Computer Networks Flashcards

1
Q

What is a computer network?

A

A connected network of computers (or printers, phones and other devices)

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2
Q

Why do we have computer networks?

A

To share data (documents, images, videos and so on)

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3
Q

How are devices connected in a computer network?

A

Wires or waves

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4
Q

Name three types of networks.

A

LAN (or WLAN) -Local
MAN - Metropolitan
WAN - Wide

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5
Q

WLAN

A

Wireless Local Area Network

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6
Q

MAN

A

Metropolitan Area Network - eg between universities or hospitals in a large city

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7
Q

WAN

A

Wide Area Network - Spans more than 30 miles, made up of multiple MANs. The Internet is the most known WAN.

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8
Q

Parts of a network

A

Nodes - the connected devices
Communications media - How data is transferred (wires or waves)

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9
Q

What is a server?

A

A special computer accessible to many users.

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10
Q

What is a webserver?

A

Webservers are special servers accessible to anyone (with an internet connection), very powerful, a lot of memory.

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11
Q

What is a request?

A

A message sent to a webserver requesting something (files)

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12
Q

What is a client?

A

A device used to access the Internet. Recives file or data from server.

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13
Q

What is a host?

A

The server, sends the file or data to the client.

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14
Q

What component is needed in a computer to access the internet?

A

NIC - Network Interface Card

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15
Q

What is a protocol?

A

A set of rules governing communication - format and order.

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16
Q

What three parts are in this URL:

http://www.website.com/file.html
A

http:// - protocol
www.website.com - server name
/file.html - file

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17
Q

What is network topology?

A

It describes different ways to lay out a network.

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18
Q

Name 4 network topologies.

A

Bus
Ring
Star
Mesh

19
Q

What defines a bus network?

A

1 main cable and a terminator at each end to absorb signal. Cheap but breaks easily.

20
Q

What defines a ring network?

A

Each node connected to the next. Data hits each node until it reaches its destination. More common to use two rings with inverse data flow.

21
Q

What defines a star network?

A

All nodes connected to central node (router). Easy to expand, most common(?) like a WLAN. If central node breaks it all breaks.

22
Q

What defines mesh network?

A

All nodes connected to all nodes. Built in protection, data always has alternate routes. Very expensive, lots of communications media.

23
Q

What layers are in the OSI - model?

A
  1. Application
  2. Presentation
  3. Session
  4. Transport
  5. Network
  6. Data link
  7. Physical
24
Q

OSI - model

A

Open Systems Interconnection - model

25
Q

Application layer?

A

The software that the user is looking at

26
Q

Presentation layer?

A

OS, letters and numbers (what we can understand)

27
Q

Session layer?

A

Conversation between two computers (getting data from a web server for example)

28
Q

Transport layer?

A

A packet is a chunk of data, packets are delivered reliably, in the proper order and according to how the protocol needs it

29
Q

Network layer?

A

Determines best route for data (routers are involved on this layer)

30
Q

Data link layer?

A

NIC’s/checking for errors in data

31
Q

Physical layer?

A

Cable/fiber optics - any electric signals involved

32
Q

What does a modem do?

A

Connects your network to internet service provider.

33
Q

What 3 things does a router do?

A
  • Connects via ethernet cable to modem.
  • Decides the route that the data is going to take.
  • Join networks together, your network with the internet for example.
34
Q

What does a switch do?

A

Give more ports in router for devices. Can be managed / unmanaged. Managed switch gives more settings and control.

35
Q

What does a repeater do?

A

Boost a weak network signal. Not only for WiFi. 100m is max for ethernet cable, use wired repeater. Switches also work as repeaters.

36
Q

What two parts are in a IP address?

A

Network id,
Host id

37
Q

What decides what part of an IP address is host / network?

A

Subnet mask

38
Q

What two problems are solved by subnet mask?

A

Networks can be different sizes
No ip addresses are wasted

39
Q

DHCP

A

Dynamic Host Configuration Protocol

40
Q

What does DHCP do?

A

Assigns IP adresses in a network to connected devices.

41
Q

What does a device do when first connecting to a network?

A

Send out ‘discover message’ from default IP 0.0.0.0

42
Q

What happens when the router hears a ‘discover message’?

A

Router looks through all IP adresses available in the network. Offers the first available to the new device - the computer requests it - router sends “Ack”.

43
Q

DNS

A

Domain name system

44
Q

What does the DNS do?

A

Translate domain names like www.google.com to IP addresses - and back.