IP Address

1. Nangarhar University
Faculty of Computer Science
Networking and Communication
Dept- Spring 2014

2. Understanding the TCP/IP
Internet Layer

3. Internet Protocol
• The IP component of TCP/IP determines
where packets of data are to be routed based
on their destination addresses.
• and IP has certain characteristics related to
how it handles this function. This topic
describes some of the key functions of IP.

4. Conti…
• IP uses packets to carry information through
the network.
• A packet is a self-contained, independent
entity that contains data and sufficient
information to be routed from the source to
the destination

6. IP Characteristics
• IP operates at Layer 3 of the OSI model
(Network Layer), and Layer 3 of the TCP/IP
stack (Internet layer).
• IP is a connectionless protocol in which a one-
way datagram is sent to the destination
without advance notification to the
destination device. The destination device
receives the data and does not return any
status information to the sending device.

7. IP Characteristics
• IP uses hierarchical addressing in which the
network ID is like a street and the host ID is
like a house or office building on that street.
• IP provides service on a best-effort basis and
does not guarantee packet delivery. A packet
can be misdirected, duplicated, or lost on the
way to its destination.

8. IP Characteristics
• IP does not provide any special features that
recover corrupted packets. These services are
instead provided by the end systems of the
network.

9. IP Addressing
• To facilitate the routing of packets over a
network the TCP/IP protocol suite uses a
logical address known as an IP address

11. Conti…
• Just as physical street addresses are necessary
to identify the location
• logical IP addresses are used to identify the
location of specific devices on an IP network
so that data can reach those network
locations efficiently
• The IPv4 address is the most common type of
address currently used on the Internet

12. Conti…
• An IP address is a hierarchical address and
consists of these two parts:
• The network address portion (network ID)
describes the network of which this IP address is
a part. The router maintains information about
routes to each network.
• The host address component (host ID) identifies a
specific endpoint. These endpoints are the
servers, computers, and other devices connected
to the network.

13. Conti…

14. Conti…
• In any given IP address, some portion of the
32-bit number represents the network and
the remaining bits represent the host. While
many computers may share the same network
address, combining the network address with
a host address uniquely identifies any device
connected to the network.

15. • For usability, these 32-bit numbers are broken
up into 4 groups of numbers called octets
(1 octet = 8 bits)
• Each octet is then represented as a decimal
number between 0 and 255 and separated by
a period, or dot.

16. Conti…
• This scheme is known as “dotted decimal
notation.”
• The IP address shown above can be written as
172.16.128.17 and spoken as “172 dot 16 dot
128 dot 17.”

17. IP Address Classes
• To accommodate different sizes of networks
and aid in classifying them, IP addresses are
divided into categories called classes. This
topic describes the IP address classes and the
structure of the IP addresses within them.

19. IP Address Classes
• Assigning IP addresses to classes is known as
class full addressing. The classes were
determined during the early days of the
Internet by the Internet Assigned Numbers
Authority (IANA).

20. IP Address Classes
• Each IP address is broken down into a network
ID and the host ID. In addition, a bit or bit
sequence at the start of each address
determines the class of the address.

21. Class A
• The Class A address uses only the first octet (8
bits) of the 32-bit number to indicate the network
address.
• The remaining three octets of the 32-bit number
are used for host addresses.
• The first bit of a Class A address is always “0.”
Since the first bit is a 0, the lowest number that
can be represented is 00000000 (decimal 0), and
the highest number that can be represented is
01111111 (decimal 127)

22. Class A
• However, these two network numbers, 0 and
127, are reserved and cannot be used as
network addresses. Any address that starts
with a value between 1 and 126 in the first
octet of the 32-bit number is a Class A
address.

23. Class B
• The Class B address uses two of the four
octets (16 bits) to indicate the network
address
• The remaining two octets specify host
addresses.
• The first 2 bits of the first octet of a Class B
address are always binary 10

24. Class B
• Starting the first octet with binary 10 ensures
that the Class B space is separated from the
upper levels of the Class A space. The
remaining 6 bits in the first octet may be
populated with either 1s or 0s.

25. Class B
• Therefore, the lowest number that can be
represented with a Class B address is
10000000 (decimal 128), and the highest
number that can be represented is 10111111
(decimal 191). Any address that starts with a
value in the range of 128 to 191 in the first
octet is a Class B address.

26. Class C
• In a Class C address, the first three octets (24
bits) of the IP address identify the network
portion, with the remaining octet reserved for
the host portion
• A Class C address begins with binary 110
Therefore, the lowest number that can be
represented is 11000000 (decimal 192), and
the highest number that can be represented is
11011111 (decimal 223)

27. • If an address contains a number in the range
of 192 to 223 in the first octet, it is a Class C
address.

28. Local Loopback Address
• A local loopback address is used to let the
system send a message to itself for testing. A
typical local loopback IP address is 127.0.0.1.

29. Auto configuration IP Addresses
• When neither a statically nor a dynamically
configured IP address is found on startup
• those hosts supporting IPv4 link-local
addresses will generate an address in the
169.254/16 prefix range.
• You will mostly see this address as a failure
condition when a PC fails to obtain an address
via DHCP.

32. Reference
• http://www.tutorialspoint.com/ipv4/ipv4_add
ress_classes.htm

33. Online you can find this slide in
• http://www.slideshare.net/nasratsellab/ip-
address-33260595