1.3.3 PART 1 Networks Flashcards
What’s a Personal area network
A connection of devices that are within a few metres of each other
What’s a Local area network
A single network covering in a small geographical area, connecting at least 2 devices
What’s a wide area network
A network that connects 2 or more networks over a wider geographical area.
How can networks be further classified
As either,
Peer-to-peer
Client-server
What’s a client
A program that typically runs on a device used by an end-user (laptop or phone)
What’s a server
A program on a computer that shares resources with or provides services to, any authorised client ( usually run 24/7 )
What’s a mainframe
A high-powered dedicated computer, able to handle lots of requests simultaneously
How does a client server network work
Clients send requests to the server
Server processes the request
The response is sent back to the client
What are the benefits of a client-server network?
Allows files and emails to be accessed from any authorized device on the network
What is a peer-to-peer network?
A network with no central servers, where every workstation can be configured to share its resources- e.g. files or software.
Devices communicate directly with each other!
What is a public telecommunications infrastructure?
A Wide area network that uses telecom links managed by ISPs and leases bandwidth from them.
What is the internet?
A global system of interconnected computer networks, that facilitates services, such as the WWW, via common set of protocols (TCP/IP stack)
How do Individuals / organizations connect to the internet?
An internet service provider (ISP) supplies a switch to a household
It offers a wide range of network features, connecting devices to the LAN
The ISP also supplies a router which manages the outgoing connection and directs data packets to their intended destination.
Providing an outgoing connection from the home network to the ISP network
Finally the ISP provides a modem which converts digital signals to analog signals for transmission over communication channels. Modems connect to the internet from internet service providers (ISPs)
What’s a router?
A networking device that forwards data packets between networks
What’s an edge router
A router that connects internal networks to external networks.
What are the two types of edge routers?
Subscriber routers and Enterprise routers
What are the features of a subscriber router?
It’s cheap
Allows for the use of multiple internet connections from different providers simultaneously, but not as many as an enterprise router
What are the features of an enterprise router?
Connects Large businesses and ISP networks to the internet
Powerful hardware
Expensive
Can support more users accessing the internet simultaneously than a Subscriber router
What’s a core router?
A router that’s part of the internets backbone
Has multiple interfaces, that can all work at the same speed simultaneously, routing data between different networks within the internal network infrastructure
What is a VPN?
It allows users to transmit data across public telecom networks, as if their devices were directly connected to the private network
What are internet registries?
They are companies that issue IP addresses to domain names, preventing DNS requests being confused.
What is the difference between IPv4 and IPv6 addresses?
Ipv4 addresses consist of 4 octet values (4 8-bit values), each separated by a full stop.
IPv6 is an Internet Protocol (IP), that provides addresses using hexadecimal
What is a data packet
A portion of data to be transported containing, a header, and payload: The actual message itself
What is packet switching
A method of sending data over a network by breaking messages/data into smaller pieces called packets
The use of small packets allows a data path to be shared
Different packets can be sent over different routes, minimizing cluttering
How the internet ensure packet switching is effective?
It has an end-to-end principle, where end-points (source and destination) are responsible for checking that everything has been sent/received (respectively)
What does a packet header contain?
Sender’s and recipient’s IP addresses
Packet number
Total number of packets in the message
Protocol details
What is a protocol?
A set of rules that specify how two (even if disparate) devices communicate, with each other.
How are internet protocols structured?
Divided up into 4 layers
Layers sit one below the other in a protocol stack
Application layer function?
Establishes the end-to-end connection, and interacts directly with software applications.
It prepares data for transmission over the network by converting it into a format that can be sent and received over the network (known as encapsulation)
On the receiving end it uses application level protocol to process data
Transport layer function?
Receives data from the application layer and splits it into packets
Applies port and packet numbers, so the data can be reassembled in the correct order at the destination
On the receiving end it re-assembles data into packets.
Internet layer function?
Receives packets from the transport layer
It adds a header to each packet, including the sender’s IP address and the receiver’s IP address
Routes each packet across the network using the IP addresses in the headers
On the receiving end it checks for and removes IP address
Link layer function?
Receives packets from the Internet layer
Prepares them for transmission over the physical network- source and destination MAC addresses added to packet headers.
Modem operates here- Translates the digital packets into analogue signals to be transmitted
Once the signal reaches the receiving end, the network layer translates it back into digital packets and checks the MAC address
What is a URL
An address that specifies the means of accessing a resource on the internet.
What are DNS servers
Dedicated computers with an index of domain names and corresponding IP addresses.
What’s a DNS resolver
The first stop in the DNS lookup process
Checks its cache to see if it has the IP address for the requested domain. If not, it sends the request to the DNS root servers
What is a root server?
The resolver asks a DNS ROOT server to find the top-level domain (like .com, .org) based on the extension of the URL
What is the top level domain server?
The root server directs the resolver to a TLD server, which stores the information of the domain
Providing the resolver with the IP address of the domain’s authoritative DNS server
What does the authoritative DNS server do>
The resolver queries the authoritative DNS server for the IP address of the domain
It responds with the IP address for the requested domain
What type of system is the Domain Name System
Hierarchial
What happens when you type a URL into a web browser?
URL Entry: The user enters the URL of a website into the web browser
The computer checks its local cache to see if it contains the IP address of the URL from a previous request
DNS Query: The web browser sends a query to a DNS server (usually hosted by your ISP) to translate the URL (domain name) into an IP address
DNS Resolver: The DNS resolver checks its cache to see if it has the IP address for the requested domain. If not, it sends the request to the DNS root servers
Root Server Query: The root server directs the resolver to a Top-Level Domain (TLD) server (like .com, .org) based on the extension of the URL
TLD Server Query: The TLD server then provides the resolver with the IP address of the domain’s authoritative DNS server
Authoritative Server Query: The resolver queries the authoritative DNS server for the IP address of the domain
Retrieve IP Address: The authoritative DNS server responds with the IP address for the requested domain
Request the Web Page: The web browser sends an HTTP or HTTPS request to the IP address it received
Server Response: The server at the given IP address processes the request and sends back the data for the web page (HTML, CSS, JavaScript, etc.)
Render the Web Page: The web browser renders the received data into the web page that you see
What is a bus topology?
A network arrangement where nodes are connected in a daisy chain, via a single central communications channel
What is a star topology?
A network arrangement where a central node (usually a switch) provides a common connection point for all other nodes
What does a switch do in a star topology?
Sends each communication to the intended device
What are the advantages of a Bus topology?
Cheap setup
Easy to add devices
Good for small networks
What are the disadvantages of a Bus topology?
Main Cable is a central point of failure
Limited cable length
Heavy use causes data collisions
Insecure
What are the advantages of a Star topology?
Easy to isolate and fix problems
Good performance
Secure if a switch is used
What are the disadvantages of a Star topology?
Central node is a point of failure
Expensive setup
What’s a physical topology?
Defines how devices are physically connected in a network
What’s a Logical topology?
Defines how devices communicate across physical topologies
What is WIFI?
A wireless networking technology
Provides high speed internet and network connections
What are examples of wireless components?
WAP, WIFI, NIC
What is a Station?
A computer with an NIC
A device that can connect to a wireless network and exchange data
What’s a Wireless Access Point?
A piece of hardware that allows wireless devices to connect to a network by creating a wireless network
It requires a connection to a router and modem.
