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Identify network hardware and protocols

Identify network hardware and protocols Identify network hardware and protocols


of 58 29th August 2017

http://www.open.edu/openlearncreate/course/view.php?id=2772



Contents

1 Layered network protocols 2 TCP/IP reference model 3 Application layer 4 Transport layer 5 Internet layer 6 Network access layer 7 Network hardware

7.1 Transmission media 7.2 Network devices

8 Network address translation 9 Using networks securely 10 Malware 11 Phishing 12 Activities 13 Resources 14 End of course quiz 15 Acknowledgements





1 Layered network protocols Network communication relies upon the interaction of

many different protocols. These protocols are

designed to implement a particular set of rules and

conventions governing particular aspects of how

devices in a network communicate.

Network protocols are arranged in layers, with each

layer providing a specialised service for the layer

above. Because each layer consists of standardised

protocols that perform functions to an agreed set of

rules, it is possible to modify individual protocols

within a layer without having to change protocols in

other layers.

To visualise this concept of layers, consider a

conversation between two people:

Content layer: ideas exchanged in

conversation.

Rules: agree to speak a common

language, take turns speaking, not to

interrupt when others are speaking.

Physical: face-to-face communication

requires speakers to be close enough to

hear each other.





In this example, the conversation has been divided

into three layers. The physical layer considers the

fundamental requirements of exchanging information

between two people using speech. This includes

considering the distance between the speakers, which

will affect how loud each person needs to talk in order

for the other to hear. Speech is a movement of air,

which is translated as sound waves. This means that

the conversation could take place in a ‘near’ vacuum

like outer space.

The rules layer defines how the speakers will talk. To

exchange information, a common language would

need to be chosen. Once the language is agreed, how

is the conversation to be managed? Taking turns is a

reasonable way to converse with another person and

interrupting would be considered rude. But what

happens if one person misses something and wishes

it to be repeated? Do they ask for it to be repeated

verbally, or do they use an agreed signal such as

raising a hand?

The content layer considers the actual message

exchanged between the two speakers, which in a

conversation may be an item of news, plans for a

holiday or just gossip.





By dividing the conversation into layers, we have

decided upon the particular functions that are required

by each layer to support communication, and in our

simple layered model, it should be possible to change

some aspects within one layer without affecting the

others. For example, if we now decide to have a

telephone conversation, how does this change the

requirements of our physical layer?

Networking protocols can be layered in a similar

manner to the voice conversation in the example

above, but has a wider range of considerations and

uses different terms:

Encoding: language to use.

Formatting: greeting, recipient identity,

closing phrase, sender identity.

Message size: segmentation of data.

Timing: flow control and timeout.

Delivery: to one host (unicast), to all

hosts (broadcast), to some hosts

(multicast).

We will discuss these terms in more detail as you

progress through the course.





2 TCP/IP reference model The protocols used within the Internet were designed

using a layered model referred to as the TCP/IP

reference model:

Figure 1

These protocols operate on your computing devices,

and allow the programs you use to access the data

network via the single network interface card (NIC)

that is fitted to most devices. Imagine how difficult this

task would be for your device if you used multiple

programs that required network access – for example,

surfing the World Wide Web (WWW), downloading a

file and sending an email.

All these different programs expect to be able to

simultaneously access your NIC in order to send and





receive data. The purpose of the TCP/IP reference

model is to allow the design and creation of protocols

that can support the network requirements of various

installed programs competing for the attention of a

single NIC.

Each layer of the model defines the function of the

protocols that operate within it:

Application: provides the interface

between the other layers and the

operating system software on your

computing device.

Transport: manages application layer

data and prepares it for transmission by

segmenting it into easily manageable

blocks. It is also responsible for allowing

multiple programs to simultaneously

access the NIC, and managing the

reliable delivery of data if required.

Internet: manages the delivery of data

encapsulated in packets across

networks.

Network access: manages the delivery

of data across local network media,

regardless of the physical media type.





