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CS P1 > Networks > Flashcards

Networks Flashcards

1
Q

What is a network?

A

Connected devices that can communicate, share resources and data

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2
Q

What are protocols?

A

Rules and standards that govern how networks should function and communicate

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3
Q

What is a topology?

A

Theoretical arrangement of the comments of a networks. Actual arrangement is influenced by physical factors and cost

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4
Q

Draw a ring, bus, star and mesh topology and explain the +/- of each

A

Picture can be found in photo Library
Star: + no data collisions, fast, robust, cheap +hub can be node switch etc, can be split into segments

Ring: +few collisions due to one way traffic, fast, one cable (cheap), passes through NIC of each node
- if one node fails the whole network could

Mesh: +Decentralised, wired or wireless, no single point of failure, no need for Internet and directly communicate, Good for communication
- lots of expensive cable

Bus: + simple, cheap (one cable)
- lots of collisions, if the cable breaks so does the network, slow with heavy traffic

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5
Q

What is a LAN?

A

Local Area Network. Nodes connected are geographically close

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6
Q

Benefits/properties of LAN?

A
  • organisation owns infrastructure
  • allows communication
  • Allows peripherals to be shared
  • Allows data to be shared
  • Can log on from any connected computer
  • easy upgrade and virus scans
  • Can run a program simultaneously on multiple devices
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7
Q

1) What is a WAN?
2) what is MAN?

A

1) Wide Area Network - result of joining multiple LANs via satellite, fibre optics cables, telephone cables, or a mixture - nodes a re geographically distant
2) Metropolitan Area Networks, provide WAN services in a city

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8
Q

Properties of WAN?

A

infrastructure owned by 3rd party
- Same properties as LAN but it allows it at a much further distance

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9
Q

What is a SAN? Give an example

A

Storage Area Network - used for large scale storage of data in data centres
Email servers, databases and high usage file servers

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10
Q

What Is a PAN?

A

Personal Area Network - Used for transmission among devices such as computers, smartphones and tablets - can also be used to connect to high level networks or Internet

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11
Q

Advantages and disadvantages of cloud storage?

A

+Data moves off site
+Maintained by third party
+Cheaper
+scalability
-Loss of control
-Security issues (?)

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12
Q

What are the properties of a peer-peer network?

A

All nodes have = status
All share files and peripherals
each node can be accessed by another peer
speed decreases due to lots of collisions
Implemented over Internet
Used for legal and illegal file sharing

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13
Q

What are the properties of a client-server network?

A

Traditional architecture
Dedicated high spec machine is server
centralised data storage
Allows processing of shared files, printing, Internet access
manages security
Clients request access to services from the servers (file server, web server, printer server etc)

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14
Q

What are data centres?

A

Multiple servers stacked together

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15
Q

What are virtualised servers? +/-

A

One server is split into multiple “virtual servers” using cloud computing.
+Efficient
+Lower energy consumption

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16
Q

What is the OSI and why was it created?

A

Open systems interconnection evolved to create a standard of communication between different device types. Describes protocols that allow comps with different architectures to be linked together so that they can share data and communicate with each other
just a model

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17
Q

Describe the 7 layers of the OSI

A

Application - Network aware applications. what the user interacts with (email, web browsing etc)

Presentation - converts data between formats required for different applications +transmission over network. Eg: Compression, encryption and translation

Session - Controls communication between connected devices. Starts connections, manages them and terminates them. User login rights, file/folder perms

Transport - Guarantees end to end delivery of data. Make sure data is present and that it gets to destination

Network - Transmits and routes data via shortest possible path across network. Shortest time not distance

Data Link - decides whose turn it is to send/receive data

Physical - Physical properties of network (cable, bit encoding, transfer rates etc)

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18
Q

What is the TCP/IP stack?

A

A suite of protocols that describes how data is sent over a network
Not just a model

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19
Q

Four layers of the TCP/IP stack?

A

Application - Production, communication and reception of data, makes sure data in correct format
Transport - Session layer + responsible for providing constant flow
Internet - provides links to transmit datagrams across different networks
Link - Passing Datagrams to local and physical network. Allows network hardware Independence therefore allowing it to operate over any transmission medium such as copper wire, optical fibre etc

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20
Q

What does PDU mean?

