What is Network Models?

What is Network Models?
1. OSI Reference Model
2. TCP/IP Reference Model

The 7 layers of the OSI model

BASIS FOR
COMPARISON
TCP/IP MODEL OSI MODEL
Expands To Transmission Control
Protocol/ Internet
Protocol
Open system
Interconnect
Meaning It is a client server model
used for transmission of
data over the internet.
It is a theoretical model
which is used for
computing system.
Number Of Layers 4 Layers 7 Layers
Developed by Department of Defense
(DoD)
ISO (International
Standard Organization)
Tangible Yes No
Usage Mostly used Never used
Obeys Horizontal approach Vertical approach
Comparison Chart

Which model is better, OSI or TCP/IP?
• Thus, we can conclude that both models have their own advantages and
disadvantages.
• If someone is focusing on the proper documentation, specification, and
modularization, they should prefer the OSI model over the TCP/IP model.
• But if someone is focusing more on the implementation, reliability, and
security of the network, they should prefer the TCP/IP model over the OSI
model.

Difference between TCP/IP and OSI Model
TCP/IP OSI Model
The full form of TCP/IP is Transmission
Control Protocol/ Internet Protocol.
The full form of OSI is Open Systems
Interconnection.
It is a communication protocol that is based on
standard protocols and allows the connection
of hosts over a network.
It is a structured model which deals which the
functioning of a network.
In 1982, the TCP/IP model became the
standard language of ARPANET.
In 1984, the OSI model was introduced by the
International Organisation of Standardization
(ISO).
It comprises of four layers:
•Network Interface
•Internet
•Transport
•Application
It comprises seven layers:
•Physical
•Data Link
•Network
•Transport
•Session
•Presentation
•Application
It follows a horizontal approach. It follows a vertical approach.
The TCP/IP is the implementation of the OSI
Model.
An OSI Model is a reference model, based on
which a network is created.
It is protocol dependent. It is protocol independent.

What is Network Protocols?

What is a network protocol?
It is a set of rules for communications.
In networking, a protocol is a standardized way of doing certain actions and
formatting data so that two or more devices are able to communicate with and
understand each other.
Example: To understand why protocols are necessary,
consider the process of mailing a letter.
On the envelope, addresses are written in the following order: name, street address, city, state,
and zip code.
If an envelope is dropped into a mailbox with the zip code written first, followed by the street
address, followed by the state, and so on, the post office won't deliver it.
There is an agreed-upon protocol for writing addresses in order for the postal system to work.
In the same way, all IP data packets must present certain information in a certain order, and all
IP addresses follow a standardized format.

What is Internet Protocol?

What is the Internet Protocol (IP)?
The Internet Protocol (IP) is a protocol, or set of rules, for routing and
addressing packets of data so that they can travel across networks and
arrive at the correct destination.
Data traversing the Internet is divided into smaller pieces, called packets.
IP information is attached to each packet, and this information helps
routers to send packets to the right place.
Every device or domain that connects to the Internet is assigned an IP
address, and as packets are directed to the IP address attached to them, data
arrives where it is needed.
• Once the packets arrive at their destination, they are handled differently
depending on which transport protocol is used in combination with IP.
• The most common transport protocols are TCP and UDP.

What is IP Address?

What is an IP address? How does IP addressing work?
An IP address stands for internet protocol address is a unique
identifier assigned to a device or domain that connects to the Internet.
Each IP address is a series of characters, such as '192.168.1.1'.
Via DNS resolvers, which translate human-readable domain names into IP
addresses,
users are able to access websites without memorizing this complex series of
characters.
An IP address allows computers to send and receive data over the internet.
Each IP packet will contain both the IP address of the device or domain
sending the packet and the IP address of the intended recipient, much like
how both the destination address and the return address are included on a
piece of mail.

How this IP address is assigned?
How automobile license plate numbers is assigned?
How this IP address is assigned?
• Users are assigned IP addresses by Internet service providers (ISPs).
• ISPs obtain allocations of IP addresses from a local Internet registry (LIR) or
National Internet Registry (NIR), or from their appropriate Regional Internet
Registry (RIR):

IP address structure
IP address structure: IP addresses are displayed as a set of four digits- the
default address may be 192.158.1.38.
Each number on the set may range from 0 to 255.
Therefore, the total IP address range ranges from 0.0.0.0 to 255.255.255.255.
• IP Address is a 32 bit binary address written as 4 numbers separated by dots.
• The 4 numbers are called as octets where each octet has 8 bits.
• The octets are divided into 2 components- Net ID and Host ID.

IP address structure
1. Network ID represents the IP Address of the network and is used to identify
the network.
2. Host ID represents the IP Address of the host and is used to identify the host
within the network.
IP Address Example-
00000001.10100000.00001010.11110000
(Binary Representation)
OR
1.160.10.240
(Decimal Representation)

Types of IP address
There are mainly four types of IP addresses:
• Public,
• Private,
• Static
• Dynamic.
Types of Website IP Addresses
Two types of website IP Addresses are
1) Share IP Address
2) Dedicated IP Address

Types of IP address
Type of IPAddress Description
Public IP
A public IP address is an address where
one primary address is associated with
your whole network.
Private IP
A private IP address is a unique IP
number assigned to every device that
connects to your home internet
network.
Dynamic IP
Dynamic IP addresses always keep
changing. It is temporary and are
allocated to a device every time it
connects to the web.
Static IP
Static IP address never changes, but it
can be altered as part of routine
network administration.
Shared IP
The IP address is not unique and it is
shared with other websites.
Dedicated IP
Dedicated IP address is assigned
uniquely to each website.