Groups of protocols that are created in accordance

with a protocol model are referred to as a protocol

suite. The TCP/IP protocol suite operates in

accordance with the TCP/IP reference model, and it is

the predominant suite used within the Internet.





3 Application layer The application layer consists of many different

protocols because it needs to provide an interface

between the many different application programs that

may be installed on a device.

The protocols in the application layer ensure that data

is exchanged between devices using an agreed

format and in an agreed manner.

Some common application protocols and the programs

they support include:

Simple Mail Transfer Protocol (SMTP): used by email programs such as Outlook

and Thunderbird when they need to send

emails.

Post Office Protocol 3 (POP3): used by

email programs when they need to

receive emails.

Hyper Text Transfer Protocol (HTTP): used by web browsers such as Edge and

Firefox to request and transfer webpages

from the WWW.

File Transfer Protocol (FTP): often used

by file sharing programs in order to send





and receive files between users across

the Internet.

Figure 2





4 Transport layer The data from multiple application layer protocols

cannot just be passed on to the lower layers in a

single block, as this would lead to severe delays in

sending data to the NIC.

To visualise this problem, imagine you are heading to

the till in a supermarket. Some shoppers have heavily

loaded trolleys, and it takes several minutes to scan,

bag and pay for all their items. Customers with fewer

items use the ‘ten items or less’ queue, and although

there may be more people in line, they are each

served much more quickly than those in the queue for

trolleys. Now imagine there is only one queue, and the

customers with a few items are forced to queue

alongside those with a trolley. The customers with

only a few items have to wait longer to be served.

This is exactly the same problem faced by the

application layer protocols, as they all send different

sized blocks of data to the NIC. FTP may try to send a

file measured in megabytes, whereas SMTP may

send an email of only a few kilobytes. If FTP gets its

data to the NIC first, then transmission of the email is

substantially delayed.





One of the primary jobs of the transport layer is to

divide all the data received from the application layer

protocols into equal segments, which can then be

mixed together (multiplexed) and passed to the next

layer for processing. This process ensures that all

protocols receive an equal share of the capacity of the

device’s NIC.

Figure 3

Once the data is divided into segments it needs to be

tracked so that if they are delivered out of sequence,

or some get lost, then steps can be taken to re-order

or recover them. The transport layer thus

encapsulates the segments it creates with a header,

which contains sequence numbering to allow for

segment tracking.





When segments are received, they need to be placed

in the correct order to recover the original data that

was sent, but this takes time, and if your device is

receiving segments from multiple applications it can

get extremely busy and may not be able to cope,

leading to data loss. To prevent this, the transport

layer can implement flow control, which allows a

device receiving segments to limit the number of

segments that are sent to it from a transmitting device.

The two most common transport layer protocols of

TCP/IP are Transmission Control Protocol (TCP) and

User Datagram Protocol (UDP).

Both protocols manage the communication of

multiple applications.

The differences between the two centre on the specific

functions each protocol implements.

TCP provides reliable delivery of data,

therefore it supports all the functions

described above – segmentation,

multiplexing, sequencing and flow control.

The disadvantages of using TCP is that,

due to its complexity, it can introduce

unwanted delays between

communicating devices.





UDP provides rapid delivery of data, but

without reliability. UDP only provides

segmenting and multiplexing of data

received from the application layer. Data

from communication programs using

voice and video are typically intolerant of

delay and therefore use UDP.

Figure 4

Both TCP and UDP keep track of the application layer

protocols they handle by using port numbers, which

act like doorways between the transport and

application layers. These range from 1 to 65535, and

protocols are associated with individual port numbers:

SMTP: port 25





POP3: port 110

HTTP: port 80

FTP: ports 20 and 21

How ports operate is slightly more complex than

indicated above, as only server processes use fixed,

or well-known ports. Client processes (e.g. a web

browser) using HTTP will select a random, unused

port. This process will be examined in more detail in a

later module.




http://www.open.edu/openlearncreate/mod/oucontent/view.php?id=129631&section=7


5 Internet layer This layer allows computing devices to exchange data

across networks. It receives segments of data from

the transport layer protocols and encapsulates them

within packets. The packets contain address

information identifying the source and destination

devices, allowing packet switching devices such as

routers to route them to the correct destination

network.

