2.2 Communications.internet Flashcards
What is the internet?
A massive network of networks made up of computers and electronic devices, using TCP/IP communication protocols.
What is the World Wide Web (WWW)?
A collection of multimedia web pages stored on websites, accessible via the internet.
What is HyperText Mark-up Language (HTML)?
A language used to design web pages and write HTTP(S) protocols.
What is a Uniform Resource Locator (URL)?
A URL specifies the location of a web page
What does a web browser do?
It connects to DNS to locate IP addresses and interprets web pages for viewing documents and multimedia.
What is an Internet Service Provider (ISP)?
A company that provides internet access, often charging a monthly fee for their service.
What is the Public Switched Telephone Network (PSTN)?
A network used by traditional telephones for calls and fax transmissions.
What is Voice over Internet Protocol (VoIP)?
A protocol that converts voice and webcam images into digital packets for transmission over the internet.
What is an Internet Protocol (IP)?
A protocol using IPv4 or IPv6 formats to assign addresses to devices connected to the internet.
What is IPv4?
An IP address format using 32 bits (e.g., 200.21.100.6).
What is Classless Inter-Domain Routing (CIDR)?
A system that increases IPv4 flexibility by adding a suffix to the IP address (e.g., 200.21.100.6/18).
What is IPv6?
A newer IP address format using 128 bits (e.g., A8F0:7FFF:F0F1:F000:3DD0:256A:22FF:AA00).
What is zero compression in IPv6?
A method of shortening IPv6 addresses by replacing groups of zeroes with “::”, which can only be used once per address.
What is sub-netting?
The practice of dividing a network into two or more sub-networks.
What is the difference between private and public IP addresses?
Private IP address: Reserved for internal network use behind a router.
Public IP address: Allocated by an ISP to identify a device’s location on the internet.
What is the Domain Name Service (DNS)?
A system that assigns domain names to internet hosts and finds the IP address associated with a domain name.
What is JavaScript?
An object-oriented or scripting programming language used mainly to enhance HTML web pages.
What is PHP?
A Hypertext Preprocessor; an HTML-embedded scripting language for writing web pages.
What is the internet?
A massive network of networks made up of computers and electronic devices, using transmission control protocol (TCP) and internet protocol (IP).
What does “internet” stand for?
Interconnected network.
What is the World Wide Web (WWW)?
A collection of multimedia web pages and documents stored on websites, accessed via the internet using web browsers.
How does the World Wide Web (WWW) use the internet?
The WWW uses the internet to access information from servers and other computers.
What protocols and technologies are associated with the World Wide Web?
- HTTP(S) protocols: Written using HTML.
- URLs: Specify the location of web pages.
What is required to connect to the internet?
- A device (e.g., computer, tablet, mobile phone).
- A telephone line or mobile phone network connection.
- A wired or wireless router (or router with a modem).
- An Internet Service Provider (ISP).
- A web browser.
How does the Public Switched Telephone Network (PSTN) support the internet?
PSTN connects computers/devices and LANs between towns and cities, using satellite technology to connect to other countries.
What are the benefits of fibre optic cables in internet connections?
- Greater bandwidth.
- Faster data transfer rates.
- Reduced risk of data corruption from interference.
What is a WLAN, and how is it supported by high-speed broadband?
A WLAN (Wireless Local Area Network) uses wireless access points (WAPs) to enable devices to connect wirelessly via high-speed broadband.
What is needed to make telephone calls using the internet?
- Internet-enabled telephone connected to a computer via USB.
- External/internal microphone and speakers.
What additional equipment is required for video calls?
A webcam.
How does Voice over Internet Protocol (VoIP) work?
- Converts voice into digital packets.
- Uses packet switching to send data over the fastest available route.
What is packet switching?
A method of splitting data into packets and transmitting them via the fastest available network route.
What does PSTN stand for, and how does it work when making a phone call?
Public Switched Telephone Network. It uses a standard telephone connected to a telephone line. The line stays open throughout the call and is terminated only when both parties replace their receivers.
How does PSTN maintain connection during a phone call?
It uses circuit switching, maintaining a dedicated connection (circuit) for the entire duration of the call.
Why is PSTN considered inefficient in terms of data usage?
Even when no one is talking, the connection remains active, transmitting around 10MB of data for a 10-minute call.
What makes PSTN reliable during a power cut?
It has its own power source, ensuring telephone lines remain active.
How do phone calls using the internet differ from PSTN calls?
- Internet calls use an internet phone or microphone and speakers (video calls require a webcam).
- The connection is active only while data (sound/video) is being transmitted.
- VoIP uses packet switching rather than circuit switching.
What is Voice over Internet Protocol (VoIP)?
A technology that converts sound into digital packets for transmission over the internet.
How does packet switching in VoIP improve efficiency?
- Data is sent through the fastest available routes without maintaining a dedicated line.
