COSC 85 | Midterms Flashcards
it refers to the transmission of digital data between two or more computers.
data communications
it refers to information presented in whatever form is agreed upon by the parties creating and using the data.
data
means communication at a distance.
telecommunication
Fundamental Characteristics of a data communication system
delivery
accuracy
timeliness
jitter
The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user.
delivery
The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable.
accuracy
The system must deliver data in a timely manner. Data delivered late are useless.
timeliness
refers to the variation in the packet arrival time. It is the uneven delay in the delivery of audio or video packets.
jitter
components of data communication
message
sender
receiver
transmission medium
protocol
is the information (data) to be communicated. It can be text, numbers, pictures, audio, video, etc.
message
is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, etc.
sender
the device that receives the message. It can be a computer, workstation, telephone handset, television, etc.
receiver
is the physical path by which a message travels from sender to receiver. Examples are twisted-pair wire, coaxial cable, fiber-optic cable, radio waves, etc.
transmission medium
is a set of rules that govern data communications. It represents an agreement between the communicating devices.
protocol
data flows
simplex
half-duplex
full-duplex
the communication is unidirectional. Only one of the two devices on a link can transmit; other can only receive.
simplex
each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa.
half-duplex
both stations can transmit and receive simultaneously.
full-duplex
a set of devices connected by communication links.
network
it can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network.
node
is where task is divided among multiple computers.
distributed processing
network criteria
performance
reliability
security
performance can be measured in many ways
transit time and response time
is the amount of time required for a message to travel from one device to another.
transit time
is the elapsed time between an inquiry and a response.
response time
a set of rules that govern data communications. it defines what is communicated, how it is communicated, and when it is communicated. The key elements of it are syntax, semantics, and timing.
protocol
the structure or format of the data, meaning the order in which they are presented.
syntax
meaning of each section of bits
semantics
refers to two characteristics, when data should be sent and how fast they can be sent.
timing
are essential in creating and maintaining an open and
competitive market for equipment manufacturers and guaranteeing national and international interoperability of data and telecommunications technology and processes.
standards
Data communication standards fall into two categories:
de facto (by fact)
de jure (by law)
standards that have not been approved by an organized body but have been adopted as standards through widespread use.
de facto (by fact)
those standards that have been legislated by an officially recognized body.
de jure (by law)
physical structures
point-to-point
multipoint
provides a dedicated link between two devices.
point-to-point
its connection is one in which more than two specific devices share a single link.
multipoint
is the physical and logical relationship of nodes in a network. It is the schematic description of a network arrangement, connecting various nodes through lines of connection.
network topology
means placement of various nodes.
physical
means it deals with the data flow in the network
logical
types of topologies
mesh
star
bus
ring
hybrid
every device has a dedicated point-to-point link to every other device.
mesh topology
Mesh has ___ physical channels to link n devices.
n(n − 1)/2
types of mesh topology
partial mesh topology
full mesh topology
some of the nodes are connected but only with fewer connections for the same number of nodes.
partial mesh topology
every node connects to every other node.
full mesh topology
each device has a dedicated point-to-point link only to a central controller, usually called a hub or a switch.
star topology
every node is attached to one shared bus cable.
- Transmits data only in one direction
- Every device is connected to a single cable.
bus topology
each device has a dedicated point-to-point connection with only the two devices on either side of it.
- Data is transferred in a sequential manner that is bit by bit. Data transmitted has to pass through each node of the network, till the destination node.
ring topology
is a mixture of two different types of topologies.
- Inherits the advantages and disadvantages of the topologies included
- Combination of two or more topologies
hybrid topology
category of networks
local area network (LAN)
wide area network (WAN)
metropolitan area network (MAN)
a group of computers connected to each other in a small area.
- Less costly as it is built with inexpensive hardware such as hubs, network adapters, Ethernet cables, etc.
- Faster data transfer.
- High Security
local area network (LAN)
a network that extends over a large geographical area such as states or countries.
- Spans over a large geographical area through telephone line, Fiber optic cable, or satellite links.
wide area networks (WAN)
a network with a size between LAN and WAN.
- Normally covers the area inside a town or a city.
