Data Transmission Flashcards
4-Layer OSI Model
a four-layer model that provides a common basis for the coordination of standards development for the purpose of systems interconnection
Application Layer (4)
combination of the application layer, presentation layer and session layer, uses protocol such as FTP, HTTP, SMTP, TELNET, PING
Transport Layer (4)
same as the transport layer in 7-Layer Model, the layer where data is split into packets uses protocols such as TCP, UDP
Internet Layer
same as the network layer in 7-Layer Model, uses protocols such as IP
Link Layer
combination of the data-link layer and the physical layer, uses protocols such as ISDN and Wi-Fi
7-Layer OSI Model
a seven-layer model that provides a common basis for the coordination of standards development for the purpose of systems interconnection
Application Layer (7)
handles initial requests to transmit data
Presentation Layer
handles how information is to be presented
Session Layer
handles requests to transmit data synchronisation of data and traffic conform information
Transport Layer (7)
standardises data being transmitted
Network Layer
handles routing/addressing between systems
Data-Link Layer
handles error checking and correction and formats data for physical transmission
Physical Layer
the physical binary data with no error correction
APIPA
Automatic Private Internet Protocol Address
a Windows feature that enables a client to automatically assign an IP address to itself when there’s no DHCP server available
Asymmetric Encryption/Public Key Encryption
uses a different key to encrypt and decrypt a message. This solves the problem of key sharing in symmetric encryption schemes. The key generation algorithm of an asymmetric generation scheme generates two keys and the keys are generated in such a way that knowing the public key does not make it easier to decrypt information, making it more secure
Asynchronous Serial Data Transmission
transmission system in which the sender and receiver have separate clocks which are not kept synchronised. Instead, the clocks are synchronised temporarily at the start of a transmission. The arrival of data cannot be predicted by the receiver; s a start bit is used to signal the arrival of data and to synchronise the transmitter and receiver temporarily
Baseband System
a system that uses a single data channel system in which the whole bandwidth of the transmission medium is dedicated to one data channel at a time
Baud Rate
the number of signalling events across a transmission medium per second
Bit Rate
the number of bits per second that can be transmitted along a digital network
Block Ciphers
these are used in modern symmetric encryption. The message is broken into blocks containing multiple bits that are encrypted. If the block length is longer than the message, it is padded out with random content to make it longer. This can help obscure the length of the message, and additional information can be hidden in the blocks, such as error checking
Bridge
used to connect two LANs or two LAN segments together, though both must use the same communications protocol
Broadband
a multiple data channel system in which the bandwidth of the transmission medium carries several data streams at the same time
Brouter
combination of bridge and router
Cabling
required to connect all devices on a network together if the network is not wireless, varies greatly depending on network configuration, provides much faster connection that wireless connection, due to less interference and greater bandwidth
Coaxial Cables
consists of a solid conductor, three coats of insulation, and a grounding conductor to conduct electricity
Fibre Optic Cables
cables which transmit signals along glass fibres using laser light signals, allowing data to be transferred much faster than in copper
Twisted Pair Cables
constitutes a combination of insulated copper wires
Circuit Switching
data is sent across a network with all parts of the message taking the same route meaning packets arrive in the order they were transmitted by this is less secure as it is relatively easy to intercept all of the packets in a single message
Client
a computer that uses the services provided by a server
Client-Sever Networking
where clients make a request for a service or resource from the server. The server responds with the required resource or a security challenge. If it fails, the service cannot be provided by the server
Crosstalk
occurs when electromagnetic interference between wires that are in proximity such as parallel links results in transmitting corrupted data that will need to be re-sent
Default Gateway
the gateway that the network looks for as default as a gateway out
Delivery Model
the sending host sends a beacon to the destination address to see if it is reachable, waits for a reply then sends the actual message. A timer is used to make sure that the message is received
Diffie-Hellman Key Exchange
involves the sender and receiver both creating a secret key (a and b). They also create a public key (g). Both raise g to the power of the keys (g^a and g^b). The numbers a, b and g must be chosen so that g^a and g^b are easy to calculate but computationally hard to reverse, meaning g^a and g^b can be broadcast. The secret keys in a Diffie-Hellman key exchange are prime numbers that are 2048 bits long. To encrypt and decrypt messages the public key must be raised to the power of the private key (g^ba).
