Data Network

Netwo rk ing

Purpose of networking

What is osi..?

It stands for Open System Interconnection.

It is an ISO that covers all aspects of network communicatio

It is a model which allows two any two different systems to communicate regardless of their underlying architecture (hardware or software).

The OSI is a model and not a protocol; it is model for understanding and designing a network architecture.

The Osi model OSI is a layered framework that allows communication across all types of computer systems. Each layer has distinct identity and specific functions. Each step is independent. Lower layer provides certain services to higher layer to carry out its functions.

Osi layers

Physical layer Defines type of encoding. Defines data rate, duration of a bit. Deals with mechanical and electrical specifications of interface and medium. The physical layer is responsible for physical transmission of individual bits from one node to the next.

Data layer Responsible for: Dividing bits into manageable data units called frames. Physical addresses of the Devices. Media access control. Node-to-node and error free delivery of data, The data link layer is responsible for transmitting frames from one node to the next.

network layer

Responsible for:

Providing logical address. Source-to-destination delivery of Individual packets across multiple links. Routing of packets. No need of this layer within one network.

transport layer Responsible for source-todestination delivery and recovery of entire message. ensures that the whole message arrives intact and in order. Segments the message into transmittable segments. At destination, message is correctly reassembled. It gives port number and port address.

Node –to-node delivery of message

End-to-end delivery of message

session layer Responsible for: Establishing, maintaining and synchronizing communicating devices. Allowing communication to take place. Checking simplex, half duplex and full duplex communication Allowing process to check points into stream of data (synchronisation points)

is the network dialog controller or network card one can say.

presentation layer Concerned with syntax and semantics of the information. Changes information into common format from sender format at the sender end. Performs data transformation for eg. Encryption ,decryption and data

application layer The top most layer of OSI model. Enables the user/software to access the network No change in data is made in this layer. No header and trailer are included. Provides user interface and support for services.

How data flows

What is Tcp/ip.? TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network. TCP stands for TRANSPORT CONTROL PROTOCOL. IP stands for “INTERNET PROTOCOL”. They are mainly transport layer and network layer protocol.

What is a protocol ?

Tcp/ip model

Unlike OSI model ,TCP/IP has only 5 layers.

Data encapsulation application

transport

Data TCP Header Data TCP Segment

UDP Header Data UDP Segment

network Data link

IP Head Fram IP e head head

TCP/U Data IPDP Datagram TCP/U DP Frame

D Trail ata er

Application using TCP

Application using UDP

DP STANDS FOR USER DATAGRAM PROTOCOL.

TFTP- Trivial file transfer protocol. - provides simple file transfer for n/w booting of devic NFS- N/w file system -ability for sharing directories between host on the n SNMP-Simple n/w management protocol. -ability to supply n/w management services. DNS-Domain name server -mapping between domain name and IP address and -Vice-versa.

Ip addresses

Ip address specifies location of hosts. It stands for internet protocol. It is a 32 bit address and each ip address is unique. IP address consists of two parts. Network ID Host ID Network ID

Host ID

No. of bits in n/w ID and host ID decides the type of IP addres

notation Binary notation

01110101   10010101   00011101   11101010 Dotted-decimal notation

Addresses types

address Original style of addressing based on few bits of Addresses. Generally used in customer Sites

classful

No class. Disregards class bit of an address and applies a prefix to determine n/w no.

classless

Classful address types Cla ss A

N

H

H

H

Cla ss B

N

N

H

H

Cla ss C

N

N

N

H

Cla ss D

MULIT CAST

Clas s E

RESEARCH

IDENTIFYING address types N/W IDENTIFIER

N/W

HOST

Cla ss A

0

7

8

8

8

Cla ss B

10

6

8

8

8

Cla ss C

110

5

8

8

8

Cla ss D

1110

MULIT CAST

Clas s E

1111

RESEARCH

statistics Class

No. of net wor ks

Cla ss A

27

= 128

Cla ss B

2 14

= 16384

Cla ss C

2 21

= 2097152

No. of H osts 2 24 = 167 77216 2 16 28

= 65536 =

256

h class first network ID is used for network address a d for broadcast address.

Range of Ip addresses Cla ss A

00000000-01111111

0-127

Cla ss B

10000000-10111111

128-191

Cla ss C

11000000-11011111

192-223

Cla ss D

11100000-11101111

224-239

Clas s E

11110000-11111111

240-255

subnetting Chopping of network into no. of smaller networks is called subnetting. Efficiently uses full network address. Subnet is a real network under a network. Allows to assign some of bits normally used by host portion of address to the network portion of the address. The network portion of the address. Any of the classes can be subnetted.

