4.9 - The Internet Flashcards
What is the Internet?
a network of interconnected computer networks, using end-to-end communication protocol
What is an ISP?
an internet service provider (ISP) is a company that provides its customers with access to the Internet
What is a packet?
A packet is a container in which data is transmitted over networks.
What is a packet switched network?
A packet switched network is one in which data is sent in packets. One message is split into multiple packets, being reassembled on the other end by the recipient.
Structure of a packet
- Sender Address - Identifies where the packet was sent from and where the response should be sent to
- Receiver Address - Identifies the packets intended recipient
- Packet contents - The location of the data being transferred
- Time To Live (TTL) - Holds the number of hops a packet can go through before being dropped
- Sequence number - Contains the number of packets in a message, and holds the packets position in relation to others so it can be reassembled in the correct order
What are routers and gateways?
network devices that connect different computer networks and allow packets to reach their destination
What is the purpose of a gateway?
To connect networks that are using DIFFERENT protocols.
They do this by stripping away most of the packet details, leaving just the contents. The gateway then gives packets new sender and receiver addresses which comply with the new protocol.
What is a URL?
Uniform Resource Locator, an address assigned to files on the Internet/
Components of a URL
https://www.bbc.co.uk/news/technology/index.html
1.https:// - the protocol being used to access the file
2. www - Subdomain for the world wide web
3. bbc.co.uk - Domain name ( .uk is a top level domain and .co is a second level domain)
4. /news - Directory of the file
5. /technology - subdirectory of the file
6. /index - name of the file
7. .html - files extension, specifying the file type.
What is a domain name?
A domain name identifies an organisation or individual on the internet.
What is an IP address?
An IP address (internet protocol address) is a unique identifier assigned to every computer on the network and every device that communicates on a network.
Why do we need Domain Names?
Because IP addresses are not easy for humans to remember, and a FQDN will map to an IP address meaning they are essentially just a more human friendly representation.
Explain the DNS (Domain Name Server) system.
- A domain name server will store a table of domain names and their corresponding IP address.
- When a DNS query is passed, the domain name server will look through the table to try and find the requested domain name.
- If the domain name is not recorded on that particular server (lesser known websites may deal with this), the query will be passed onto another domain name server.
- Some very small websites will require numerous changes of servers before a record can find them, whilst more commonly used websites will only take one server.
- This is why lesser known websites may be slightly slower to access than large websites.
What are internet registries are their purpose?
An internet registry is an organisation responsible for the allocation of IP addresses.
They work to protect the worlds depleting pool of unallocated IP addresses. When a new IP address is requested, an internet registry will first look for a previous allocated IP address that is no longer in use rather than allocate a brand new IP address.