DNS
Domain Name System
matches up a user-friendly domain name with an IP address
DNS Servers
have a directory serve which translates domain names to IP addresses
Dotted Decimal Notation
a presentation format for numerical data expressed as a string of decimal numbers each separated by a full stop
Duplex
two-way communication; nodes can both send and receive and can do so simultaneously
Dynamic IP Address
a temporary address for devices connected to a network that continually changes over time and are allocated by your router
Dynamic Web Page Content
content that is generated when the web browser request is sent
End-to-End Principle
where two equivalent hosts are used in communication
Enler’s totient functiton
Ф=(p-1)(q-1)
Forwarding Table
contains addresses to output links
Frame
a group of data packets
Gateway
a device used to connect networks using different protocols so that information can be successfully passed from one system to another
Half-Duplex
two-way communication but only one way at a time
Handshaking
the process used to control the flow of data between devices, happens at the start of communication, confirms the speed of transmission and the protocols that will be used
Hopping
going from router to router, changing addresses at each hop
Host Names
a human-readable label made of up to 255 characters that is assigned to a network device
Hub
distributes all data received to all other devices it is connected to, sometimes used in a star network which can cause security problems as well as causing frequent data collisions which slows down the network
International Router
connects international networks
Internet
consists of a network of interconnected computer networks using a globally unique address space based on the IP and the TCP to support public access
Internet Registrars
responsible for registering internet registries
Internet Registries
online retailers where domains can be bought
LAN
Local Area Network
used for small, localised networks, such as in homes or schools
Local Router
connects LANs
Layered Protocol
where several transmission protocols are layered and each layer controls a different feature of transmission, eg the OSI model
Mapping
distributed across the DNS servers, one cannot hold all
MAC Address
Media Access Control Address
the computer’s physical address, a unique number written onto the NIC by the manufacturer composed of 6 pairs of hexadecimal characters separated by hyphens
MAN
Metropolitan Area Network
connects devices within a metropolitan area such as a single large city; this is larger than a LAN but smaller than a WAN
Modem
a device that changes signals from one type of device to a form compatible with another
Multiplexing
a method by which multiple analog and digital signals are combined into one signal over a shared medium in order to share a physical transmission medium
National Router
connects national networks
NIC
Network Interface Card
a piece of hardware that is required to connect a device to a LAN. It allows the device to communicate either by wires or wirelessly with the rest of the network. It prepares and sends the data to other devices on the network
Network Protocol
a set of rules governing the exchange or transmission of data between devices, including rules on how to start or end a transmission, format of data to be exchanged, how to detect or correct errors or any compression to be used
DHCP
Dynamic Host Configuation Protocol
a client/server protocol that messages a pool of IP addresses and the client configuration process
DNS
FTP
File Transfer Protocol
the second-oldest protocol after IP, used for file transfer
FTPS
File Transfer Protocol Secure
used to transfer files securely by encrypting data
HTTP
Hyper Text Transfer Protocol
allows data transfer across the internet, allows HTML, CSS and JavaScript to be transferred from servers to browsers
HTTPS
Hyper Text Transfer Protocol Secure
allows secure data transfer across the internet by using encrypted data, allows HTML, CSS and JavaScript to be transferred from servers to browsers
ICMP
IMAP4
Internet Message Access Protocol 4
similar functionality to POP3 but can be used on multiple devices because mail is stored on the server and mail is not deleted from the server when it is downloaded
IOMP
IP
Internet Protocol
works together with TCP to transfer data over a network, handles routing. Sending data involves adding a destination and source address to each packet. Receiving data involves checking packet destination addresses, accepting packets destined for this address and ignoring packets with other destinations
NTP
OSI
PING
POP3
Post Office Protocol 3
provides basic client/server features, enables e-mail download from the server, but mail was deleted from the server on download and could only be used with a single device
RIP
SMB
Server Message Block
a communication protocol mainly used by Microsoft Windows equipped computers normally used to share files, printers, serial ports, and miscellaneous communications between nodes on a network
SMTP
Simple Mail Transfer Protocol
protocol for internet e-mail, transfers e-mails between computers
SNMP
SSH
Secure Shell
a protocol that provides secure file transfer and manipulation capabilities
SSL
TCP
Transmission Control Protocol
works together with IP to transfer data over a network, is in charge of reliable delivery of information by dividing data into packets. Sending data involves splitting the data into packets, adding a packet sequence number and adding a checksum or error correction data. Receiving data involves checking packets for errors and fixing them if needed, identifying missing packets, reassembling packets in the correct order and sending complete data to relevant applications
Telnet
UDP
NAT Table
Network Address Translation Table
allows devices on a private network to access a public network, such as the internet
One Way Functions
functions that are very simple to perform one way but computationally hard to reverse
Open Architecture Networking
