2.1 Networks including the internet continued Flashcards
Why use IP addresses in the transmission of data over the internet?
The Internet is based on TCP/IP protocols. Protocols define the rules that must be agreed by senders and receivers on the internet.
An IP address is a unique numerical code assigned to every device on a TCP/IP network. Just like your physical home address lets people know where to send your birthday card, IP addresses identify computers and devices and lets them communicate with each other. It gives a unique identify to each device and location addressing for communication on a network.
The IP address (IPv4 typically) is made up of 2 parts - the NetID and the Host ID.
What is IPv4 addressing?
IPv4 (IP version 4) is the most common type of addressing on the internet.
It is a 32 bit address, split into 4 sections
e.g. 255.255.255.255
Range 0 – 255 (256 Possibilities in each)
Total addresses = 256 x 256 x 256 x 256 = 4.3 Billion.
4.2 Billion Addresses is not enough for the modern world as the world has 7 Billion plus inhabitants and many people have more than one internet connected device.
What is IPv6 addressing?
IPv6 has been developed to overcome some of the problems associated with IPv4 - to allow the internet to grow in terms of number of hosts and potential
amount of data traffic.
The system uses 128-bit addressing, which allows for much more complex addressing structures.
An IPv6 address is broken into 16-bit chunks and because of this, it adopts hexadecimal notation.
For example: A8FB:7A88:FFF0:0FFF:3D21:2085:66FB:F0FA
What is zero compression and what is it used for?
IPv6 addresses can be quite long; but there is a way to shorten them using zero compression
For example, 900B:3E4A:AE41:0000:0000:AFF7:DD44:F1FF can be written as:
900B:3E4A:AE41::AFF7:DD44:F1FF
The section 0000:0000 has been replaced by ::
The zero compression can only be applied once to an IPv6 address, otherwise it would be impossible to tell how many zeros were replaced on each occasion where it was applied.
8055:F2F2:::FFF1::DD04 is not a legal way of compressing the original address – we have no way of knowing what the original address was and would therefore be regarded as ambiguous
What benefits are there of IPv6 over IPv4?
- IPv6 has no need for NATs (Network Address Translation)
- IPV6 removes the risk of private IP address collisions
- IPv6 has built-in authentication
- IPv6 allows for more efficient routing
What is sub-netting used for in a network?
Sub-netting means dividing a LAN into two or more smaller networks. Such as a school splitting the devices in each department of education (maths, science, english) into smaller networks. This helps reduce network traffic, making managing them easier and can also hide the complexity of the overall network.
Explain how an AND mask is used to obtain the Net ID from an IP address
To obtain the Net ID from the IP address we can apply the AND mask (recall Boolean Truth Tables)
Thus, if a device has an IP address of 11000000.11001000.00010100.011 00011 We can apply the AND mask: 11111111.11111111.11111111.111 00000 Which results in the NetID value 11000000.11001000.00010100.011 00000
What is the difference between a public IP address and a private IP address and are the implications for security?
• Public address can be reached across the Internet. Private address can only be reached internally/through the LAN/Intranet.
• NAT (Network Address Translation) is necessary for a private IP address to access the Internet directly. A public address is less secure than a private address.
• Public addresses are provided by ISP / assigned by InterNIC. Private addresses are assigned by the router (of the network concerned).
• Public addresses are unique (to the Internet) // Private addresses (are unique within their network, but) can be duplicated within other (discrete) networks.
• 10.0.0.1 to 10.255.255.254 and 172.16.0.1 to 172.31.255.254 and 192.168.0.1.to
192.168.255.254 form the private address space // IP addresses from the private address space are never assigned as public.
What is the difference between a static IP address and a dynamic IP address?
A static IP address is an address that doesn’t change, typically used for servers and other important devices. They are assigned by Internet Service Providers (ISPs). Once a device is assigned a static IP address, that number typically stays the same until the device is decommissioned or the network architecture changes.
A dynamic IP address is an address that are subject to change, typically used for consumer devices. Dynamic addresses are assigned, as needed, by Dynamic Host Configuration Protocol (DHCP) servers. The concept of dynamic IP addresses means that ISPs can provide their subscribers an IP address that In essence is borrowed or “leased” to you whenever you go online.
If a static IP was given to every ISP subscriber would have been very expensive taking into account all the logistics involved. This also allows static IP addresses to be reserved for businesses and other entities with large networks who need them in a professional setting.
Describe how the browser uses the Domain Name Service (DNS) to display the web page
- When a user inputs the URL to a web browser, a request is sent to the nearest DNS server for the IP address of the website.
- DNS server stores a database / list of URLs and matching IP addresses.
- If the DNS server is unable to locate the IP address, it may send a request to another DNS server.
- When the secondary DNS server locates the URL, the IP address is sent back to the first DNS server, where it is added to its database
- Once mapped to the first DNS server, the IP address is sent back to the user’s computer.
- The computer can now set up a communication with the website’s server and the required pages to be downloaded. The web browser will then interpret the HTML and display the information on the user’s screen.
Consider the URL: http://cie.org.uk/computerscience.html
Give meaning of the different parts of the URL
- http – enables browser to know what protocol is being used to access information in the domain
- cie.org.uk – cie.org.uk is the domain name
- computerscience.html – actual web page / file being viewed
Sometimes the URL contains the characters %20 and ?
Describe the function of these characters.
%20 – because not allowed in a URL, %20 is the coding for a space (32 in denary)
? – separates the URL from all parameters or variables
What are web browsers and what are URLs?
Web browsers are software that allow users to access and display web pages on their screens. They interpret the HTML/CSS sent from websites to display the results
Web-browsers use uniform resource locators (URLs) to access websites; these are represented by a set of 4 numbers, such as 109.108.158.1
URL addresses looks similar to IP addresses, because they are a type of IP address
• We know that an IP address consists of 4 bytes that can be split into NetID/HostID
• A URL use the format Protocol://web address/path/filename
Explain the parts of the following domain name: https://www.bbc.co.uk/
Website domains can be broken down into the host, name, & type.
- bbc.co.uk specifies the domain name and type/country code (company, uk)
- www. specifies the host
- www.bbc.co.uk is the fully qualified domain name (FQDN) for the BBC website
What is DNS and why is it used?
The domain name service (DNS), also known as the domain name system, gives domain names for internet hosts and is a system for finding IP addresses of a domain name.
There are several DNS servers that work together to catalogue every web domain name. These are segmented into geographical groupings or levels.When the IP address of a given domain is not known, a query is referred to a related domain server that might know.
Domain names eliminate the need for a user to memorise IP addresses. The DNS process involves converting a host name into an IP address the computer can understand.
