Yarmouk University Hijjawi Faculty for Engineering Technology Computer Engineering Department CPE-562 Computer Networks Final Exam: A Date: 09/01/12

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Yarmouk University

Hijjawi Faculty for Engineering Technology

Computer Engineering Department

CPE
-
562 Computer Networks

Final Exam: A

Date:
09/01/12


Student Name
:
------------------------------------------------------------------------------------------

Student Number:
------------------------------------------------------------------------------------------



INSTRUCTIONS (please read carefully)

1.

TURN OFF YOUR
CELL PHONE
NOW

2.

Time allowed 120 minutes

3.

Provide your answers on this page. Answers elsewhere will not be looked at.

4.

Return all pages.

5.

Provide only
one answer

to each question. Giving more than one answer for the same question
will result in zero credit for

that question.

6.

Mark the right answer with (×).




A

B

C

D

E



A

B

C

D

E



A

B

C

D

E

1







18







35






2







19







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3







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37






4







21







38






5







22







39






6







23







40






7







24







41






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26







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10







27







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13







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14







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15







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1.

Whi ch of the fol l owi ng statements i s
correct?

a.

Forwardi ng and routi ng are the
two most
i mportant functi ons i n a
datagram network

b.

Cal l setup and forwardi ng are the
two most i mportant functi ons i n a
datagram network

c.

Cal l setup and routi ng are the two
most i mportant functi ons i n a
datagram network

d.

Routi ng and Congesti on control are
the two most

i mportant functi ons
i n a datagram network

e.

Cal l setup and Congesti on control
are the two most i mportant
functi ons i n a datagram network

2.

Tradi ng i s used i n ____________.

a.

Skype

b.

Bi tTorrent

c.

Instant messagi ng

d.

Voi ce over IP

e.

Real
-
ti me vi deo conferenci ng

3.

Whi ch of
the fol l owi ng statements i s
wrong?

a.

RIP al l ows mul ti ple same
-
cost
paths

b.

Al l OSPF messages authenti cated

c.

OSPF adverti sements are
di ssemi nated to the enti re AS vi a
fl oodi ng

d.

RIP routi ng tabl es are managed by
an appl i cati on
-
level process

e.

Poi son reverse i s used
i n RIP to
prevent pi ng
-
pong l oops







4.

Consi der a si ngl e sender and 32 recei vers.
Suppose the sender i s connected to the
recei vers by a bi nary tree of routers. What
i s the cost of sendi ng a broadcast packet
usi ng the uni cast approach to achi eve
broadcast?

Here, each ti me a packet (or
copy of a packet) i s sent over a si ngl e l i nk, i t
i ncurs a uni t of cost.

a.

32

b.

64

c.

96

d.

128

e.

160

5.

Gi ven the IPv4 address 1001 1100 0000
0101 1000 0110 1110 0011. Usi ng the
a.b.c.d notati on, what i s thi s address?

a.

156.5.134.227

b.

9.192.88.110

c.

192.88.110.3

d.

78.2.67.113

e.

Thi s i s not an IPv4 address. So, i t
cannot be represented usi ng the
a.b.c.d notati on

Questions (6


8)
: A 3480 octet datagram (consi sti ng
of 3440 TCP payl oad pl us 20 octet TCP header pl us
20 octets IP header) i s to be
transmi tted and needs
to be fragmented because i t wi l l pass through an
Ethernet wi th a maxi mum payl oad of 1740 octets.

6.

What i s the val ue of the Total Length fi el d
of the fi rst fragment?

a.

1700

b.

1720

c.

1740

d.

1760

e.

3480

7.

What i s the val ue of the Offset fi el d of the
thi rd fragment?

a.

214

b.

215

c.

428

d.

430

e.

There i s no thi rd fragment


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8.

Whi ch of the fol l owi ng fragments has a
val ue of 0 i n the More Fl ag fi el d?

a.

The fi rst

b.

The second

c.

The thi rd

d.

The fourth

e.

The fi fth

9.

To whi ch of the fol l owi ng protocol s proxy
servers are i mportant?

a.

FTP

b.

DNS

c.

HTTP

d.

SMTP

e.

POP3

10.

Gi ven that at ti me t: Sampl eRTT = 10 ms,
Esti matedRTT = 20 ms, DevRTT = 3 ms. Fi nd
the ti meout i nterval at ti me t+1.

a.

36.5 ms

b.

11.2 ms

c.

4.75 ms

d.

18.3 ms

e.

27.5 ms

11.

Whi ch of the fol l owi ng functi ons can be
consi dered among the most i mportant for
a
vi rtual
-
circuit network?

a.

Error control

b.

Fl ow control

c.

