1.5- Network Protocols, Topologies & Layers

Star Network Topology

Mesh Network Topology

WiFi

Frequency & Channels

Encryption

Ethernet

Uses of IP Addressing & MAC Addressing

Concept of Layers

Packet Switching

Uses of Protocols

TCP/IP- Transmission Control Protocol/Internet Protocol is made up of 2 protocols, which, when combined, allow communication between devices

HTTP-HyperText Transfer Protocol is used to control format & transfer of web pages from Internet

HTTPS- HyperText Transfer Protocol is a secure version of HTTP (all files sent & received are encrypted)

FTP- File Transfer Protocol is used to send files between computers

POP- Post Office Protocol is used to retrieve emails from a remote mail server

IMAP- Internet Message Access Protocol is an advanced version of POP

SMTP- Simple Mail Transfer Protocol is used to send emails to a mail server

A protocol is a set of rules which control communication between devices on a network

TCP on sending device breaks data into smaller parts (packets) so it can be transported. TCP on receiving device puts packets back together correctly

IP is responsible for packet switching

When a file is sent over a TCP/IP network, it is split into packets which travel separately on different routes

They reach (using IP address) and reassemble at the receiving device back into the original file

Each packet contains a packet number, sender's IP address, receiver's IP address, relevant protocol, actual data and error check (checksum number)

Packet switching allows for faster and more secure data transmission

Ethernet is a standard for network technology which is used for communication on a wired LAN

It is a layer 2 standard & ensures reliable, error-free communication

Systems communicating over Ethernet divides data into small pieces called frames

Each frame includes actual data, source & destination MAC addresses and a cyclic redundancy check, used to check for errors

IP Addressing

MAC Addressing

A Media Access Control address is unique to every device which can communicate with other devices

They are embedded into a device's NIC when manufactured (cannot be changed by owner)

A MAC Address uniquely identifies a device on a network by identifying its the network adapter it uses

They're made of 48 bits and usually written in hexadecimal

Static IP Addresses don't change but dynamic IP Addresses change depending on location

IPv4 was previously used but IPv6 is now being used as we're running out of static IP addresses

An Internet Protocol address is a unique string of 4 numbers between 0-255, separated by full stops (dotted decimal notation), used to identify every computer

Used to route frames on LANs

Used to route packets on WANs

General

WiFi is a common standard for wireless networks

Advantages- users can move around freely whilst being connected, easier to set up, less expensive, increased convenience, transfer to social media is easier, can handle lots of users

Disadvantages- slower than wired networks, relies on signal strength to WAP, signal can be obstructed, less secure than wired networks

A channel is a small range of WiFi frequencies

Wifi mainly uses 2 radio frequency bands to connect devices- 2.4GHz & 5GHz

Each frequency band is split into numbered channels, each of which cover a small frequency range. Where these overlap, there will be interference (more overlapping in 2.4GHz band than 5GHz)

Data broadcasted on wireless networks must be encrypted to be kept secure

As long as 2 devices are transmitting & receiving on the same channel, they will be able to communicate

Encryption is done by scrambling data into cipher using a 'master key'. This same 'master key' is used by the receiving device to decrypt the data

Layers are used to reduce the complexity of a problem by splitting it into sub-manageable problems

Devices can be manufactured to operate at a particular layer

The layers are as follows:

Layer 4 (Transport Layer)- includes TCP/IP, error checking of packets, creating & sequencing of packets

Layer 3 (Network Layer)- includes IP addressing, routing packets on a WAN, TCP/IP

Layer 6 (Presentation Layer)- includes encryption

Layer 2 (Data Link Layer)- includes MAC addressing, error checking of frames and creating & routing of packets on LAN

Layer 7 (Application Layer)- includes HTTP, HTTPS, SMTP, POP, IMAP, FTP, web browser, emailing, file management

Layer 1 (Physical Layer)- includes MAC addressing, frequency & channels and encoding bits into wires & wireless

All devices in a star topology are connected to a central switch or server that controls the network (similar to a client-server network)

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Advantages- easy to add more devices, if one device fails the rest is unaffected, better performance than other setups (few data collisions & all devices can transmit data at once)

Disadvantages- if the switch has an issue then the rest fails, hardware for a wired star topology is expensive

All devices in a mesh topology are connected to each other without a central switch (similar to a peer-to-peer network)

A full mesh network topology is where every device is connected to every other device and a partial mesh network topology, is where all devices are somehow connected but every device isn't connected to every other device

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Advantages- (in theory) no node should be isolated, each node can communicate with more than one at once, roughly same connection everywhere

Disadvantages- lots of maintenance, more interference, less secure, higher cost than other topologies