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Networking and communication
Transcript of Networking and communication
Network types and technologies used
& Andrew Hobson
Range of topologies, Logical and Physical
Range of topologies, Logical and Physical
Local area network (LAN)
A local area network (LAN) is a computer network which covers a small geographical location. Local area networks are often used within office buildings, businesses and within schools. A wireless local area network (WLAN) allows you to link devices wirelessly giving the user the mobility to move around within a local coverage area and still be connected to the network. Most WLans are based on IEEE 802.11 standards. Ethernet is a family of computer network technologies for local area networks and has widely replaced wired LAN technologies.
Topology is how the computers in a network are connected together. The terms logical and physical topologies refer to how the network is connected. A logical topology is how the data passes through a network while a physical topology is how the workstations in a network are connected. It is helpful to be able to differenciate between logical and physical in order to be able tounderstand how some topologies may be working. There are five main types: bus, ring, star, tree and mesh. The topology used in the network can affect the performance of the network. There can be some problems with certain topologies when one computer breaks it can cause all the computers in the network to not be able to connect through the network. This is especially a problem with the ring topology.
Network topology is the way a network is set out. There are five main topologies: star, bus, ring, tree and mesh.
The ring topology is where the computers are connected to each other in a ring and information is passed through each computer. This means that each computer gets an equal share in the bandwidth, however it means that everyone can see all traffic which means there is not very much security.
The tree topology is centrally controlled and is designed in a hierarchical way. It is easy to add more components to it, however, if the central control fails, the whole network fails.
The mesh topology has multiple wires which connect the computers to each other which mean there are multiple routes to the data. Even if a computer fails, the network can still continue working. However, it is very complicated to manage.
Carrier sense multiple access (CSMA)
Carrier sense multiple access (CSMA) is a protocol for carrier transmission access in Ethernet networks in which a connection point verifies the absence of other traffic before transmitting on a shared transmission medium. Each device is able to sense whether the line is not transferring data and therefore available to be used. if the network is free and two devices access the line at exactly the same time, their signals collide.
Carrier sense multiple access with collision detection (CSMA/CD)
If a collision is detected, they both back off and wait a random amount of time before retrying, this is known as carrier sense multiple access with collision detection and prevents the collision of data within the network.
Token passing is a communication protocol where the system uses a signal called a token which is passed between communication points that authorizes the point to communicate. When a terminal wants to send data, it will wait for an empty token, when a token arrives it fills it with the data and the address of the destination and sends it off. One example of token passing is a token ring.
Access methods are the functions of a mainframe operating system which enables access to data on a disk or other external devices. Access methods provide ease of programming, ease of hardware replacement and ease shared data set access.
Network types and technologies used
Personal area network (PAN)
A personal area network (PAN) is a computer network used for communication among a computer or laptop and other devices close to an individual. A wireless personal area network is a personal area network in which the connections are wireless. Wireless PANs are based on the standard IEEE 802.15. Bluetooth is an example of wireless technology used on a wireless personal area network and can be composed of up to 8 active devices. Bluetooth devices such as keyboards and printers can be connected to computers wirelessly.
Wide area network (WAN)
A wide area network (WAN) is a computer network which covers an extensive area such as any telecommunications networks that link across metropolitan, regional or national boundaries. Many businesses operate wide area networks to transmit data amongst employees and clients from various geographical locations.
Frame relay is a high performance wide area network protocol which operates at the physical and data link layers. Multiprotocol label switching (MPLS) assigns short labels to network packets, the label describes how to forward the packet through the network.
Peer to peer and client server networks
A peer to peer network links computers directly, this allows users to access programs and other resources on other computer’s hard drive. Peer to peer networks can be set up within a home, a business or over the internet. In a peer-to-peer network if one of the computers does not work, all the other computers will not be affected and will continue to work, this is not always the case in a client server network.
A peer-to-peer network is much easier to set up rather than a client server network, as no specialist knowledge is needed when setting up a peer-to-peer network. On the other hand specialist knowledge is needed when setting up a client server network and a network manager.
Peer to peer network
Client server network
Token ring technology is a protocol which exists in the data link layer of the OSI model. T
he system uses a signal called a token which is passed between communication points that authorizes the point to communicate. The token system can be used with bus topology LANs.
A diagram displaying
the token ring system
Network operating system (NOS)
A network operating system is the software which runs on a server and enables the server to manage data, groups, security, applications and other networking functions. Network operating systems are implemented to allow file sharing and printer access among multiple computers within the network (LAN). Some examples of network operating systems include Microsoft Windows Server 2003 and Microsoft Windows Server 2008. Network operating systems are based on a client server architecture in which a server enables multiple clients to share resources.
