3213 Quiz 1 Flashcards
What is ARPANET
-Type of connection, and name?
Computer to computer network
Wide area network
How does ARPANET work
Switched network infrastructure
Packets of fixed size
What is circuit switching? (Wired telephone network)
Pros/Cons?
Dedicated path between 1 or more links
Pros: Guaranteed QoS, fixed transmission rate, no data loss
Cons: Inefficient, and complex. One connection suffocates link vs packet switching
What is Packet switching (ARPANET, Internet, 3G+)
Pros/Cons?
No dedicated path, packets transmitted independently.
Pros: links shared by many packets, packets accepted even under heavy traffic.
Cons: No QoS guarantee, packet delay/loss during traffic, overhead encapsulation traffic.
LAN network topologies
Bus Topology
- Simple/inexpensive
- Single point of failure, collision = diminishing capacity
Ring Topology
- small frame (token) circulates dictating who can transmit data
- Fair access
- Breaks if any link fails
Star topology
- Each station connected directly to central node
- Central node broadcast and/or switch
Hub vs Switch?
Only one station can transmit otherwise collision occurs, and broadcast data to all connected computers
Switch: Sends data only to specified computers.
IP Addressing (Address format + Routing)
IP Address = Net ID + Host ID
IP Packets are routed only based on Net ID in destination IP Address
- Only has to know major networks/ smaller routing table -> Faster routing
What is a protocol and its data unit type?
Set of rules that govern how two or more entities in a layer are interacting
ex: HTTP, TCP, IP
Communicate by exchanging Protocol Data units (PDU’s)
What are services
Services wrapped in PDU’s, available at Serice Access Points (SAP)
layer n+1 transfers info by invoking services by layer n
What is a Data link layer?
4 Main actions
Attempts to provide reliable communication over physical layer(same network)
Divides stream of bits into frames
adds header to specify address of receiver (MAC)
Adds trailer to header to detect/recover lost frames
Flow control
What is a Network Layer
- Addressing, Routing, frag
Oversees delivery of packets between devices across multiple networks/links
- Logical addressing / scale to large networks
- provides routing for optimal path across large internetwork
- Fragmentation and reassembly of packets to accommodate different media.
What is a transport layer?
Purpose
Network layer gets packet to receiver, transport gets entire message to correct process on receiver.
- Reliable mechanism for process to process
- Ensures data units are delivered error free, in sequence, with no loss/dup
Transport Layer supporting purpose
- Addressing, segment, flow
Port addressing: Specifies port address to send to receiver
Segmentation and reassembly: Divide into segments containing sequence number, to reassemble message correctly, and identify/replace missing packets.
Flow and error control: Performed end to end
The application layer does what?
Provides actual service/ interface to the user
OSI Downfall reason?
TCP/IP Launched same time with 5 layer, less complex, more efficient
TCP/IP Address model
Port address: Locally unique to differentiate different applications using same IP Address
IP Address: Globally unique, corresponding node in entire internet.
Physical Address: Globally Unique, or MAC Address, used to locate on LAN
TCP/IP Encapsulation Model
TCP Header contains source and destination port numbers
IP Header contains source and destination IP addresses (Transport and protocol type)
D.L Header contains source and dest. MAC addresses (network protocol type)
Analog Data
Refers to info that is continuous, continuous values in some interval
Digital Data
Refers to discrete states, finite/countable number of values in range
How many links for Mesh, ring, bus, and star topology
Mesh = n(n-1)/2
Ring = n links
Bus = n+1 (backbone link required)
Star = n + 1 (backbone link required)
Sine wave components
Simple - cannot be decomposed further
Peak amplitude
Frequency
Phase
Phase and deg/rad conversion
%offset respect to time = 0
360 = 2 pi rad
radians = degrees * pi / 180
Freq/period relation
Frequency = completed cycles per second
Freq = 1/T
Period = Time to complete 1 cycle
Period = 1/f
Inversely proportional
If composite signal is periodic, decomp of signals give signals with?
discrete freq
If composite signal is non-periodic, decomp of signals give signals with?
continuous freq
f is referred to as? (ex: freq = 3f)
int multiples of f are referred to as?
fundamental frequency
harmonics
bit interval?
bit rate?
time required to send single bit
number of bit intervals per second
A digital signal has 8 levels. How many bits can be represented per level?
log base 2 (8) = 3
3 bits represented per level
digital signal, with all its
sudden changes mean what?
composite signal with infinite # of frequencies
Note: To create a perfect square wave of a composite signal, we must add all harmonic frequencies up to infinity to flush out the square shape.
Thus infinite # of frequencies.
Bandwidth of a composite periodic analog signal is found how?
Why not digital?
Difference between highest and lowest frequencies in that signal
(B = f high - f low)
Digital has infinite frequency
A nonperiodic composite analog signal has a bandwidth of 200 kHz,
with a middle frequency of 140 kHz and peak amplitude of 20 V.
The two extreme frequencies have an amplitude of 0. What is the lowest freq, and highest?
low=40, high = 240