- Conversations are split into data packets that are reassembled at the receiving end.
- Only active data is transmitted, saving bandwidth (e.g., a 10-minute call might transmit only 3MB of data).
What additional features does VoIP provide?
VoIP performs file compression to reduce the amount of data transmitted.
How do mobile phones connect to the telephone network and the internet?
They use the cellular network, where mobile phone providers act as ISPs. Phones contain communication software for accessing the telephone network and the internet.
Why are satellites important in network communications?
Satellites facilitate communications over vast distances, compensating for the Earth’s curvature.
What is a Geostationary Earth Orbit (GEO) satellite?
- Provides long-distance telephone and computer network communications.
- Orbits the Earth with a period of 24 hours.
What is a Medium Earth Orbit (MEO) satellite?
- Used for GPS systems.
- Orbits the Earth with a period of 2 to 12 hours.
What is a Low Earth Orbit (LEO) satellite?
- Used by mobile phone networks.
- Orbits the Earth with a period of 80 minutes to 2 hours.
- Over 100 LEO satellites are currently in operation.
What are the advantages of satellites over underground/undersea cables?
- Provide complete coverage.
- Less prone to signal attenuation.
- Avoid the difficulty of isolating and resolving faults in seabed cables.
What is the internet based on?
The internet is based on TCP/IP protocols, which define the rules for communication between senders and receivers.
What is IPv4 addressing, and how is it structured?
- IPv4 uses 32 bits, giving 2³² (4,294,967,296) possible addresses.
- The 32 bits are split into four groups of 8 bits, each ranging from 0 to 255 (e.g., 254.0.128.77).
How does IPv4 addressing divide the address space?
It divides into two parts:
NetID: Used for routing initial transmission to the correct network.
HostID: Identifies the specific device within the network.
What are the five classes of IPv4 networks?
Network Class IPv4 Range NetID Bits HostID Bits Types of Network
A 0.0.0.0 - 127.255.255.255 8 24 Very large
B 128.0.0.0 - 191.255.255.255 16 16 Medium size
C 192.0.0.0 - 223.255.255.255 24 8 Small networks
D 224.0.0.0 - 239.255.255.255 - - Multicast
E 240.0.0.0 - 255.255.255.255 - - Experimental
Why is the IPv4 system considered insufficient?
- IPv4 has limited address space.
- For example, a class B licence allows for 65,534 addresses, but a medium-sized network with 284 machines wastes many host IDs.
How does Classless Inter-Domain Routing (CIDR) improve IPv4 flexibility?
CIDR uses a suffix to define the division of bits for NetID and HostID.
Example: 192.30.250.00/18 allocates 18 bits for NetID and 14 bits for HostID, unlike the standard 24 bits for NetID in a class C network.
What is IPv6 addressing, and why was it developed?
IPv6 uses 128-bit addressing, allowing for more complex structures and a vast address range.
It was developed to address the limitations of IPv4, such as insufficient address space.
How is an IPv6 address structured, and what notation does it use?
IPv6 addresses are broken into 16-bit chunks, represented in hexadecimal.
Example: A8FB:7A88:FFF0:0FFF:3D21:2085:66FB:F0FA.
Colons (:) separate the chunks instead of decimal points (.).
What are the key benefits of IPv6 over IPv4?
- Eliminates the need for NAT (Network Address Translation).
- Prevents private IP address collisions.
- Includes built-in authentication.
- Allows for more efficient routing.
What is zero compression in IPv6, and how does it work?
Zero compression shortens IPv6 addresses by replacing consecutive 0000 chunks with ::.
Example: 900B:3E4A:AE41:0000:0000:AFF7:DD44:F1FF → 900B:3E4A:AE41::AFF7:DD44:F1FF.
Rule: Zero compression can only be applied once in an address to avoid ambiguity.
Why is 8055:F2F2::FFF1::DD04 not a valid IPv6 address?
Applying zero compression twice makes it ambiguous, as the original sequence of zeros cannot be determined.
What is sub-netting, and what is its purpose?
Sub-netting divides a LAN into smaller networks.
It reduces network traffic and hides network complexity.
How does sub-netting work with IPv4 addresses?
The hostID is split into sub-net IDs and smaller hostID portions.
Example: A university network with netID 192.200.20 and 8 departments splits the hostID as:
- 000 00000 → 3 bits for sub-net IDs, 5 bits for hostIDs.
- Each sub-net (department) has a unique range of hostIDs.
How is the netID extracted from an IP address using an AND mask?
Apply the AND mask to the IP address.
- Example IP: 11000000.11001000.00010100.011 00011.
- AND mask: 11111111.11111111.11111111.111 00000.
- Resulting netID: 11000000.11001000.00010100.011 00000 (or 192.200.20.03).
How does CIDR compare to sub-netting?
