A Study on Comparison and Contrast between IPv6 and IPv4 Feature Sets J. Hanumanthappa 1 and Manjaiah D.H 2 Abstract--- This document provides an analysis and comparison of IPv4 and IPv6 under various circumstances. It is well understood that IPv6 has been designed to replace IPv4. We have done a feature-by-feature comparison and contrast of IPv6 versus IPv4 and found that IPv6 offers many unique opportunities for increasing a network architectures efficiency and agility. In some sense, there is a competition going on between these protocols, as they are not directly compatible, and network providers and users are being forced to determine whether to support one or both protocols for various network services. The new version of IP,(i.e. IPv6), constitutes an effort to overcome the inborn limitations of IPv4, in order for the new protocol be able to respond to the new needs as they shape today in the Internet. This paper is aimed to discuss about various comparison issues when porting an IPv4 application to IPv6 with focus on issues that an application developer would face rather than a complete API reference.IPv4 is the incumbent and currently has the most widespread usage for conventional Internet applications.IPv6 is a large-scale re-design and re-engineering of IPv4, based on many lessons learned as the IPv4-based Internet grew and was used in unforeseen ways. Keywords-- IPv4, IPv6, Multicast, Quality of service (QOS), Routing. I. INTRODUCTION HE primary motivation for change arises from the limited address space. When IPV6 deployed on a large scale it has solved many current networking problems. When IP was defined , only a few computer networks has existed Then the designers decided to use 32 bits for an IP address because doing so allowed the Internet to include over a million networks. However, the global Internet is growing exponentially, with the size doubling in less than a year. Currently, two versions of the Internet Protocol (IP) are in use on the Internet. In some sense, there is a competition going on between these protocols, as they are not directly compatible, and network providers and users are being forced to determine whether to support one or both protocols for various network services. IP version 4 (IPv4) is the incumbent and currently has the most widespread usage for conventional Internet applications. IP version 6 (IPv6) is a large-scale re-design and re- engineering of IPv4, based on many lessons learned as the IPv4-based Internet grew and was used in unforeseen ways. Hanumanthappa .J., Dos in Computer Science, University of Mysore, Manasagangothri, Mysore, Karnataka .INDIA ( phone: +091- 821-2419552; fax: +091-0821-2510789,Email: hanums_j@yahoo.com ) Dr.Manjaiah.D.H., Reader, Mangalore University, Mangalagangothri , Mangalore, Karnataka, INDIA. (phone: +091 - 0824 - 2287670; fax: +091 - 0824 - 2287424 Email: ylm321@yahoo.co.in ) Although it would seem obvious that IPv6 is a superior and valuable protocol to deploy, there is often considerable resistance to enabling IPv6 because Decision-makers have difficulty in seeing a business case for IPv6, unsure of how it can be less costly, more efficient, more productive, etc than the IPv4 status quo. Also, some analysts have propagated significant amounts of misinformation about IPv6 over the last several years. The primary motivation for the defining a new version of IP arises from the address space limitation- larger addresses are necessary to accommodate continued growth of Internet. The secondary motivation for the changes in IP has arisen from the new Internet applications. For example, an applications that deliver audio and video need to deliver data at regular intervals. In this paper we have also contrasted the various features of IPv4 and IPv6. A. The serious problems of IPv4 are as follows 1. Insufficient number of unique “valid” addresses. 2. Routing tables at core are becoming unmanageably large. 3. Fixed length headers are not flexible enough for new functionality. 4. Packet size (and Practice of fragmentation) is inefficient. B. The next–generation IPv6 has some advantages over IPv4 that can be summarized as follows (i). Larger address space: An IPv6 address is 128 bits long. Compared with the 32-bit address of IPv4, this is a huge (2 96 ) increase in the address space. (ii). IPv6 addressing: An IPv6 address consists of 16 bytes (octets).It is 128 bits long. To make address more readable, IPv6 specifies hexadecimal colon notation. In notation 128 bits are divided into eight sections, each 2 bytes in length. Two bytes in hexadecimal notation require four hexadecimal digits. Therefore address consists of 32 hexadecimal digits with T