designers of networks are free to design them however they want as they can all be connected to and communicate over the internet and each network is connected through a router
Packet
structures are defined by the protocol, if you have a big unit to download or send, it has to be broken down into small packets. Each packet is then labelled with both the destination and source address, so it can be routed through the internet
Packet Switching
data is sent across a network with individual parts of the message each taking their own route to the destination meaning packets arrive in a random order and have to be reassembled to recreate the original message making it more secure as it is relatively easy to intercept all packets in a single message, used to send data through a network consisting of many different nodes
PAN
Personal Area Network
connects devices to the user, such as a wireless keyboard, mouse or computer
Parallel Transmission
each bit in the byte is transmitted along a separate path simultaneously
Paul Baran and Donald Davies
invented the idea of a distributed fishnet-style network in the 60s
Peer to Peer Networking
all computers are of equal status and no computer acts as a server. All peers must work together to fulfil the required task and file sharing is common
Port
the address for a specific application or process within the computer to which data is sent. Port 80 is used by HTTP and port 53 is used by DNS
Private IP Address
IP addresses that are reserved for internal use behind a router or other device, and cannot be used to access the internet directly
Private Key
used for decrypting data
Public IP Address
IP addresses that allows content to find its way to your device that your router receives from your Internet Service Provider
Public Key
used for encrypting data
Regional Router
connects networks within a specific region
Router
used to connect parts of networks together by looking at the address of data packets to send them down the best route to their destination
Routing Algorithm
calculate paths and performing packet switching
Routing Table
used in routers to program different routes for different types of data or to use different routes at different times of the day
RSA Encryption
Rivert, Shamir and Adleman Encryption
asymmetric encryption system named after its creators. Published in 1977, it uses prime number to prevent eavesdropping on the private key whilst still broadcasting the public key
Robert Khan and Vint Cerf
the first to conceive the idea of connecting packet-switched networks between North America and Europe
Sequence Number
- included in the header of the packet to rearrange packets
Serial Tranmission
each bit in the byte is transmitted along a separate path simultaneously
Skew
occurs when bits that are transmitted across parallel links travel at different speeds. In synchronous data transmission, this can result in data falling out of sync with the clock signal and therefore not being read correctly
Socket
the full destination address to which data is sent, includes the IP address and port number
Stand-Alone Computers
computer not networked, requiring its own printer and other peripherals plus its own installation of application software
Static IP Address
IP address that are manually configured and never change
Stream Ciphers
used in modern encryption and is applied to each bit of the message individually; the message is broken up into individual bits sand each is altered by the algorithm. This is useful when you don’t know how big your message is and is useful when you have a continuous stream of data
Suite of Protocols
where networking protocols work together, for example, IP and TCP
Symmetric Encryption
where the same key is used to encrypt and decrypt the data. This is quick to set up and easy to execute, but is less secure and less modern, and is used in payment applications and banking
Synchronous Communication
where the sender and receiver are synchronised using a common clock signal
TCP/IP Protocol Stack
a set of networking protocols represented in four layers, data packets move between layers during network communication and each layer has its own role
Application Layer (TCP/IP)
layer closest to the user, collects data from and delivers data to other applications, for example: e-mail, web browser, print server, network drive, social media
Transport Layer (TCP/IP)
creates end-to-end encryption, splits data into packets, adds headers to packets, ensures all packets are sent and received to ensure all data is there, in the correct order and that the destination address exists
Internet Layer (TCP/IP)
adds source and destination IP address to packets, routers inspect IP addresses on packets and transmit and route packets via the shortest possible path
Link Layer (TCP/IP)
physical connections on the network, adds MAC address to packets and used to identify unique NICs
Thin-Client Network
network where all processing takes place in a central server; the clients are dumb terminals with little or no processing tower or local hard disk storage
Tim Burners-Lee
invented the world wide web and hypertext markup language
Timeout Limit
the amount of time packet transfer is expected to take
Transmission Modes
describe the characteristics of sending data over a link between two nodes
Web Server Extension
program written in native code, ie an executable or a script that is interpreted by an interpreter running on the web server that extends the functionality of the web server and allows it to generate content at the time of the HTTP request
Web Services
self-contained, modular applications that can be described, published, located and invoked over a network, generally the web
WAN
Wide Area Network
connects devices but extends a large geographical distance such as leased telecommunications networks
WAP
Wireless Access Point
allows a network to be connected using radio waves, obviating the need for cabling
WHOIS
details of registrants and IP addresses
