1.3 Computer Networks, Connects and Protocols Flashcards
1.3.1 Network topologies 1.3.2 Network and wireless networks, protocols, and layers
Local Area Network (LAN)
-Covers a small geographical area located on a single site
-All the hardware for a LAN is owned by the organisation using it
-LANs are wired with UTP cables, fibre optic or wireless using Wi-Fi
Wide Area Network (WAN)
-Covers a large geographical area connecting LANs together.
-Infrastructure between LANs is leased with telecommunication companies who own and manage it.
-WANs are connected with telephone lines, fibre optic cables or satellite links.
How are computers in a LANs connected?
By a switch
How are computers in WANs connected?
By a router
What are the advantages of networking?
-Users can share files
-Users can share peripherals, such as printers, and connect to other networks, e.g. The Internet
-Users can access their files form any computer on the network
What are the disadvantages of networking?
-Increased security risks to data
-Malware and viruses spread very easily between computers
-If a server fails, the computers connected to it may not work
-The computer may run more slowly if there is a lot of data travelling on the network
What are the factors that affect the performance of networks?
-Bandwidth
-Number of Users
-Transmission Media
-Error rate
-Latency
Bandwidth
-The amount of data that can be sent and retrieved successfully in a given time.
Measured in bits per second or bit rate.
The Number of Users
-Too many users or devices on the same network can cause the network to slow down if there is insufficient bandwidth for the data.
Transmission Media
-Wired connections have a higher bandwidth than wireless connections
-Fibre optic cables have a higher bandwidth than copper cables
The Error Rate
-Less reliable connections increase the number of errors that occur when data is transferred
-This means that data has to be resent until it arrives correctly
What is the signal quality of wireless connections dependent on?
The range of devices from the WAP and other environmental factors
What is the signal quality of copper cables determined by?
The grade of material used which reduces interference
T/F - The length of the cable is a factor of error rate?
True
Latency
The delay from transmitting data to receiving it
What causes latency?
-Bottlenecks in the infrastructure of the network e.g., not using switches appropriately segment traffic on a network.
-Hardware such as switches and transmission media may not operate at the same speed
Client-sever model characteristics
-A server controls access and security to one shared file store
-A server manages access to The Internet
-A server manages printing jobs
-A server provides email services
-A server runs a backup of data
-A client makes requests to the server for data and connections
Advantages of Client-Server model
-Easier to manage files
-Easier to take backups of all shared data
-Easier to install software updates to all computers
Disadvantages of Client-Server model
-Can be expensive to set up
-Requires IT specialists to maintain
-The server is a single point of failure
-Users will lose access if the server fails
Characteristics of Peer-to-peer model
-A peer is a computer on a network and is equal to all other peers
-Peers serve their own files to each other
-Each peer is responsible for its own security and backup
-Peers usually have their own printer
-You can send print jobs to another peer to process, but that peer would need to be switched on to be able to connect with the connected printer
Advantages of Peer-to-peer model
-Very easy to maintain
-Specialist staff not required
-No dependency on a single computer
-Cheaper to set up
-no expensive hardware required
Disadvantages of Peer-to-peer model
-The network is less secure
-Users will need to manage their own backups
-Can be difficult to maintain a well ordered file store
Network Interface Card/Controller (NIC)
-Connects a device to wired/wireless networking connection
-Uses a protocol to ensure successful communication
Wireless Access Point (WAP)
-Allows wireless-enabled devices to connect to the internet
Advantages of WAP
-More convenient as it avoids the need to install cables
-Less bandwidth than a wired connection
Disadvantages of WAP
-Security is more of a concern with wireless connections
-Connections is sometimes not as strong or reliable as wired connections
Switch
-Sends data between computers on LAN
-They segment by forwarding traffic to the correct location
-Switches learn which devices are connected and understand how to forward traffic in an intelligent way
Router
-Sends data between networks
-It creates a WAN from a number of LANs
-Uses and IP address (Internet Protocol) to route traffic
What can you not connect to a WAN without?