Subnetting with two bits

Lets take the example of class C address type. The class C address format is something like this.. Cla ss C

N

N

N

H

ubnetting with two bits means that two bits in the host ID ill remain fixed in one subnet. e cannot change the Network ID but can only change host ID nce subnetting is with two bits ,no. of subnets will be 22=4.

CONTD… SUBNETS AND THEIR RANGE SUBNE T SUBNE T1

NETWORK ID

HOST ID

N/W ADDRESS 00000000

B.ADDRE SS 00111111

N

N

N

00000000 – 00111111

SUBNE T2

N

N

N

01000000 -01111111

01000000

0111111 1

SUBNE T3

N

N

N

10000000 -10111111

10000000

10111111

SUBNE T4

N

N

N

11000000 -11111111

11000000

11111111

CONTD… 0/26 represents that it starts from 0 and has 26 bits fixed in this subnet. Subnet SN 1

No. of compute rs

62

SN 2

62

SN 3

62

SN 4

62

SN-3 128/26 0

1

SN-2 64/26

10 1

SN-4 192/26

0 SN-1 0/26

Variable length subnet

Subnetting creates equal no. of hosts in a network.

Length of network mask will be same for all subnets.

To cope up with variable number of hosts in a subnet, no. of subnetted bits i.e. length of subnet mask will vary.

The method of achieving subnet of variable number of host is called VARIABLE LENGTH SUBNET MASK.

Contd…

Contd…

A=30

25=32

B=60

26=64

C=15

24=16

D=12 0

27=12 8

N.N.N.000…. . N.N.N.10…… N.N.N.1111… . N.N.N.0…….

ROUTING Movements of packets within the inter-network.

ROUTING Direct routing If packets moves within the same network.

Indirect routing If packets moves from one network to another network.

Ethernet port N E T W O R K 2

N E T W O R K 1 Serial port

Static ROUTING Routes to destinations are set up manually. Network reachability is not dependent on existence and state of network. Route may be up or down but static routes will remain in routing tables and traffic would still be sent towards route. Not suitable for large number of network. It is also known as non-adaptive routing.

Dynamic ROUTING

Routes are made via internal and external routing protocols Network reachability is dependent on the existence and State of network. It is also known as adaptive routing. The routing protocols are: - RIP (routing information protocols) - OSPF (open shortest path first)

Masking concept An IP address has two components, the network address and the host address. A subnet mask separates the IP address into the network and host addresses. Subnetting further divides the host part of an IP address into a subnet and host address (<subnet>). It is called a subnet mask because it is used to identify network address of an IP address by performing bitwise AND operation on the net mask.

Masking concept

en an address from a block of addresses, we can find network address by bit wise AND operation with a ma

Default masks

How Router finds network address…?? IP m ask

SUBNETTED MASK IS 11111111111111111111111 11011 00000 10000 111100000

000

011

000

00001 100

(216.003.128 .12)

(255.255.255 11111 11111 11111 11100 NETWORK ADDRESS IS .224) and 111 11011000000000111000000 111 111 000 Network address is 216.003.128.0 000000000

11011 000

00000 10000 011 000 IP ADDRESS

11011000000000111000000 000001100

But how…??

00000 000

(216.003.128 .00)

NETWORK TOPOLOGY

The physical topology of a network refers to the configuration of cables, computers, and other periphera The way in which the network is laid physically or logica

Me sh topology

Every computer is connected to each ot

Advantages:

•Dedicated link eliminates traffic problem. •Failure of link does not affects other link. •Privacy of link is maintained. •Fault identification and fault isolation is easy.

Disadvantages:

Hardware requirements and i/o ports increases. More space is required.

Star t opology Each computer has a dedicated link to a central Controller called HUB or SWITCH..It acts as an exchange.

Advantages:

• less expensive. •Fault identification and isolation is easy. •Failure of one link does not affect other.

Disadvantages:

•If HUB or SWITCH fails , then whole network will be down.

Tree topology

There is one main backbone (central) HUB and seconda HUB emerges out from it. Central HUB is active while secondary can be active or passive. Active HUB contain Repeater.

dvantages:

ore and more devices can be attached. llows network to identify and isolate faults. oint to point wiring for individual segments.

sadvantages: isadvantages:

backbone gets down then whole system fails. fficult to configure.

Bus topology

nsists of a main run of cable with a terminator at eac

Advantagesdisadvantages: •If backbone fails, whole network cease : •Difficult to add new devices. •Ease in installation. •Uses less cable.

Ring topology Each device is connected to only two devices.

Advantages:

•Easy in installation. •To add and delete only 2 connections are altered. •Fault isolation is simplified.

Disadvantages:

•Break in ring ceases whole network. •Difficult to add new devices.

Hybrid topology Combination of all the topologies.

Advantages:

•Increased number of devices. •Contains all topologies.