CSMA / CSMA/CD Diagram
Network software is designed to help set up, manage and monitor computer networks. Network software applications are available to manage networks of all sizes such as home networks to large business networks.
Network models, OSI model
Network models, TCP/IP model
The star topology has a central core with the other computers positioned around connected in a star shape. This system works well as other computers can be added to the network without causing a problem and if one computer breaks it doesn’t affect the network. However if the core fails, the whole network will go down.
The bus topology is where each computer is connected to a main cable. The bus connection means people within the network can have private interaction. The bus system means new computers can be added without problem, however, if the cable is cut, part of the network will fail.
Packet and circuit switching
Packet switching is a protocol where messages are divided up into packetsbefore they are sent and each packet is sent individually and can follow different routes to their destination. Most modern wide area networks use this method.
Circuit switching is where messages are sent through a dedicated channel especially for the duration of the transmission. Circuit switching usually uses the telephone lines.
ISDN stands for integrated services digital network and is a data transfer technology which enables wide bandwith transmission over telephone lines. These connections usually transfer up to 128k of data per second. ISDN is much faster than dial up and can send to data at a time.
ATM stands for asynchrounous transfer mode is where packets of data are tranferred in a fixed size. The small constant cell makes it easier to tranfer audio, data and video files over the same network without a particular type of data taking up more of the line than other types.
ADSL stands for asymmetrical digital subscriber line and is a type of DSL broadband. To be able to use it, users need to have a modem specifically for ADSL an the user must be close to the providers central office. The phone can be used at the same time as ADSL due to a microfilter
The OSI model describes organisation of data and is used for creating protocols. There are seven layers of the OSI model. These are: Physical, Data Link, Network, Transport, Session, Presentation and Application.
is the connections which make up the network, such as cables, devices and network cards.
data link layer
is where raw bits are translated from data packets to be sent on to the physical layer. This layer also separates a switch from a hub.
is in charge of logical addressing and ensures that the computers group together.
ensures complete data transfer, including error recovery and flow control.
deals with conversations between computers, including name recognition and security,
which is usually part of an operating system, converts data to different formats, including data encryption and text compression.
gives applications access to the netwrok and therefore deals with software such as database access and email.
The TCP/IP model stands for transmission control protocol/ internet protocol and is the set of communications protocol used to connect hosts to the internet. It can also be used in a private network such as an intranet. There are four layers in the TCP/IP model: application, transport, internet and network access.
gives details on how the data is sent through the network. This includes how data is signalled by hardware devices that interface with a network medium.
packages data- these packages also contain the source and the destination address in order for the packages to be sent between hosts and across networks.
provides communication management between hosts. It also defines the level of service and the status of the connection used.
defines the TCP/IP protocols and also defines how host programs interface with the transport layer in order to use the network.
DHCP stands for dynamic host configuration protocol and is a configuration protocol used on networks. It helps the function of a network as it keeps record of IP addresses instead of having an administrator to complete the task.
DNS stands for domain name system.
It translates domain names to IP addresses so that the network understands it. This helps the network as the user does not have to remember IP addresses.
SMTP stands for simple mail transfer protocol. It is a protocol for sending emails between servers. It helps the function of a network as it enables emails to be passed without too much difficulty.
FTP stands for file transfer protocol and is used to exchange files over the internet. It helps the function of a network as it lets files be transferred without too much difficulty.
It is important to have standards and protocols for a network in order for the computers within the network to be able to communicate, authenticate and detect errors between eachother. They ensure that all computers are 'speaking the same language by setting ground rules, without these ground rules there would be no standard on how they would communicate. Network standards are also ground rules that are set by commissions so that hardware is compatible among similar computers. It is important to ensure each company does not create their own protocol standards as it would not be able to communicate with other protocols resulting in a lack of communication from computers.
The most common network protocols are TCP/IP, IP, FTP, Ethernet, Local Talk, Token Ring, FDDI and ATM.
Although the protocols all work slightly differently, they are all similar in that they have a way of working for everyone on the network in order for the netwrok to work in the best possible way.
Network connection software
Network connection software is software that is used by the administrators of the network to check for connectivity in a network. The software is able to monitor your bandwidth and ensure that you are always online. The software is also used to maintain and disconnect network connections. Most network connection software offers administrators with an interface for quick access to network resources and configurations.
Server 2008 interface