Congesti on control

d.

Cal l setup

e.

Securi ty

12.

Whi ch of the fol l owi ng protocol s uses UDP?

a.

DHCP

b.

FTP

c.

TELNET

d.

SMTP

e.

HTTP






13.

Suppose an ISP owns the bl ock of addresses
of the form 101.101.128/17. Suppose i t
wants to create four subnets from thi s
bl ock, wi th each bl ock havi ng the same
number of IP addresses. What are the
prefi xes (of form a.b.c.d/x) for the four
subnets?

a.

101.101.
128/19, 101.101.160/19,
101.101.192/19, 101.101.224/19

b.

101.101.128/20, 101.101.160/20,
101.101.192/20, 101.101.224/20

c.

101.101.128/21, 101.101.160/21,
101.101.192/21, 101.101.224/21

d.

101.101.128/22, 101.101.160/22,
101.101.192/22, 101.101.224/22

e.

101.101.128/
23, 101.101.160/23,
101.101.192/23, 101.101.224/23

14.

Whi ch of the fol l owi ng answers has correct
statement(s)?

a.

Forwardi ng tabl es are used i n both
datagram networks and vi rtual
-
ci rcui t networks. IP addresses are
used for forwardi ng i n both types
of networks.

b.

F
orwardi ng tabl es are used i n both
datagram networks and vi rtual
-
ci rcui t networks. IP addresses are
used for forwardi ng i n vi rtual
-
ci rcui t networks but not i n
datagram networks.

c.

Forwardi ng tabl es are used i n both
datagram networks and vi rtual
-
ci rcui t networ
ks. IP addresses are
used for forwardi ng i n datagram
networks but not i n vi rtual
-
circui t
networks.

d.

Forwardi ng tabl es are used i n
datagram networks but not i n
vi rtual
-
circuit networks.

e.

Forwardi ng tabl es are used i n
vi rtual
-
circuit networks but not i n
datagr
am networks.


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15.

Whi ch of the fol l owi ng choi ces has correct
statement(s)?

a.

RPF and Stei ner are exampl es of
the source
-
based tree

b.

RPF and Stei ner are exampl es of
the group
-
shared tree

c.

RPF i s an exampl e of the source
-
based tree. Stei ner i s an exampl e
of the grou
p
-
shared tree

d.

RPF i s an exampl e of the group
-
shared tree. Stei ner i s an exampl e
of the source
-
based tree

e.

Center
-
based tree i s an exampl e of
the source
-
based tree

16.

Suppose a router uses l ongest prefi x
matchi ng and has the fol l owi ng forwardi ng
tabl e


Prefix
Match

Interface

0001 0110 1000 1111 0101
1000 1

0

0001 0110 1000 1111 0101
1000 11

1

0001 0110 1000 1111 0101
1000 111

2

Otherwise

3


How many addresses are associated with
Interface 1?

a.

16

b.

32

c.

64

d.

128

e.

256

17.

Suppose there are three routers between a
source

host and a desti nati on host. Ignori ng
fragmentati on, an IP datagram sent from
the source host to the desti nati on host wi l l
travel over how many i nterfaces?

a.

2

b.

3

c.

5

d.

6

e.

8


18.

What does IMAP stand for?

a.

Internet Mai l Access Protocol

b.

Internet Management And
Provi di n
g

c.

Internet Mai l Address Protocol

d.

Internet Mai l Agent Protocol

e.

Internet Management Appl i cati on
Packet

Use the fol l owi ng fi gure for answeri ng questi ons
(19
-
23)
:


19.

Duri ng whi ch of the fol l owi ng i nterval s the
TCP sl ow start i s operati ng?

a.

[1,10]

b.

[6,16]

c.

[17,22]

d.

[6,22]

e.

[23,26]

20.

After whi ch transmi ssion round the
segment l oss i s detected by a tri pl e
dupl i cate ACK?

a.

1

b.

6

c.

16

d.

22

e.

23

21.

Assumi ng a packet l oss i s detected after the
26
th

round by the recei pt of a tri pl e
dupl i cate ACK, what wi l l be the val ue of the
congesti on wi
ndow si ze?

a.

1

b.

2

c.

4

d.

21

e.

32

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22.

Duri ng what transmi ssion round i s the 70
th

segment sent?

a.

6
th

b.

7
th

c.

8
th

d.

9
th

e.

10
th

23.

What i s the val ue of Threshol d at the 24
th

transmi ssion round?

a.

13

b.

21

c.

26

d.

32

e.

42

24.

Whi ch of the fol l owi ng statements i s
correct?

a.

Packet l oss may occur at
router’s
i nput ports but not at the output
ports

b.