There are two Internet layer protocols currently in use:

Internet Protocol v4 (IPv4): this is the most

popular TCP/IP Internet layer protocol,

which uses 32-bit addresses,

superseding historically previous

versions. The networking industry is

slowly phasing out IPv4 due to the rapid

growth of the Internet and the increasing

demand for IP addresses, which it can no

longer support. However, this will take

considerable time as there are many

systems and devices still dedicated to

IPv4.





Internet Protocol v6 (IPv6): this is the

replacement for IPv4. It uses a 128-bit

address and is capable of supporting the

expected future growth of devices

connecting to the Internet.

The switchover from IPv4 to IPv6 was facilitated by the

layered approach to network protocols. Because IPv6

can perform the same function as IPv4, there was no

requirement to redesign the protocols above (TCP

and UDP) or below the Internet layer.

Figure 5

Activity: Compare IPv4 to IPv6As you have seen previously, bits are meaningful: the number of

bits used increases the size of a network or the number of

addresses available.

1. Go to Google and enter this search term: 2^32. (The

up arrow or power symbol can be found by pressing

shift+6.) Write down the result:




http://www.google.co.uk/


Provide your answer... 1. Now search for 2^128 on Google and record the

result: Provide your answer...

1. Which number is the biggest and why?Provide your answer...

1. What does the 'e+38' mean in 2^128?Provide your answer...

1. What is the name of this number? (Hint: you will have

to research the answer.)Provide your answer...

1. Now try 2^128 in Wolfram Alpha.

Provide your answer...




http://www.google.co.uk/


6 Network access layer This layer is responsible for preparing the data

packets it receives from the Internet layer for

transmission to the physical media connecting devices

within the local network. There are three main types of

physical media available:

Copper: coaxial, twisted pair.

Optical: single mode, multi-mode.

Wireless: WiFi, satellite.

Due the wide range of media, and supported

technology, the network access layer is more complex

than the other layers. Additionally, while the upper

layer protocols within the TCP/IP suite are

implemented in software, the network access layer

must provide physical connectivity, thus it has both

hardware and software components, typically

implemented within a device’s NIC.

The primary functions of the network access layer are:

Accepting packets from IP and

encapsulating them within frames.

Different protocols can use different types

of frames.





Converting the binary bits that make up

the frame into a signal suitable for the

type of media that is in use. For example,

the bits are converted into an electrical

signal for copper media and into pulses of

light for optical media. Bits are converted

to ultra high frequency radio waves on a

wireless network.

Whereas the upper layer protocols are controlled by

the agencies charged with maintaining the Internet

(primarily the Internet Engineering Task Force), the

sheer number of physical media available has led to

many different protocols being designed and

produced, often by commercial organisations.

Figure 6

Over time, many of these protocols have become

standardised and thus have become available for

general use. The most commonly used network





access Local Area Network (LAN) protocol is

Ethernet and its derivatives.

The frames used by Ethernet totally encapsulate the

IP packets sent from the network layer, so devices

cannot directly read the IP addresses they contain.

This makes it necessary for frames to carry their own

source and destination addresses to ensure frames

are delivered to the correct devices in the local

network.

In an Ethernet network, this address is known as a

Media Access Control (MAC) address.





7 Network hardware A network is made up of hardware, which can be

categorised as either:

transmission media

devices.

Hardware devices make forwarding decisions to send

data between user devices across interconnecting

pathways created using copper, optical or wireless

transmission media.

7.1 Transmission media Most home networks use a combination of copper

and wireless transmission media to interconnect

devices.

The copper wiring normally used to support the

operation of Ethernet within homes is referred to as

unshielded twisted pair (UTP). This consists of four

insulated twisted copper pairs within a protective outer

jacket:





Figure 7

The advantages of using UTP in the home is that pre-

made cables are easily available, and they are

cheaper than coaxial cables, which they have largely

replaced.

