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1.5 Network Topologies, Protocols & Layers - Coggle Diagram
1.5 Network Topologies, Protocols & Layers
Star/Mesh Topologies
Star
Large networks using a star topology are usually controlled by one or more servers. Hence, the client-server model usually uses a star topology. However, peer-to-peer networks can also have a star topology. Even though no single computer controls the network, all communications still pass through the central switch.
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In a star topology all nodes indirectly connect to each other through one or more switches. The switch acts as a central point through which all communications are passed.
Mesh
With a partial mesh, not all nodes are connected directly to each other. A partial mesh therefore has fewer routes for a message to travel along than a full mesh but is simpler to implement.
With a full mesh, each node is directly connected to every other node. This enables a message to be sent along many individual routes.
each node is connected to at least one other node and usually to more than one. Each node is capable of sending messages to and receiving messages from other nodes. The nodes act as relays, passing on a message towards its final destination.
Packet switching
With packet switching, messages are broken up into very small pieces, called packets. Each packet consists of two parts: header - sender's and recipient's IP addresses, the packet number, the total number of packets, plus the details of any protocols used; payload - the actual message itself
The packets are sent individually across the network and put back together to reform the message at the other end.
Packets may or may not follow the same route - they are sent along whichever route allows the quickest transmission. Packets, therefore, may arrive out of sequence. The recipient takes each packet, makes a note of its number and assembles them into the correct order.
Addresses and protocols
Protocols
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HTTP and HTTPS - Hypertext Transfer Protocol - governs communication between a webserver and a client. HTTPS (secure) includes secure encryption to allow transactions to be made over the internet.
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SMTP - Simple Mail Transfer Protocol - governs the sending of email over a network to a mail server.
POP and IMAP - Post Office Protocol and Internet Message Access Protocol - govern retrieving emails from email servers. POP is an older implementation, largely replaced by IMAP.
MAC address- a unique serial number assigned to each network interface controller (NIC). This allows a network to uniquely identify any device, even when a dynamic IP address is assigned using DHCP, each time the device connects to a network. The device’s IP address changes depending on the network and the MAC address is unique to the device.
IP Address- When connected to a network each device is given a unique IP address. This address consists of four sets of up to three digits, each with a maximum value of 255, which are separated by dots. An example is: 192.168.0.254
Ethernet
Ethernet is a type of wired network media that allows data to be transferred between devices connected to both LANs (Local Area Network) and WANs (Wide Area Network. It is the most common type of wired connection within a LAN.
Ethernet cables use copper wires to transfer data between devices. These wires are organised into ‘twisted pairs’ each enclosed inside it’s own non-conductive shield.
Layers
In networking, layering means to break up the sending of messages into separate components and activities. Each component handles a different part of the communication. This can be referred to as the Transmission Control Protocol/Internet Protocol (TCP/IP) model.
Application layer - encodes/decodes the message in a form that is understood by the sender and the recipient.
Transport layer - breaks down the message into small chunks (packets). Each packet is given a packet number and the total number of packets. The recipient uses this information to assemble the packets together in the correct order. It also allows the recipient to see if there are any missing packets.
Network layer - adds the sender’s IP address and that of the recipient. The network then knows where to send the message, and where it came from.
Data link layer - enables the transfer of packets between nodes on a network, and between one network and another.
Wifi
Wi-Fi signals use radio frequencies in the 2.4 gigahertz (GHz) and 5 GHz wavebands. Each node has a radio transceiver, which allows it to connect to a wireless access point (WAP).
Wi-Fi wavebands can be separated into channels, or sub-frequencies. WAPs use several channels to allow many devices to connect wirelessly without their transmissions interfering with one another.
Wi-Fi signals can suffer from electromagnetic interference from other devices and even other Wi-Fi signals. They can also be blocked by walls, leading to dead spots where no signal can be found.