • Door controllers
  • Point of Sale terminals
  • Digital or CCTV cameras with pan, tilt and zoom functionality
An example of a PoE installation.  The small silver/black box next to the network port enables splitting of the electrical (power) supply and data connection.
Many network switches provide PoE directly from the ports on the switch, without the need for any further connections.  This is often used to power Voice over Internet Protocal (VoIP) telephones that are plugged directly into the switch.
Another common way to implement PoE is a midspan device that plugs into the mains AC power at the wall.  Once example of such a device is an external PoE injector.  The PoE injector makes it possible for PoE compliant devices, such as IP cameras and wireless access points to connect to a non-PoE compliant network switch.
A PoE enabled 48 port network switch
The PoE Injector inserts DC voltage into the Ethernet cable that is connected to the PoE device, enabling it to be mounted in a location that would not normally be possible (under the eave of a roof, for example).  The injector itself would normally be located in the wiring closet fairly close to the network switch.
Routers
A router is simply a device that enables the connection of multiple networks, although it’s worth noting that traffic from one network does not always have to travel through the same router as another.  For example, traffic being received from the Internet will be routed according to the best available path at the time.
A small home or office DSL router with 4 RJ-45 Ethernet ports (Yellow) and 1 RJ-11 telephone line port (White) to connect it to the Internet
As with switches, troubleshooting routers is made easier though the use of indicator lights on individual ports.
Access Points
Access Points (APs) are devices or software that provide enhanced security and facilitate communication to wireless devices.  Commonly, they also extend the physical range of a Wireless Local Area Network (WLAN).  The AP functions as a bridge between wireless stations (STAs) and the existing network backbone that enables access to the network.
An example of a Wireless Access Point (WAP)
Repeaters and Extenders
Repeaters are commonly used with co-axial media, such as cable television installations and, historically, were also used in network installations that utilised coax media.  On today’s networks, it’s rare that repeaters are required due to other devices performing the same function.  However, they are still sometimes used in Fiber networks.
Wireles repeaters and bridges are more common in today’s networks, frequently being used to extend the range of a Wireless Access Point (WAP).  Repeaters are not required in twisted-pair networks (such as PoE) due to other devices performing that function.
Modems
The name ‘Modem’ comes from a combination of the words modulate and demodulate, the functions that a modem performs to translate digital data into analogue data which can be sent over a telephone line.
Various modems – from the 300bps telephone to modern DSL
Modems connect to the Internet in order to translate information to and from your computer.  Depending on the nature of the connection used, the type of modem will vary from cable modem, to DSL modem, wireless modem, voice modem or radio modem.
A laptop modem can either be an internal device or it can be added to a system as an external device through use of an expansion card.
Firewalls
A firewall is a hardware device (or software program) that prevents unsolicited traffic from entering a network, thereby protecting it from unauthorised data.  Firewalls allow incoming traffic that has specifically permitted by a system administrator and other incoming traffic that has been requested from internal systems.
Where a firewall should be located within a network
Patch Panels
A patch panel is the connection point for network drop and patch cables.  Under normal circumstances, a patch panel has one or more rows of RJ-45 connectors (common Ethernet cable connections).  Drop cables are connected to those connectors and these have cables which run between them to connect them as required. Patch cables plug into the patch panel in order to connect the drop cables. These are normally stranded, rather than solid core cables.
An example of a patch panel
Patch panels are ordinarily kept inside a wiring closet (also known as network closet or telecommunications closet).  In most cases, wiring closets are small rooms within an office space, allowing the drop cables to radiate out from it to other components and devices on the network.
Study Reference Disclaimer.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s