Cmpen/EE 362
Practice Exam 1 solution.
Fall 2010
Problem 1 [28 crs., 4 each] For each of the following
statements choose the one best answer.
Solution in bold
1. In connecting N communicators to a central office as opposed
to a separate connection between
Compen/EE 362
Exam 1 Solution
Fall 2013
Problem 1. [36 crs., 4 each] For each of the following statements choose the one best answer.
Solution in bold
1. If a frame contains C check bits and K bits of data and overhead for a total of N = K + C bits,
the c
NOISE: Random disturbances, usually
additive
Thermal noise
Burst-type noises
Impulse noise
Atmospheric noise
THERMAL NOISE
Due to random electron motion
Proportional to absolute
temperature
Proportional to bandwidth
Spectral density concept:
S(f) measures
Before studying all the details from bottom to
top layers, it is useful to get an overall view of
basic networks.
Switching and routing are complex tasks,
Different networks perform switching and
routing differently.
Also:
how networks developed
how layer
M ultiplexing
M any users sharing a common link cable, wire or optical fiber.
Reason for multiplexing
One high capacity link serves many
users needs simultaneously.
Categories of multiplexing
1. Time division multiplexing.
Synchronous time division multip
June 20, 2011
EE 362 , Summer 2011
Homework 1
Pennsylvania State University
Michael Lin
Homework 1 Solutions
103
Note: the book uses
bits for 1 kb, 106 bits for 1 Mb, etc. I will accept both this usage and the
traditional 1 kb = 1024 bits usage.
Problem 2
Error Detection and Error Correction
We have seen that with c check bits,
the chance of undetected error is about
2-c.
If there is no possibility of
retransmission, error correction can
reduce the number of incorrectly
received packets.
A best option is t
Protocol Verification
Communication protocols with
feedback acknowledgments often are
complex.
There are important models for formal
verification of protocols.
These are based on Finite State
Machine models and Petri Nets.
Time does not permit study of th
Return to Link Error detection and
correction
k = number of "data" bits in the frame.
c = number of checking bits.
n = k+c = total frame length, excluding flags.
Example: c = 3 check bits, k = 4 data bits.
[ P1 P2 P3 ] = [ D1 D2 D3 D4 ]
P1 = D1 + D2 + D4
Additional on error correction on a noisy link:
The added correction redundancy is needed
only on the noisy link.
Chapter 4: Medium Access Control
Sublayer
This chapter deals with broadcast channels.
In a broadcast channel, a message sent goes
through som
Carrier Sense Multiple Access (CSMA) and
with collision detection CSMA/CD.
CSMA/CD forms basis for ETHERNET.
By listening before transmission, the chance
of collision is greatly reduced, especially if
propagation time < frame duration.
But there still can
Sections 1.5.2 - 1.5.4 deal with specific networks
(discuss later) - X.25, Frame Relay, ATM, Ethernet.
Sec. 1.6 - Standardization - read for details.
Compatibility, economies of mass production.
De facto- standards that arose from popular use.
De jure- fo
Communication Satellites
Satellites primarily receive signals
from earth in a certain frequency band,
amplify them and retransmit in a
different frequency band.
Most common is the Geostationary
Orbit - at an altitude of 35,800 km.
Allocation of position a
Computer Networking has grown
rapidly
Mainly through the Internet.
As capabilities of the network have
grown, applications using the network
have grown even faster.
General Capabilities of Computer
networks
# gathering information
# processing of informat
June 28, 2011
EE 362
Homework 2 Solutions
Pennsylvania State University
Michael Lin
Homework 2 Solutions
Problem 7
The total amount of time to get the IP address is:
RTT1 + RTT2 + + RTTn
Once the IP address is known, it takes RTT0 time to set up the TCP c
CMPEN/EE 362 Midterm Extra Credit
Name:
Pick one of the two following questions to do.