A

Protocol Data Unit - Term used to describe data on any given layer of the stack
Application = data
Transport = Segment/Datagram
Internet = Datagram
Network access layer = frame/bits

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21
Q

What term is used to describe data on all levels instead of there associated PDU?

A

Packet

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22
Q

How do each of the four layers identify the source and destination address of data?

A

Application - just data no addressing needed
Transport - Data broken into segments that use ports to identify services
Internet - Devices have unique IP address, IP datagrams use IP address to reach correct destination
Link - Ethernet splits packets into frames. Frames use MAC address of device to reach it

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23
Q

What devices are used on each layer of the TCP/IP stack and OSI and what do they do?

A

Physical = devices that extend the physical network (repeaters/transceivers)
Data Link = Devices that make decisions based on MAC address of sender/recipient (bridges forwards frames to destination MAC address and switches which are bridges with multiple ports)
Internet/Network = devices examine data packets and make decisions based on IP address of sender/recipient (Router examines contents and finds appropriate network to route data to based on IP)
Transport = devices examine segments and make decision base on port number. Firewalls use port numbers
Application = devices examine contents of data and make decision based on content (Checking email for spam). Application layer gateway

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24
Q

What is a Datagram?

A

A self contained unit of data that is the basic unit of data used in transmission. Allows data to be treated independently from one another which increases reliability

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25
Q

Negatives of Datagram?

A

Sent without a pre defined route meaning no guarantee that it will reach destination
No confirmation of successful transmission
Order of sending/receiving not considered

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26
Q

What is a domain name?

A

Name for location of resources on the Internet - unique to each site. Stored in DN server and each have a corresponding IP

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27
Q

What is a domain name server?

A

Phone book of Internet - translates URLs into IP address. Easy and quick to update. No meaningful characters to remember

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28
Q

Properties of circuit switching?

A

Data split into packets
Connection established via dedicated route
No other traffic can use route till transmission has ended
Packets of data all follow same route
continuos flow of data
Arrive in sent order
Hacker can intercept data as route is known

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29
Q

Example of circuit switching?

A

Telephone calls

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30
Q

Properties of packet switching?

A

Data broken into packets
Packets travel multiple routes
More efficient
No dedicated route
best path for packet is determined along the way by the router
Takes longer to assemble
Hackers can’t intercept

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31
Q

Describe each part of a data packet?

A

Header - Contains source and destination address, sequence number and protocol
Payload - Contains data
Trailer - Contains checksum and end of packet

32
Q

What is a WAP? +/-?

A

Allows wireless devices to connect to a wired network
Uses WI-FI Bluetooth or related standards
usually connects to routers
Can rely data between wireless and wired devices

+No physical setup
+Quick to add new nodes
+Flexible deployment of nodes
+Allows visitor access
-Lower performance

33
Q

Advantages of private network?

A

Control over security
control over who has access to what
Control over what software is provided
Confidence of availability

34
Q

What methods are employed in order to minimise risks of private networks?

A

Redundancy = essential equipment is duplicated
Sensible backup regime = there is always a copy of essential data stored somewhere else
failover systems = detect abnormalities and automatically transfer operations to an alternative system
Disaster recovery plan =necessary so that in the event of a major failure, procedures are in place to limit the impact of the failure and remedies are applied effectively

35
Q

What is network layering?

A

Problems can be broken into components each of which is easier to solve than the whole
Example of divide and conquer
different aspects of the networks functionality are conceptualised and developed separately
Each layer concentrates on itself and only communicates with layers adjacent to it
Are an abstraction: solve problems by identifying common patterns in real situations

36
Q

What are the levels of domains?

A

Top level = .uk, .edu, .fr, .com
second level = .org, .co
Third level = OCR, BBC, hodder

37
Q

What is a NIC?

A

network interface controllers. Work on physical layer
Circuits that were plugged into a computers bus to produce signals that are placed on the transmission medium and also receive signals from it
designed to work with particular network standards (most commonly Ethernet)
Most computers now built with Ethernet circuitry built into their motherboards rather than requiring cards as ads-on

38
Q

What is a MAC address?

