Network and Web Technologies- S5 Flashcards
Internet
is a network of networks set up to allow computers to communicate with each other globally, using the same protocol.
The World Wide Web (WWW)
is a collection of web pages that resides on computers connected to the Internet.
Internet Service Providers
distributes internet connection to smaller providers who provide it to individual homes.
Uniform Resource Locators(URLs)
the full address of an Internet source.
Internet Registrars
Companies that hold records of all existing website names and the details of all the domain names that are available to purchase.
Internet Registries
Five global organisations with databases that hold records of all the domain names that have been issued and the details. The registries allocate IP addresses to the Domain name.
Domain Names
identifies the area that an internet resource resides in
Domain Name System(DNS)
a hierarchical decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It catalogues all domain names and has a table corresponding domain names to IP addresses
Fully Qualified Domain Name (FQDN)
www.websitename.co.uk
Why do domain names sometimes have more than one IP address?
because if millions of people are requesting the same page, one computer/IP address could not process all of the requests.
What happens when the a URL is searched for in a web broweser
Web Page is requested using URL a user enters
The browser requests the corresponding IP address from a local DNS
If the DNS doesn’t have it, it goes up the hierarchy to a larger DNS database
When the IP address is located a data request is sent by the user’s computer to the location for the web page data.
Internet Protocol (IP addresses)
A unique address that is assigned to a network device.
Wide Area Networks (WANs)
are distributed around different regions and can connect to multiple LANs. Also uses packet switching.
Local Area Networks (LANs)
Is small and local consisting of a number of computing devices on a single site, connected by cables. Users on the network can communicate with each other and share data and hardware devices like printers.
Physical Bus Topology(Bus network)
in a LAN each node is connected to a main cable.
What are the pros and cons of a Bus network
Pro:- Less cable so cheaper
Con:- main cable fail=network data cannot be transmitted to any of the nodes.
-Performance degrades with heavy traffic because collision of data. Data then has to be sent again after a random time has passed.
-Low security (all computers on network can see all data being transmitted).
Physical Star Topology
Has a central node (switch, computer) which acts as a router to transmit messages.The switch keeps record of the MAC address of each device on the network so it can identify where to send the data too.
What are the pros and cons of a Star network
Pro:-If one cable fails, only one station is affected
-Performance stays the same when network heavily used
-Higher transmission feel=better performance
-No collisions (own cable)
-Secure (sent direct)
-Easy to add new station
Con:-Costly to install because of length of cables.
-If central device goes down, data can not be transmitted to nodes.
Physical topology
how the network is interconnected with wires and cables.
Logical topology
the communication mechanism for all nodes in a network and how they communicate across physical topology.
Wi-fi
a local area wireless technology that enables you to connect a device such as a PC to a network resource
Circuit switching
creates a direct link between two devices for the duration of the communication.
What are the pros and cons of circuit switching
Con: - bandwidth is wasted not alway is use
-two devices must send and receive at same rate
-Switched used to connect and disconnect circuits, electrical interference= may corrupt or lose data
Pro: packets arrive at same order so easier to put the message back together.
Packet switching
Splits data into packets and send the data across a network. There can be multiple transmission at different frequencies meaning the bandwidth is in constant use
Whats contained in Packet Switching
The header included the sender’s and the recipient’s IP addresses, the protocol being used, the packet number and a Time to Live (TTL) or hop limit, e.g an expiry date.
The payload contains the data being sent. And a checksum
Routers
used to connect to another network, traversing between them is called a hop.