Packet l oss may occur at router’s
output ports but not at the i nput
ports

c.

Packet l oss may occur at both
i nput and output router’s ports

d.

Packet l oss does not occur at
router’s i nput ports nor at the
output po
rts

e.

The network l ayer at the
desti nati on host has no way to
know to whi ch hi gher l ayer
protocol i t shoul d pass the
segment (that i s the payl oad of the
datagram)

25.

The DNS ___________ server i s the defaul t
name server

a.

Root

b.

TLD

c.

Authori tati ve

d.

Local

e.

Org

26.

The conc
ept of soft state i s used i n:

a.

RIP

b.

OSPF

c.

BGP

d.

IGMP

e.

DVMRP

27.

Whi ch of the fol l owi ng statements i s
correct?

a.

HOL bl ocki ng may occur at the
i nput port but not at the output
port

b.

HOL bl ocki ng may occur at the
output port but not at the i nput
port

c.

HOL bl ocki ng may occ
ur at both
the i nput and output ports

d.

HOL bl ocki ng does not occur at the
i nput port nor at the output port

e.

Router’s i nput ports use
central i zed swi tchi ng

28.

Whi ch of the fol l owi ng types of del ays
contri butes the most to congesti on?

a.

Processi ng del ay

b.

Transmi ssion del ay

c.

Propagati on del ay

d.

Queui ng del ay

e.

None of the gi ven choi ces

29.

Compani es and uni versi ti es typi cally use
_________ to get access to the Internet.

a.

Cabl e modem

b.

Ethernet

c.

ADSL

d.

Di al
-
up Modem

e.

Satel l i te

30.

Host A and B are communi cati ng over a TCP
conn
ecti on, and Host B has al ready recei ved
from A al l bytes up through byte 248.
Suppose Host A then sends two segments
to Host B back
-
to
-
back. The fi rst and second
segments contai n 40 and 60 bytes of data,
respecti vel y. Host B sends an
acknowl edgment wheneve
r i t recei ves a
segment from Host A. If the second
segment arri ves before the fi rst segment, i n
the acknowl edgment of the fi rst arri ving
segment, what i s the acknowl edgment
number?

a.

248

b.

249

c.

289

d.

348

e.

349

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31.

What source IP address shoul d be used i n a
DHCP request

message

a.

0.0.0.0

b.

255.255.255.255

c.

1.1.1.1

d.

255.255.0.0

e.

Any randoml y pi cked address

32.

Whi ch of the fol l owi ng appl i cations i s the
most ti me sensi ti ve?

a.

Web documents

b.

E
-
mai l

c.

Interacti ve games

d.

Fi l e transfer

e.

Stored audi o/vi deo

33.

Whi ch of the fol l owi ng statements i s
correct?

a.

When IPv6 tunnel s through IPv4
routers, the enti re IPv6 datagram
(i ncl udi ng header fi el ds) i s
encapsul ated i n an IPv4 datagram

b.

When IPv6 tunnel s through IPv4
routers, the enti re IPv4 datagram
(i ncl udi ng header fi el ds) i s
encapsul ated i n an IPv6 d
atagram

c.

When IPv6 tunnel s through IPv4
routers, the IPv6 datagram payl oad
(wi thout header fi el ds) i s
encapsul ated i n an IPv4 datagram

d.

When IPv6 tunnel s through IPv4
routers, the IPv4 datagram payl oad
(wi thout header fi el ds) i s
encapsul ated i n an IPv6 dat
agram

e.

When IPv6 tunnel s through IPv4
routers, the outer address i s an
IPv6 address







34.

Suppose datagrams are l i mi ted to 1500
bytes (i ncl udi ng header) between source
host A and desti nati on host B. Assumi ng a
20
-
byte TCP header and a 20
-
byte IP
header, ho
w many datagrams woul d be
requi red to send an MP3 consi sting of 4
mi l l i on bytes?

a.

2666

b.

2667

c.

2703

d.

2739

e.

2740

35.

Whi ch of the fol l owi ng uses of ICMP does
not requi re i ncl udi ng the fi rst 8 bytes of the
ori gi nal datagram?

a.

Echo repl y

b.

TTL expi red

c.

Desti nati on network
unreachabl e

d.

Source quench

e.

Bad IP header

36.

Wi Fi i s a protocol of the ___________ l ayer.

a.

Physi cal

b.

Li nk

c.

Network

d.

Transport

e.

Appl i cati on

Consi der the network shown bel ow for answeri ng
questi ons
(37
-
38)
. Suppose that AS1 and AS2 are
runni ng OSPF for thei r i ntra
-
AS routi ng protocol.
Suppose that AS3 i s runni ng RIP for
i ts

i ntra
-
AS
routi ng protocol. Suppose eBGP and i BGP are used
for the i nter
-
AS routi ng protocol.


