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Summary CCEA GCE A2 Unit 1 Digital Technology
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My summary document will cover all topics needed for the CCEA A2 Unit 1 - Information Systems, Digital Technology written exam. I hope it is of some use to you :)
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Topic 1 – Network ResourcesDescribe networks by their scope:
local area network (LAN) – Is a network that is spread of a small geographical area
such as a building or a school.
metropolitan area network (MAN) – Is a network that interconnects computers over a
geographical area. It is smaller than a WAN but larger than a LAN.
wide area network (WAN) – Is a network that is spread over a vast geographical
area even on a global scale.
Describe the purpose of the network resources:
network card/NIC – Is an electronic circuit board that needs to be pre-installed onto a
computer/device to allow it to connect onto a network
server – Is a dedicated computer on a network that manages resources such as: File
storage/backup, Printer Management, Providing application software.
switched hub – Is a hardware device that acts as a single connection point for
computers on a network. It checks the destination of data packets and forwards them
onto the intendent recipient via the optimum route.
repeater – Is a hardware device used in the transmission of data. So if the data
signal is distorted the signal can still travel.
wireless access point (WAP) – Is a hardware device that enables Wi-Fi enabled
devices to connect to a wired network.
media converter – Allows for 2 dissimilar media types to connect to one another. It
changes the physical signals from one media type to another such as fibre optic and
copper.
IP address – Internet Protocol address is a unique address assigned to any device
that is connected to the internet uniquely identifying them
media access control (MAC) address – Is another unique address assigned to a
computer’s Network Interface Card (NIC) during manufacturing uniquely identifying
the physical address.
Define the purpose of an IP address and a MAC address
MAC: Identifies the physical address of a computer’s NIC card on a LAN
IP: Identifies the connection address of a computer on the Internet
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,Describe the features of a peer-to-peer (P2P) and server-based networks
Peer-to-Peer – This network topology describes when a number of nodes are
networked to one another either by physical cable or wireless technology without a
central server in between. Each Node can be described as a consumer and supplier
of resources so they can make requests for resources but also share resources.
Server-Based – This network topology describes when there is a dedicated
computer on the network called the Server which performs tasks on behalf of 1 or
more different client computers. Client computers make requests to the server and
the server responds to these requests. Some functions the server can carry out
include: File storage/Backup, Printer management and providing application
software. A log in and password is required to use the server.
Evaluate the bus, star and ring network topologies
Ring – This network topology describes when a number of nodes are networked to
one another either by physical cabling or wireless technology without the need for a
fileserver in between. A special message called a token travel through all nodes and
can add message data to the network with data travelling in 1 direction.
Advantages: Data travels in 1 direction so there are no data collisions, it is easy to
add new nodes/work stations.
Disadvantages: If one cable/Node is switched off or stops working the rest are
impacted, Data must pass through all computer so its slow.
Bus – All nodes are connected onto the main cable (The backbone) via their own
cables. At the end of the backbone terminators are used to prevent the data
bouncing back. Data travels in both directions and computers check If they are the
intended recipient and if they are data is accepted.
Advantages: Easy to install, Uses less cable than a star and best choice for
temporary network.
Disadvantages: Problems with backbone can cause major faults, Data travels slow
with lots of stations and limited cable length.
Star – There is a central file server whereby each node is connected to the fileserver
by their own cable. The fileserver controls communication with all the nodes and
transfer of data packets.
Advantages: Very reliable as if 1 connection fails the rest work, Good security with
fileserver
Disadvantages: Expensive, Extra hardware required, all relying on file server.
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, Topic 2 – Protocols
Explain the need for communication protocols
A communication protocol is a set of rules/procedures that allows devices on
different topologies to communicate with one another. They are implemented in
hard/software and networks cannot exist without them.
Describe the Open Systems Interconnection (OSI) network organisation model and
each of its component layers
OSI Model – Is a reference model for how messages should be transmitted between
any 2 points in a telecommunication network. With its main purpose to guide product
implementers so that their products will consistently work with other products.
Application Layer – This is the top layer of the OSI model. The application layer is
only concerned with presenting information in a human friendly way. It only interacts
with the Presentation Layer.
Presentation Layer – Is concerned about presenting information in an electronic
format so the computer can understand it. It defines how two devices should encode,
encrypt, and compress data so it is received correctly on the other end. It interacts
with the Application and session Layer.
Session Layer – Is when 2 devices want to communicate with one another so a
session is formed It is responsible for opening sessions, ensuring they remain open
and functional while data is being transferred, and closing them when
communication ends. It interacts with the Presentation and Transport Layer
Transport Layer – Will divide information into convent sized packets which will be
sent on different routes. It interacts with the Session and Network Layer.
Network Layer – The network layer has two main functions. One is breaking up
segments into network packets, and reassembling the packets on the receiving end.
The other is routing packets by discovering the best path across a physical network.
It interacts with the Transport and Data link layer.
Data Link Layer – The data link layer establishes and terminates a connection
between two physically-connected nodes on a network. It breaks up packets into
frames and sends them from source to destination. It interacts with the Network and
physical Layer.
Physical Layer - The physical layer is responsible for the physical cable or wireless
connection between network nodes by converting the bits into a physical signal such
as pulses of light. It only interacts with the data link layer.
Describe communication protocols:
Transmission Control Protocol/Internet Protocol (TCP/IP) – TCP is responsible for
checking that data has been delivered correctly. If data is lost, TCP requests the
data to be resent. IP is responsible for moving data from 1 part of the network to
another
Ethernet – Is a hardwired network that defines not only the working protocol but the
physical plugs and sockets used.
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