The Internet
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What is an ISP?
An internet service provider is a company that provides customers with access to the Internet.
What do National ISP’s provide?
National internet service providers provide internet access to smaller regional ISPs
What is a packet switched network?
• A network in which data is sent in packets. • Data is split into multiple packets, each of which is sent to its recipient via the best possible route before being reassembled with other packets by its recipient.
What happens when a packet is sent through a network?
• It passes through a number of routers before reaching its destination. • A router uses the recipient address on a packet to determine where to send the packet.
What is the definition of a hop?
• A hop occurs every time that a packet passes through a router. • Packets have finite numbers of hops
What is a packets TTL?
A packet’s time to live is the number of hops the packet can partake in before it’s dropped.
What happens when a packet’s TTL expires
The packet is said to be dropped. The recipient will notice a missing packet and request for it to be sent again
What are the components of a data packet?
• Sender’s address • Receiver’s address • Packet contents (known as the payload) • Time to live • Sequence number (some packets have a checksum in their trailer)
What does URL stand for and what are they used for?
• A uniform resource locator is the full address for an internet resource • It’s what typed into the search bar
What does TLD stand for? Give some examples
Stands for Top level domains : .com .net .org .uk
What are domain names and why are they used?
• A domain name identifies a website on the Internet. • IP addresses are hard to remember, so domain names map to IP addresses • Domain names use alphanumeric characters so are easier for humans to remember.
What does FQDN stand for and what is it?
• A fully qualified domain name specifies an exact resource on the internet. • It must include the host server name (www/mail/ftp)
What do domain name servers do?
• When you enter a domain name into your browser’s address bar, a domain name server is used to translate the domain name into its corresponding IP address.
How do domain name servers store domain names?
They store a table of domain names and their corresponding IP address.
What happens if a domain name server does not have a record of the domain that you want to access?
The request is passed to another larger domain name server.
What is an internet registry and what do they do?
• An internet registry is an organisation allocates of IP addresses. • They protect the depleting pool of unallocated IP addresses. • They check for previously allocated, now unused IP addresses before allocating a brand new one.
What ia an internet registrar?
• They ensure domain names are only used by one organisation. • They hold records of all the existing domain names
What route do data packets take?
The fastest or least congested route