A router
Transmission media - Copper Cables (UTP)
-The wires are twisted around each other to reduce interference
-Normally a set of wires for transmission and receiving
-Copper cable is cheap and flexible which makes it easy to install
Transmission Media - Fibre Optic
-Uses light to transmit data
-Cover much longer distances and greater bandwidth than copper and suffers from less interference
-The backbone of The Internet uses fibre optic cables
The Internet
A global connection of interconnected networks
Domain Name Service (DNS)
Converts web addresses (which are easier for humans to remember) into IP addresses for routers
What are Domain Name Services made up of?
Multiple domain name servers
Hosting
Hosting is the storing of files and data on a web server. The web server is referred to as a
host.
What do hosted solutions provide?
Hosted solutions provide 24/7 access, multiple users and greater security
Cloud Storage
Servers that store data and programs remotely that can be accessed and used over The Internet are referred to as cloud storage.
What do servers provide?
Servers provide services (e.g. Web server→ Web pages, File server → file storage/retrieval)
T/F - Clients request/ use services from a server?
True
Advantages of The Cloud
-Access anytime, anywhere, from any device
-A large storage capacity
-Automatic backup
-Easy online collaboration
Disadvantages of The Cloud
-There is no guarantee that someone else is not accessing your data and that your data is being backed-up
-Access to data is only possible with an internet connection - no connection means no access to data
Network Topology
A given arrangement of all the elements that you need for networking
Star Topology
-Most popular wired type of network
-Central switch
-All devices connect into central switch
Advantages of Star Topology
-Transfer speeds are generally faster as there are minimal network collisions
-Improved security because data packets are sent directly to and from the switch
Disadvantages of Star Topology
-Extra hardware is required to be purchased, installed and maintained.
-If central system fails, then the whole network will be unusable until the error is fixed.
Full Mesh Topology
-Every device is connected to every other device
Advantages of Full Mesh Topology
-If you get a break in any of the connections you can still route your traffic via another route
-New networks can be added to the network without disrupting the entire topology
Disadvantages of Full Mesh Topology
-There is a lot more cabling and switch hardware required which will add to the cost for large networks
-Redundant cabling should be avoided
Partial Mesh Topology
-Multiple routes exist between different devices
-However, every device is not connected to every single other device
-This lowers the amount of hardware needed compared to full mesh network
Ethernet
-A standard for networking topologies
-Includes a number of associated protocols
What is Ethernet used for?
Used for communicating on a wired LAN
Advantage of Ethernet
Provides reliable, error-free, fast communication between two points
How is data transmitted in Ethernet?
Disadvantages of Ethernet
-Users location is limited by the need for physical cable connection
-A set-up relying on Ethernet relies on lots of cables, connections, ports and physical hardware which will affect cost
Adavantages of Wi-Fi
-Users can move around freely
-Easier to set up, and less expensive
-Convenient to use
-Can handle a large number of users
-Transfer of information to social media is much easier
-It has a range, around 100 meters
Disadvantages of Wi-Fi
-Speeds are slower than wired networks
-Relies on signal strength to the WAP
-Signal can be obstructed
-Less secure than wired networks
-It has a high power consumption
Advantages of Bluetooth
-It is ideal for connecting personal devices e.g. Bluetooth enabled headphones to connect to a mobile
-It has low power consumption
Disadvantages of Bluetooth
-It has a very short range, around 10 meters
-It has a low bandwidth
What is encryption?
When data is scrambled into cipher text using a master key created from the SSID of the network and password.
Why are wireless networks encrypted?
Wireless networks broadcast data, so it must be encrypted to be secure.
How is data decrypted?
The receiver uses the same master key, so this key is not transmitted.
What are MAC addresses used for?
MAC addressing is to route frames on a LAN:
Each MAC address is unique to every NIC
What are IP addresses used for?
To route packets on a WAN:
What are the 2 versions of the IP addresses?
IPv4
IPv6
IPv4
-32 bits in size
-Written as 4 numbers separated by (.), each number is in range of 0-255
IPv6
-128 bits in size
-Written as eight groups separated by (:)
-Each group is made up of four hex values representing 16 bits
What will a router have?
A unique WAN facing IP address and a LAN facing IP address
-This enables a LAN device to have the same IP address as another device on another LAN