One disadvantage of UTP is that it is vulnerable to

electromagnetic noise signals. Noise signals are

created by other electromagnetic sources, such as

power cables, lighting and power tools.

Electromagnetic noise can appear on the UTP copper

pair and interfere with the data signals it is carrying.

This can lead to data loss or data corruption.

To minimise the effects of noise, the copper pairs are

twisted together, which helps cancel out noise signals





travelling down the pair. Additionally, UTP cable

lengths are limited to 100m when carrying Ethernet to

guarantee that they can support the required data

rates in the presence of noise.

UTP cables have to be wired correctly to allow the

twisted pairs to perform noise cancellation, and this is

achieved using a standard plug, called an RJ45, and a

particular wiring convention. A correctly built UTP

cable with an RJ45 connector can be connected to the

Ethernet NIC ports of most devices:

Figure 8

Wireless is a very popular transmission media within

home networks, as the lack of physical cabling makes

connecting new devices relatively straightforward. In a

home environment, the WiFi system requires a WiFi

NIC fitted to the user’s computing device, allowing it to





connect to a compatible wireless access point (WAP),

which will itself generally connect to the rest of the

network using a UTP connection:

Figure 9

WiFi is a popular network access technology as it is

derived from Ethernet, and there are many devices

available that provide both Ethernet and WiFi

capability. This is especially true at home, as the

‘home router’ you use to connect to your Internet

Service Provider (ISP) will provide both Ethernet and

WiFi connectivity, as it contains an integrated WAP.

WiFi wireless is also affected by noise signals, but to a

far greater degree than UTP as it is impossible to

protect a wireless signal from external interference.

Whereas UTP will guarantee a fixed data rate over

100m, the rate achieved over wireless will steadily





reduce as the user device moves away from the

access point.

WiFi introduces another serious problem, as the signal

it produces does not stop when it reaches the limits of

your property. This makes it possible for other people

to ‘hijack’ your network by connecting to it wirelessly.

It is therefore extremely important to use some form of

security, such as a password, to prevent such access.

7.2 Network devices Networks require a variety of different devices, each

with a particular function, in order to provide

connectivity and data forwarding. In a home network,

the router provided by your ISP will provide all these

functions, but in larger networks within businesses

and schools, discrete devices are required.

7.2.1 Switches Switches provide connectivity points within a network,

allowing you to add a large number of devices to a

network, typically using UTP cabling. Because the

most common network access protocol is Ethernet,

most switches will support it and are thus referred to

as Ethernet switches. Ethernet switches have now





largely replaced the older and much slower Ethernet

hubs.

Figure 10

Switches provide multiple Ethernet NICs, which are

referred to as ports. You can use a UTP cable to

connect multiple computing devices to the ports:

Figure 11

The term used to describe the layout of your devices is

‘network topology’. The simple layout shown above is

referred to as a star topology, as it resembles a multi-

pointed star. Note that each of the UTP cables shown

must be no longer than 100m.

The number of computing devices you can connect

using a single switch is limited to the number of ports





that are available. If you need to add more devices, or

you wish to extend the size of your network, you can

connect two switches together. This topology is

referred to as an extended star:

Figure 12

The Ethernet network access protocol was originally

designed to support data rates of 10Mbps. This is too

slow to support modern networks, so the protocol has

evolved to support greater data rates.

Most Ethernet switches are capable of supporting

several Ethernet variants on each port. Although it is

possible to configure each port to operate at a

particular data rate, most Ethernet switches will

negotiate with the connected computing device and

set themselves to the highest data rate that they both support. It is best practice to connect switches

together using the fastest data rate port available.

Switches forward data between computers using the

destination MAC addresses contained in the frames

they receive. This means that switches have no

knowledge of the IP addresses of the packets





contained within the frames, so they cannot be used

to join together different IP networks. Referring to the

diagram below, all the PCs are addressed within the

same IP network and the switches will successfully

forward data between them.

