6.2 Networks

Network adapter

A computer communicates using a network adapter/network interface card. Data is received using parallel transmission, into the buffer and data is called a block. block then given checksum, source address and a destination address. now called a frame, sent along using serial data transmission.

Stand-alone Computer

A computer that is not networked. It requires its own printer other peripherals plus its own installation of application software.

Client

A computer that uses the services provided by a server.

Router

A device that receives packets from one host or router and uses the destination IP address the packets contain to pass them correctly to another host or router.

Gateway

A device used to connect networks using two different protocols so that data can be passed from one system to another. A LAN is connected to the internet using a ______. -LAN = doesn't use TCP/IP protocol -_______translates the LAN packets to WAN packets and sends on to the internet

Protocol

A set of agreed Communication rules to make sure that everyone speaks the same language.

Wide Area Network

A set of links that connect geographically remote computers and LAN's

Ajax

A web technology that allows only part of the web page to be fetched from the web server without reloading the page.

Bluetooth

A wireless protocol for exchanging data over short distances from fixed and mobile devices.

ADV Networking

Advantages -Improved communication. can email with other users. -Adding users easier than stand-alone machines. -Apps stored and run from server. -Data shared = avoid duplication. -Routine maintenance performed by server. -Resources shared.

Wireless network

Any type of LAN in which the nodes (computers or computing devices) are not connected by wires but user radio waves to transmit data between them. -SLOWER THAN BUS AND STAR -VULNERABLE as radio waves can be intercepted.

IP address

Assigned to each device in a network that uses the internet. Defines where host computer is on the internet.used for locating hosts worldwide.

Segmentation

Bus networks split into segments because each computer added to the network slows it down due to more collisions. Router holds table of IP addresses of computers in network. Reduces collisions by reducing the number of computers connected to each section.

Carrier Sense Multiple Access Collision Detection (CSMA-CD)

Bus protocol to handle collisions. -Bus = quiet, Transmit frame -Bus = Busy, Listen until idle If collision detected, transmit a jamming signal to let computers know there is a collision. After jamming signal, wait a random amount of time then transmit frame again.

Star network with HUB

Central node = HUB - data will be re-transmitted to all of the other nodes in the network.

DIS Networking

Disadvantages -People depend on maintenance done by server. -Resources are interdependent - peripherals won't work if network is down. -As traffic increases on the internet, performance can degrade. -Security can become more of an issue.

Star topology

Each of the nodes of the network is connected to a central node. -Data is transmitted to the central node from individual links to computers/devices/nodes. -If link to a node/device goes down, other links and nodes are unaffected. -If central node goes down the whole network will fail.

Routers

Get packets to destination. Table of other routers it is directly connected to. Knows IP route and Destination IP address. Checks Destination address routing table packet sent to network. If address is not in the routing table it sends the packet on a predefined default route.

Peer-to-Peer LAN's

Good choice when fewer than 10 users - Users located in same location and Security is not an issue. It is a network with limited growth.

Comparison of star and bus networks

In a star network each client is connected directly to the other without passing the other computers so is hence more secure from eavesdropping. If the cable in a bus network breaks the whole network stops working. If the switch in the star network stops working, the whole network goes down. Buffers in switches may overflow in high volume traffic.

Domain Name Server

Keeps track of association between domain names and IP addresses.

Switched Ethernet

LAN wired in star topology = behaves as a bus -Central switch queues frames -Switch ensures collisions do not occur -Outperforms Ethernet LAN's based on Coaxial cable -Performance affected when traffic volumes high, buffers in the switches suffer overflow

Local area Network

Linked computers in close proximity. - More economical to have smaller computers with applications rather than a large one. - High speed communications and low error rates.

Collisions

Occur when 2 computers transmit onto the bus at the same time. -Voltage pulses collide, resulting in higher voltage swings. - To reduce, Transmission duration limited to one frame of pulses. - Frame has minimum number of pulses to enable a computer to detect a collision by a rise in pulse voltage.

Internet Assigned Numbers Authority (IANA)

Responsible for IP addressing System.

Web2.0

Software that becomes a service accessed over the internet. - Software is never distributed only performed.

Wi-Fi

Trademarked technologies that support wireless networking of home and business networks.

Internetworking

Two LAN's connected by a WAN so that computers on one network can communicate with computers on the other network.

Bus Network Repeaters

Used to make signal travel further by amplifying the signal

Internet

a collection of LAN's and computers that are interconnected by a WAN.

Server

a computer that provides shared resources to network users.

Software as a Service (SaaS)

a model of software deployment and where an application is hosted as a service provided to customer across the internet.

Server-based Network

a network in which resources security and administration and other functions are provided by dedicated servers. - Servers insure the security of files and directories.

Peer-to-Peer Network

a network that has no dedicated servers. All computers are equal, so they are called peers. - Users determine what data, disk space and peripherals are shared. - Security set on individual computers (passwords). Organised in to work groups of up to 10 computers

Thin-Client Network

a network where all processing takes place in a central server; the clients are dumb terminals with little or no processing power or local hard disk storage.

Bus topology

all of the nodes are connected by a backbone which has two endpoints Terminators. -All data is transmitted between nodes in the network - Via the Backbone.

Subnet Mask

enables network administrator to further divide host part of the IP address into two or more subnets. Part of host address is reserved to identify particular subnet. small network put 255.255.255.0 Tells computer which LAN connected to and addresses can't reach.

Circuit Switching

established between two nodes and all data follows this path. Mobile Networks needs to find a complete pathway before a call is made.

Network Segment

in Ethernet, a run of Ethernet Cable to which a number of workstations are attached.

Topology

in the context of networking, the shape, layout, configuration of structure of the connections that connect devices to the network.

Polling Protocol

one computer acts as a traffic controller, asking each terminal (bus topology) in turn if they wish to transmit. Collisions are therefore avoided.

Subnet

Logical group of connected network devices. Partition networks into logical segments for greater ease of admin. Performance and security Improved.

Thick-Client Network

Most applications are run on the client Computer - Must have local processing power. Spec of Workstation affects performance.

Packet Switching

SMS can be sent immediately without setting up a path. Data, split into a number of smaller packets that may take different routes to reach the destination.

Terminator

Stops signals Bouncing back down the network. (Bus Topology)

Peer-to-Peer WAN's

Such as P2P over internet, used to share files among a large number of users connected temporarily.

Star network with Switch

Switch data will be retransmitted to one node in the network.