1.3 Computer networks, connections and protocols Flashcards
1
Q
What are the advantages of networks?
A
- File-sharing
- Peripheral-sharing
- File-accessing from anywhere
- Centralised security, software updates and backup data
- Communication e.g. email & social networking
- Access Levels - different users can be given different access rights.
- user monitoring - network managers can monitor what users do on a network
2
Q
What is a Network?
A
Networks
A network is two or more computers (or other electronic devices) that are connected together for the purpose of communication. They are connected by a wired medium such as cables, or by a wireless medium such as Wi-Fi.
A computer or device that is not connected to a network is called a stand-alone.
3
Q
What is LAN?
A
Local Area Networks(LAN), It is a network:
- 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 cable, Fibre optic or wireless using Wi-Fi
4
Q
What is WAN?
A
Wide Area Network(WAN), it is a network which:
- Covers a large geographical area, connecting LANs together
- Infrastructure between the LANs is leased from telecommunication companies who own and manage it.
- WANs are connected with telephone lines, fibre optic cables or satellite links
5
Q
What are disadvantages of Networking?
A
- Cost of hardware
- Increased security risks as Malware and viruses spread easily
- Reliance on Server - if the server fails the computer might not run
- The computer may run more slowly if there is a lot of data travelling on the network.
- Specialist staff required
6
Q
What are the Factors which affect the performance of Networks?
A
Bandwidth
Latency
Error Rate
Number of Users
Transmission Media
BLENT
7
Q
Factors that affect the performance of networks: Bandwidth
A
Bandwidth is a measure of the amount of data that the medium can transfer over a given period of time.
Each transmission medium has a different bandwidth. Measure in bits per second, often called bit rate
Each connected device requires bandwidth to be able to communicate. The bandwidth of the medium is shared between each connected device. For example, a home Wi-Fi network with one device would allocate 54 Mb per second to that device. If a second device joins the network, the bandwidth would be split between the two, giving 27 Mb per second to each, and so on.
8
Q
Factors that affect the performance of networks: Number of Users
A
Too many users can cause the network to slow down if there is an insufficient bandwidth for the data as it has to be shared.
9
Q
Factors that affect the performance of networks: Transmission media
A
- Wired connections have a higher bandwidth than wireless connections
- Fibre optic cables have a higher bandwidth than copper cables.
10
Q
Factors that affect the performance of networks: Error Rate
A
Less reliable connection increase the number of errors that occur when data is transferred. This means data has to be resent until it arrives correctly
- The signal quality of wireless connections is dependant on the range of devices from the wireless access point and other environmental factors.
- The signal quality of copper cables is determined by the grade of material used which reduces interference
- The length of the cable is also a factor.
11
Q
Factors that affect the performance of networks: Latency
What is the benifit of using switches
A
- The delay from transmitting data to receiving it
- Latency is caused by bottlenecks in the infrastructure of the network
- For example, by not using switches to appropriately segment traffic on a network.
- Hardware such as switches and transmission media may not operate at the same speed.
A network with low latency experiences few delays in transmission, whereas a high latency network experiences many delays. The more delays there are, the longer it takes to transmit data across a network.
Latency is affected by the number of devices on the network and the type of connection device. A hub-based network will usually experience higher latency than a switch-based network because hubs broadcast all messages to all devices. Switch-based networks transmit messages only to the intended recipient.
12
Q
What is Client-Server model?
What does the Client do?
What does the Server do?
A
A server is a computer that manages and stores files, whereas a client is a computer that relies on other computers(servers) to provide and manage data.
server is a computer that manages and stores files, or one that provides services to other computers on the network. They control the network and allow other computers to share and communicate. In effect, they serve other computers.
Servers tend to be quite powerful machines. They need the processing power because many other computers connect to them.
Clients do not usually store data. Furthermore, they have no control over the network as a whole or over individual computers. Clients send requests to the server asking for data and the server processes this request and responds. This is client server relationship.
Client-server networks are best suited to organisations with many computers, or to situations where many computers need access to the same information. Many schools use this type of model.
Typical servers include:
- file servers - hold and maintain user files
- applications servers - allow programs to be run over a network
- web servers - hold and share web pages
- print servers - manage printing across a network
- mail servers - handle emails between users
13
Q
What are disadvantages and advantages of the client-server model?
A
ADvantages:
- Centralised backups, security and operating system updates
- Easier software updates
- Easier File and user management
Disadvantges:
- Expensive to set up and requires It specialists
- Server Dependence
14
Q
What is the Peer-to-Peer Model?
What do Peers do?
A
- 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 & its own backup
- Peers usually have their own peripherals
- You can send print jobs to another peer to process, but that peer would need to be switched on to be able to communicate with the connected printer.