Types of IP address
1. Static IPAddress-
• Static IP Address is an IP Address that once assigned to a network element
always remains the same.
• They are configured manually.
2. Dynamic IPAddress-
• Dynamic IP Address is a temporarily assigned IP Address to a network element.
• It can be assigned to a different device if it is not in use.
• DHCP or PPPoE assigns dynamic IP addresses.

What are the types of IP
Addressing?

IP addressing
There are two systems in which IP Addresses are classified-
Classful Addressing-
In Classful Addressing System, IP Addresses are organized into following 5 classes-

Classes of IP Address
Class of IP
Address
Total Number of
IPAddresses
1st Octet
Decimal
Range
Number of
Networks
available
Hosts per
network
Default
Subnet Mask
Class A 231 1 – 126 27 – 2 224 – 2 255.0.0.0
Class B 230 128 – 191 214 216 – 2 255.255.0.0
Class C 229 192 – 223 221 28 – 2 255.255.255.0
Class D 228 224 – 239 Not defined Not defined Not defined
Class E 228 240 – 254 Not defined Not defined Not defined

Classless Inter-Domain Routing (CIDR)
Sometimes called supernetting (in contrast to subnetting).
• Representation: It is as also a 32-bit address, which includes a special number
which represents the number of bits that are present in the Block Id.
• a . b . c . d / n Where, n is number of bits that are present in Block Id /
Network Id.
Example:
20.10.50.100/20

What are versions IP Address?

Version of IP address
Two types of IP addresses are
1)IPV4 and
2) IPV6.
IPV4
IPv4 was the first version of IP. It was deployed for production in the ARPANET in
1983. Today it is the most widely used IP version. It is used to identify devices on a
network using an addressing system.
The IPv4 uses a 32-bit address scheme allowing to store 2^32 addresses, which is
more than 4 billion addresses. To date, it is considered the primary Internet Protocol
and carries 94% of Internet traffic.
Following are the features of IPv4:
• Connectionless Protocol
• Allow creating a simple virtual communication layer over diversified devices
• It requires less memory, and ease of remembering addresses
• Already supported protocol by millions of devices
• Offers video libraries and conferences

Version of IP address
IPV6
It is the most recent version of the Internet Protocol. Internet Engineer
Taskforce initiated it in early 1994. The design and development of that suite is
now called IPv6.
This new IP address version is being deployed to fulfill the need for more
Internet addresses. It was aimed to resolve issues which are associated with
IPv4. With 128-bit address space, it allows 340 undecillion unique address
space.
Here are the features of IPv6:
• Hierarchical addressing and routing infrastructure
• Stateful and Stateless configuration
• Support for quality of service (QoS)
• An ideal protocol for neighboring node interaction

IPv4 vs. IPv6
The fourth version of IP (IPv4 for short) was introduced in 1983.
However, just as there are only so many possible permutations for
automobile license plate numbers and they have to be reformatted
periodically, the supply of available IPv4 addresses has become depleted.
IPv6 addresses have many more characters and thus more permutations;
however, IPv6 is not yet completely adopted, and most domains and
devices still have IPv4 addresses.

What happen to other version ?
IPv1
IPv2
IPv3
IPv5

What is an IP packet?
• IP packets are created by adding an IP header to each packet of data before it is
sent on its way.
• An IP header is just a series of bits (ones and zeros), and it records several
pieces of information about the packet, including the sending and receiving IP
address.
• IP headers also report:
– Header length
– Packet length
– Time To Live (TTL), or the number of network hops a packet can make before it is discarded
– Which transport protocol is being used (TCP, UDP, etc.)
• In total there are 14 fields for information in IPv4 headers, although one of
them is optional.

What is TCP/IP?
• The Transmission Control Protocol (TCP) is a transport protocol, meaning it
dictates the way data is sent and received.
• A TCP header is included in the data portion of each packet that uses TCP/IP.
• Before transmitting data, TCP opens a connection with the recipient.
• TCP ensures that all packets arrive in order once transmission begins.
• Via TCP, the recipient will acknowledge receiving each packet that arrives.
• Missing packets will be sent again if receipt is not acknowledged.
• TCP is designed for reliability, not speed.
• Because TCP has to make sure all packets arrive in order, loading data via
TCP/IP can take longer if some packets are missing.
• TCP and IP were originally designed to be used together, and these are often
referred to as the TCP/IP suite.
• However, other transport protocols can be used with IP.

What is UDP/IP?
• The User Datagram Protocol, or UDP, is another widely used transport
protocol.
• It's faster than TCP, but it is also less reliable.
• UDP does not make sure all packets are delivered and in order, and it doesn't
establish a connection before beginning or receiving transmissions.