Figure 13

The diagram below shows the same topology, but this

time the PCs have been placed in different IP

networks. While the switches will forward data

between the PCs based on the MAC addresses in the

Ethernet frames, the PCs will refuse to communicate

with devices outside their own IP network.

Figure 14

Activity: Data ratesResearch the data rates supported by the following Ethernet

variants:





Protocol Data rateEthernet 10MbpsFast Ethernet Provide your answer... Gigabit Ethernet Provide your answer... 10 Gigabit Ethernet Provide your answer...

7.2.2 Routers Routers provide connectivity between different IP

networks and are responsible for forwarding IP

packets based on their destination IP addresses. It is

the job of the router to connect many different

networks – this is how the internet operates. Routers

provide multiple Ethernet NICs, which are referred to

as interfaces. Typical routers do not have many

interfaces, as they are not designed to provide

connectivity between different IP networks rather than

for individual hosts.





Figure 15

Each router interface must be addressed with an IP

address within the network to which they connect.

This IP address will act as the default gateway

address configured on all the host devices within the

IP network:





Figure 16

Although Ethernet is the most common network

access protocol you will meet in LANs, there are many

other types of protocols available, especially within

Wide Area Networks (WANs). Because routers are

designed to connect networks together, they must be

capable of supporting multiple network access

protocols. Some routers are specifically designed to

connect to particular types of WANs, whereas others

are modular in design, allowing you to add the correct

NIC for the WAN network access protocol in use.

7.2.3 Wireless Access Points (WAP) You can send data directly between two devices using

WiFi provided that the devices have compatible

wireless NICs fitted. This is very useful if you wish

create a temporary connection between the devices,

but it can prove difficult to manage as you try to

connect more devices.

Using a wireless access point in your network provides

a central WiFi connection point to which all WiFi

capable devices must connect in order to exchange

data. In effect, you have created a star topology

without wires:





Figure 17

While a single star topology WiFi network can be

useful, you are more likely to meet WAPs connected

to Ethernet switches, allowing the network to provide

both wired and wireless network access:

Figure 18

7.2.4 Modem





The function of a modem is to MOdulate and

DEModulate data to and from a transmission media.

In the early days of the Internet, computers sent

binary bits, which alternated between 0 and 5v,

towards an ISP using the telephone system, which

was (and still is) designed to process audio signals

from telephones.

The modem was required to convert the binary

electrical signal from the computer into an audio

signal suitable for transmission over the telephone

system, and vice versa. So it was used to modulate

data onto the phone line, and demodulate data

received from the phone line:

Figure 19

You will not see many individual modems in modern

networks as they are now integrated within other

devices, such as home routers. They are still needed

as home Internet access via Digital Subscriber Line

(DSL) utilises the telephone system, albeit using

different frequencies. Cable Internet providers also

utilise modems, as the binary electrical signal from a





computer has to be converted into the radio

frequencies used within the cable transmission

system.

There are also some legacy systems that still require

modems, such as some older chip and pin systems.

Network engineers also use modems as a secret back

door into their networks, just in case the main

connection fails and they need to remotely find the

cause of the issue.

7.2.5 Home router If you have an Internet connection at home, you are

probably using a home router given to you by your

service provider. Although it is often referred to as a

router, it is actually a combination of all the devices

that we have discussed so far:

Wireless Access Point: provides

wireless connectivity for WiFi devices.

Switch: provides Ethernet ports for the

connection of devices using UTP cables.

Router: provides routing between the

home and ISP IP networks. Also

performs Network Address Translation

(NAT) and firewall security.





Modem: converts the router output to a

format suitable for transmission over the

link used to connect to the ISP, usually

DSL or cable.

Figure 20





8 Network address translation You will have read about NAT when exploring IP

packet forwarding, but it is covered in more detail

here.

If you examine the diagram below, you will see that the

home LAN is using IP addresses in IP network

192.168.0.0/24, which will be the case for all the ISP’s

customers who are using the same type of home

router. This will cause problems, as the source and

destination addresses have to be unique in every

communication unicast (sending packets between two

devices).

Figure 21

Why do home routers use the same address on the

home LAN if it will cause problems within the Internet?

