Communication Flashcards
Define network
A collection of computers, servers and other devices (nodes) connected to one another to allow the sharing of resources and data.
Define internet
A global computer network providing information and communication facilities; consisting of many interconnected networks
Define network topology
The arrangement of the nodes (computers, switches, routers etc.) and of the connections between them that make up a network.
Define data packet
A formatted unit of data that is transmitted over a packet-switching network
Define protocol
An agreed format, or set of rules, which allows differing networked devices to communicate.
Define connectivity
Connecting devices to each other in order to transfer data, including cabling and wireless
Advantages of networks (6)
• Share hardware, software, and data/files
• Easier for internal communication/can send email
• Central backup
• Easier to monitor network activity
• Centrally controlled security
• Can access data from any computer
Disadvantages of networks (5)
• A network manager may need to be employed – expensive
• Security problems – files sent between computers could spread a virus
• Hackers can gain access to data more easily
• If the server is down, all workstations on the network are affected
• Initial cost of servers, communication devices, etc. can be expensive
Define LAN and WAN
Local Area Network- computer systems located relatively close e.g. a school
Wide Area Network- computer systems located relatively distant e.g. the internet
Common network topologies (4)
Bus
Ring
Star
Mesh
Layout and process of a bus network
Nodes are connected to a single cable on which data can be sent, called the bus with terminators on each end.
The bus carries packets along the cable and checks the destination address in the packet at each node.
The node either ignores the packet or processes the data.
Advantages of a bus network (3)
• Easy to implement and add more computer systems to the network
• Quick to set up – well suited for temporary networks
• Cost-effective – less cabling
Disadvantages of a bus network (6)
• Difficult to troubleshoot the bus
• Performance degrades as additional computers are added
• If there is a problem with the main cable or
connection, the entire network goes down
• Low security – all computers on the bus can
see all data transmissions
• Proper termination is required
• Data collisions (two computers trying to send a packet at the same time) are more likely, which causes the network to slow down
Layout and function of a ring network
Nodes are connected in a ring or a loop. Packets are sent around the ring, being passed from one node to the next until they arrive at their destination
Advantages of a ring network (4)
• Data is transferred quickly and consistently
• Data transmission is relatively simple as
packets travel in one direction only
• Adding additional nodes has very little impact
on bandwidth
• It prevents network collisions
Disadvantages of a ring network (4)
• If any of the nodes fail, the ring is broken and data can’t be transmitted efficiently
• If there is a problem with the main cable or
connection, the entire network goes down
• It is difficult to troubleshoot the ring
• Because all nodes are wired together, to add a
another you must temporarily shut down the
network
Layout of a star network
Each node is connected to a central node, also known as the hub
Advantages of a star network (6)
• Good performance/fast network speed
• Easy to set up
• Possible to add more nodes without taking the network down
• Any non-centralised failure will have very little
effect on the network
• Minimal network collisions
• Better security
Disadvantages of a star network (2)
• Expensive to install – more cabling required
• Extra hardware required, such as a hub
Define circuit switching
A network technology that provides a temporary dedicated link between two nodes regardless of the number of switching devices through which the data has to travel. During the connection, no other data can be transmitted along the same route.
Define packet switching
Packets take different routes to the destination. When all packets have arrived, the data is reassembled. The Internet is example of a packet-switching network
Advantages of circuit switching (3)
• Reliable connection (once the connection is established)
• Fast
• Usually error free
Disadvantages of circuit switching (2)
• Takes time to establish the connection.
• If anywhere on the route fails, the connection breaks
Contents of a packet (6)
• The source address
• The destination address
• Information for reassembling data
• Tracking information
• The data itself
• A checksum that checks for data corruption
Define routing
The method of selecting paths, along which packets are sent on a computer network
Define MAC address (media access control address)
A unique hexadecimal number given to any communication device. The address is usually stored in a communication device’s ROM
What does a routing table store (3)
• Efficient paths to send packets along
• MAC addresses of communication devices on its network
• Corresponding IP addresses
Define IP address
An address allocated to a computer system on a network. This can be assigned by a DHCP (dynamic host configuration protocol) server or by yourself.
Define DNS (Domain Name System)
A distributed database that matches IP addresses to computer system resources.
Define TCP/IP (transmission control protocol/Internet protocol)
Protocol combined to allow communication between computer systems on a network.
IP is a protocol that sets out the format of packets in an addressing system
TCP is a protocol that allows packets to be sent between computer systems
Define HTTP (hypertext transfer protocol)
A protocol that can be used to transfer multimedia webpages over the Internet
Define FTP (file transfer protocol)
Copies a file from one location to another via a network or the Internet. Typically used to transfer larger files as it allows broken communications to resume transferring a file rather than having to restart
Define protocol stack
A set of protocols that work together to provide networking capabilities
What are the 5 layers to a TCP/IP protocol stack
- Application
- Transport
- Network
- Data link
- physical
Define application layer
Provides interfaces to the software to allow it to use the network.
Protocols that use the application layer
Hypertext transfer protocol (HTTP)
Simple mail transport protocol (SMTP)
File transfer protocol (FTP)
Define transport layer
Ensures that data is sent and received in the correct order from one point to another.
Implemented in the sending and receiving computers, but not in the routers on the path between.
Acts as an interface between the communicating computers and the network.
Protocols that use the transport layer
Transmission control protocol (TCP)
Define network layer
Responsible for the addressing and routing of data.
Routers belong to this layer as they use logical addresses to direct the data from the sender to the receiver.
Determines the path the data should take based on network conditions and manages traffic problems to minimise the congestion of data
Protocols that use the network layer
Internet protocol (IP)
Define data link layer
Sends data from the network layer to the physical layer. Divides the data to be sent into data frames (link layer header followed by a packet).
Handles acknowledgements sent from the receiver and insures that incoming data has been received correctly by analysing bit patterns in the frames.
Protocols that use the data link layer
Ethernet protocol
Define physical layer
Transmits the raw data. Consists of hardware such as switches and routers.
Responsible for setting up and maintaining a link between communicating computers.
Protocols that use the physical layer
Physical connection using a NIC (network interface card) to connect to the internet
Define Ethernet protocols
Describes how network devices can format data for transmission using frames and packets. Also used to define standards for types of network cabling used at the physical layer, and the corresponding transmission speeds
Define WiFi protocol
Standards for transmitting data using electromagnetic waves in place of cables, including 802.11 and Bluetooth.
Define Wireless Application Protocol (WAP)
Standardises the way that wireless devices can be used for Internet access.
Define email protocol
Standards for communication between email clients and mail servers
Examples of email protocols
Instant messaging access protocol (IMAP)
Post office protocol 3 (POP3)
Simple mail transfer protocol (SMTP)
Define IMAP
Stores email messages in a mail server so the user can handle their messages as if stored locally.
Define POP3
Stores emails in a single file on the mail server then downloaded to the users computer when they log in (deleted after being downloaded)
Define SMTP
Delivers email from sender to email server or from one server to another.
