IP Address

Contents
• What is IP Address ?
• Understanding IP Addressing
• The Format of an IP Address
• Different Classes of IP address
• A brief description on IPv4

What is IP Address ?
An IP address (abbreviation of Internet Protocol address) is an
identifier assigned to each computer and other device (e.g.,
printer, router, mobile device, etc.) connected to a TCP/IP
network that is used to locate and identify the node in
communications with other nodes on the network. IP addresses are
usually written and displayed in human-readable notations, such as
172.16.254.1 in IPv4, and in IPv6
2001:0db8:85a3:0000:0000:8a2e:0370:7334

Understanding IP Addressing
• The IP address space is managed globally by the Internet Assigned
Numbers Authority (IANA), and by five regional Internet registries (RIR)
responsible in their designated territories for assignment to end users
and local Internet registries, such as Internet service providers.
• The IPv4 standard is most familiar to people and supported
everywhere on the Internet, but the newer IPv6 standard is gradually
replacing it. IPv4 addresses consist of four bytes (32 bits), while IPv6
addresses are 16 bytes (128 bits) long.

Understanding IP Addressing
There are private IP addresses, public IP addresses, static IP addresses, and dynamic IP
addresses.
• private IP addresses are used "inside" a network, like the one you probably run at
home. These types of IP addresses are used to provide a way for your devices to
communicate with your router and all the other devices in your private network.
Private IP addresses can be set manually or assigned automatically by your router.
• Public IP addresses are used on the "outside" of your network and are assigned by
your ISP. It's the main address that your home or business network uses to
communicate with the rest of the networked devices around the world (i.e. the
Internet).
• Both private IP addresses and public IP addresses are either dynamic or static, which
means that, respectively, they either change or they don't.
• An IP address that is assigned by a DHCP server is a dynamic IP address. If a device
does not have DHCP enabled or does not support it then the IP address must be
assigned manually, in which case the IP address is called a static IP address.

The Format of an IP Address
• An IP address consists of 32 bits, often shown as 4 octets of numbers from 0-255
represented in decimal form instead of binary form. For example, the IP address:
168.212.226.204 in binary form is 10101000.11010100.11100010.11001100.
• But it is easier for us to remember decimals than it is to remember binary
numbers, so we use decimals to represent the IP addresses when describing them.
However, the binary number is important because that will determine which class
of network the IP address belongs to.

The Two Parts of an IP Address
• IP address have two parts prefix and suffix
• The address prefix identifies the physical network to which the computer is
attached , While suffix identifies the individual computer on the network
• Prefix is also called network address
• Suffix is also called host address

Different Classes of IP address
Class A Network
In a Class A Network binary address start with 0, therefore the decimal
number can be anywhere from 1 to 126. The first 8 bits (the first octet) identify the
network and the remaining 24 bits indicate the host within the network. An example
of a Class A IP address is 102.168.212.226, where "102" identifies the network and
"168.212.226" identifies the host on that network.
Class B Network
In a Class B Network, binary addresses start with 10, therefore the decimal
number can be anywhere from 128 to 191. The number 127 is reserved
for loopback and is used for internal testing on the local machine. The first 16 bits (the
first two octets) identify the network and the remaining 16 bits indicate the host within
the network. An example of a Class B IP address is 168.212.226.204 where "168.212"
identifies the network and "226.204" identifies the host on that network.

Class C Network
Binary addresses start with 110, therefore the decimal number can be
anywhere from 192 to 223. The first 24 bits (the first three octets) identify the network
and the remaining 8 bits indicate the host within the network. An example of a Class C
IP address is 200.168.212.226 where "200.168.212" identifies the network and "226"
identifies the host on that network.
Class D Network
In a Class D Network, binary addresses start with 1110, therefore the decimal
number can be anywhere from 224 to 239. Class D networks are used to
support multicasting.
Class E Network
In a Class E Network, binary addresses start with 1111, therefore the decimal
number can be anywhere from 240 to 255. Class E networks are used for
experimentation. They have never been documented or utilized in a standard way.

ADDRESS
CLASS
BIT IN
PREFIX
MAX.NO OF
NETWORKS
BIT IN
SUFFIX
MAX.NO OF
HOSTS PER
NETWORK
A 7 128 24 1,67,77,216
B 14 16,384 16 65,536
C 21 20,97,157 8 256

IPv4
• Internet Protocol version 4 (IPv4) is the fourth version of the Internet Protocol (IP). It is
one of the core protocols of standards-based internetworking methods in the Internet.
• IPv4 uses 32-bit addresses which limits the address space to 4294967296 (232)
addresses.