Remember, IPv4 cannot provide sufficient IP

addresses for all the devices that want to use IP, so

certain ranges of IP address, including

192.168.0.0/16, are set aside as private addresses.







Private IP addresses can be used by anyone, at any

time, within a private network. This addresses the

issue of not having sufficient IP addresses, but

creates a problem in that the IP address cannot be

used to communicate over the Internet as it is not

unique. However, you will have a unique, public IP

address assigned to your home router on the interface

that connects to the ISP, which in the diagram above

is 82.10.250.19.

The idea of NAT is to convert the source address

from all outgoing LAN packets into the unique public

address assigned to the home router, and vice versa

for incoming packets from the Internet.

IP addresses in packets The image below shows a packet transmitted from the

home PC towards the web server, which needs to be

routed towards the Internet by the home router:

Figure 22

Note that in the diagram above the source address is

192.168.0.101, which is private.





The packet will be received by the home router, which

will perform NAT, converting the source address to its

own WAN interface IP address (82.10.250.19):

Figure 23

The packet can now be forwarded through the Internet

to the destination web server, which will return the

requested webpage in a series of packets:

Figure 24

The IP packet is now addressed with the web server

acting as the source, and the public address of the

home router WAN interface as the destination. The

home router will accept the incoming packet, and

translate the destination address back to the private

IP address of the home PC:





Figure 25

The use of NAT and private IP addresses has

extended the life of IPv4 well beyond what would have

been possible with the original range of addresses it

provided. Private IP addresses and NAT are

implemented within most home and business

networks.





9 Using networks securely You need to consider the security of your home

network in order to protect your personal security. If

your network is not secured, or you use it in an

insecure way, then you increase the risk of threats to

yourself and your data.

Consider some of the activities that you undertake via

the Internet:

emailing

sending photographs

chatting

posting to wiki

shopping

banking.

What would be the impact if someone was able to

intercept any information you sent while doing these

activities? It could range from personal

embarrassment to severe financial loss. You would

probably not do any of these things with a stranger sat

next to you, but when you do them over the Internet,

there is a risk that your data can be intercepted by

others.





What could be the motivation for trying to access your

information? The list is long, but some popular

reasons are:

general nosiness

a wish to bully or get you into trouble

a wish to steal your money or data

a desire to impersonate you while carrying

out a criminal activity.

To start securing your network, consider the

passwords that you use to protect access to your

online accounts, and to your network devices such as

PCs, tablets and home routers.

Your passwords need to be strong. Use a

mix of numbers, letters and special

characters. Do not use anything that

could be guessed, such as a pet’s name

or a birthday.

You need to change your passwords

regularly in case other people learn them.

Do not tell your passwords to anyone.

Ever.

If you have set up a password hint, do not

make the hint too obvious.

Do not use the same password across

multiple accounts and devices. If of 58 29th August 2017




someone learns it, they have access to

everything.

Do not write your passwords down.

You also need to consider how your devices handle

your passwords, as some will try to be helpful and

store them for you. If you are using a public computer

to access a website that requires you to enter a

password, the browser may offer to store it for you.

This is not a good idea, as the next user of the

computer can access your passwords.

If you log into your account and then walk off to do

something else, leaving the computer unattended,

anyone else who is present can access your account.

If you leave your PC or device, logout from it first.

Most PCs, tablets and smartphones can be configured

to automatically logout after a short period of

inactivity, so find out how to set this up.





10 Malware Malware is a type of computer program created by

criminals with the intention of stealing or damaging

data and perhaps disrupting network operation. There

are three main types of malware:

1.Virus: malicious software attached to

another program to execute a particular

action on a computer. Viruses normally

require the intervention of humans in

order to propagate themselves, and are

commonly received as attachments to

emails or as files stored on USB memory

sticks.

2.Worms: self-contained malware programs

that attack a computer and try to exploit a

specific security ‘hole’ or vulnerability in a

software program installed on it. Once

they have successfully attacked the

vulnerability, the worm copies its program

across the network to attack other

devices on the network.

