Shared Flashcard Set

Details

Basic Communication Systems
Midterm Set
47
Computer Science
Graduate
04/27/2011

Additional Computer Science Flashcards

 


 

Cards

Term
T-1 Frame Format
Definition

n  Each DS-0 is called a time slot

n  8000 frames/sec * 8 bits/slot = 64 Kbps

n  24 * 8 (bits/slot) + 1 = 193 bits/frame

n  8000 Framing bits sent per second

n  8000 frames/sec * 193 bits/frame = 1.544 Mbps

Term
Half-Duplex Communication
Definition

A half duplex connection transmits data in both directions but in only one direction at a time. Example:  e-mail, CB radios (circa 1970s).

Term
How high up are LEO satellites and how many are needed to cover the earth?
Definition
Low Earth Orbit - 100 miles to 1000 miles (above Earth).  Requires 48-56 satellites to provide full Earth coverage.
Term
Do Parity Checks catch all transmission errors?
Definition

Cyclic Redundancy Checksum catches most error transmissions while Simple and Longitudinal parity checks only catch specific types of errors. So no, not all errors can be caught by parity checks.

Term

What is more efficient? Synchronous or Asynchronous connections

Definition

A synchronous connection is more elaborate but transfers data in a more efficient manner.  Asynchronous transmission is inefficient (about 20% of the bits are overhead – Start/Stop frames)

Term

What is roll call polling?

Definition
The mainframe polls (checking the terminal to see if it has information to send to the mainframe) each terminal in a round-robin (daisy chain) fashion.
Term

Terminal to Mainframe connections

Definition
These connections can either have point-to-point connection which is a direct, unshared (“dedicated”) connection between a terminal and a mainframe computer or a multipoint connection which is a shared connection between multiple terminals and a mainframe computer.
Term
What is a byte?
Definition
1 byte = 8 bits
Term
What is the most popular and prevalent LAN topology?
Definition
Star wired bus topology
Term

What is Jitter?

Definition

Jitter is the deviation in or displacement of some aspect of the pulses in a high-frequency digital signal.  As the name suggests, jitter can be thought of as shaky pulses.

Term

What does a Bridge do?

Definition
 Connects a LAN to another LAN using the same protocol
Term
What is the second name given to the Network Layer of the OSI Model?
Definition
IP Layer
Term
What is the key differentiator for 2G cellular service?
Definition

Start of all digital service

Term

What is a protocol?

Definition

Special set of rules that end points in a network connection use when they communicate.

Term
What is the difference between Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM)?
Definition
FDM is assignment of non-overlapping frequency ranges to each “user” or signal on a medium while TDM is sharing of the signal is accomplished by dividing available transmission time on a (transmission) medium among many users.
Term
What is the difference between logical and physical connections?
Definition

Logical connections exist in Software and Physical connections exist in hardware and cables

Term

Which Department of US Govt developed the TCP/IP protocol suite?

Definition

U.S. Department of Defense (DARPANET)

Term

Are Token Ring Topologies popular?

Definition
NO, these topologies are pratically extinct
Term

Are the vast majority of signals transmitted in networks analog or digital?

Definition
Digital signals are mostly transmitted over networks today
Term
Is digital considered to be 1s and 0s?
Definition
No, this is considered to be binary code.
Term
What standard is CSMA/CD known as?
Definition

802.3 standard

Term
What is more efficient? Synchronous TDM or Statistical TDM
Definition
Statistical Time Division Multiplexing as it offers a more efficient use of bandwidth
Term

What is attenuation?

Definition
Continuous loss of a signal’s strength as it travels through a medium
Term
Is the DSN signal system (DS-1s and DS-3)hierarchical?
Definition
Yes
Term
Is Instant Messaging a form of peer to peer communication/networking?
Definition
Yes
Term

What transmission media requires line of sight?

Definition

Licensed and Unlicensed Microwave Antennas

Term

What is a parity check and what does it do?

Definition
A technique of checking whether data has been lost or written over when it's transmitted between computers
Term

What three things can receivers do for error control?

Definition

Do nothing (discard the data), return an error message to the transmitter, fix the error with no further help from the transmitter

Term

What is the basic definition of Bluetooth technology?

Definition
 A radio frequency specification for short-range, point-to-multipoint voice and data transfer.  Typical link range is from 10 centimeters to 10 meters, but can be extended to 100 meters by increasing the power levels.
Term
What networking device is needed to make a LAN to WAN connection?
Definition
Router
Term
What is connection negotiation in regards to modems?
Definition
Ability of a modem to automatically fall forward or fall back to faster or slower speeds, respectively.
Term
What does a regenerator do?
Definition
Regenerates signal to comepensate for weakening of signal traveling through medium (attenuation)
Term
Define Frequency
Definition
The number of times a signal makes a complete cycle within a given time frame.
Term

How does Pulse Code Modulation work?

Definition

The analog waveform is sampled at specific intervals and the “snapshots” are converted to binary values

Term
What 3 ways can be used to convert digital data into analog signals?
Definition
3 types of modulation can be used: Frequency, Phase and Amplitude
Term
What dual capabilities does a channel bank possess?
Definition
Acts as a multiplexor and an analog-to-digital conversion device
Term

What does White Noise (Gaussian Noise) do to a signal?

Definition

It’s relatively constant and can be reduced but if too strong can completely disrupt signal

Term

 What is the sliding window protocol and what does it do?

Definition
A technique, also known as windowing, is used by the Internet's Transmission Control Protocol (TCP) as a method of controlling the flow of packets between two computers.  TCP requires that all transmitted data be acknowledged by the receiving host.  It is a method by which multiple packets of data can be affirmed with a single acknowledgment.
Term
What are the basics of OSI Model Layers 1 and 2
Definition

Layer 1 – Physical Layer - Defines hardware specs such as Transmission Rate, Bit encoding method and Cable types.  Responsible for establishing, maintaining, and terminating physical connections between communicating devices.

Layer 2 – Data Link Layer - Responsible for taking the data and transforming it into a frame with header, control and address information, and error detection code.  Sets up communications link between hardware devices.

Term

Which OSI Layer was broken into 2 sublayers and what are those layers?

Definition

Data Link Layer and the sublayers are Logical link control (LLC) sub layer and Medium access control (MAC) sub layer

Term
What are the 3 concepts that make cellular technology work?
Definition

Frequency Reuse, Frequency Agility, and Call Handoff

Term
How does an Ethernet switch work?
Definition

On an Ethernet local area network (LAN), this device determines - from the physical device (Media Access Control or MAC) address in each incoming message frame  -   which output port to forward it to and out of.

Term
What is a MAC address?
Definition
The Source Address - identifies the hardware number hardcoded into the NIC (Network Interface Card) of your workstation.  It can also be known as the “serial number” for your workstation on the network.
Term
What are the 4 components that make up interface standards?
Definition
Functional, Procedural, Mechanical, and Electrical
Term
What is the OSI Model?
Definition
A standard description or "reference model" for how messages should be transmitted between any two points in a telecommunication network.
Term
What is a port?
Definition
In programming, a port (noun) is a "logical connection place" and specifically, using the Internet's protocol, TCP/IP, the way a client program specifies a particular server program on a computer in a network.
Term
What is a router?
Definition
A device or, in some cases, software in a computer, that determines the next network point to which a packet should be forwarded toward its destination.   It is connected to at least two networks.
Supporting users have an ad free experience!