Networking 3 – Hardware

What Hardware is Needed for a Local Area Network?

Revision & recap: from KS3 you should know about the difference between LAN and WAN and remember the pros and cons of networking https://www.bbc.co.uk/bitesize/guides/zc6rcdm/revision/1
You should also have looked at different types of networks, and factors that affect their performance, in the first two lessons of this topic.

To get a computer to communicate with other computers and devices in a network you need some hardware devices (i.e. physical bits of equipment). They are listed below (click on each title to expand and learn more):

Network Interface Card (NIC)

Every device that can connect to a network (computer, mobile phone, laptop, smart TV, Amazon Echo (Alexa puck), smart lightbulb) has a Network Interface Card (NIC). This allows the device to send and receive data in a network.

Back in “the old days” it would often be a physical card (plug-in circuit board) that you could buy and fit yourself if you wanted to venture into the world of networking, but nowadays they usually come built-in (and often integrated into the main circuit board on a single chip).

Every NIC has a permanent address “burned” into it, called a MAC (Medium Access Control) address, which makes that device uniquely identifiable in the whole world, so that it can be found on a network and have the right data sent to it.

NICs can be wired (i.e. you need to plug an Ethernet cable into it – like those beigey-grey ones that are always falling out of the backs of the computers in the labs at school) or they can be wireless (e.g. to connect via Wi-Fi) … some devices (e.g. laptops) will have both. Wireless NICs are sometimes called WNICs to make it clear what type we’re talking about.

Switch

A switch is a device that connects together all the Ethernet cables coming from the users’ computers – like a big, intelligent junction box.

The intelligent bit is that the switch remembers the (MAC) address of every device connected to it. It then only forwards traffic/packets to the device that it’s meant to go to. Note that the switch is able to send and receive data at the same time. So imagine a super-fast postman standing in the middle of your street, pulling letters out of a never-emptying sack of mail and throwing them with pinpoint accuracy into the right letter box on every door according to the address on the envelope.

And how does the switch learn these addresses? When the switch first gets set up, it doesn’t know where any of the addresses are (no idea what’s been plugged into each port), so it has to just transmit every packet on every port (junk mail!). But, every packet has both a “destination” and a “source” address (i.e. where it’s going, where it came from) – so as packets arrive at the switch, it can work out what addresses are connected to each port, and start to route messages for just that those addresses down the corresponding port. If, in the future, a packet turns up with a destination address that the switch doesn’t recognise, it’ll default to spamming all of the ports until it is able to learn which port that address is actually connected to (which it’ll be able to work out as soon as the device with that address sends a packet).

Router

A router (pronounced “rooter” because it’s related to the word “route” – you’ll find various American videos online where they pronounce it “row-ter” *shudder* – in the UK, a “row-ter” is a tool for cutting grooves in wood) is a device which allows one network to communicate with other networks by routing (i.e. directing, forwarding, passing) packets between them. It also needs to route packets that arrive from the WAN/Internet to the right device in this network.

Note the difference: a switch works within a single network (using those “layer 2” MAC addresses) whereas a router is working between networks, at a higher level (“layer 3”, the networking layer, when you study the Protocol Stack later) – and uses IP addresses instead.

For example, consider your school network, and you want to send an email to someone in another school. Obviously, those two schools are not on the same network (it wouldn’t be a very Local Area Network if they were!). Your network’s switch sends your data to the router, which it knows to do with data heading out of the network. The router then sends the data out onto a WAN (e.g. the Internet), wrapping it up nicely and addressing it to the IP address for the destination school. At the other end, the data arrives at the other school’s router, at which point it gets unpacked, pointed at the right MAC address for the email to go to, and passed around that school’s network to get there.

