Internet
A network of Interconnected Networks
World Wide Web
A collection of resources accessed via the Internet
Backbone
A set of dedicated connections that connect several large networks at various points on the globe
URL (Uniform Resource Locator)
Used to specify means of accessing a resource across a network and its location
URL components
Web protocol, domain name, name of resource
DNS (Domain Name System)
Translates between domain names and IP addresses using DNS servers
DNS Server
Dedicated computer with an index of domain names and their corresponding IP addresses
Internet Registries
5 global Internet Registries are responsible for allocating IP addresses to specific domain names, and maintain a database of address assignments that ensure IP addresses and domain names are unique
LAN (Local Area Network)
Two or more computers connected together within a small geographical area
Network Topology
The arrangement of various computing devices which make up a computer network
Bus topology
An arrangement where nodes are connected in a daisy chain by a single central communications channel (backbone cable)
Star topology
An arrangement where a central node or hub provides a common connection point for all other nodes
Peer-to-peer topology
An arrangement where each node is connected to each other
Ring topology
An arrangement where each node is connected in a circle fashion
Hub
Transmits communication with every computer it is connected to
Switch
Transmits communication to only the computer it is intended for
Wi-Fi
A wireless networking technology providing high-speed Internet and network connections
Wireless Access Point (WAP)
A device that creates a WLAN
Network Interface Card (NIC)
A hardware component that enables computers to communicate over a network
Circuit Switching
Assigns a temporary and dedicated link between source and destination with dedicated bandwidth until transmission is complete
Packet switching
Breaks data into packets and sends them staggered via routes with lowest latency Allows communication channels to be shared
Gateway
A bridge between networks that use different protocols Header data is removed and reapplied using the correct format of the new network
Protocol
A set of rules for data communication
TCP/IP stack
Application, Transport, Internet, Link
Application Layer (sending)
Provides interface for applications to communicate across networks Decides which protocol to use
Transport Layer (sending)
Uses TCP to establish end-to-end connection with recipient computer Splits data into packets and numbers them sequentially Adds port number to use based on protocol
Internet/Network Layer (sending)
Uses IP to address packets with source and destination IP addresses A router forwards each packet towards an endpoint, defined by the combination of IP address and port number Each router uses a routing table to instruct each hop
Link Layer (sending)
Operates across a physical connection Adds MAC address of physical NIC card that packets should be sent to based on destination hop MAC addresses change with every hop
Link Layer (receiving)
removes MAC address from each packet
Internet/Network Layer (receiving)
removes IP address from each packet
Transport Layer (receiving)
Confirms packets have been received and requests any missing to be resent Removes port number from each packet Reassembles packets in correct order
Application Layer (receiving)
Presents meaningful data for user
MAC address
Uniquely identifies a physical device with an NIC
File Transfer Protocol (FTP)
An applications-layer protocol used to transfer files across a network
Simple Mail Transfer Protocol (SMTP)
Used to send emails and forward them between mail servers to their destination
Post Office Protocol v3 (POP3)
Downloads email stored on a remote server to a local client, then removes from server after download
Interim Mail Access Protocol (IMAP)
Manages emails on a server so multiple clients access the same email account simultaneously
Time to Live (TTL)
the maximum amount of time a packet is allowed to circulate through a network before it is destroyed/ hop limit
Latency
The time data takes to travel across a network from source to destination
Packet trailer
Contains error checking components, i.e. checksums or Cyclic Redundancy checks; end of packet flag
Packet Header
Contains source and destination IP address, packet number, protocol/port number
Routing
Routers forward data packets from one network to another, and each looks up destination IP address in routing table to find best route
Application Programming Interface (API)
A set of tools that can be used for building software applications