IP Address Classification Based on Operational Characteristics:
According to operational characteristics, IP address is classified as follows:
Broadcast addressing–
The term ‘Broadcast’ means to transmit audio or video over a network. A broadcast
packet is sent to all users of a local network at once. They do not have to be explicitly
named as recipients. The users of a network can open the data packets and then interpret
the information, carry out the instructions or discard it. This service is available in IPv4.
The IP address commonly used for broadcasting is 255.255.255.255
Unicast addressing–
This address identifies a unique node on the network. Unicast is nothing but one-to-one
data transmission from one point in the network to another. It is the most common form
of IP addressing. This method can be used for both sending and receiving data. It is
available in IPv4 and IPv6.
Multicast IP addresses–
These IP addresses mainly help to establish one-to-many communication. Multicast IP
routing protocols are used to distribute data to multiple recipients. The class D addresses
(224.0.0.0 to 239.255.255.255) define the multicast group.
Anycast addressing–
In anycast addressing the data, a packet is not transmitted to all the receivers on the
network. When a data packet is allocated to an anycast address, it is delivered to the
closest interface that has this anycast address.

Differences between IPv4 and IPv6 Addresses
Basis for differences IPv4 IPv6
Size of IP address IPv4 is a 32-Bit IP Address. IPv6 is 128 Bit IP Address.
Addressing method
IPv4 is a numeric address,
and its binary bits are
separated by a dot (.)
IPv6 is an alphanumeric
address whose binary bits
are separated by a colon (:).
It also contains
hexadecimal.
Number of header fields 12 8
Length of header filed 20 40
Checksum Has checksum fields
Does not have checksum
fields
Example 12.244.233.165
2001:0db8:0000:0000:0000:
ff00:0042:7879
Type of Addresses
Unicast, broadcast, and
multicast.
Unicast, multicast, and
anycast.
Number of classes
IPv4 offers five
different classes of IP
Address. Class A to E.
lPv6 allows storing an
unlimited number of IP
Address.

Configuration
You have to configure a newly
installed system before it can
communicate with other
systems.
In IPv6, the configuration is
optional, depending upon on
functions needed.
VLSM support
IPv4 support VLSM (Variable
Length Subnet mask).
IPv6 does not offer support for
VLSM.
Fragmentation
Fragmentation is done by
sending and forwarding routes.
Fragmentation is done by the
sender.
Routing Information Protocol
(RIP)
RIP is a routing protocol
supported by the routed
daemon.
RIP does not support IPv6. It
uses static routes.
Network Configuration
Networks need to be
configured either manually or
with DHCP. IPv4 had several
overlays to handle Internet
growth, which require more
maintenance efforts.
IPv6 support
autoconfiguration capabilities.
Best feature
Widespread use of NAT
(Network address translation)
devices which allows single
NAT address can mask
thousands of
non-routable addresses,
making end-to-end
integrity achievable.
It allows direct addressing
because of vast address
Space.

Address Mask
Use for the designated network
from host portion.
Not used.
SNMP
SNMP is a protocol used for
system management.
SNMP does not support IPv6.
Mobility & Interoperability
Relatively constrained network
topologies to which move
restrict mobility and
interoperability capabilities.
IPv6 provides interoperability
and mobility
capabilities which are embedded
in network devices.
Security
Security is dependent on
applications – IPv4 was not
designed with security in mind.
IPSec(Internet Protocol
Security) is built into the IPv6
protocol, usable with
a proper key infrastructure.
Packet size
Packet size 576 bytes required,
fragmentation optional
1208 bytes required without
fragmentation
Packet fragmentation
Allows from routers and sending
host
Sending hosts only
Packet header
Does not identify packet flow for
QoS handling which includes
checksum options.
Packet head contains Flow Label
field that specifies packet flow
for QoS handling
DNS records
Address (A) records, maps
hostnames
Address (AAAA) records, maps
hostnames

Address configuration Manual or via DHCP
Stateless address
autoconfiguration using Internet
Control Message Protocol
version 6 (ICMPv6) or DHCPv6
IP to MAC resolution Broadcast ARP Multicast Neighbour Solicitation
Local subnet Group
management
Internet Group Management
Protocol GMP)
Multicast Listener Discovery
(MLD)
Optional Fields Has Optional Fields
Does not have optional fields.
But Extension headers are
available.
IPSec
Internet Protocol Security
(IPSec) concerning network
security is optional
Internet Protocol Security
(IPSec) Concerning network
security is mandatory
Dynamic host configuration
Server
Clients have approach DHCS
(Dynamic Host Configuration
server) whenever they want to
connect to a network.
A Client does not have to
approach any such server as they
are given permanent addresses.
Mapping
Uses ARP(Address Resolution
Protocol) to map to MAC
address
Uses NDP(Neighbour Discovery
Protocol) to map to MAC
address
Combability with mobile
devices
IPv4 address uses the dot-
decimal notation. That’s why it
is not suitable for mobile
networks.
IPv6 address is represented in
hexadecimal, colon- separated
notation.
IPv6 is better suited to mobile
networks.