Computer network

Computer Network
ROUTING, BROADCASTING AND
MULTICASTING

IP addresses
 Every computer has a physical address which is

called as MAC address(LAN Card address/hardware
address) or NIC card address, this address is 48 bit
address.
 Communication in internetworking is not possible
with the MAC address, because computer
manufactured by different companies and they don’t
follow the same format of generating the MAC
address. General MAC address format
1. 00-10-FA-6E-38-4A OR 2. 50-1A-DE-90-42-DC

IP address
 There will be a IANA(Internet Assigned number







authority)(www.iana.org). These are generally assigned a
logical addressing system(called as ip address) and in system
its store in Cache memory.
A system in networking world is identify by ip address.
The designer of internet protocol define as an ip address as a
32 bit number and this system is known as IPV4 (internet
protocol version 4) is still we use today. However due to the
enormous growth of internet and predicted
depletion(decrease) of available addresses a new version IPV6
using 128 bit for the address was developed in 1995.
Ipv4 address are 172.16.254.1
Ipv6 address are 2001:db8:0:1234:0:567:8:1

Classification of computer network by ip address
 Classes are generally divided into two parts:

1. Net Id.
(32 bit)
2. Host Id.
 Classes are divided into five classes:
1. Class A- unicasting.
2. Class B- unicasting.
3. Class C- unicasting.
4. Class D-Multicasting.
5. Class E- Research work.

 Class A:

0

(2^7-2)

(2^24-2)

(8 bits) Net ID
Host ID (24 bits)
As octet value of class A is (0-127). There will be a special
address (0.0.0.0) which is a default address or the DHCP
client(Dynamic Host Configuration protocol).
127.x.y.z it is a Loop back address. Where x,y,z is from (0255).
Number of network= 2^7-2= 128-2=126. So the range of
class A is (1-126) and each network have host id (2^242).
* Network Mask : 255.0.0.0

 Class B: 10 2^14

(2^16-2)

(16 bits) Net ID Host ID (16 bits)
The range of ip address is (128-191). There will be no
special address.
Number of networks = 2^14.
* Network Mask: 255.255.0.0
 Class C: 110 (2^21) (2^8-2)
Net ID(24 bits) Host ID(8 bits)
The range of class C is (192-223). There will be also no
special address.
* Network Mask: 255.255.255.0 (Default Mask)

 Class D: During unicasting we require Net id and

Host Id where as during Multicasting we don’t
require Net id and Host id.
1110

The Range is from(224-239).
 Class E: This is for research area.

1111
The range is from (240-254), 16.257.11.13 is a wrong
ip address because 257 is not a valid address.

Calculating the Net id and Host id with
Network mask
 63.14.19.67 calculate the net id?

63.14.19.67 63: 00111111
255.0.0.0
255:11111111
63.0.0.0 (Net id) :0011111
Net ID
63.0.0.0

Host ID
63.0.0.1

Host ID
63.0.0.2

Net ID
63.14.19.67

Host ID
63.255.255.
254

* 63.255.255.255 is the direct broadcast address.

Characteristic of loop back address
 It is used to test if the ip address packets are coming

from the other system or going out of the system.
 Physical port are used to transfer the data. Loop back
address will always used as a destination address. It
is used for inter process communication with in the
same system.
 In class A 126 network have 2^24-2 host which
approx 80,00,00 host if we use only 15000 then the
large number of ip address are going to be waste. So
this will be use in multinational company use.

 And in class B 2^14 network each network have

(2^16-2) host 65,534 host here also the ip address
are waste.
 Class C have 2^21 network and each network have
(2^8-2)= 254 hosts. So that in institution and small
companies are used this because the ip address are
not to be wasted over this.

Router
 Router is a WAN device(where different LAN

network are connected).

 Connecting to different router with different model

network we use GATEWAY. Suppose we use TCP/IP
model network and X.25 model network. We use
gateway to communicate with these two routers.

Router sending and receiving
Data| 46.0.0.1 (SIP) | 130.12.0.1(DIP). In this the
data is transmit to class A to class B.

Data| 46.0.0.1 (SIP) | 46.1.2.24(DIP). In this the
data is send and receive to same class A this is called
as a unicasting.

Data| 46.0.0.1 (SIP) | 255.255.255.255 (DIP). In
this the DIP is the limited broadcast address. Which
broadcast with in the network of Class A.

Data| 46.0.0.1 (SIP) | 130.1.255.255 (DIP). In this
class A send the data to broadcast to all the network
class B.


Working of Ping?
 When you start window-> goto command prompt

and Run cmd.
 This will be you see:
C:>ping 11.1.2.3 Enter.
Ping (packet internet grapher). Ping is a client
to server utility that is provided by operating system.
C:> ping 11.1.2.3 Enter
TTL=2 MS RTT=4MS
C:> ping 11.1.2.3 Enter
Destination unreachable(DIP is not configure)

 TTL is time to line, Its going to indicate the no. of

hops the packets are traverse before reaching the
destination.
 Distance from one router to another router is called 1
HOP.
 RTT is Round Trip Time; Time taken for the data to
reach the destination and coming back on
acknowledgement to the centre.

How to transmit the data and calculate the time
 Suppose if the size of the message is 1 KB. And







Bandwidth is 1 Mbps then the transmission time;
TT= (1*10^3 ) B / (1*10^6) bits per sec
= 8*10^-3 sec
= 8 millisec.
Propagation time= Distance/ Velocity.
Acknowledgement size<< message size.
TT ack= ack size/bandwidth.
TT ack<< TT msg data.

 PT ack= distance/ velocity.
 Total time= TT data + PT data + TT ack + PT ack.

TT ack is negligible.
Total time= TT data + 2*PT
RTT(Round Trip Time) =2*PT
Link Utilization of sender= TT/ (TT data + 2*PT)

Routing Algorithm
 Static Algorithm: These are the algorithm which

doesn’t take the network load as consideration.
* Flooding is as a static algorithm.
 Dynamic Algorithm: The algorithm that contain
network load as consideration.
 1. If the routing of packets are done with in the
autonomous system, it is known as inter routing
protocol; example : Distance vector routing
algorithm, Link State routing algorithm.
 2. If the routing of packets are done between
autonomous system is known as inter domain routing
algorithm. Example : Path vector routing algorithm.

Flooding

B
p

p
p

flooding

p

A

C
p

p

p

p
EE

D

Distance Vector Routing Algorithm

New
routing
table
Packet
transfer to
router A

Vector
table

A

B
E

D

F
C

Linked State Routing Algorithm
5

2

C

B

A

3

3

G

4

4

1

D

5

E

2

F

Shortest path tree from Router A

A

3

5

2

C

B

G

4

1

D

E

2

F

Conclusion
 Computer network is the very large area. And

generally we want a network which have a high
speed of transmission and very less of error while
communicating. Computer network wants
speed, accuracy, adequacy and security. These are
the all future aspects of computer network which we
will have to consider.

Computer network

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