A

48 bit ID allocated to a network device by the manufacturer
quoted in readable groups of six bytes (octets as there are 8 bits in each byte) and then converted in hexadecimal (eg; 08:01:27:0E:25:B8).
The first 3 octets ID the manufacturer of the equipment. The others are allocated in a way decided on by the maker too ensure each address is unique

39
Q

What is a router?

A

Device that connects networks together.
receives data packets from one network and forwards them to another network based on the address information in the packet
work out where to send a packet according to either a table of info about neighbouring networks or by using an algorithm to determine the optimum next step for the packet.
each router knows its closest neighbours and can therefore work out the optimum route.

40
Q

How do routers differ between needs?

A

home use = small routers that connect the users computer to the ISP
business use = powerful high speed routers which are able to direct traffic according to the needs of the moment

41
Q

What is a wireless access point?

A

allow temporary connection of devices to a network
BOYD common in business, university and public WI-FI
allow connection of up to 100 meters. Allows signals to be intercepted

42
Q

How does a WAP protect its ID?

A

-Hiding the SSID: A broadcast signal that ID’s a WAP, useful when network is to be used by outsiders

43
Q

How does a WAP protect its signals?

A

-Encryption: WEP (Wired equivalent privacy) uses a static key of 40/60 bits to encrypt data. Drawback is all devices have to know the key. WPA and WPA2 have replaced this. They involve once-only cryptographic keys

44
Q

What is the other way WAP protect themselves?

A

-limiting access: only allowing a certain list of MAC addresses to connect. Not practical when many new and unknown devices are likely to be connected

45
Q

What is authentication? +/-

A

Users ID themselves with a user ID and confirm they are who they say they are with a password.
-easy to obtain a users password
-can be brute forced
+Most corporate networks require additional security such as a security device
+Captchas used to prevent automated attempts to gain access

46
Q

What are Firewalls?

A

Hardware, software (or a combination of the two) that control the traffic into and out of a network
can be set up as a series of rules so that individual web addresses or specific computers can be blocked from accessing the network, or cannot be reached from within the network
rules can be applied that cause messages containing certain words or other streams of bits to be filtered out

47
Q

What is Packet filtering?

A

Used in firewalls
examines data packets as they pass the firewall and can reject them if they match a preset pattern.
Operates at the lowest 3 levels of the OSI model
other methods retain packets until it is established whether they are part of an existing message of the start of a new connection (check in revision textbook if this is right)

48
Q

What are proxies?

A

Proxy servers can act as firewalls. Computers interposed between a network and a remote resource
if a user on the network requests a resource such as a web page, the request is picked up by the proxy server. This then either passes on the request to the destination or does not if the resource is on a banned list.
The response is passed back to the proxy server, which may or may not forward it to the user.
Never any direct contact between the users computer and the remote resource

49
Q

What is encryption?

A

transformation of data in such a way that unauthorised people cannot make sense of it

used in networks because of risk that data might be intercepted

Secret key is used to transform the original data and an algorithm is applied to that key

critical part of VPN’s because the infrastructure is shared with a number of users

50
Q

What is special about the algorithm applied in encryption?

A

The algorithm is called a ciphertext
the receiving device needs to have access to that key to decrypt the ciphertext and restore the original plain text message
large keys more successful than small ones (64 bit mainly used)
keys often subdivided so that parts are used to produce successive stages of encryption

51
Q

What is a server?

A

A special computer on a network that is not used as a workstation, but rather a computer dedicated to serving files and managing varies other services.

52
Q

What is a network that uses a server called?

A

Client-Server model

53
Q

What is a network that doesn’t use a server called?

A

Peer-to-Peer model

54
Q

What is a client-server model used for? with an example

A

Controls access and security to one shared file store.
- Manages access to the internet
- Manages printing jobs
- Provides email services
- Runs a backup of data

55
Q

Name some advantages of a client-server model

A

+ Easier to manage security files.
+ Easier to take backups of all shared data
+ Easier to install software updates to all computers.

56
Q

Name some drawbacks of a client-server model

A
  • Can be expensive to setup and maintain
  • Requires IT specialists to maintain
  • The server is a single point of failure
  • Users will lose access if the server fails.
57
Q

What is a peer-to-peer model?

A

A peer is a computer on a network and is equal to all other peers.
Each peer is responsible for:
- Serving their own files to each other.
- It’s own security
- Own Backups

Peers can also send jobs to another peer to process, however that peer would need to be switched on to be able to communicate.

