The network IP
layer of TCP/IP protocol stack is considered the most crucial component of the
whole Internet architecture. With the Internet growing exponentially due to the
emerging IoT revolution, IPv4 had shown limitation in terms of scalability and
capability. Therefore, IPv6 was introduced not only as an extension to solve the
problem of IPv4 address space exhaustion but it provides is a complete
implementation of the TCP/IP protocol stack network layer and it provide a lot
more than the addresses space extension from 32 to 128 bits. This research
would present both protocols in details highlighting their main differences.

The Internet
Protocol (IP) is the principal communications protocol in the Internet protocol
suite for relaying datagrams across network boundaries. Its routing function
enables internetworking, and essentially establishes the Internet. IP has the
task of delivering packets from the source host to the destination host solely
based on uniquely identifying IP addresses in the packet headers.

For this purpose, IP defines packet structures that encapsulate the
data to be delivered. It also defines addressing methods that are used to label
the datagram with source and destination information. IP applies layering concept that software of the receiving machine N layer
should receive the same message that is sent by the software of the sender
machine N layer.

There are five layers in the Internet model. The lower four layers
match the OSI model lower four layers in a rough way. Most of the OSI model topmost
three layers’ responsibilities were assigned to the application layer of the Internet
model, and some of the duties of the session layer were assigned to the
transport layer (2).

The Current IP versions are IP Version 4 (IPV4) and IP Version 6 (IPV6) (5).  IPv4 was designed in 1970 and introduced to the
industry in 1981. With number of interconnected computers grows dramatically,
this situation leads to depletion of IPv4 address space. Consequently, a new
version IPv6 was designed in 1995 and deployed in 1999.

This research presents the definition of the two protocols, their features,
a description of their address architecture or address space, the fields in their
headers, and a related work over the two protocols to be able to compare
between them.