- CIDR (192.200.20.0/27) extends the netID to 27 bits and reduces hostID to 5 bits.
- Sub-netting reduces network complexity; CIDR is less effective at simplifying the network but allows greater flexibility in netID/hostID allocation.
What are private IP addresses, and what are their characteristics?
- Reserved for internal use behind a router or NAT device.
- Cannot be accessed directly from the internet.
- Allow networks to use separate internal address spaces without using public IPs.
What are the reserved ranges for private IP addresses?
Class A: 10.0.0.0 to 10.255.255.255 (16 million possible addresses).
Class B: 172.16.0.0 to 172.31.255.255 (1 million possible addresses).
Class C: 192.168.0.0 to 192.168.255.255 (65,600 possible addresses).
What are public IP addresses, and how are they used?
- Allocated by ISPs to identify devices on the internet.
- Devices with public IPs can be accessed from the internet.
- Used by DNS servers, network routers, and directly-controlled computers.
What is a uniform resource locator (URL)?
- A URL is a format used by web browsers to access websites and resources.
- Example format: protocol://website_address/path/filename.
What does each part of a URL represent?
1) Protocol: Communication method, e.g., http or https.
2) Website Address: Includes:
- Domain host: e.g., www.
- Domain name: e.g., hoddereducation.
- Domain type: e.g., .com, .org.
- (Optional) Country code: e.g., .uk, .de.
3) Path: Specifies the webpage (if omitted, it is the root directory).
4) Filename: The specific item or file on the webpage.
Provide an example of a URL and explain its components.
http://www.hoddereducation.co.uk/computerscience
Protocol: http.
Domain host: www.
Domain name: hoddereducation.
Domain type: .co.uk.
Path: /computerscience.
What is the purpose of the domain name service (DNS)?
- Converts domain names into IP addresses for internet hosts.
- Eliminates the need to memorise IP addresses.
- Example: Converts www.hoddereducation.co.uk into 107.162.140.19.
Describe the steps involved in the DNS process.
- The user types a URL (e.g., www.hoddereducation.co.uk) into a web browser.
- The web browser requests the IP address from DNS server (1).
- If DNS server (1) cannot find the URL, it sends a request to DNS server (2).
- DNS server (2) maps the URL to an IP address (e.g., 107.162.140.19) and sends it back to DNS server (1).
- DNS server (1) caches the IP address and sends it to the user’s computer.
- The computer establishes communication with the website server to download the required pages.
Why do DNS servers cache IP addresses?
To store mappings of domain names and IP addresses temporarily, enabling faster responses for future requests.
What is the purpose of scripting in HTML?
- Used to create and enhance web pages.
- Allows interaction between a web browser and a server.
- Examples include client-server-based applications using JavaScript and PHP.
What steps are required to develop a client-server web application?
- Download and install server software.
- Develop and install the application on the server.
- Use a web browser to access and interpret the application’s web pages.
- Purchase a domain name from a web-hosting company.
- Upload HTML files to the allocated server.
How are HTML files structured?
HTML uses tags to define the structure and content of a webpage. Example:
~~~
<html>
<body>
<p>Example</p>
</body>
</html>
~~~
What scripting languages can be included in HTML files?
JavaScript: For interactive and dynamic content.
PHP: For server-side processing and creating web applications.
What is the key difference between client-side and server-side scripting?
Client-side: Script runs on the user’s computer that is requesting the webpage; processes data sent from the server.
Server-side: Script runs on the web server, processes the data, and sends results back to the user’s computer.
Provide an example of client-side scripting.
JavaScript Example:
This program inputs a temperature and outputs results based on the value:
~~~
<html>
<body>
<p>Enter the temperature</p>
<input></input>
<button>Enter</button>
<script>
function checkReading() {
var temp, result;
temp = document.getElementById("Temp").value;
if (temp >= 200) {
result = "HIGH";
} else if (temp >= 100) {
result = "OK";
} else {
result = "LOW";
}
alert("The result is " + result);
}
</script>
</body>
</html>
~~~
What language is commonly used for server-side scripting, and how does it differ from JavaScript?
- PHP is commonly used for server-side scripting.
- Unlike JavaScript, PHP code is executed on the server, and the processed results are sent to the user’s browser.
- PHP variables begin with $ and are case-sensitive
How is PHP embedded in HTML?
PHP code is embedded inside HTML and saved as a .php file. Example:
~~~
<html>
<body>
<p>Enter the temperature:</p>
<form>
<input></input>
<button>Enter</button>
</form>
</body>
</html>
~~~
In JavaScript, how are HTML elements accessed and manipulated?
By using the document.getElementById() method. For example:
document.getElementById("Temp").value retrieves the value of the input element with the ID Temp.
Why is PHP considered a server-side language?
- PHP code is executed on the web server.
- The output (HTML or other results) is sent back to the client’s browser for rendering.