- Government agencies use MAN to connect the citizens and private industries.
metropolitan area networks (MAN)
it is a conceptual framework used to describe the functions of a networking system
OSI Model or Open Systems Interconnection
OSI Model uses _____ to give visual description of what is going on with a particular networking system
layers
7 layers of OSI
Physical
Data Link
Network
Transport
Session
Presentation
Application
End User layer (HTTP, FTP, IRC, SSH, DNS)
Application
Syntax layer (SSL, SSH, IMAP, FTP, MPEG, JPEG)
Presentation
Synch and send to port (API’s, Sockets, WinSock)
Session
End-to-end connections (TCP, UDP)
Transport
Packets (IP, ICMP, IPSec, IGMP)
Network
Frames (Ethernet, PPP, Switch, Bridge)
Data Link
Physical Structure (Coax, Fiber, Wireless, Hubs, Repeaters)
Physical
it was established in 1947, dedicate to worldwide agreement on international Standards
International Standards Organization
International Standards Organization (ISO) was established in ____
1947
An ISO standard that covers all aspects of network communication is the _____
Open Systems Interconnection Model (OSI)
Open Systems Interconnection Model was first introduced in the late ______
1970s
it is used by Network Applications
Application layer
it enables the user to access the network. It provides user interfaces and support for services
Application layer
Network services of Application layer
File Transfer – FTP (File Transfer Protocol)
Web Surfing – HTTP/S (Hypertext Transfer Protocol)
Emails – SMTP (Simple Mail Transfer Protocol)
Virtual Terminals – TELNET
it receives data from applications layer. These data are in the form of numbers or characters.
Presentation layer
it is concerned with the syntax and semantics of the information exchanged between two systems
Presentation layer
it converts data to binary format for the machine to understand
Translation
it reduces the number of bits that are used to represent the original data
data compression
it enhances the security of the data
encryption
it is used in the encryption and decryption of the data
Secure Sockets Layer (SSL)
it helps in setting up and managing connection enabling sending and receiving of data followed by termination of connections or sessions
Session layer
it keeps track of the files being downloaded
Session layer
the session layer allows a process to add checkpoints, or synchronization points, to a stream of data
Synchronization
it allows the communication between two processes to take place in either half-duplex or full-duplex mode
Dialog control
a process of verifying the user
authentication
a process used by server to determine if the user have the permission to access a file or a site
authorization
it is responsible for process-to-process delivery of the entire message
Transport layer
it provides enhancements to the services of the network layer. Its main tasks are to ensure that data sent from one computer arrives reliably, in the correct sequence and without errors at the receiving computer
Transport layer
data received from session layer is divided into small data units called
segmentation
segments
data received from session layer is divided into small data units called ____
segments
Each segments contains a ____ and ____
source and destination port and sequence number
In _____, transport layer controls the amount of data transmitted to a level that the receiver can process
Flow Control
In ____, if some data units never arrive the destination, transport layer uses Automatic Repeat Request schemes to retransmit the lost or corrupted data
Error Control
2 protocols in transport layer
Transmission Control Protocol
User Datagram Protocol
- Connection-Oriented Transmission
- Gives feedback, therefore data that is lost can be retransmitted.
- Internet surfing, Emails, FTP, etc.
Transmission Control Protocol
- Connectionless Transmission
- No Feedback whether data is really delivered or not
- Streaming, Music, Gaming, Voice calls, DNS, etc.
User Datagram Protocol
it works for the transmission of received data segment from one computer to another located in different networks
network layer
IP addressing (IPv4 or IPv6) is done in network layer
logical addressing
it is a method of moving data packet from source to its destination. It is based on the logical address format of the logical addressing
routing
it is a method which choosing the best possible path for data delivery from source to destination
path determination
it receives packet from network layer which contains IP addresses of sender and receiver
data link layer
two kinds of addressing
logical addressing
physical addressing
it is done at network layer where sender and receiver’s IP Addresses are assigned to each data packet
logical addressing
it is done at data link layer where MAC addresses of both devices are assigned to receive the data packet
physical addressing
the data link layer divides the stream of bits received from the network layer into manageable data units called frames
framing
the data link layer divides the stream of bits received from the network layer into manageable data units called ____
frames
the data link layer imposes a flow control mechanism to avoid overwhelming the receiver
flow control
adding mechanism to detect and retransmit damaged or lost frames
error control
data link protocols are necessary to determine which device has control over the link at any given time
access control
it converts the binaries into signals (either electrical, radio or optical)
physical layer
it defines the interface between the device and the transmission medium. It also defines the type of transmission medium.
physical layer
its data consists of a stream of bits with no interpretation. To be transmitted, bits must be encoded into signals, electrical or optical
physical layer
the physical layer defines the duration of a bit, which is how long it lasts
data rate
the sender and the receiver clocks must be synchronized
synchronization of bits
concerned with the connection of devices to the media
line configuration
it defines how devices are connected to make a network
physical topology
it defines the direction of transmission between two devices
transmission mode
