Structure of the internet Flashcards
How do computers communicate with each other?
Using networks
What is the internet?
• The internet is a network of networks set up to allow computers to communicate with each other globally.
Alternatively:
• A network of inter-connected networks.
What is the world wide web?
The world wide web is a collection of resources accessed via the internet.
What is the back-bone of the internet?
• A set of dedicated connections that connect several large networks at various points on the globe.
What do ISPs do?
- Connect directly to this backbone and distribute the internet connection to smaller providers who provide access to individual homes and businesses.
- Provide access to individual end-users.
What is a uniform resource locator?
A uniform resource locator is the full address of an internet resource
What does a uniform resource locator do?
Specifies the location of a resource on the internet, including the resource name and usually the file type, so that a browser can request it from the website server.
What is required of each device on a network?
Each device on a network needs to be uniquely identified so that data can be sent to the correct destination.
What do internet registrars do?
- Internet registrars hold records of all existing website names and the details of those domains that are currently available to purchase.
- Issue available domain names.
What are internet registries?
Five global organisations governed by the ICANN, with worldwide databases that hold records of all the domain names currently issued, and their details.
What are IPv4 Addresses?
Addresses that are made up of four octet values, each separated by a full stop.
What are octet values?
numerical values described by 8 bits.
What are URLs used for?
To specify the means of accessing a resource across a network and its location.
What are the different bits of the URL?
- Protocol
* Domain Name
What are DNS servers?
- Dedicated computers with an index of domain names and their corresponding IP addresses.
- There are 13 Root DNS servers
What does a domain name do?
Identifies the area or a domain that an internet resource resides in.
What is the process of resolving an IP address?
- Find domain name, resolved right to left.
- Local DNS doesn’t know, refer to root.
- Root may know .uk server is.
- refers to .co server.
- finds servers and resolves ip address.
What happens if a client has a no cached record of an ip address?
Sends a DNS query for the domain to its specified DNS server
What happens if the DNS server does not have a record for a particular domain?
• Recursively handles the request so that it can eventually deliver an IP address, or an error message.
OR
• Provides client with a referral to a DNS server authoritative, client follows this and subsequent referrals to successively lower level DNS servers
What does the DNS do?
Catalogues all domain names and IP addresses in a series of global directories that domain name servers can access in order to find the correct IP address location for a resource.
What happens when a webpage is requested?
- User enters a URL
- Browser requests the corresponds IP address from a local DNS
- if that DNS does not have the correct IP address, search is extended up the hierarchy to another lager DNS database
- The IP address is located and a data request is sent by the user’s computer to that location to find the web page data.
Why must domain names be unique?
DNS requests could be confused and deliver the wrong IP address.
What is responsible for allocating IP addresses?
- Five global internet registries are responsible for allocating IP addresses to specific domain names.
- These registries work together to maintain a database of address assignments that ensure an IP is used once and the domain names are distinct.
What is a fully qualified domain name?
A fully qualified domain name is one that includes the host server name.
OR
ftp depending on whether the resource being requested is hosted on the web, mail or ftp server.
What is an IP address?
IP ( Internet Protocol ) is a unique address that is assigned to a network device.
What does the IP address do?
• Indicates where a packet of data is to be sent or sent from.
How can routers make use of IP address?
direct the data packet accordingly.
