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Flashcards in networking Deck (13):
1

Why Networks?

Applications that require computers to “talk to” each other
Email
WWW
Sharing resources, files
Video conferencing
Games
Course website

2

How are computers connected

Solution: computer networks
Routers, end nodes

3

Types of Networks

Local Area Network (LAN)
home, whole building, campus, company
Ethernet most common
Metropolitan Area Network (MAN)
whole city
Optical fibre
Wide Area Network (WAN)
whole country, whole world (Internet)
Operated by telecommunications companies
Technologies depend on distance

4

How are computers connected

Guided (physical wires)
Copper (electrical signals)
Twisted Pair
Coaxial
Optical Fibre (light pulses)
Unguided (wireless)
Microwave – satellite
Radio

5

Limitations

Speed of light (300,000 km/s) maximum, slower for copper cable
Distance: delay, degradation
Interference from other sources, electrical and radio signals
Cost

6

Other unguided media

Bluetooth
A standard for "desktop" communication between computers, fax, printers, PDAs.
WiFi (IEEE 802.11)
A standard for local area radio networking.
WAP
A standard for wireless devices, eg. phones, to access the Internet

7

Bandwidth

Bandwidth = transmission speed
“how many bits per second can we send through a communication channel”
1 byte (B) = 8 bits (b)
Watch out!
1 kilobit (kb) = 1000 bits

8

Ethernet

By far most common LAN technology used today
Standard transmission rates 10mbps, 100mbps, 1000mbps
Communications are directed from one computer to another via a hub, and from one network to another via a router

9

Modems

Literally MODulator – DEModulator (digital  analogue, analogue  digital)
This is how we can encode digital data onto an analogue signal
Allows use of ordinary phone service (common and cheap)
We encode digital data onto a voice grade signal (the whistles and squeaks you sometimes hear

10

Dial-up Modem

33.6kbps max speed
Compression  faster
53-56kbps receive
33.6-48kbps send
Uses small range of frequencies

11

DSL Modem (Digital Subscriber Line)

uses wider range of frequencies, entire bandwidth broadband
Transmits data above and below voice range

12

Satellite Dish

For remote areas.
(4/1) Mbps
Points at geostationarysatellite.

13

Mobile Phone Network

Uses mobile phone network.
Can use your phone, or USB stick.
Speed ranges from 1Mbps to 14 Mbps