37.

Router 1b l earns about
x

from whi ch
rout
i ng protocol?

a.

OSPF

b.

RIP

c.

eBGP

d.

i BGP

e.

DVMRP

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38.

Router 1a l earns about
x

from whi ch
routi ng protocol?

a.

OSPF

b.

RIP

c.

eBGP

d.

i BGP

e.

DVMRP

39.

Consi der a
si m
pl ex communi cati on over the
Internet:

a.

Encapsul ati on i s done at the source
onl y

b.

Encapsul ati on i s done at the
desti nati on onl y

c.

Encapsul ati on i s done at the router
onl y

d.

Encapsul ati on i s done at the source
and the router

e.

Encapsul ati on i s done at the source
and the desti nati on

40.

RIP: Consi der the fol l owi ng fi gure:


Suppose next that router D recei ves the
fol l owi ng adverti sement from
router A:


What i s the new di stance to go from router
D to subnet z?

a.

7

b.

8

c.

9

d.

10

e.

11




41.

Consi der a subnet wi th prefi x
101.101.101.64/26. Whi ch of the fol l owi ng
IPv4 addresses can be assi gned to thi s
network?

a.

101.101.101.20

b.

101.101.101.40

c.

101.101.101.60

d.

101.10
1.101.80

e.

101.101.101.180

42.

Whi ch of the fol l owi ng protocol s uses TCP?

a.

OSPF

b.

ICMP

c.

IGMP

d.

BGP

e.

None of the gi ven choi ces

43.

Whi ch of the fol l owi ng statements i s
wrong?

a.

Rel ayi ng i s used i n Skype to
overcome the NAT traversal
probl em

b.

The Uni versal Pl ug and Pl ay (UPnP)
Internet Gateway Devi ce (IGD)
Protocol al l ows a NATed host to
l earn the publ i c IP address

c.

NAT routers use 32
-
bi t port
-
number fi el d

d.

NAT vi ol ates the end
-
to
-
end
argument

e.

NAT was proposed to overcome
the address shortage pro
bl em

44.

Suppose Host A sends one segment wi th
sequence number 38 and 4 bytes of data
over a TCP connecti on to Host B. In thi s
same segment the acknowl edgment
number i s:

a.

38

b.

39

c.

42

d.

43

e.

The i nformati on gi ven i n the
questi on i s i nsuffi cient to answer



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45.

The
--------
-

BGP message l i sts mul ti ple
routes to be wi thdrawn

a.

Open

b.

Update

c.

Keepal i ve

d.

Noti fi cati on

e.

None of the gi ven choi ces

46.

Whi ch of the fol l owi ng statements i s
wrong?

a.

The dense mode of PIM uses fl ood
-
and
-
prune RPF

b.

The dense mode of PIM

has data
-
dri ven constructi on o
f mul ti cast
tree

c.

The concept of rendezvous poi nt i s
used i n the sparse mode of PIM

d.

In the sparse mode of PIM, no
membershi p unti l routers expl i ci tly
joi n

e.

The dense mode of PIM

has
conservati ve bandwi dth and non
-
group
-
router processi ng

47.

Suppose Host A sends
two TCP segments
back to back to Host B over a TCP
connecti on. The fi rst segment has sequence
number 90; the second has sequence
number 110. How much data i s i n the fi rst
segment?

a.

1 byte

b.

20 byte
s

c.

90 bytes

d.

110 bytes

e.

The i nformati on gi ven i n the
questi on i s
i nsuffi cient to answer

48.

Suppose a router uses the prefi x match
1100 1000 0001 0111 0001 0

for one of i ts
l i nk i nterfaces. Represent thi s prefi x match
usi ng the a.b.c.d/x notati on.

a.

200.23.2/21

b.

200.23.1/21

c.

200.23.16/21

d.

200.23.2/22

e.

200.23.16/22


49.

Whi ch of the f
ol l owi ng i s an exampl e of
di stance vector routi ng?

a.

OSPF

b.

RIP

c.

ICMP

d.

IGMP

e.

None of the gi ven choi ces

50.

Whi ch of the fol l owi ng statements i s
wrong?

a.

Intra
-
AS routi ng focuses on
performance

b.

Intra
-
AS routi ng saves tabl e si ze
and reduces update traffi c

c.

Pol i cy i s very
i mportant i n Inter
-
AS
routi ng

d.

AS
-
PATH and NEXT
-
HOP are two
attri butes used i n BGP

e.

Gateway routers recei vi ng route
adverti sement use i mport pol i cy to
accept/decl i ne