Wired, Wi-Fi and Protocols

Key Words:

Protocols-the rules that govern the workings of a network

Packet Switching-the method of routing data packets towards their destination according to the available routes at that time

Data transfer medium-the mechanism used to transfer data(via wires or Wi-Fi)

Data transfer media:

All networks must enable computers to communicate with one another.

This can be done using two main data transfer mediums:

wired(ethernet) or wireless(Wi-Fi and Bluetooth)

Cables(Ethernet):

Two types:

Copper cables:

made up of twisted pairs of copper wires with the data being transported via electrical signals. Because they can carry electrical signals, they may suffer from interference.

Fibre Optic Cables:

made up from glass fibres with data being transported via light signals. They are more effective-nothing travels faster than the speed of light. They also do not suffer from interference. However, they are more expensive than copper cables.

Ethernet is considered standard as it has good balance between speed, cost and ease of installation and this makes it used by most manufacturers for compatibility with other devices.

Wireless(Wi-Fi):

Wi-Fi allows network access to portable devices using radio waves to send data.

Wi-Fi is a standard. When we say it is a standard, it means it is a set of rules and specifications, developed by the IEEE that defines how wireless devices communicate and connect to networks.

In particular, they send and receive data using standard radio frequency bands:

2.4GHz between 2.4 and 2.5 GHz

5GHz between 5.725 and 5.875GHz

Furthermore, each band is split into channels that cover smaller frequency ranges within the band.

If two devices send signals using the same band, they can use different channels and slightly different frequencies so they do not suffer interference from each other.

Wireless(Bluetooth):

Bluetooth is another wireless data transfer medium, allowing devices to connect and share data without wires.

Unlike Wi-Fi which can support the transfer of data amongst multiple devices at once, Bluetooth can only support data transfer between a small number of devices at any one time.

Bluetooth has a shorter range than Wi-Fi- two communicating devices will need to be relatively close to one another for the transfer of data to work.

Generally easier to use/setup compared to Wi-Fi. It is less secure than Wi-Fi.

Encryption:

To ensure that communication between devices is secure, data can be encrypted.

Encryption is where data is scrambled before being sent across a network so that it is unreadable if intercepted.

To encrypt data, an encryption key is used which will convert plain text into cipher text.

An encryption key is an algorithm which will systematically alter each piece of data in a file. For example, a key may convert each letter in a text file to the next letter in the alphabet.

For the cipher text to be converted back to plain text, the same key is required by the recipient to reverse the encryption.

Data Packets:

When files are sent over the internet, they are split into millions of data packets.

Packets get sent by different routes according to availability.

When you send a file online, the parts of the file might travel one way around the world and the other parts may go in the opposite direction.

Packets are reassembled at the receiving ends,

Packet Header: Contains sequence numbers and return addresses

Destination Address: stores the destination address so that the data can be routed to the correct location.

Sequence Number: As data is split into packets, the sequence number allows the file to be rebuilt by putting the packets back together in the correct order.

Return Address: When data arrives the computer which sent the data can be notified that it arrived safely and if the packet arrives corrupted, the computer which sent the data can be asked to send it again.

An error check is an important aspect of the data packet.

This aspect of the packet is a checksum numbers. A checksum is made up of a calculation and its correct answer. Once the packet has been received by the destination computer, if the calculation is run, and still produces the same answer, then we know the data has not been corrupted on its journey.

Every network card in the world has a MAC address.

A MAC address is hardcoded into each and every network device and cannot change.

It is a 12 digit hexadecimal number separated by colons.

e.g. 56:b3:8f:90:64:ef

It is there so that data being sent over a network can be sent to the correct network card.

It is also known as a physical address.

IP Addresses:

Every computer on a network will also have an IP address.

IPv4:

They are usually a 32bit number written as 4 decimal numbers

e.g. 129.168.1.101

they are required for the same reason:

    so that data being sent over a network can be sent to the correct node.