IPv4
Version: Version no. of Internet Protocol used (e.g. IPv4).
IHL: Internet Header Length; Length of entire IP header.
DSCP: Differentiated Services Code Point; this is Type of Service.
ECN: Explicit Congestion Notification; It carries information about the congestion seen in the
route.
Total Length: Length of entire IP Packet (including IP header and IP Payload).
Identification: If IP packet is fragmented during the transmission, all the fragments contain
same identification number. to identify original IP packet they belong to.
Flags: As required by the network resources, if IP Packet is too large to handle, these ‘flags’
tells if they can be fragmented or not. In this 3-bit flag, the MSB is always set to ‘0’.

IPv4
Fragment Offset: This offset tells the exact position of the fragment in the original IP
Packet.
Time to Live: To avoid looping in the network, every packet is sent with some TTL value
set, which tells the network how many routers (hops) this packet can cross
Protocol: Tells the Network layer at the destination host, to which Protocol this packet
belongs to, i.e. the next level Protocol.
Header Checksum: This field is used to keep checksum value of entire header which is
then used to check if the packet is received error-free.
Source Address: 32-bit address of the Sender (or source) of the packet.
Destination Address: 32-bit address of the Receiver (or destination) of the packet.
Options: This is optional field, which is used if the value of IHL is greater than 5. These
options may contain values for options such as Security, Record Route, Time Stamp, etc.

IPv6
• Internet Protocol version 6 (IPv6) is the most recent version of the Internet
Protocol (IP), the communications protocol that provides an identification and
location system for computers on networks and routes traffic across the Internet. IPv6
was developed by the Internet Engineering Task Force (IETF) to deal with the long-
anticipated problem of IPv4 address exhaustion. IPv6 is intended to replace IPv4.
• An IPv6 address is represented as eight groups of four hexadecimal digits, each
group representing 16 bits (two octets). The groups are separated by colons (:).
• The hexadecimal digits are case-insensitive, but IETF recommendations suggest the
use of lower case letters. The full representation of eight 4-digit groups may be
simplified by several techniques, eliminating parts of the representation.

IPv6
Version (4-bits): It represents the version of Internet Protocol, i.e. 0110.
Traffic Class (8-bits): These 8 bits are divided into two parts. The most significant 6 bits
are used for Type of Service to let the Router Known what services should be provided to
this packet.
Flow Label (20-bits): This label is used to maintain the sequential flow of the packets
belonging to a communication. The source labels the sequence to help the router
identify that a particular packet belongs to a specific flow of information.
Payload Length (16-bits): This field is used to tell the routers how much information a
particular packet contains in its payload.
Next Header (8-bits): This field is used to indicate either the type of Extension Header, or
if the Extension Header is not present then it indicates the Upper Layer PDU.

IPv6
Hop Limit (8-bits): This field is used to stop packet to loop in the network infinitely.
Source Address (128-bits): This field indicates the address of originator of the packet.
Destination Address (128-bits): This field provides the address of intended recipient of
the packet.

Difference between IPv4 vs Ipv6
IPv4 IPv6
IPv4 addresses are 32 bit length. IPv6 addresses are 128 bit length.
IPv4 addresses are binary numbers represented in
decimals.
IPv6 addresses are binary numbers represented
in hexadecimals.
IPSec support is only optional. Inbuilt IPSec support.
Fragmentation is done by sender and forwarding
routers.
Fragmentation is done only by sender.
No packet flow identification.
Packet flow identification is available within the IPv6
header using the Flow Label field.
Checksum field is available in IPv4 header No checksum field in IPv6 header.
Options fields are available in IPv4 header.
No option fields, but IPv6 Extension headers are
available.
Broadcast messages are available.
Broadcast messages are not available. Instead a link-
local scope "All nodes" multicast IPv6 address (FF02::1)
is used for broadcast similar functionality.
Manual configuration (Static) of IPv4 addresses or
DHCP (Dynamic configuration) is required to
configure IPv4 addresses.
Auto-configuration of addresses is available.

Conclusion
• What is IP Address ?
• Understanding IP Addressing
• The Format of an IP Address
• Different Classes of IP address

Knowledge is
having the right
ANSWER.
Intelligence is
asking the right
QUESTION.
?

IP Address

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