Tutorial 5 - Portal

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29 Οκτ 2013 (πριν από 3 χρόνια και 11 μήνες)

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CHAPTER
8


Q1.

Identify the address class of the following IP addresses: 200.58.20.165; 128.167.23.20;
16.196.128.50; 50.156.10.10; 250.10.24.96


Q2.
Convert the IP addresses in Q1 to their binary representation.


Q3.

A university has 150 LANs with 100 h
osts in each LAN.

Suppose the university has one
Class B address. Design an appropriate subnet addressing scheme.


Q4.
A small organization has a Class C address for seven networks each with 24 hosts. What
is an appropriate subnet mask?


Q5.
Consider
a s
ite that has been assigned a

Class B IP address of 1
50.100.0
.1, as shown in
Figure 1
. The site has a number of subnets and many hosts (H) connected by routers (R).
Assume that the subnet ID field is nine (9) bits long and the host ID field is seven (7) bit
s
long.


A packet with IP address 1
50
.1
00
.12.55 arrives at router R1. Explain how the packet is
delivered to the appropriate host.






















Figure 1



Q6.
Explain how the use of hierarchy enhances scalability in the following aspects of
Intern
et:

(a) Domain name system

(b) IP addressing

(c) OSPF routing

(d) Interdomain routing

H1

H2

H5

H3

H4

R1

150
.1
00
.12.154

R2

150.100
.12.176

150.100
.12.128

150.100
.12.129

150.100
.0.1

150.100
.12.4

150.100
.12.24

150.100
.12.55

150.100
.12.0

150.100
.12.1

150.
100
.15.54

150.100
.15.11

150.100
.15.0

Q7.
What is the maximum width of a RIP network?


Q8. RIP runs over UDP, OSPF runs over IP, and BGP runs over TCP. Compare the merits of
operating a routing protocol

over TCP, UDP, IP.


Q9.
Compare

RIP and OSPF with respect to convergence time and the number of messages
exchanged under several trigger conditions, that is, link failure, node failure, link coming up.


Q10
. Identify elements where OSPF and BGP are simi
lar and elements where they differ.
Explain the reasons for similarity and difference.


Q
11
.

RIP, OSPF and BGP are three dynamic routing protocols used in the Internet today.


(a
) OSPF and RIP use fundamentally different algorithms, but OSPF is said to con
verge
faster than RIP. By comparing the two protocols with respect to convergence, briefly
describe the statement and why is this so?


(b
) The Border Gateway Protocol (BGP) uses path
-
vector routing. Describe how path
-

vector enhances distance
-
vector an
d the advantage with the enhancement?


(c
) Give an example of a situation when redistribution of routes between two routing
protocols is useful.


Q1
2
.
Consider the autonomous system and BGP routers as shown in the figure
2
.


(a)

Suppose a certain network pre
fix belong to AS4. Over which router pairs will the route
to the given network be advertised?


(b)

Now suppose the link between R1 and R2 fails. Explain how a loop among AS1, AS2,
AS5, and AS6 is avoided.


(c)

Suppose that R9 is configured to prefer AS1 as transit

and AS6 is configured to prefer
AS1 as transit. Explain how BGP handles this situation.


















Figure 2

AS1

AS6

AS5

AS4

AS2

AS3

R7

R6

R4

R3

R2

R1

R5

R8

R9

Q1
3.

Consider the virtual
-
circuit
packet network in Figure 3
. Suppose that
node 4

in the
network fails.

(a)
Reroute the affected virtual ci
rcuits

(b)
Write the new set of routing tables















Figure 3



A

C

B

D

1

6

3

4

5

2