The main difference is that an IP address is not hardcoded into the computer, It can change and is therefore said to be DYNAMIC.

The reason for this is so that on a network, similar types of hardware can be grouped by being assigned similar IP addresses.

For example, computers could all be given IP addresses all starting with 190, printers starting with 200 etc.

This means that different types devices can be managed more easily managed on a network.

IPv6:

IPv6 stands for Internet Protocol version 6 and is the most recent version of the Internet Protocol.

It uses 128bit addresses represented as eight groups of four hexadecimal digits separated by colons, to uniquely identify devices on a network, offering a significantly larger address space than its predecessor, IPv4.

e.g. 2001:0db8:85a3:0000:00008a2e:0370:7334

TCP/IP Protocols:

This is probably the most important protocol as it determines how all data is sent over the internet. Actually it is made up of two protocols:

TCP: Transmission Control Protocol

TCP defines rules for how data is split up into packets before being sent across the internet.

It ensures all data is split up into data packets in the same way.

It ensures that these data packets are put back together when received by the destination device.

It also ensures that any data device received is the same as that sent.

IP Protocol:

This rule is in place to ensure that data packets are directed towards their destination in the most appropriate may which may not be the shortest way.

This is called Packet Switching.

Packet Switching:

The TCP/IP Protocols govern packet switching:

1. A file is split into data packets.

2. Routers follow the IP rules and direct data packets towards their destination.

3. Due to network traffic, packet switching may occur where the packets may take different routes and be directed to other routers before arriving at the destination.

4. If the packets are in the wrong order, the packet number can be used to reorder them back into the original file.

Packet Switching ensures that data gets to its destination as fast as possible - this may not be the shortest distance however.

World Wide Web Protocols:

HTTP - Hyper Text Transfer Protocol.

This protocol governs the way in which websites and web servers are accessed by web browsers. By conforming to the same standards, it means that all browsers can access all websites on the WWW.

HTTPS - Hyper Text Transfer(SECURE)

This protocol is almost identical to HTTP. The only difference is that it ensures all data being sent is encrypted and so makes web data communication far more secure.

File Transfer(upload, download. read and write) Protocols:

FTP - File transfer protocol:

If you have your documents/ files stored on a file server, the way you access them will be governed by the FTP.

This standard ensures that all clients/computers on a network can access files from a server in the same way.

Email Protocols:

POP - Post Office Protocols:

Governs how emails are accessed from a server. Email clients will use this protocol to access emails from a server in the same way.

IMAP - Inter Message Access Protocol:

This is similar to POP but with one IMPORTANT difference. With IMAP, the email will remain on the server once it has been downloaded by a mail client, This allows other devices to also access the emails which is important for users with multiple devices- they can synchronise their emails across all devices.

SMTP - Simple Mail Transfer Protocol:

Governs how data is sent between mail servers. By conforming to the same standards, emails can be sent to and from all mail servers across the internet.

Layers of a network:

All of these protocols which enable the internet to function correctly can be divided into layers of the internet.

Each layer has similar functions and each layer provides a base for the layer above it- In other words, each layer does all the hard work for the layer above it.

Application Layer - LAYER 4:

examples: FTP, HTTP AND SMTP:

purpose: provide user access to applications, websites, files and emails.

Transport Layer - LAYER 3:

example: TCP

purpose: provide transport of data between devices by splitting files into data packets and checking that they have been sent and received correctly.

Network Layer - LAYER 2:

example: IP

purpose: provides the routing of data across the network by making use of addressing.

Data Link Layer and Physical Layer - LAYER 1:

example: Ethernet

purpose: provides the physical transport of data through electrical signals etc.

For example, if you are accessing a website(HTTP- LAYER4), it requires data to be split into packets and sent across the internet(TCP-LAYER3/IP-LAYER2), which in turn requires the physical transport of data via cables(cables/Wi-Fi-LAYER1).