Transcript Jeopardy-application - CSE Labs User Home Pages

CSCI 4211
Introduction to Computer Networks
Jeopardy Review
Application Layer
Rules
• Up to 5 groups. Group membership will be
determined before break.
• After the questions show up, the team
raises the # card first to get called on
and MUST start to answer the question
when TA calls on them within 20 seconds
• Each team determines one spokesperson
to shout out the answer
• Each team gets one AND ONLY ONE
answer per question
Difference from normal Jeopardy! game
• Questions are given, you provide the answer.
(not vise versa)
• Only one Jeopardy Round.
• For fairness, each group gets one question at
a time.
• When a group cannot answer the question, it
is up for grabs. The first group that raises
their card get to answer the question.
Other logistics
• Phil is in charge of book keeping on white
board (one score per group).
• To ensure the smoothness of the game,
lecturer makes the FINAL decision whether
an answer is correct or not, we can resolve
disagreement later.
• Some questions were picked from previous
midterms and finals.
Extension at stake
The winning team wins 24 hours
for late submission of an
assignment.
Click to begin.
Level
a
b
c
d
e
Easy
100 $
100 $
100 $
100 $
100 $
Medium
200 $
200 $
200 $
200 $
200 $
Hard
300 $
300 $
300 $
300 $
300 $
Daunting
400 $
400 $
400 $
400 $
400 $
Impossible
500 $
500 $
500 $
500 $
500 $
Question 1a
The name of an internet application
protocol for which the applicatiion
listens to the port number 80 is
______
Answer 1a
HTTP
BACK
Question 2a
A special application layer protocol
that is essential to the operation of
other Internet applications, such as
HTTP is __________
Answer 2a
DNS
Domain Name System
BACK
Question 3a
Name three protocols commonly
used for sending and receiving
emails
Answer 3a
SMTP
IMAP
POP3
BACK
Question 4a
(T/F) Both HTTP and TCP are
examples of transport layer protocols
that provide reliable data transfer
between application processes.
Answer 4a
False. HTTP is an application
layer protocol
BACK
Question 5a
How many DNS requests are needed to
resolve the domain name www.b.com
iteratively
root DNS server
2
3
Answer 5a
TLD DNS server
.com
4
5
local DNS server
Dns.a.com
1
8
If not cached, at least 4
7
6
authoritative DNS server
dns.b.com
m.a.com
www.b.com
BACK
Question 1b
How many sockets in total are
created at both client and server
sides, when 11 users query a DNS
server at the same time?
Answer 1b
1 socket at the server side, 11
sockets at the client side, in
total 12.
BACK
Question 2b
Name one advantage of packetswitching over circuit-switching
Answer 2b
More efficient, bandwidth sharing,
allocation of bandwidth based on demand
BACK
Question 3b
Name at least two key functions
provided by TCP and not provided by
UDP
Answer 3b
Reliable data transfer, flow control, congestion
control
BACK
Question 4b
State whether you agree with this
statement or not: An overlay network
represents a graph in which the vertices
represent hosts, routers and all network
devices and edges are connections
between these entities? Please explain
your answer.
Answer 4b
Wrong.
Nodes are only peers and edges are TCP
connections between peers
BACK
Question 5b
Name 2 problems with the centralized
architecture in p2p?
Answer 5b
Single point of failure and performance
bottleneck
BACK
Question 1c
What is the difference between a host
and an end system.
Answer 1c
No difference
BACK
Question 2c
(T/F) DNS queries are transmitted over UDP, because they
are sent over reliable network layer connections.
Answer 2c
False. UDP is transmitted over IP which is not
reliable.
BACK
Question 3c
What information is needed by a
process running on one host to identify
a process running on another host?
Answer 3c
The IP address of the destination host
and port number of the destination
scocket
BACK
Question 4c
In a scenario in which a client
retrieving a web document from a
server the IP address of which is
unknown, what are the application
and transport layers protocols needed
Answer 4c
App: DNS and HTTP
Transport: UDP for DNS and TCP for
HTTP
BACK
Question 5c
(T/F) Packet
switching is used in
computer networks because it is fast.
Answer 5c
False. Circuit-switching can be as fast. Packet-switching is
used for resource utilization
BACK
.
Question 1d
(T/F) Both HTTP and TCP are
examples of transport layer protocols
that provide reliable data transfer
between application processes.
Answer 1d
False. HTTP is an application layer.
BACK
Question 2d
(T/F) DNS uses UDP to transfer DNS
queries and replies because UDP is more
efficient.
Answer 2d
True
BACK
Question 3d
What is meant by handshaking
protocols?
Answer 3d
A protocol in which the two
communicating entities first exchange
control packets before sending data to
each other.
BACK
Question 4d
For an organization’s web server and
mail server that have the same exact
alias for a host name, what information
in the DNS query needed to map the
hostname of the mail server to an IP
address?
Answer 4d
The “MX” record is used for the type of
the RR
BACK
Question 5d
Does web-caching reduce the delay of all
objects or only cached objects requested by
a user?
Answer 5d
Delay can be reduced even for unchached objects since caching reduces
traffic on links.
BACK
Question 1e
List 3 Internet applications and their
corresponding application layer
protocol
Answer 1e
Web: HTTP, file transfer: FTP,
remote-login: Telent
BACK
Question 2e
For each of the following applications,
list their corresponding application- and
transport-layer protocols:
E-mail, file-transfer and name
resolution
Answer 2e
E-mail: SMTP: TCP
File-transfer: FTP: TCP
Name resolution: DNS: UDP
BACK
Question 3e
Name 2 types of delays in packet-switched
networks?
Answer 3e
Processing delay, queuing delay,
transmission delay and propagation
dealy
BACK
Question 4e
Name one advantage and disadvantage of
p2p over traditional client-server
architectures (e.g. HTTP)
Answer 4e
Advantage: scalability
Disadvantage: Peer churn
BACK
Question 5e
Why do HTTP, FTP, SMTP and Pop3 run on top
of TCP?
Answer 5e
Because their associated applications
require that data be received in the
correct order and without gaps.
BACK
Question 1f
Answer 1f
Question 2f
Answer 2f
Question 3f
Answer 3f
Question 4f
Answer 4f
Question 5f
Answer 5f
Make your wager up to what you have
Write down the wager along with the
answer on the back of the index card.
Finish in 3 minutes!!!
Final Question
Suppose initially all ARP tables and
switching tables are empty. Suppose now
host A sends an IP data packet to host C.
How many Ethernet frames are sent?
Switch
A
Host
S1
D
S2
S3
B
C
Formal Class Evaluation
Lecturer: Tian He
TA: Pengkui Luo
TA: Jaehoon Paul Jeong
Term: Fall Current Year: 2009
Course ID: 24513
Section: 001
Your positive feedback is very
important to me and TAs! Thank you
Final Answer
14 frames
6 frames for the ARP request
4 frames for the ARP reply
4 frames for data
Question 1b
How many sockets are created
totally at both client and server
sides, when 11 users query a DNS
server at the same time?
Answer 1b
1 socket at the server side, 11
sockets at the client side, totally
12.
BACK