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24 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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Mwenya Mwansa

Info 465, Assign2

Prof. Dr. H. Marzi

Chapter 5

1. Question 5.2: What tasks are p
erformed by the transport layer?


Ans: Ensure that data is exchanged reliably; that is transmitting data to the
destination application where they

should arrive in the same order in which they were sent.

2.

Question 5.7: There are several protocol models that have been developed. Examples of these include
SNA, Appletalk, OSI, and TCP/IP as well as more general models such as thre
e
-
layer models. Wh
at
model is
actually used for communications that travel over the Internet?

Ans: TCP/IP

3.

Question 5.8: What are some advantages of layering as seen in the TCP/IP architecture?

i
)


Ea
ch layer
being able to
perform

a certain task to transfer data

allows for increase in reliability.

ii)
I
t

is

more manageable

as it promotes standards

iii
)
One layer can be modified without affecting other layers

iv
)

It h
elps in

troubleshooting error
r in data transfer processes

2.
Question 5.11: Compare the address
space between IPv4 and IPv6. How many bits are used in each?

Ans:

IPv4 = 2
32

Addresses (32 bits used)

IPv6 = 2
128

Addresses (128 bits used)

Problems
:

1
.
Problem 5.5:
A TCP segment consisting of 1500 bits of data and 160 bits of header is sent to the IP layer,
which appends another 160 bits of header. This is then transmitted through two networks, each of which uses a
24
-

bit packet header. The destination network has a

maximum packet size of 800 bits. How many bits,
including headers, are delivered to the network layer protocol at the destination?

Header

(160 + 160 + 24 + 24)

368

368

368

368

Segment

(1500)

432

432

432

204

Packet Size Received(
800)

800

800

800

572


Therefore, t
o
tal d
elivered: 800 + 800 + 800 + 572 = 2972bits


2
.
Problem 5.15:

Fig
ure 5.8 shows the protocols that
operate directly on top of IP. Ping is a program used to
test connectivity between machines and is available on all operating systems. Which
of

the built
-
in protocols
does Ping use and what does the payload data consist of? Hint: You can use Ethereal to help you determine the
answers.

Ans:
ICMP = Internet Control Message Protocol

ICMP Payload

i)
Type of Message

ii)
Code

iii)
Checksum

iv)
Quench

v)
Data

3
.
Problem 5.16:

What other programs are built into your operating system to help you troubleshoot or
provide feedback about your connectivity.

i)
P
ing
: Sends ICMP Echo Request messages to verify that TCP/IP is configured correctly and that
a TCP/IP
host is available.

ii)
ipconfig
: Displays current TCP/IP network configuration values, updates, or releases, Dynamic Host
Configuration Protocol (DHCP) allocated leases, and display, register, or flush Domain Name System (DNS)
names.

iii)
Hostname
: D
isplays hostname

iv)
nbstat
: Displays the status of current NetBIOS over TCP/IP connections, updates the NetBIOS name cache,
and displays the registered names and scope ID.

v)
pathping
: Displays a path of a TCP/IP host and packet losses at each router a
long the way.

vi)
Route
: IP routing table and adds or deletes IP routes

vii)
tracert
:
This is the p
ath of TCP/IP

host

Chapter 8

1.
Question 8.1: Describe the five classes of Internet addresses.

Ans:

Class
A
-

has a few networks, each with many hosts.

Class B
-

Has a medium number of networks, each with a medium number of hosts
.


Class C


Has m
any networks, each with a few hosts
.


Class D


One network with a group of hosts.

Class E


One network serving a number of hosts

2.
Question 8.3: What is the

purpose of the subnet mask?


It used to determine the destination address of a datagram, as to either a particular host or LAN in an extended
network.
It is also employed by hosts to help make routing decisions.

3.
Question 8.1
2: What is the purpose of a

DS c
odepoint?


It is used to classify differentiated services.

4.
Question 8.13: List and briefly explain the
five main functions of DS traffic

conditioning.

i) Classfier: s
eparates submitted packets into different classes, only on the basis

of the DS
codepoint or on

multiple fields
within

the packet header, or even the
packet payload.

ii) Meter: Measures submitted traffic for conformance to a profile, by determining

whether a given packet stream class is within or exceeds the service level guarantee
d for that class.

iii) Marker: Re
-
marks packets with a different codepoint as needed for either best effort handling, or at the

boundary between two DS domains.

iv) Shaper: Delays packets
as necessary to ensure that the packet stream in a given class

does not exceed the

traffic rate specified in the profile for that class.

v) Dropper
: Drops packets when the rate of packets of a given class exceeds that sp
ecified in the profile for that

class.

Problems

1.

Problem 8.5:

Given a network address of 192.168.100.0 and a subnet mask of 255.255.255.192,

a. How many subnets are created?

If 192 = 11000001,

110 =

6

subnets

b. How many hosts are there per subnet?

31 hosts per subnet
: xxx11111

2. Problem 8.6:

Given a company with six individual departments and each department having ten
computers or networked devices, what mask could be applied to the company
network

to provide the
subnetting necessary to divide up the network equally?

110
-
0
-
1010 (1010 = 10)

19
2.168.100.202