In a peer-to-peer (P2P) network, all computers have equal status - no computer has control over the network. Instead, each computer is known as a peer. Peers store their own files, which can be accessed by other peers on the network. Therefore, a peer is both a client and a server.
P2P networks are best suited to smaller organisations that have fewer computers, or where fewer computers need access to the same data.
15
Q
Peer to Peer model advantages and disadvantages?
A
Pros:
- Easy to maintain
- No specialist staff
- No dependency
- Cheaper
- No expensive hardware
Cons:
- Network is less secure
- will need to manage their own backups
- difficult to maintain a well ordered file store
16
Q
What does a NIC do?
A
An NIC connects a device to a wireless or wired network connection. and it uses a protocol.
17
Q
What is the internet?
A
Most known WAN
18
Q
What do web servers do?
How are webpages stored?
How does a URL request pull up the requested webpage?
A
Web servers host sites and deal with client requests.
The web page is stored as text
- First a URL Request is made from browser
- Browser sends domain name to a Domain Name Server
- DNS maps Domain name to an IP address and sends it back to browser
- GET request for webpage/resource is sent to the web server using the IP address
- Requested webpage/resource is returned to the clients web browser
19
Q
How does a domain turns a human readable URL into a IP address
A
20
Q
What is hosting
A
Hosting is the storing of files and data on a web server.
The web server is referred to as a host .
21
Q
What is Bus topology?
What is Ring topology?
A
22
Q
What is Star topology?
A
Each computer is connected to a central switch(which segments traffic) however the switch is still a central point of failure.
23
Q
What are the advantages and disadvantages of using a star topology?
A
Pros:
- If a node fails the other nodes still work increasing reliability
- New nodes can be added easily
- Have higher performance as they use a switch which only sends data to where it needs to go.
- Less data collisions
Cons:
- The whole network fails if the switch fails
- Requires Hardware which is expensive
24
Q
What is a Mesh topology?
A
A mesh topolgy is when every device is connected to every other device so if one node fails there are still multiple pathways for the data to travel but there is a lot more cabling and switch hardware required.
25
What is the advantages and disadvantages of Mesh topology?
Advantages:
* messages should always get through as t**hey have many possible routes on which to travel**
* multiple connections mean (in theory) that no **node should be isolated**
* multiple connections mean each **node can transmit to and receive from more than one node at the same time**
* **new nodes can be added easily**
However, mesh topologies also have their disadvantages:
* full mesh networks can be impractical to set up because of the **high number of connections needed**
* many connections require a lot of maintenance
* **Expensive and IT specialist staff required.**
* **More power consumption**
26
What are the two types of connection?
Wired
Wireless
27
Types of wired connection?
Ethernet?
Fibre Optic
28
Types of wireless connection?
Wifi and Bluetooth but:
Bluetooth has **very low power consumption, short range and is ideal for connecting personal devices**
29
How are wireless networks identified?
Wireless Networks are identified using a service set identifier(SSID)
All devices
30
What is Encryption and how does it take place?
Encryption basically scrambles data into cipher text using a SSID created from the SSID of the network and password. Data is decrypted by the reciever using the same master key so this is not transmitted. Protocols are used for encryption. A handshaking protocol is used to make sure the device has a valid master key before transmission begins.
31
What is Mac Address?
What is an IP Address?
MAC addresses are used to route **packets on a LAN** and is **unique to every NIC.**
IP addresses are used to **route packets on a WAN** and have 2 versions
An **IP address is the location of your device on the internet**, whilst a **MAC address identifies the actual device.**
32
What are standards?
They are a **set of specifcations for hardware and software which make it possible for manufacturers and producers to create products/services which are compatible with each other.**
**Without standards** most **devices wouldn't be able to communicate**. e.g. ASCII and HTML
33
What is a protocol
A protocol is a set of rules that allow for communication
34
What is TCP
TCP provides error free transmission between two routers
35
What is IP
Routes packet along a WAN and makes up the TCP/IP stack
TCP/IP enables communication over the internet.
36
What is HTTP?
HTTP is **A client server method of requesting and delivering HTML webpages**
37
What is HTTPS
**Encryption and Authentication for requesting HTML web pages and** **used** for **sensitive data** like **bank details**
38
What is FTP?
FTP
**Client-Server method Used for sending files between computers on a WAN**
39
What is POP
Post office protocol
**Retrieves emails from a mail sever**. **Removes it from Server and Transfers it to your device**
40
What is SMTP
SMTP **sends Email to email server**.
41
What is IMAP
Internet Message Access Protocol - is **Used by mail clients to manage remote email boxes** and **retrieve emails from a email server.**
42
Why do we need layers
* Network communication components are standardised which helps to ensure that different types of hardware and software are able to communicate.
