1.5.3

DNS

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Domain Name Service (DNS)

When a client sends a request to the server, it has to use an Internet Protocol (IP) address so that we can find the correct server. Modern web browsers allow us to enter a domain name instead, which the DNS translates.

Why use the DNS?

Why use the DNS?

  • Domain names are much easier to read and remember than IP addresses.
  • Computers have to use IP addresses to communicate over the Internet Protocol.
  • The DNS converts these domain names into IP addresses for us.
DNS lookup

DNS lookup

  • When we have a domain name, we send a request to the nearest DNS server asking for the IP address associated with that domain name.
  • The DNS server responds with the correct IP address.
  • The client can then use this IP address to send their original request.
DNS miss

DNS miss

  • If a DNS server does not have an IP address associated with a particular domain name (a DNS miss), then it can ask other DNS servers that it knows about.
  • By continuing to ask other, larger DNS servers, we will eventually resolve the IP address and send this to the original client.
Jump to other topics
1

Computer Systems

1.1

Data Representation

1.1.1Binary Numbers1.1.2Negative Binary Numbers1.1.3Hexadecimal1.1.4Using Hexadecimal1.1.5Converting Binary & Hexadecimal1.1.6Converting Denary & Hexadecimal1.1.7Capacity1.1.8Calculating Capacity Requirements1.1.9Binary in Computer Systems1.1.10Data Compression1.1.11Run Length Encoding1.1.12File Formats
1.2

Data Transmission

1.2.1Packet Switching1.2.2Data Transmission1.2.3Universal Serial Bus (USB)1.2.4Parity Check1.2.5Checksum & Echo Checks1.2.6Encryption
1.3

Hardware

1.3.1Elements of Computer Systems1.3.2Types of Computer System1.3.3Von Neumann Architecture1.3.4The Fetch, Decode, Execute Cycle1.3.5Factors Affecting CPU Performance1.3.6Computational Logic1.3.7Input Devices1.3.82D & 3D Scanners1.3.9Code Readers1.3.10Solid State Storage1.3.11Magnetic Storage1.3.12Examples of Magnetic Storage1.3.13Optical Storage1.3.14Examples of Optical Storage1.3.15Types of Optical disk1.3.16Storage Requirements1.3.17Translation - Compilers1.3.18Translation - Interpreters1.3.19Translation - Assemblers1.3.20Acoustic Sensors1.3.21Flow Sensors1.3.22Gas Sensors1.3.23Humidity Sensors1.3.24Infrared Sensors1.3.25Level Sensors1.3.26Light Sensors1.3.27Magnetic Field Sensors1.3.28Moisture Sensors1.3.29pH Sensors1.3.30Pressure Sensors1.3.31Proximity Sensors1.3.32Temperature Sensors1.3.33Network Hardware
1.4

Software

1.4.1Operating Systems1.4.2Interrupts1.4.3High-Level Languages1.4.4Low-Level Languages
1.5

The Internet & its Uses

1.5.1The Internet1.5.2Uniform Resource Locators (URLs)1.5.3DNS1.5.4HTML1.5.5Cookies1.5.6Web Hosting1.5.7Digital Currency
1.6

Cyber Security

1.6.1Forms of Attack1.6.2Penetration Testing1.6.3Types of Malware1.6.4How Malware Spreads1.6.5Protecting Against Malware1.6.6Information Security1.6.7Structured Query Language (SQL) Injection1.6.8Firewalls1.6.9Authentication: User Access Levels1.6.10Authentication: Passwords1.6.11Social Engineering1.6.12Phishing1.6.13Denial of Service Attacks
1.7

Automated & Emerging Technologies

1.7.1Automated Systems1.7.2Robotics1.7.3Artificial Intelligence
2

Algorithms, Programming & Logic

2.1

Algorithm Design & Problem Solving

2.1.1Computational Thinking - Abstraction2.1.2Computational Thinking - Decomposition2.1.3Computational Thinking - Algorithmic Thinking2.1.4Pseudocode2.1.5Flow Diagrams2.1.6Interpreting, Correcting & Completing Algorithm2.1.7Correcting Algorithms2.1.8Completing Algorithms2.1.9Testing2.1.10Types of Testing2.1.11Test Plans2.1.12Validation & Sanitation2.1.13Authentication & Contingencies
2.2

Programming

2.2.1Programming Fundamentals - Variables & Constants2.2.2Programming Fundamentals - Comments2.2.3Programming Fundamentals - Input & Output2.2.4Data Types2.2.5Casting2.2.6Controlling Program Flow - Sequence2.2.7Controlling Program Flow - Selection2.2.8Controlling Program Flow - Iteration2.2.9Modularity - Subroutines2.2.10Modularity - Scope2.2.11Arrays
2.3

Databases

2.3.1Structuring Data - Records2.3.2Structuring Data - Databases2.3.3SQL
2.4

Boolean Logic

2.4.1Binary Systems2.4.2Logic Circuits2.4.3Truth Tables2.4.4Evaluating Expressions2.4.5Boolean Operators2.4.6End of Topic Test - Logic

Practice questions on DNS

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

  1. 1
    Why do we use domain names instead of IP addresses?Multiple choice
  2. 2
    What happens when we have a DNS lookup?Put in order
  3. 3
    What is it called if a DNS server does not have an IP address associated with a particular domain name?Multiple choice
  4. 4
    What happens when we have a DNS miss?Put in order
  5. 5
    What is the format of a URL?Multiple choice
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Uniform Resource Locators (URLs)

HTML