Summer 2011
Grade:
1. (6 points) Probability
Consider sending a le of length L bytes over a network route consisting of N links, each with
identical packet loss probabi
Cmpen/EE 362
Asst. 6
Fall 2013 Due Friday October 18
Problem 1. In slotted ALOHA, suppose 10 senders send independently with probability 0.1 each
and 1 sender sends independently with probability 0.3. Assume if there is a collision there is no
success. Wh
CSE/EE 362
Asst. 8
Fall 2013 Due Nov. 1
Problem 1. In the following network the costs are the same in both directions.
a) Find the tree of best routes from A to each of the different destinations.
b) Find the minimum weight spanning tree for minimum cost
CSE/EE 362
Asst. 7
Fall 2013 Due October 25
Problems 1,2.Text Problems 4.27, 4.39
Problem 3. Consider the collision resolution splitting algorithm example in Lecture 18, page 4.
Suppose instead the three numbers are: A = .3, B = .55 and C = .65.
a) Draw t
CMPEN/EE 362
Asst. 11
Fall 2013
Due Friday, December 6
Problem 1-3.Text Problems 6-23, 6-27, 7-4
Problem 4. Suppose host H needs to use some resource that can be supplied by source SA at a
cost of 5 or from source SB at a cost 15. But SB will send the res
Compen/EE 362
Asst. 5
Fall 2013
Due October 11
Problem 1. Make the assumption transmission is over a single link, so frames cant jump over
each other in time.
a) Consider a go-back protocol with 3-bit sequence numbers and a window range of 7
frames. After
UNGUIDED MEDIA
Electromagnetic radiation omnidirectional or directed
Wireless advantages
Communication from anywhere Mobile communication
Fixed devices - save on installing
wires or optical fiber.
Disadvantages
Less private
Interference with other wireles
Wireless LAN protocols
In a building, a room could be a cell, with
one base station. The base stations could be
wired together with high speed links.
Equipment in the rooms can communicate
wirelessly: Possibly directly to equipment in the
same room, or vi
Quality of Service
The network wants low congestion for better
performance.
The user needs a good quality of service.
Show Fig. 5-27 (old Fig. 5-30)
In delay, Low means low sensitivity to delay
(or jitter), not low delay (or jitter).
High means high sensi
The label switching idea - MPLS
(Multiprotocol Label Switching).
This is basically the same idea as Virtual
Circuit Switching in ATM or Frame Relay,
except applied to Datagram networks.
Uses a label, like a virtual channel number
in VC switching, instead
Propagation Delay in CMOS Logic
Lecture 42 Page 1
EE 310 Lecture 42
Propagation Delay in CMOS Logic (Continued)
Lecture 42 Page 2
EE 310 Lecture 42
CMOS Logic - NOR Gates
EE 310 Lecture 42
Mechanical Switch Analogy:
A
B
Y
Y = A +B
Truth Table:
A
0
0
1
1
B
Cmpen/EE 362
Practice Exam 2
Fall 2010
Problem 1.[20 crs. 4 each] For each of the following statements choose the one best answer.
Answers in bold.
1) In CSMA/CD Ethernet, A and B are separated by seconds of propagation. Let the frame
duration of all fram
Penn State University
School of Electrical Engineering and Computer Science
CMPEN/EE 362 Computer Networks, Problem Set 2
Due Wednesday September 16, 2015 in Class
Solve the following problems from the text book:
1- Problem 2.2
A noiseless channel can car
Penn State University
School of Electrical Engineering and Computer Science
CMPEN/EE 362 Computer Networks, Problem Set 1 Solution
Due Friday September 4, 2015 in Class
Solve the following problems from the text book:
1- Problem 1.1
The dog can carry 21 g
Penn State University
School of Electrical Engineering and Computer Science
CMPEN/EE 362 Computer Networks, Problem Set 5 Solution
Due Friday October 23 (changed to Monday Oct 26), 2015 in Class
Solve the following problems from the text book:
1- Problem