* Through separating the **overall network communication processes it makes troubleshooting easier** should an error occur.
* To ensure that if **changes are made in one layer they do not affect any other layers**
* **Through dividing overall network communication** into smaller, individual components **it makes the software development process more straightforward.**
43
What is a layer?
**A division of network functionality**
Layering **means to break up the sending of messages into separate components and activities**
The Hardware and/or software for each layer has a defined responsibility
Each layer provides a service to the layer above it.
44
Advantages of Layering?
* It is **self-contained**
* it **allows different developers to concentrate on one aspect of the network**
* A layer can be **taken out and edited without affecting other layer**s
* it **promotes interoperability between vendors and system**s
45
What does layering allow?
Layering allows \*\*standards\*\* to be developed, but also to be adapted to new \*\*hardware\*\* and \*\*software\*\* over time. For example, different software packages (applications) may use the same transport, network and link layers but have their own application layer. The way the program encodes the message changes - the rest of communication method remains the same.
\*\*Layering allows standards to be put in place and simply adapted as new hardware and software is developed.\*\*
Similarly, the move from \*\*IPv4\*\* addressing to \*\*IPv6\*\* affects only the network layer - the other layers remain unaffected. This allows improvements to be made without having to redefine
46
What is Packet switching and how does it take place?
With packet switching, messages are broken up into very small pieces, called packets. Each packet consists of two parts:
- **header** - this includes the **sender's and recipient's \*\*IP addresses\*\*, the packet number, the total number of packets the message contains, plus the details of any \*\*protocols\*\*** used
- **payload** - this is part of 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.
Sending small packets allows a node to send more than one message at the same time. It is rather like speaking to two people at the same time, saying one word to each person in turn.
Packet switching also helps to ensure messages arrive complete without slowing down a network. If the recipient finds packets are missing, it can request that just those packets are re-sent. This saves having to resend the whole message, which is especially useful if the message is a large video file.
\*\*Packet switching breaks messages up into small sections known as packets. Each packet is sent separately across the network.\*\*
47
What is the cloud?
Advantages and Disadvantages of the cloud?
The cloud is a generic term for **remotely accessed storage**. This storage is **accessed through the internet.** Users **do not actually know where their data is stored**. Users only need to know that their data is stored on a server connected to the internet.
Using cloud storage brings several advantages:
* It would **offer additional storage** so the company can **take on more cases.**
* It is a **very efficient method of backing up data** and so saves the firm **time and money.**
* It would allow their employees to **work from anywhere** so they can t**ake cases from other countries**
* You **don’t need specialist network skills** so the firm **don’t need to employ more staff**
* The **third party** **provides security** so the company saves money on **staff and software/hardware.**
* The third party **provides backup so the company saves money** on **staff and software/hardware.**
* **Cheaper** as **don’t need own infrastructure** and and you **can easily increase capacity**
There are disadvantages to using the cloud:
* You need a **constant internet connection** which people who **travel a lot may not always have**
* Reliant on third party to **carry out security procedures** but the firm are still **legally responsible** if things go wrong.
* Reliant on **third party for back up connection**
* Data stored in the Cloud will be **vulnerable to hacking and other threats** **which the firm have no control ove**r (1)
48
What is a NIC?
What is a Switch?
What is a Router?
**Network interface controllers**
A network interface controller (NIC) provides a method of connecting to a network. A NIC offers an interface **port** for a wired connection. A wireless NIC provides a radio **transceiver** for connecting wirelessly.
Most modern PCs come with a NIC and wireless NIC built in, providing the option of either connection method. However, mobile devices such as tablets, smartphones and many embedded devices only feature a wireless NIC, giving only wireless connection.
**Switches**
Switches are similar to hubs, with one important difference - a switch records which computers are connected to which ports. When traffic is received, the switch forwards the traffic to its intended recipient only. This improves network performance by cutting down on unnecessary transmissions.
**A hub broadcasts messages to all devices on the network. A switch sends the message to the intended recipient only.**
**Routers**
Routers are one of the most commonly used connection devices. They are used to send data signals across the **internet**. Routers work by collecting knowledge of available routes to transmit data. They then determine the most suitable route for sending data.
Routers are also commonly used in homes. These types of router usually contain a hub and a WAP, enabling a small **peer-to-peer** network to be formed. Additionally, they contain a **modem**, which allows users to connect to the internet.
49
What are the different types of wired connections?
**Ethernet**
Coaxial made of copper and insulation to prevent interference
Fibre Optic cables can **transmit data as light** so they **don't get effected by electrical interference** and can **transmit data for long distances with loss of signal**.
50
What is a Domain Name Server?
**A domain name server translates a domain name into an internet address.**
Domain names are much easier for users to remember.
51
What are Virtual Networks?