3.Trojan horse: similar in operation to a

worm, except it is disguised to look like a





useful software program that you may

want to install on your computer. Once

you have installed the Trojan, it will act as

if it is normal software, but will be secretly

carrying out some criminal activity such

as logging the keys you are typing in an

attempt to copy your passwords. Trojans

are normally capable of transmitting the

information they steal to interested

criminals via your network connection to

the Internet.

There are many precautions you can take to protect

yourself from malware:

Always install antivirus software on your

computers and make sure it is kept up-to-

date.

Always keep your operating system

updated, as updates include patches for

any vulnerabilities that may be exploited

by malware. Most operating systems can

be configured to do this automatically for

you.

Never open email attachments from

people you do not know. Always scan





email attachments from people you do

know.

Always scan your USB memory sticks with

your antivirus software after inserting

them into your computer. Never plug in a

memory stick that you have ‘found’.

Always keep copies (backups) of your

important files on a separate hard drive,

preferably one that is not kept connected

to your network. You can then retrieve

your data if malware damages the

originals.





11 Phishing Many criminals will try to get you to reveal passwords

and other account information by pretending to be

someone else. This shouldn’t be an issue if you follow

the advice already covered in this course – in

particular that you should never share your

passwords. However, some criminals are very skilled,

and send emails and texts that appear to come from

legitimate sources, such as a bank or a government

agency:

Figure 26

These messages will normally direct you to a website,

which may appear very convincing but is designed to

capture all your login information. To protect yourself

from phishing, remember that legitimate organisations

do not conduct sensitive business via email or text –

they will generally use the telephone or send a letter.

When they do email, it will be a request for you to





login to your account securely, so be suspicious of

any links to websites that could be run by fraudsters.

Always check the address bar of your web browser to

see which application layer protocol is being used to

send your sensitive information to a website.

Responsible organisations will use HTTPS, which is a

secure version of HTTP and can prevent your data

being intercepted by Internet-based criminals:

Figure 27





12 ActivitiesActivity: Investigating your home networkMake sure you have your parent or carer’s permission to

investigate this at home. If you are doing this at school, make sure

you have permission from a teacher or IT Technician.

1. What devices are wired on your LAN via UTP cable?Provide your answer...

1. Does the cable go into an Ethernet switch or into

sockets and disappear?Provide your answer...

1. Where is the switch located?Provide your answer...

1. How do you know if it is an Ethernet switch?Provide your answer...

1. Do you have any wireless devices connected?Provide your answer...

1. Where is the wireless access point?Provide your answer...

1. How does your network connect to the Internet?Provide your answer...

1. What type of WAN connection does your network have

and what connectors does it use?Provide your answer...

1. Is there a modem and, if yes, where is it situated?Provide your answer...





1. If at home can you find the address given to your

router from the ISP? (It is called your ‘public’ address.)Provide your answer...

1. How much you have learnt about networking?Provide your answer...

Activity: Network devices and protocols – Packet TracerWe connect our devices to the Internet and the Internet connects

them all together. But what is the Internet made of? We say it

interconnects all the devices, but how?

Network devices are mainly hubs, switches or routers. There are

lots of other specialist bits, but the bulk of the interconnectivity is

done by switches and routers. In this course you have looked at

client server models, web requests and emails. What do these

messages look like and how are they sent?

For each type of communication over the network there are a set

of rules and specifications as to what format and order the

information is sent. These are called protocols and they are

fundamental in understanding how the Internet works.

This Packet Tracer lab explores the devices and protocols used in

computer networks. You will need:

Lab Book: Identify Devices and Protocols Used in Computer Networks




http://www.open.edu/openlearncreate/mod/oucontent/olinkremote.php?website=Identify%20network%20hardware%20and%20protocols&targetdoc=Lab%20Book:%20Identify%20Devices%20and%20Protocols%20Used%20in%20Computer%20Networks

http://www.open.edu/openlearncreate/mod/oucontent/olinkremote.php?website=Identify%20network%20hardware%20and%20protocols&targetdoc=Lab%20Book:%20Identify%20Devices%20and%20Protocols%20Used%20in%20Computer%20Networks


Packet Tracer CASBIT.pkz

Activity: Password hints Companies do not store a user’s passwords in clear text – they

send it through a scrambling algorithm to produce a 'hash', and the

hash is then saved. The hash algorithm does not work in reverse,

so you can't unscramble a hash to get the original password.