58
Q

Name some advantages of a peer-to-peer model

A

+ Very easy to maintain
+ Specialist staff are not required
+ No dependency on a single computer
+ Cheaper to set up
+ No Expensive hardware required

59
Q

Name some drawbacks of a peer-to-peer model

A
  • The network is less secure
  • Users will need to manage their own backups.
  • Can be difficult to maintain a well-ordered file store.
60
Q

What is a network switch?

A

A switch is a device used to direct the flow of data across a network. (SENDS and RECEIVES Packets)
Switches are most commonly used in networks using a star topology. (Multiple devices to one network)
Joins computers together on a LAN.

+ Switches are typically much faster than hubs in terms of data transfer.

61
Q

What is the functionality of a HUB?

A

Allows you to connect multiple devices to one network.

Operates on the physical layer and is considered a passive device.

Drawbacks
- This means the network can easily become flooded with unnecessary traffic.
- Hubs are typically much slower than switches in terms of data transfer.

62
Q

What’s a hacker? And name 3 types of hackers

A

A hacker is a person who attempts to gain access to a computer system with the intent of damaging data or somehow harming the system.

Black-hat hackers
Attempt to gain access, to typically steal company secrets or cause damage.

Grey-hat hackers
Typically what they do is illegal, but they then inform the company of the flaw so the company can fix it.

White-hat hackers
Ethical hackers. They use their expertise to try and find vulnerabilities and fix them.

63
Q

What is Malware? And name some types of malware

A

Often exploit bugs in code that enable them to take hold of a computer system.

Viruses
Worms
Trojans
Spyware

64
Q

What is a Malware Worm?

A

Worms are pieces of malicious software that can self-replicate between computers, either within a network or by users downloading and running a malicious file.

65
Q

What is a Trojan.

A

A Trojan is a type of malware that is disguised as a benign file that users can be tricked into opening. These are often spread as email attachments or downloaded from malicious websites

66
Q

What’s a Virus?

A

These files are typically executable files, meaning that viruses can lie dormant in a computer until their host file is opened or run. Viruses can spread between computers over a private network, the Internet, or even through the use of physical media like hard drives, flash drives, and optical disks.

67
Q

What is Spyware?

A

Malware that covertly obtains information about a user’s computer activities but transmits data from their device.

Personal data such as:
Internet surfing habits
Email addresses
Visited web pages
Downloads/Download habits
Passwords
Credit card numbers
Keystrokes
Cookies

68
Q

What are some other attacks that a hacker can perform to potentially get access of a computer?

A

Denial-of-service attack (DoS)
Phishing

69
Q

What is meant by Phishing?

A

An attempt to steal data by fraudulently appearing as a legitimate email, by a legitimate sender.

70
Q

What is meant by a Denial-of-service attack? (DoS)

A

This is when an attacker overloads a server with useless traffic, causing the server to become overloaded and effectively disable access for legitimate users.

DoS mainly attacks target web servers.

71
Q

What is meant by a Distributed Denial of Service? (DDoS)

A

A DDoS attack occurs when multiple systems orchestrate a synchronized DoS attack against a single target.

Essentially a DoS attack, but instead of being attacked from one location the server is attacked from many different locations at once.

72
Q

What is an SQL Injection?

A

a code injection technique used to attack data-driven applications.

73
Q

What are some ways to prevent/minimise network threats?

A

Penetration testing
Firewalls
Secure passwords
Anti-virus/Anti-spyware software
User Education
Proxies
Encryption
Keep up-to-date software

74
Q

What is penetration testing?

A

this is where the white/grey hat hackers try to “penetrate” the current defense system and if they do they provide feedback on how to patch it.

75
Q

What is meant by Secure passwords?

A

This means having a secure password system, these systems are often made more secure by implementing password rules.
Some rules could be:
A minimum length
Needed Uppercase, Lowercase, And numbers in password
Can’t be the same as your last x passwords
Must be changed every x days
Can’t be based on your name

76
Q

What is meant anti-virus?

A

Come pre-installed with your operating system however, you can purchase others from a dedicated vendor.

These simply work by scanning through all the files on a computer and checking them against a list (known as definitions) of known malware.

CS P1 (16 decks)

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