A virtual **network** is a network of geographically unrelated computers connected together via the **internet**.
Virtual networks **form their connections through the internet**. Virtual network servers create a network that **has no direct physical connection**, but one that allows **file sharing** and **communication**.
Some organisations use virtual networks to enable users at home to connect to the organisation's **data** and facilities. Users can then work at home as if they were at their place of work or study.
52
What is Wifi?
A wireless network uses wireless **Wi-Fi** signals to connect **nodes**. 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)**. WAPs can be physically connected by wire to a network **switch**, or wirelessly to other WAPs.
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.
53
What is a MAC address?
MAC addressing
## Footnote
A MAC address is 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.
A MAC address c**onsists of a string of hexadecimal numbers**.
The MAC address is **assigned by the NIC’s manufacturer and cannot be changed**. If a device has more than one NIC, for example a wired NIC and a wireless NIC, each NIC will have its own MAC address.
54
What are IP addresses?
What is the difference between a static and dynamic IP address?
IP Addressing
## Footnote
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
When a **node** wants to send a message to another node, it uses the recipient node's address as the destination. A **switch** on the network knows where the node with this address is and routes the message to it accordingly.I
55
What is the Cloud and its Pros and cons?
56
How do transmission Errors effect the network?
Transmission errors
Inevitably there will be times when devices try to communicate with each other at the same time. Their signals collide with each other and the transmission fails.
A collision occurs when two devices on a network try to communicate simultaneously along the same communication channel.
The greater the number of devices on a network, the more chance of a collision occurring, and the longer it takes to transmit a message.
57
What happens when packets are sent
* Data is split into individual packets.
* Each packet is given a packet number which shows the numerical order of the packet.
* The router reads the packet and sends it on to the next location.
* The receiving device will read the packet number and reassemble the data in the correct order.
* As the device reassembles the data from the packets if a packet is missing it will send an error message to the sending device requesting that the packet is resent.
* The sending device will resend the packet.
* Once all of the packets are received and reassembled the receiving device will calculate the checksum to ensure that none of the data has become corrupted
58
What is the difference between IPv4 and IPv6
IPv4 – 4 blocks of denary digits between 0 and 255
Values separated by full stops.
32 bit
Addresses must be reused
IPv6 – 8 blocks of 4 hexadecimal digits
Values separated by colons.
128 bits
Each device has its own address
59
What is the role of a web client?
Sends requests for web pages
Sends DNS requests for IP addresses
Displays the results of web requests
60
Why is fibre optic better than copper?
* Fibre optic cables transmit data through light so **do not suffer from electrical interference.**
* Data can be **transmitted over very large distances without any loss of signal quality.**
* They are able to transmit data at a **higher bandwidth**
61
What is a WAP?
WAP **allows devices to connect to wireless networks.**
They have **less bandwidth** than wired and are **more convinient.**
Connection is **not always reliable or as strong**
62
What is a Switch
They send data between a **computer and a LAN.**
They segment the network by **forwarding the traffic to the correct location.**
It stores th**e MAC addresses of devices on a network and filters data packets to see which devices have asked for them**. This makes a switch **more efficient when demand is high**. If, for example, a game involved lots of data being passed between machines, then a switch could **reduce the amount of latency.**
63
What is a Router?
A router send d**ata between networks.**
A router also sends data from **LAN to WAN**.
A router uses IP address on a device t**o route traffic to other routers instead of MAC address like the switch does.**
64
What is a HUB
A **hub broadcasts data to all devices on a network.** This can use a **lot of bandwidth as it results in unnecessary data being sent** - not all computers might need to receive the data. A hub would be useful to link up a few games consoles for a local multiplayer game using a wired LAN.
65
Wifi pros and cons
* handle **large number of users**
* **Movement**
* **Easier to set up**
* **Cheaper** than Wired
* **Nodes** **easier to add**
However:
* **Slower**
* Signals **can be obstructed**
* **Less secure**
* Limited **range**
66
What is Static and Dynamic IP addresses?
A node given a **static address always keeps the same address**. A node given a **dynamic address has a different address assigned to it each time it connects to the network**. This method is known as **dynamic host configuration protocol (DHCP).**
Static addressing makes it **easy for network managers** to **know which device is which on a network**. However, dynamic addressing allows more devices to connect than there are available addresses. When a device disconnects from the network, its address is freed up for another device to use. When the first device reconnects it is assigned any free address.
This method of addressing using **four sets of digits is called IPv4.** When IPv4 was devised, the range of addresses allowed was deemed to be enough. However, the **huge increase in internet enabled devices has seen IPv4 run out of addresses.** A new version, **IPv6, which includes six sets of three digits,** has been introduced, **greatly increasing the number of possible addresses to** **trillions**.
