Chapter 2 Flashcards
What are the 3 groups networks are classified into?
- LAN
- WAN
- MAN
What is a LAN?
• A network covering a small geographical area
(e.g. a building) connecting computers & shared devices
• Uses dedicated infrastructure
What are devices connected to in a LAN?
• Computers and devices connected to hubs or switches
What is a hub?
• Hardware used to connect together a number of
devices to form a LAN that directs incoming data
packets to all devices on the LAN
All packets will be sent to every device
• If the address in packet matches the deviced address ➔ packet is accepted; otherwise it is rejected
What is a switch?
• Hardware used to connect together a number of
devices to form a LAN that directs incoming data
packets to a specific destination address only.
- It stores the 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.
• More powerful/secure
• Packets will only be sent to devices where the address matches the recipient address
What is the hub/switch connected to and for what reason?
• One of the hub/switch is connected to a router and/or modem to allow the network to connect to the Internet
What is a router?
- Connects devices to form a LAN
- Connects different networks together
- Homes and businesses use it to connect to the Internet
- Can often incorporate a modem within the hardware
What is a modem (Modulator/Demodulator)?
- Enables a computer to connect to the Internet over a telephone line
- Converts digital signals from a computer to analogue signals that are then sent down the telephone line
- A modem on the other end converts the analogue signal back to a digital signal which another computer can understand
What is a WLAN (Wireless Local Area Network)?
- Wireless network communications over short distances
* Uses: Infrared/Radio signals
WAP – Wireless Access Point
- Connects the devices to the wired network
- Uses
- Spread spectrum technology – wideband radio frequency
- Infrared – very short range & easily blocked
Where can a LAN be applied?
- Sending and receiving email
- A company or school centrally storing files
- Using a print server
- Using a file server
What is a WAN (Wide Area Network)?
• Network covering a very large geographical area
(worldwide)
• Multiple LANs are joined together using a router/modem to form a WAN
• Consists of LANs connected via:
-Telephone lines
- Satellites
What do WANs use to connect to each other?
• Public communication networks (Broadband & Fibre)
OR
• Dedicated/leased lines
+ Faster connection / transmission of data
+ Usually more consistent transmission speed
+ More secure (less risk of hacking)
- More expensive to set up/maintain
- Disruption will leave no alternative
What are the characteristics of telephone lines used to transmit data?
- Transmission of data using telephone lines (PSTN)
- The PSTN consists of many different types of communication lines
- Data is transmitted in both directions at the same time // (full) duplex data transmission
- The communication passes through different switching centres
What is a MAN (Metropolitan Area Network)?
- Network which is larger than a LAN but smaller than a WAN, which can cover several buildings in a single city, such as a university campus
- Size restriction – a single city
+ of networking computers?
+ Devices can be shared (e.g.: printers) ➔ costs are reduced
+ Data and files can be shared
+ Licences for software on network are cheaper than buying licences for the same number of individual stand alone computers
+ Access to reliable data from a central source (e.g.: file server)
+ Data & files can be backed up centrally at the end of the day
+ Users can communicate using email and instant messaging
+ Apply/restrict access to certain files and/or networks (e.g. Internet)
- of networking computers?
- Cabling and servers can be an expensive initial cost
- Managing a large network can be complex and difficult
- Malfunction of devices (e.g.: file servers) can affect the whole network
- Malware and hacking can affect entire networks (although afford some protection)
Characteristics of public networks?
- Owned by a communications carrier company
- Many organisations use it
- Usually no specific password requirements to enter it
- Sub-networks may be under security management
Characteristics of private networks?
- Owned by a company/organisation
- LANs/intranets
- With restricted user access, passwords are required to enter
What are the two types of Networking Models?
- Client-Server
* Peer-to-peer
How does a client-server model work?
• Uses separate dedicated servers and client computers connected to the servers
• A server:
- provides services to other computers on the network (e.g.: sending and receiving of email - to a number of “client” computers on the network)
- provides a resource to the other machines on the network (e.g.: File server, Print server)
• A client is a computer that relies on servers to provide and manage data
What do 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
Characteristics of a client-server model?
• Users can access files stored on dedicated servers
• Server dictates which users can access which files
• Allows installation of software onto a client’s computer
• Server is responsible for the authentication of user log-ons
• More secure as clients have access to only those resources and files assigned by the network
administrator
• Can be as large as you want – easier to scale up
• If a shared resource is deleted form the server, the back-up would restore it
• Can become bottlenecked if there are several requests at the same time
Where can client-server models be used?
- A web browser is the client software which makes a request to the server, the server finds the website on a webserver and it sends the website to the browser
- An email client is another client program (Client is the front end of an application): provides the interface between the user and the application
• Bank:
When checking your bank account from your computer: your client computer forwards a request to a server program at the bank, the program may then turn forward a request to its own client program, which then sends a request to a database server at another bank computer and once your account balance has been retrieved from the database, it is returned back to the bank data client, which in turn serves it back to your personal computer, which then displays the information to you