Because routers are exposed to the “scary” outside world of the Internet (as opposed to our nice, safe LAN in the building that we can control and look after), they usually have built-in security features to protect the network (sometimes these functions can be performed by stand-alone dedicated pieces of equipment instead). Obviously, all of this extra functionality makes a router much more expensive than a switch … and is a reason why there is usually only one router per network. These bonus features include:

  • Firewall: blocks traffic, packets and hackers from the outside coming into the network according to a set of rules configured on the firewall – note that on a school or business network, these rules could also include logging/reporting every site you go to, so think before you surf!;
  • Packet Inspection: analysing the data coming in and out the network to make sure there’s nothing nasty in there;
  • MAC Address Filtering: only allowing certain devices onto the network according to a pre-authorised list of allowed MAC Addresses – remember that a MAC Address is for life, and is unique. Imagine a bouncer or security guard stood there with a list of who’s allowed to come in and who isn’t.
    NB: It’s not perfect – rogue devices could easily claim to have a different MAC address to try to gate-crash the party (“No, I’m Brian, … and so’s my wife!“);
  • Modem: the piece of hardware that actually connects to whatever external hardware is outside the home, converting signals from those used inside the router to what is used outside (e.g. the OFDM signals going over the copper or fibre optic in the Virgin Media cables outside your home) – see below;
  • Wireless Access Point: some routers, especially our home ones (e.g. the box from Virgin Media or Sky) have built in Wi-Fi for devices needing to connect using wireless (see below).
Modem

A device that converts a digital signal (a signal that a computer understands) into a signal that can be sent over telephone wires / underground cables / satellite connections / microwave links / etc. The modem at the other end converts the signal back to a computer signal.

NB: Modem is short for (a portmanteau of) “modulator / demodulator” – because converting a signal from one type to another is called modulating. So it just means “converter / unconverter”!

If you get a router from Talk Talk or Sky etc., then there is a modem hidden in there too. It could be modulating a signal over your telephone lines (nowadays at frequencies that you can’t hear, so you can use your phone at the same time), or over a dedicated copper/optic-fibre cable outside your home, or even over a wireless cellular link (e.g. if you have a 5G modem, for example).

Those dial-up Internet connections from “the old days” B.B. (Before Broadband) were dial-up modems. They used your telephone line, but unlike today’s broadband modems, they sent the signals to and from the Internet at frequencies you could hear. Keep an ear out for it in older movies (pre-2000 I guess) – e.g. https://www.youtube.com/watch?v=gsNaR6FRuO0. Makes me quite nostalgic…

Wireless Access Point

A Wireless Access Point ((WAP or sometimes just AP, especially in the Wi-Fi / IEEE 802.11 specifications) is a device on your network that can receive wireless signals and pass them onto the rest of the network (and vice versa – i.e. receive signals from the network and transmit them wirelessly).

Remember that a network won’t be wireless unless it’s built that way, that is, someone (your school’s IT department, the owner of that Starbucks or Costa Coffee, etc.) has connected a Wireless AP and set it all up.

You then need the rest of the network (switch, router, firewall etc.) to connect that Wireless AP to the Internet. Often routers (as explained above) will come all in one package, combining WAP/router/firewall etc., especially in the home, but that’s not the case for business. You could easily have a WAP that just connects to a LAN, with no router or Internet connectivity.

Tasks

A) What networking hardware would you need to have in a stand-alone computer that you’re never going to connect to anything (e.g. you’re working on something Top Secret that must never be shared!)

B) What networking hardware would you need to have in a device that you want to connect to a LAN?

C) You’re now the IT Administrator, and you want to connect your LAN to the Internet – what networking hardware do you need to add (or make sure you’ve already got)?

D) Having set all that up, now your boss has said that she wants wireless access to the network too. What networking hardware do you need to add now? (Think also about what you might need to add to the users’ devices if they want to connect wirelessly.)

Extended Learning

Hub, Switch, Router or Modem: Guess Who?
Before we had intelligent switches, we languished in the Dark Age of hubs; there is also, as we explored above, the router and the modem. It’s very easy to muddle these up, so, using the resources below, and any other resources you can locate online, write a flowchart that will enable you (or anyone else) to work out, by asking a series of simple true/false questions*, whether a box is a hub, a switch or a router.

* No, the questions can’t be “Are you a hub?“, “Are you a router?” etc. I mean questions like “Do you route packets using just MAC Addresses?

Quizizz

To wrap up your learning on this, try this Quizizz quiz, “Year 9 – Computing – Networking – Hardware“.