Quiz 1 Content (Ch. 1&2) Flashcards
Define: Distributed Systems
a computer network made to appear as a single coherent entity
Define: Computer Networks
Autonomous computers that are often connected by a single technology
Identify the two contrasting categories of network hardware technologies.
broadcast vs point-to-point
In a short phrase, indicate the essential conclusion from theoretical work in data communication during the 1920s and 1940s
finite capacity
For fibre optical technology,
the benefit is?
the challenge/ limitation is
benefit -> substantial capacity (how much info you send)
challenge -> electro-optical conversion
Identify the two promary design issues for the data link layer
Error handling and flow control
Identify four generally accepted levels of networking based on scope of area
PAN (personal area network)
LAN (local area network)
MAN (metropolitan area network)
WAN (wide area network)
Define: Protocol
An agreement between communication entities or roles and conventions to follow
The two forms of communication that can be supported by protocols are
connection-oriented and connectionless
The Nyquist formula for maximum data rate depends on two aspects:
channel bandwidth and number of discrete signal levels
Whaat is a key physical difference of coaxial cable related to twisted pair?
And what is the benefit?
difference -> Shielding
Benefit -> More bandwidth
What is the main reason for the layered architecture used in networking?
To reduce complexity (details of each layer hidden from the layer above)
Identify issues that protocols in various network layers should address
- flow control
- congestion
- error detection
- quality of service
- security
- data integrity
The shannon formula for maximum data rate depends on two aspects
channel bandwidth and signal-to-noise ratio
A single-bit-correcting Hamming code has m message bits and r redundant bits. How many valid code words?
Invalid but correctable code words?
valid -> 2^m
invalid -> nx(2^m)
where n = r + m
What technique can help address the possibility of burst errors?
Interleaving (reordering of bits)
Compare the achknowledgement frame contents between Protocol 2 (simplex stop-and -wait) and Protocol 3 (PAR). Identify any difference(s) between them.
Stop-and-wait: ack frame itself is sufficient - no contents needed
PAR: need sequence number information in the ack frame because errors can occur
In Protocol 3 (PAR), how does the receiver know that an ack frame transmission sicceeded? A brief but technically pecific answer is expected for this question.
For PAR, sequence number must be 0 or 1. After reciever transmits an ack, if it recieves a message with sequenece number opposity of the last ack, that means sender has seen ack and advanced to next packet.
What is the purpose of the physical layer?
Transport bits from one machine to another
What is the most important element that makes packet delivery possible?
Internet Layer
What did Nyguist realize (in 1942)?
That a perfect channel has a finite capacity for data transmission
What did shannon do in 1948
Carried Nyguist’s idea to a noisy channel and also proved important sampline theorem
Why are twisted wire pairs used?
Cancel radiation and use differential signaling for immunity to noise
What is the crudest (most basic form) of Guided transmission media?
vehicle carrying recorded media
