SCSC 412 midterm (60 minutes, 100 pt)

nullpitNetworking and Communications

Oct 23, 2013 (3 years and 10 months ago)

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1


SCSC
4
12


midterm (60 minutes, 10
0 pt)

I.
Completion (2
8

pt
, answer

with acronym is OK)

1. ____ applications have specific throughput requirements.
Elastic

applications can
make use of as much, or as little, throughput as happens to be available.

2.
Port numbers are assigned in various ways, based on three ranges:

0
-
1023 are _____,

1024
-
49151 are _____
, and
49152
-
65535 are
Dynamic and/or
Private

Ports
.


3
. Each URL has two components:
t
he
______
and _____.

4
. A HTTP Request message contains
request li
ne
,
___, and entity body.

5
. FTP protocol uses port 20 as _____ and port 21 as ____.

6
. The mail receiver's user agent normally uses ____ protocol or ____ protocol to
retrieve

emails.

7
. The DNS protocol runs over ___ protocol and uses port ___.

8
.

The j
ob of gathering

data chunks at the source host from different sockets,
encapsulating each data chunk with header information to create segments, and
passing the segments to the network layer is called ___________. The job of
delivering the data in a tran
sport
-
layer segment to the correct socket is called _______.

II. T
rue
/

F
alse

(
9

pt)

1.

UDP header include source port, destination port, length and checksum.

2.

UDP at the sender side performs the 1s complement of the sum of all the 8
-
bit words
in the
segment.

3.

SMTP is primarily a pull protocol.

4.

Every organization with publicly accessible hosts on the Internet must provide
publicly accessible DNS records, which are stored at a Top
-
level domain (TLD)
server.

5.

In Bit Torrent, a
host

uses a clever trading algorithm to determine, which chuck to
request from her neighbors.

6.

Many
W
eb sites use cookies

to store state information. The cookie files are store at
Web server.

7.

SMTP
normally uses intermediate mail servers for sending mail.

8.

Simil
ar to HTTP, FTP is a stateless protocol.

9.

In a type MX DNS record, the value is
mail

server associated with name
.

2


10.

In packet switching network, the resources needed along a path to provide for
communication between the end
-
systems.


III. Short Answer (6
8

pt
, answer sheet)



































3


SCSC 412


midterm (
60 minutes, 100 pt)

Name
_____
__
______________

I. Completion (2
8
pt)

1

2

3

4

5

6

7

8


II. True / False (
10
pt)

1

2

3

4

5

6

7

8

9

10


II
I
. S
hort Answer

(6
2

pt
.
You

must show steps to get full credit at any calculation questions.)

1
.
List

at least

four
physical media used in the Internet

(
5
pt)






2. Draw OSI reference model.

What does OSI stand for?


(5 pt)





4


3
.
Draw the interaction (i.e. message flow) of the various DNS servers when using
iterative

query
. (Assume there is no caching.) Also
mark

a

sequence
number
for

each
message to indicate its order.

(
5

pt)


4
.
What are the

f
our
s
ources of Packet Delay
? (
10 pt)







5
.
To design a reliable data transmission RDT, a number of protocols are built. 1)
Specify the assumption of RDT2.0


2) What is the mechanism of RDT2.0 to handle
transmission errors?
(10 pt)




5


6
. What is the difference of
a
UDP socket and
a
TCP
socket

is

identified
at transport
layer?
(10 pt)






7
.



The above formula is the time of file distribution in P2P network

1) E
xplain the meaning of terms: F, Us, di, N, Ui

2)
From this formula,
explain why P2P file sharing is more efficient than traditional
client/server file
sharing. (
1
0

pt)






8. Two hosts A and B are separated by
4
0,000 km, and are connected by a direct link of R= 1

Mbps. The propagation speed over the link is 2x10^8 m/s. 1) Sending a file of 500,000 bits from
host A to host B. Suppose the file is sent continuously as one large message.

1
) What is the
width of a bit in the link? 3) From host A starts sending the fi
le, how long it takes for the last bit
of this file arrives host B? (
10

pts)