1. IntroductionWhen TCP/IP was created in the 70s, the Internet started running on it until today. In 1981, since the introduction of IPv4 (Internet Protocol Version 4); it has served the Internet from a small research group of just a few universities to a global network all over the world for over thirty years. However, as the number of computers and other network devices increases dramatically around the world, IP addresses are almost exhausted due to the disadvantages of IPv4. Demanding IP address and security requirements therefore require a new protocol to handle these issues. To eliminate these problems, a new version of the Internet Protocol (IPv6) was introduced in the 1990s. For the main reason, this new network layer protocol was designed to increase the size of the IP address from 32 bits to 128 bits, which could provide almost unlimited IP address to all services and devices. Additionally, compared to IPv4, the IPv6 protocol provides safer and more secure communications and data transfers. The new features, capabilities and improvements of the IPv6 protocol would significantly improve the performance of today's network. Although IPv6 has many advantages, implementations and applications of IPv6 in a real network are still slow and difficult. Due to the size of the global network, the transition from IPv4 to IPv6 cannot be instantaneous. This means that when migrating between these two protocols, several issues would appear. Additionally, providers, ISPs and associated companies are waiting for a suitable market opportunity as most of them feel that there is no rush to join the crowd boasting of being the first to deploy the IPv6 protocol. In Canada today, more than twenty-five ISPs have started to replace ...... in the middle of paper addresses ......09). This is enough for billions of addresses to be assigned to every human being on the planet. Additionally, these address bits are split between the network prefix and the host identifier portions of the address. The network prefix designates the network on which the host with the address resides. The host ID identifies the node or interface within the network on which it resides. The network prefix may change while the host ID may remain static. The static host identifier allows a device to maintain a consistent identity despite its location within a network. This enormous number of addresses enables end-to-end communication between devices with globally unique IP addresses and can better support the delivery of peer-to-peer services with data-rich content such as voice and the video. Chapter 3 describes IPv6 addressing in detail.