When you enter your password the site uses the same algorithm to

make a hash, which it then compares to the hash saved against

your details.

Some sites allow you to store password hints, and they save these

as clear text. Adobe was hacked in 2013, and its hashed

passwords and hints were stolen for thousands of customers. The

hackers looked at all the hints that gave the same hash (hence

were the same password). Because they had lots of hints for the

same password it was easy to guess what they were.

Can you guess the passwords used in this puzzle based on the

stolen hints?




https://zed0.co.uk/crossword/%20

https://blogs.adobe.com/conversations/2013/10/important-customer-security-announcement.html

http://www.open.edu/openlearncreate/mod/oucontent/olinkremote.php?website=Identify%20network%20hardware%20and%20protocols&targetdoc=CASBIT

https://www.netacad.com/courses/packet-tracer-download/


13 ResourcesFor more information, take a look at the following resources.

Watch this computer networking tutorial to explore

what is a protocol:

Watch the video at YouTube.com.

For a detailed look at the complexity of what happens

when you click a URL read Igor Ostrovsky’s blog post.

Read Google's guide to online safety.

Read How-To Geek’s guide to choosing a good password and watch the following video:


Read Action Fraud’s guide to phishing and watch

the following video:


Watch this video on being cautious when using public

WiFi:





https://www.youtube.com/v/XcghUy-8VRA&hl=en&fs=1&rel=0

https://www.youtube.com/v/9TRR6lHviQc&hl=en&fs=1&rel=0

http://www.actionfraud.police.uk/fraud-az-phishing

https://www.youtube.com/v/aEmF3Iylvr4&hl=en&fs=1&rel=0

http://www.howtogeek.com/195430/how-to-create-a-strong-password-and-remember-it/

http://www.howtogeek.com/195430/how-to-create-a-strong-password-and-remember-it/

https://www.google.com/safetycenter/everyone/start/

http://igoro.com/archive/what-really-happens-when-you-navigate-to-a-url

http://igoro.com/archive/what-really-happens-when-you-navigate-to-a-url

https://www.youtube.com/v/VlKks__ZhI0&hl=en&fs=1&rel=0


14 End of course quizNow it’s time to test what you’ve learned in a quiz.




http://www.open.edu/openlearncreate/mod/oucontent/olinkremote.php?website=Identify%20network%20hardware%20and%20protocols&targetdoc=Network%20hardware%20and%20protocols%20quiz


15 AcknowledgementsGrateful acknowledgement is made to the following sources:

Figure 1: Birmingham City University (BCU)


Figure 3: Cisco



Figure 6: CommScope. This file is licensed under the Creative

Commons Attribution-Noncommercial-NoDerivatives Licence

http://creativecommons.org/licenses/by-nc-nd/2.0/

Figure 7: tlsmith1000. This file is licensed under the Creative

Commons Attribution-Share Alike Licence

http://creativecommons.org/licenses/by-sa/2.0/

Figure 8: Bull3t Hughes. This file is licensed under the Creative

Commons Attribution-Share Alike Licence


Figure 9: Cisco






http://creativecommons.org/licenses/by-nc-nd/2.0/


Figure 10: Cisco/Birmingham City University (BCU)





Figure 15: Cisco




Figure 19: Publisher unknown

Figure 20: Cisco/BCU





Figure 25: Birmingham City University (BCU) of 58 29th August 2017




Figure 26: Publisher unknown

Figure 27: Screenshot taken from Barclays, example of

phishing.

Every effort has been made to contact copyright holders. If any

have been inadvertently overlooked the publishers will be pleased

to make the necessary arrangements at the first opportunity.




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